Microscopy Conference 2023

Prof. Dr.

Session chairs

The impact of rapid thermal annealing on ferroelectric HfO2 analyzed by conventional TEM in plan-view and in cross-section

MS 4: Functional thin films

MS 7: Ceramics and composites

Abstract text (incl. figure legends and references) Introduction HfO2 and related compounds attracted considerable interest for different non-volatile storage elements. The functionality and device performance of memory related applications is strongly affected by oxygen vacancies, which can stabilize the metastable ferroelectric phase of HfO21. The wake-up effect of ferroelectric HfO2 was attributed to defect related changes2, phase transitions3 and structural transformations4. Objectives Ferroelectric capacitors consisting of TiN electrodes and sputtered HfO2 on an 1 cm2 Si substrate showed different ferroelectric properties due to a temperature gradient during rapid thermal annealing (RTA). Devices from the hot corner had low remnant polarization of 10 µC/cm2 without changing during field cycling, while devices from the cold corner showed a strong wake-up effect with 0 µC/cm2 in pristine devices and up to 26 µC/cm2 after 106 cycles. TEM analysis of devices from both positions was applied to correlate the electrical characteristics with microstructural differences. Materials &amp; methods These devices were prepared by reactive sputtered TiN electrodes and RF sputtered HfO2. TiN top electrodes were deposited after RTA and patterned with UV lithography. In the RTA set-up, approximately 600 °C were applied for 10 s in N2 atmosphere. IR thermal imaging after RTA revealed a thermal gradient due to a disaligned filament inside the projector lamp used for heating. Plan-view TEM samples from the hot and the cold corner were prepared by PIPS after the devices in the center were trained for 105 cycles with +/- 3 V (see Fig. 1). Additionally, cross-sectional TEM samples were prepared by FIB. TEM analysis in plan-view and in cross-section via electron diffraction (ED), HRTEM and EELS was correlated with the electrical characteristics. Fig. 1: The Si substrate with TiN/HfO2/TiN capacitors is shown on the left with trained devices marked with blue circles. On the right the PIPS sample is shown with two trained devices close to the hole. Results The combination of ED in plan-view and cross-sectional TEM analysis, revealed different microstructures and interfaces to the TiN top electrodes. At the interface to the TiN top electrode a TiOxNy interlayer was confirmed with EELS, which was thicker in the cold corner. Regarding the microstructure, the cold corner shows a stronger [110] texture while in the hot corner the &lt;111&gt; oriented grains became dominating due to Ostwald ripening. The in-plane polarization of the [110] textured HfO2 and the observed structural transformation of the ex situ trained devices hints towards a ferroelastic switching during wake-up. Conclusion In-depth structural characterization in close correlation with the electrical response of ferroelectric TiN/HfO2/TiN capacitors revealed a strong structural influence on the wake-up effect induced by a temperature gradient during RTA. The hot corner showed wake-up free remnent polarization due to increased &lt;111&gt; texture, while the cold corner has a strong wake-up effect due to [110] oriented grains with a pristine in-plane polarization. Gradual ferroelastic switching to [011] and [101] orientations increases the remnent polarization with field cycling. References 1 T. Mittmann et al., Adv. Mater. Interfaces 1900042 (2019). 2 S. Starschich et al., Appl. Phys. Lett. 108, 032903 (2016). 3 E.D. Grimley et al., Adv. Electron. Mater. 2, 1600173 (2016). 4 T. Shimizu et al., Appl. Phys. Lett. 113, 212901 (2018).

Poster

Epitaxial growth mechanism of magnetic Fe4N thin films - Intrinsic formation of metastable interface layers

Abstract text (incl. figure legends and references) Introduction Due to its ferromagnetic properties, γ´´-Fe4N can be applied in spintronic applications, while the microstructure and crystal orientation influence the switching behavior 1. The focus of this contribution is set on the deposition of epitaxial thin films on single-crystal substrates like MgO by reactive magnetron sputtering. In contrast to other physical or chemical vapor deposition methods (molecular beam epitaxy, electron beam physical vapor deposition, atomic layer deposition) 2, phase-pure epitaxial vapor deposition by magnetron sputtering is more challenging, however, this method is much more widely used and allows easier scaling of the production process. Objectives The analysis of the γ´´-Fe4N thin films allows to elucidate the growth conditions of epitaxial thin films. In particular, conclusions may be drawn about the nucleation phase of thin film growth by reactive DC magnetron sputter deposition. An interface layer, between the substrate and the film, might originate from a tetragonal distortion of the cubic γ´´-Fe4N crystal structure or a phase transformation with local variations in chemical composition. Materials &amp; methods The microstructure, chemical composition, and the magnetic properties of γ´´-Fe4N thin films are investigated by XRD, vibrating sample magnetometry, magneto-optical microscopy, and spectrum imaging including high resolution scanning transmission electron microscopy, energy dispersive X-ray, and electron energy-loss spectroscopy. To verify the chemical composition of the thin (5 nm) interface layer, EDX and EELS spectroscopy has to be to be applied. Results The epitaxially grown γ´´-Fe4N thin films indicate the formation of an interface layer between the substrate and the thin film with a tetragonal distortion of the cubic crystal structure and a lower nitrogen concentration. This observation indicates the formation of a metastable tetragonal phase such as α´´-Fe8N 3. Next to the inhomogeneous interface layer, the epitaxial γ´´-Fe4N thin film is rotated against the substrate by 2.4° along the growth direction, which agrees with the observed tilting of cubic magnetocrystalline anisotropy. Conclusion The analysis of the chemical composition of the interfacial layer of γ´´-Fe4N thin films provide insight into the growth conditions of epitaxial thin films. In particular, the nucleation phase of thin film growth by reactive DC magnetron sputter deposition is investigated. The intrinsic interface layer shows a tetragonal distortion of the cubic γ´´-Fe4N crystal structure and a phase transformation with local variations in chemical composition. 1 Seema, P. Gupta, D. Kumar, V. R. Reddy and M. Gupta, Applied Surface Science Advances, 2021, 5, 100088. 2 N. I. M. Nadzri, D. M. S. Ibrahim and S. Sompon, IOP Conf. Ser.: Mater. Sci. Eng., 2019, 701, 012047. 3 I. Dirba, P. Komissinskiy, O. Gutfleisch and L. Alff, Journal of Applied Physics, 2015, 117, 173911.

Prof.

Extended grain boundary structures in quasi-epitaxial TiN1-x electrode thin films grown on c-Al2O3

MS 2: Metals and alloys

Abstract text (incl. figure legends and references) Titanium nitride (TiN) thin films are intensively studied in their application at room temperature (RT) as electrode materials in oxide electronics[1] and at low temperatures (LT) for microwave resonators and superconducting (SC) Josephson junctions.[2, 3] In these applications, low surface roughness, high electrical conductivity and high critical temperatures (TC) for SC applications are essential.[4] Here, TiN1-x films of 25 nm thickness have been deposited by reactive molecular beam epitaxy (RMBE) on c-cut sapphire substrates. For the sample series, increasing nitrogen deficiency was introduced by lowering the substrate temperature and increasing the Ti deposition rate. In their application as bottom electrodes in oxide electronic valence change memories (VCM) the nitrogen deficiency is discussed to enable electrical device performance.[5] Besides characterization of the RT and LT electrical conductivity, a scale bridging set of characterization methods has been employed to create a global (mm scale) down to atomistic (Å scale) understanding of the microstructure and resulting grain boundaries. Starting from X-ray diffraction (XRD) over backscatter electron (BSE) imaging and ion channeling contrast imaging (iCCI) and atomic resolution high-angle annular dark-field (HAADF) STEM imaging, a comprehensive analysis has been carried out. All samples showed highly textured out-of-plane growth (TiN (111)||Al2O3(001)) and two options for in-plane orientations, separated by 60°, for the TiN grains. iCC imaging revealed near identical grain sizes for all samples. For the low film thickness of 25 nm, the lateral grain size of over 100 nm indicated quasi-epitaxial growth introduced by domain matching epitaxy. The grain boundaries present are mainly twin boundaries of the &lt;112&gt; type. For the most deficient TiN0.7 sample, these twin boundaries emit &lt;112&gt; {111} stacking faults, resulting in a low transparency for electrical transport of the extended grain boundary. Critical temperatures of up to 4.9 K are reported for the first time for TiN films of low thickness on c-cut sapphire. Figure 1: (a,b) BSE images of the surfaces of the TiN (A) and TiN0.7 (B) thin film showing GBs in BSE contrast only for TiN0.7. (c,d) iCC images for the same samples, indication the two in-plane oriented grain types (60° in-plane rotation) and near identical grain sizes for both samples. (e,f) HAADF-STEM images of twin boundaries of the same samples, the TiN0.7 GB shows an extended GB structure resulting from the emission of stacking faults into the neighboring grain. (g) Temperature dependent resistivity measurements showing the anomalous increase in resistivity for the TiN0.7 sample and SC transition temperatures of the 25 nm TiN1-x films. [1] Sharath SU, Vogel S, et al., Adv. Funct. Mater. 31 (2017) 10.1002/adfm.201700432 [2] Gao R, Yu W, et al., Phys. Rev. Materials 3 (2022) 10.1103/PhysRevMaterials.6.036202 [3] Krockenberger Y, Karimoto S, et al., Journal of Applied Physics 8 (2012) 10.1063/1.4759019 [4] Zintler A, Eilhardt R, et al.,(2022) 10.1021/acsomega.1c05505 [5] Niu G, Calka P, et al., 3 (2019) 10.1080/21663831.2018.1561535

Microstructure of GeTe-Sb2Te3 heterostructures grown by pulsed laser deposition

Abstract text (incl. figure legends and references) Introduction: Ge-Sb-Te based phase change memory (PCM) is a highly promising technology for e.g., in memory or neuromorphic computing application. Relying on reversible amorphous-crystalline phase change, PCM is non-volatile, scalable, and fast. Heterostructured PCM show optimized performance, especially regarding power consumption and multi-level operation [1,2]. However, further investigations are necessary to understand in-detail the relationship of structure and properties. Objectives: The influence of systematically varying deposition parameters on the microstructure of GeTe-Sb2Te3 heterostructured thin films was investigated to comprehend their outstanding properties. Materials &amp; methods: Non-periodic (npHS) and periodic (pHS) GeTe-Sb2Te3 heterostructures were deposited at room temperature by pulsed laser deposition (PLD). Detailed microstructure analysis was performed by combination of advanced transmission electron microscopy and X-Ray measurement techniques. Results: For the npHS a decreased laser fluence and number of pulses resulted in a decreased layer thickness which goes along with an increased intermixing and a composition approaching GeSb2Te4 (Fig. 1a-d). Unlike amorphous GeTe layers, the Sb2Te3 layers are nanocrystalline after PLD growth. Similar to fully crystalline Sb2Te3 [3], the nanocrystals consist of different defects like grain boundaries and bi-layer defects (Fig. 2a, b). Moreover, the grain size and crystalline phases vary (Fig. 2a, c). Apart from the known t- and c-phases, a vacancy-ordered (vo) phase was observed [4]. Similar to vo-Ge2Sb2Te5 [5], this structure transforms into the c-phase by electron beam exposure (Fig. 2d). Confirmed by XRD, overall, the Sb2Te3 layer mainly consists of {00l}-textured t-Sb2Te3 phase. Despite the small layer thickness, the layers of the pHS are still separated with alternating Sb- and Ge-rich layers, respectively (Fig. 1e-h). Conclusion: Whereas the layers intermixing depends on the deposition parameters and despite the room temperature deposition as well as the use of an amorphous substrate, as-grown Sb2Te3 layers are nanocrystalline while GeTe layers are amorphous in the HS. Since for Sb2Te3-GeSb2Te4-HS already an enhanced operation energy efficiency was reported [6], the results of the present work provide a starting point to establish structure-property relationships for PLD grown GeTe-Sb2Te3-HS in addition. References [1] T. C. Chong et al., Appl. Phys. Lett. 88, 122114 (2006). [2] L. Zhou et al., Adv. Electron. Mater. 6, 1900781 (2020). [3] J.-J. Wang et al., Phys. Status Solidi RRL 13, 1900320 (2019). [4] Y. Zheng et al., Nano Res. 9, 3453 (2016). [5] A. Lotnyk et al., Acta Mater. 105, 1 (2016). [6] J. Feng et al., ACS Appl. Mater. Interfaces 12, 33397 (2020). Acknowledgements We thank Mrs. A. Mill for assistance in the FIB preparation. This work was supported by the German Research Foundation (DFG 445693080). Figure 1: Overview TEM images and EDX maps of npHS deposit with the highest (a,b) and lowest (c,d) laser fluence, respectively, and two pHS (e-h). Figure 2: Local structure of npHS. TEM images showing Sb2Te3 nanocrystallites characterized by multiple grain sizes (a), crystal defects (a, b), and phases (c, d).

Phase transitions in Cu-Sb2Te3 thin film systems induced by focused ion beam milling

Abstract text (incl. figure legends and references) Specimen preparation for transmission electron microscopy (TEM) using focused ion beam (FIB) is a commonly used method [1]. While it offers many advantages over other methods, like site specific specimen preparation, it also suffers from many disadvantages. Artifacts induced by FIB range from ion implantation to thermal effects [2,3]. In this work, we study the impact of FIB milling on the microstructure of Cu (electrode)-Sb2Te3 (thin films) systems used for memory applications [4]. The influence of different factors such as ion beam current, layer stacking sequence, Sb2Te3 structure and layer thickness are evaluated. Sb2Te3 thin layers are epitaxially grown on p-type Si (111) substrates, while polycrystalline Sb2Te3 thin films are grown on SiO2 using pulsed laser deposition (PLD) [4]. Cu, Pt/Cu and Cr layers are deposited by magnetron sputtering on top of the Sb2Te3 layers. TEM specimens are prepared at varied beam currents using a standard cross-section FIB preparation method [1]. FIB specimens are investigated using advanced methods of aberration-corrected scanning TEM such as atomic-scale HAADF imaging and atomic-scale chemical analysis (EDX and EELS). In situ x-ray diffraction heating of the Cu-Sb2Te3 thin film is performed to confirm structural changes. Dependent on beam current used during FIB lamella preparation and Sb2Te3 layer thickness, hole formation in the Cu layer, thickness change and chemical changes of the Sb2Te3 layers are observed (Fig. 1). Samples with a 17 nm Sb2Te3 layer show uniform intercalation of Cu while a sample with 100 nm thick Sb2Te3 layer exhibits differential intercalation behavior. In specimen prepared from the in situ heated samples Sb2Te3 and Cu-Te grains are observed. The introduction of a Pt layer between the Cu electrode and Sb2Te3 layers hinders structural changes caused by FIB (Fig. 2). Moreover, Cr-Sb2Te3 and a Cu-GeTe layer systems show no modifications of Sb2Te3 and GeTe thin films during FIB preparation. In polycrystalline Sb2Te3 specimen the intercalation of Cu and formation of new phases is also observed. This work demonstrates that structural changes in Sb2Te3 thin film systems can be induced during FIB specimen preparation of Cu (electrode)-Sb2Te3 (thin films) systems. The changes are thermally induced transitions caused by FIB process due to local heating, while redeposition of Cu plays a minor role. The authors thank P. Hertel for magnetron sputtering. We acknowledge the financial support by the German Research Foundation (DFG 448667535). [1] T. Ishitani, et al., Microscopy 43.5 (1994): 322-326. [2] J. Mayer, et al., MRS bulletin 32.5 (2007): 400-407. [3] R. Schmied, et al., Physical Chemistry Chemical Physics (2014), 6153. [4] H. Bryja, et al., 2D Materials (2021), 045027. Fig. 1: (a) EDX Map of a lamella prepared with FIB, (b-c) Overview HAADF-STEM images of specimen prepared with normal and reduced FIB beam currents. (d) Atomic-resolution HAADF-STEM image showing new Cu-Te phases. Fig. 2: Cu/Pt/Sb2Te3 layer stack. (a) Overview HAADF-STEM image. (b) Overview EDX elemental map. (c) Atomic-resolution HAADF-STEM image, showing initial Sb2Te3 structure.

Diffusion processes in HfO2-based memristors investigated by in situ STEM and atom probe tomography

IM 7: In situ/operando electron microscopy

Abstract text (incl. figure legends and references) Ionic movement is an essential part of Resistive Random Access Memory[1]. During resistive switching (RS) operations, the memory type determines the diffusing species: in the case of electrochemical metallization memory (ECM), the electrode material migrates and for the valence change memory (VCM) type, the oxygen anions and vacancies[2]. Moreover, the interfacial interactions in the metal-insulator-metal (MIM) RRAM cell can further impact RS[3]. To give insight into the diffusion processes for both ECM and VCM type HfO2-based memristors we have employed in situ scanning transmission electron microscopy (STEM) in combination with atom probe tomography (APT). The goal is to reveal the role of the microstructure of the insulator and the impact of the metal electrode on the ionic migration process. The investigated memristive devices consist of highly textured TiN (M) and HfO2 (I) thin films subsequently grown on c-cut sapphire by using reactive molecular beam epitaxy (RMBE), complemented by sputter deposition of Cu and Pt (M). These result in an ECM and VCM devices, respectively. From the VCM device, focused ion beam (FIB) lamellae for STEM and APT tips were prepared for a pristine device and a device that has been operated for 100 bipolar resistive switching (BRS) cycles. From the ECM device, FIB lamellae were transferred onto Micro Electrical Mechanical System (MEMS) based heating chips (DENSsolutions) for in situ STEM. For the BRS cycled VCM device, Figure 1 shows the Hf+O density variation retrieved from one APT data set overlaid on a medium-angle annular dark-field (MAADF) STEM plan view image of TiN. The highest variation occurs along a distinct line which, based on the feature size, is related to a TiN grain boundary (GBs). This indicates that the RS operation could be confined to the TiN GBs. For the ECM device, a low-loss electron energy loss spectroscopy (EELS) spectrum image (SI) map is overlaid on a cross-sectional high-angle annular dark field (HAADF) STEM image after in situ heating, shown in Figure 2. Cu diffusion started at ~350°C and the Cu feature in the EELS map at ~19.6 eV becomes present at a HfO2 GB. This demonstrates that Cu diffusion could primarily occur along GBs. We have shown that GBs influence and locally confine diffusion processes. For filament-type RS like in metal-oxide based memristor, this could lead to an improvement in variability and reliability by providing pre-defined diffusion pathways and thus, avoiding random diffusion. References: [1] R. Waser et al., Advanced Materials 21, 2632 (2009). [2] I. Valov, Semicond. Sci. Technol. 32, 093006 (2017). [3] S. R. Bradley et al., Microelectronic Engineering 109, 346 (2013). Figure 1: The Hf+O2 density variation retrieved from one APT data set for a VCM HfO2-based memristor cycled for 100 BRS operations shows the highest variation along a distinct line. As overlaid here with a plan-view MAADF STEM image from TiN it becomes clear, that the feature shown in the Hf+O density variation must be related to a TiN grain boundary based on the feature size. Figure 2: The EELS SI map overlaid on the cross-sectional AADFSTEM image of an ECM type HfO2-based memristor after in situ heating reveals, that the Cu feature located at ~19.6 eV becomes present at the grain boundary (GB). This showcases, that Cu should primarily diffuse along GBs. The authors acknowledge funding from the ERC "Horizon 2020" under Grant No. 805359-FOXON and Grant No. 957521-STARE.

Depicting atomic-resolution orbital occupation in hole doped high-tc superconducting superlattices

IM 2: Spectroscopy

Abstract text (incl. figure legends and references) La2CuO4 changes from an antiferromagnetic Mott-insulator into a superconductor upon hole doping. This phase transition can be observed via spectral features in the pre-edge region of the O-K edge by means of electron energy-loss spectroscopy (EELS). The O-K energy-loss near-edge structures (ELNES) allow the direct probing of this hole doping with atomic resolution. We designed superlattices for the observation of evolving mobile carrier peaks (MCPs), the presence of the upper Hubbard band (UHB), and different Sr and Oxygen concentrations in direct proximity to each other. We link such electronic configurations and chemical distributions to the subsequent physical properties. Direct probing at the atomic-scale in order to differentiate between superconducting, metallic, and insulating parts in one single sample is unique, which to the best of our knowledge has not been shown before. This prospect, however, is of paramount interest for exploring future oxide-based quantum technologies, such as Josephson junctions. The two heterostructures presented here consist of five repetitions of a bilayer with four and three unit cells La2CuO4 (LCO) and one unit cell Sr2CuO3 (SCO) with an additional capping layer of three and four unit cells La2CuO4, respectively. All superlattices have been grown via molecular-beam epitaxy (MBE) monitored by in-situ reflection high-energy electron diffraction (RHEED) under an ozone atmosphere on a LaSrAlO4 (LSAO) (001)-oriented substrate. The samples have been characterized by resistance (R) versus temperature measurements, and scanning transmission electron microscopy (STEM); including EELS and high-angle annular dark-field (HAADF) imaging. Transport properties of both heterostructures (Fig. 1) yield critical temperatures (Tc) of 32K for the 5x[4LCO + SCO] and 40K for the 5x[3LCO + SCO] superlattices, respectively. Due to the chemical potential between LCO and SCO, different amounts of intermixing between La and Sr can be observed at the top and bottom interfaces. This leads to a partial formation of insulating areas without charge carriers, superconducting areas with mobile carriers, and metallic areas with mobile carriers and oxygen vacancies. These phase-separated sample regions are further discussed with respect to their orbital occupation via a combination of atomically resolved EELS mappings and O-K ELNES analyses (Fig. 2). Further investigations of the blue-shaded area in Figure 2 highlight differences in the out-of-plane and in-plane orbital occupation by the introduced electron holes. Here, we show for the first time that one can distinguish insulating, superconducting, and metallic areas within one single sample via O-K ELNES analyses and atomically resolved EELS. We want to highlight, that EELS experiments gave direct insights into the differences in orbital occupation of out-of-plane and in-plane orbitals, which open new possibilities for analyses of high-Tc superconductors answering open questions with respect to superconductivity. Figure1: Resistance vs temperature of the two superlattices 5x[3LCO + SCO] (blue), and 5x[4LCO + SCO] (red). Figure2: (a) 2D elemental EELS mapping (Sr: blue, Cu: green, La: red) of three different regions highlighting areas without Sr intermixing (red) and heavy Sr intermixing (blue). (b), (c) and (d) Gaussian fits with energy constraints for the MCP (blue) at 528 eV, the UHB (red) at 530.5 eV, and for the leading O-K edge-onset, a peak at 534 eV (turquoise).

Revealing the nanostructure of filamentary HfO2-based memristors by scanning precession electron diffraction (SPED)

IM 6: Phase-related techniques & 4D STEM

Abstract text (incl. figure legends and references) Introduction: Resistive random-access memory (RRAM) devices are under intense research as they have low-power consumption, excellent scalability, enhanced storage density and, high speed operation [1]. The resistive switching phenomenon is thought to be governed by the formation and dissolution of a conductive nanofilament when a voltage is applied [2,3]. As previously investigated, the electrical behaviour of hafnia-based RRAM devices is correlated to the local crystallographic texture and microstructure [4]. Objectives: SPED was used to investigate two different Cu/HfO2/Pt RRAM devices. The layer structure is shown in fig1(a). The goal was to map the microstructure and establish a structure-property correlation. Materials &amp; methods: By using reactive molecular beam epitaxy (RMBE) 20 nm thick HfO2 thin films were grown on top of sputtered Pt bottom electrodes. The top Cu electrode was deposited with different ways by an (i) ion beam etching (IBE) procedure and by (ii) simple lift out (SLO). Electron transparent cross sectional TEM lamellas were fabricated using a JEOL JIB 4600F Focused Ion Beam. For SPED acquisition, a scanning nanoprobe (in 2D real space) was controlled with a NanoMEGAS P1000 scanning unit integrated into a JEOL-ARM200F and a dynamic Medipix3 detector was used for synchronized electron diffraction patterns (EDP) acquisition (in 2D reciprocal space). Results: Experimental EDP was cross correlated and statistically matched with suitable simulated EDP with the software ASTAR to generate the orientation fig2(a,c) and phase fig2(b,d) maps. For both devices the orientation and grain size (5 -20 nm) of the dielectric is similar as they were grown under the same conditions. From the phase maps, the monoclinic phase of the HfO2 is revealed and matches to the XRD data. The results show that the Cu is homogeneously grown on the SLO devices and that it is not well distributed in the IBE devices. In the last ones, unexpected Pt traces were found which might have an influence on the electrical performance of the device. In fig1(b) the leakage currents of both devices are shown, in SLO the magnitude is lower than in IBE which could be due to the inhomogeneous Cu and the Pt traces on top of HfO2. Conclusion: The generated maps confirm the monoclinic phase of the HfO2 dielectric layer and reveal a similar grain distribution in both SLO and IBE devices. Also, from the phase maps, the SLO devices show well distributed layers which might explain their electrical performance. [1] Zahoor et al. Nanoscale Res Lett 15 (90) (2020) [2] R Waser et al., Adv. Mater. 21 (25–26) (2009) 2632-2663 [3] M. Lanza et al., Appl. Phys. Lett. 100 (12) (2012) 123508. [4] S. Petzold, A. Zintler et al., Adv. Electron. Mater. 5 (10) (2019) 1900484 The authors acknowledge funding from the ERC &quot;Horizon 2020&quot; Program under Grant No. 805359-FOXON and Grant No. 957521-STARE, from the DFG grant No. 384682067, from the BMBF under contract 16ESE0298 and 16MEE0154, from the DAAD, from the EPSCR and support by the framework of the the WAKeMeUP and StorAIge projects. Fig1: (a) The thin film stacks of the two different studied devices: IBE and SLO. (b) Their corresponding leakage current measurements. Fig2: SLO devices: (a) orientation map of Cu/HfO2/Pt device. Each colour reveals an orientation and (b) phase map of the three layers: Cu in red, m-HfO2 in blue and Pt in green. IBE devices: (c) orientation map and (d) phase map. Scale bar: 50 nm.

Study of local indium concentration in Ga(1-x)InxN quantum wells using quantitative scanning transmission electron microscopy

MS 3: Low-dimensional and quantum materials

Abstract text (incl. figure legends and references) Multiple quantum wells (MQW) and single quantum wells (SQW) of Ga(1-x)InxN on GaN are promising candidates for nanooptical light emitters due to high quantum efficiency. The band gap of Ga(1-x)InxN can be controlled over a wide wavelength range by tailoring the variation of the indium concentration [1]. In addition, the epitaxially grown quantum well structures can be easily modified using chemical etching for the formation of a pyramid containing quasi quantum dot structure. As the dimension of the quantum structure shrinks, the variation of the local indium concentration becomes detrimental to the optical properties. Therefore, a robust characterization technique is required to understand and optimize such complex structures on the atomic scale. In this study, a single quantum well of Ga(1-x)InxN between GaN layers on an Al2O3 substrate was grown using metal organic vapor phase epitaxy. The cross-sectional specimen was prepared using focused ion beam (FIB), including the final low kV milling step. The prepared specimen was characterized using a double-aberration corrected JEOL NeoARM 200F equipped with a cold field emission gun. We directly measured local lattice parameters based on the analysis of individual atomic column positions obtained from the high-angle annular dark-field (HAADF) image in real space. For a precise local lattice parameter analysis, drift-corrected HAADF imaging was utilized based on a sequential imaging technique with reasonably short acquisition time (1 sec/frame) accompanied by post rigid registration technique for drift correction between acquired images (Fig. 1). Then, the local indium concentration was derived using a modified Vegard's law including biaxial elastic strain effects. Fig. 2(a) shows the HAADF image of the epitaxially grown GaN/Ga(1-x)InxN/GaN structure and the individual indium contents derived using the modified Vegard's law is shown at the unit cell level in Fig. 2(b). The mean indium concentration inside the single quantum well from this analysis was 15.7 at. %, showing a very good agreement with the X-ray diffraction (XRD) analysis result. This result was compared with the local composition information obtained from a quantitative intensity analysis of the HAADF image. Absolute quantification of scanning transmission electron microscopy (STEM) - HAADF intensity (normalized intensity by the incident electron beam) was applied based on frozen phonon multislice calculation results [2]. The local thickness information obtained using position averaged convergent beam electron diffraction (PACBED) supported the quantitative intensity analysis [3]. In addition, the local composition information obtained from the intensity analysis was compared with the results from the quantitative STEM – electron energy-loss (EEL) spectroscopy analysis on the unit cell level. The combination of STEM imaging, PACBED and spatially resolved EEL spectroscopy techniques shows the validation of Vegard&quot;s law for the Ga(1-x)InxN quantum well, providing more detailed information at the interfaces. The relationship between atomic structure and composition could be thoroughly studied. This robust combined STEM techniques will be ultimately applied to understand the effect of the changes in indium concentration on complex quantum dot structures. [1] U. Rossow et. al., Phys. Status Solidi B, 258, (2021) [2] J. LeBeau et. al., Physical review Letters, 100, (2008) [3] J. LeBeau et. al., Ultramicroscopy, 110(2), (2010)

Identification of a new structural polymorph of quenched high-pressure CrTe3 (P2/m)

Abstract text (incl. figure legends and references) CrTe (P21/c) is of potential interest for spintronic devices because of its layered structural motif and antiferromagnetic and semiconducting properties (Eg = 0.3 eV)[1]. Modifying these properties towards a ferromagnetic state and metallic-like conduction upon structure deformation is suggested by theoretical studies which describe a high strain sensitivity of the material when the dimensions are reduced to a monolayer of CrTe3 [2]. Such studies are motivation to investigate the CrTe3 system further. In the past, structural polymorphs of binary TE have been identified and described using high-p and high-T experiments as a vital approach to explore structural modifications with unprecedented properties [3,4]. In this work, the layered phase of CrTe3 was used as a starting material and subjected to pressures as high as 6GPa at an applied temperature of 250°C to investigate new structural polymorphs of CrTe3 and their magnetic properties. The structural polymorph of the quenched CrTe3 high-p phase was investigated by the combined methods of synchrotron radiation scattering experiments (PDF and XRD) and PED as well as atomic resolution STEM. Model-based simulations of STEM and ED data were conducted and compared with structural refinements by Rietveld analysis for structure determination. With our experiments, we were able to identify a phase transition from the monoclinic CrTe3 phase (P21/c) into a structural polymorph with space group P2/m. At first, the superposition of two potential structure candidates of CrTe2 (Pnn2) and CrTe4 (P21/m) were refined. These initial models were tested to PED data which excluded the CrTe2 model and suggested the introduction of a 1/3 occupied Cr position at the corners of the unit cell into the supposed CrTe4 structure to explain the kinematic intensity patterns. Further, large area EDX analysis confirmed the chemical homogeneity within large grains of the CrTe3 polymorph with stoichiometry of Cr:Te 1:3. The here proposed structure of the new polymorph after refinement to the synchrotron diffraction data is depicted in Figure 1. Atomic scale imaging by aberration corrected STEM supported the proposed model by imaging the Te sub-structure. In conclusion, a new structural polymorph of the CrTe3 system was identified after high-pressure synthesis and subsequent quenching by the combined approach of TEM and synchrotron diffraction. In ongoing research, first SQUID measurements indicate interesting changes of the magnetic properties which could provide similarities to the theoretical calculations made by Z.-W. Lu et al[2]. [1] M. A. McGuire et al., Phys. Rev. B, vol. 95, no. 14, p. 144421, Apr. 2017, doi: 10.1103/PhysRevB.95.144421. [2] Z.-W. Lu, S.-B. Qiu, W.-Q. Xie, X.-B. Yang, and Y.-J. Zhao, J. Appl. Phys., vol. 127, no. 3, p. 033903, Jan. 2020, doi: 10.1063/1.5126246. [3] A. Pawbake et al., Phys. Rev. Lett., vol. 122, no. 14, p. 145701, Apr. 2019, doi: 10.1103/PhysRevLett.122.145701. [4] W. C. Yu and P. J. Gielisse, Mater. Res. Bull., vol. 6, no. 7, pp. 621–638, Jul. 1971, doi: 10.1016/0025-5408(71)90011-0. Figure 1: Crystal structure of the quenched high-pressure phase of CrTe3 with space group P2/m shown for a unit cell of 2x2x2 size. The corner-sharing motif can be best seen by a view along the crystallographic b-axis(a). Golden atoms are Te, blue are Cr. The edge-sharing motif and columnar ordering of the CrTe6 octahedra can be best seen by a view along the crystallographic c-axis (b).

Insight into the atomic structure and misfit relaxation mechanisms in micrometer-thick SrMoO3 oxide electrodes grown on scandate substrates

IM 5: Quantitative image and diffraction data analysis

Abstract text (incl. figure legends and references) Introduction: Understanding the microstructure and related defect structures and their relationship with the physical properties is fundamental for the realization and optimization of oxide electronics-based devices. For instance, in the case of varactors or so-called metal-insulator-metal (MIM) tunable ferroelectric microwave capacitors, the tunable permittivity of the insulator layer and/or the thickness of the bottom oxide electrode exceeding the skin depth is crucial for its performance. To investigate the relationship between the thickness and other structural properties of these oxide thin films, i.e., alteration of stoichiometry and lattice constants, we performed Scanning Transmission Electron Microscopy along with X-ray diffraction (XRD) and Photoemission spectroscopy (PES). Objectives: We characterized a set of heterostructure multilayer devices (scandates/SrTiO3/SrMoO3) by STEM. For the analysis of the HAADF-STEM images we implemented an automated-quantitative STEM method that allows to analyze a set of real-space images to (i) extract atomic position information and (ii) to identify local structural defects. The goal was to provide insight into the underlying strain accommodation mechanism in micrometer-thick SrMoO3 (SMO) oxide electrodes grown on various scandate substrates. Materials and methods: The preparation procedure of the oxide-based multilayer devices can be found in P. Salg et al. [1]. The TEM lamellae were obtained using a JEOL JIB 4600F. For STEM, images with 5x5 frames along [001] and [100] directions of the epitaxial SMO layer were obtained using a JEOL ARM200F. Local in-plane/out-of-plane lattice constants were extracted along [001] growth direction by implementing customized codes, based on the python packages Atomap and Hyperspy. Picometer level precision was achieved. First principal calculations for SMO using density function theory (DFT) with the CASTEP package. Results: Both, XRD and STEM imaging (Fig.1a) confirmed the epitaxial growth (in-plane locked) of the SMO layer on top of all scandate substrates used. By performing automated-quantitative STEM analysis, atomic position information was obtained, as well as statistical out-of-plane/in-plane lattice constants (Fig.1b). The variation of this statistical lattice constants implies another strain accommodation mechanism, i.e., off stoichiometry, in heterostructure material in addition to interfacial defects. The DFT calculations for SMO layer confirmed the relationship between the variation of lattice constants and the off stoichiometry. Conclusions: A set of heterostructure multilayer devices were characterized by the combination of PES, XRD and STEM. The use of the automated-quantitative image analysis showed a reliable way to measure the local lattice constants with picometer-scale accuracy. Together with the help of DFT calculations, the relationship between the interfacial defects, the lattice constant, the off stoichiometry, and the accumulative strain was studied. References: [1] P. Salg, D. Walk and L. Zeinar et al., APL Mater., vol. 7 (2019), p. 051107. doi: 10.1063/1.5094855. The authors acknowledge funding from the ERC &quot;Horizon 2020&quot; Program under Grant No. 805359-FOXON and Grant No. 957521-STARE. Fig 1(a). HAADF-STEM image of heterostructure interface scandate/SrTiO3/SrMoO3. (b) Atom position information were extracted using customized codes based on the Atomap python package.

Ordering of scandium into monolayers of aluminium nitride and its implication for AlScN based nitride semiconductor devices

MS 1: Energy-related materials and catalysts

Abstract text (incl. figure legends and references) Recently the incorporation of scandium (Sc) into aluminium nitride (AlN) attracted severe attention for III-V nitride semiconductors. The sufficiently larger ionic size of Sc increases significantly the spontaneous polarisation of AlN (1), which is e.g. responsible for the formation of a two dimensional electron gas at the heterojunction to another, compositional slightly different nitride compound (2). This allows to fabricate high-electron mobility transistors (HEMT) with very high switching frequencies and high efficiencies. However, the growths of well-crystalline AlScN material is impeded by a huge immiscibility gap between AlN and ScN. The material films deposited by magnetron sputtering or recently epitaxy are considered to exist only metastable (3). Intense annealing at temperatures beyond 1400°C for three hours, lead in this study to the formation of a layered structure of the compound, observed for the first time. The structural properties were intensely studies by atomic resolution STEM-HAADF images, EDS and EELS spectroscopy and will be reported in this contribution. The results from STEM-HAADF images show clearly that bright atomic monolayers are developed every 5-8 layers, after annealing at 1700°C. They run straight through the whole crystal and extend several µm (Fig. 1a) along the basal plane. Following EDS data, the bright appearance is due to an ordering of Sc into these layers (Fig. 1 b,c) coupled to a strong increase in oxygen content. The Sc coordination changes from four-fold in the wurtzite structure to six-fold as preferred by Sc. Whereas the sequence of cation positions in atomic STEM-HAADF images is strongly determined, the sequence of bright layers varies randomly between 5 and 8, leading to a partial disorder along c-direction. Further structural observations after annealing of samples at 1400°C allow some insight into their formation. Rarely platy seed of two octahedral Sc-bearing layers with only one intermittent AlN layers were observed. They are assumed to be thermodynamically favourable, similar to GdN platelets formed in Gd-doped GaN (4), but in contrast, significantly lower strain allows their two dimensional growths in the Sc-bearing system. Hence, this model of metastable formation resembles thermodynamical exsolution lamellae of mono-atomic widths. The presented observations are not only intriguing from a structural point of view, the obtained insight into the material behaviour has also implications on the growths of future ScAlN material for semiconductor devices as well as their long-time stability during device operation. References: (1) Akiyama et al., Adv. Mater. 21, 593–596 (2009). (2) Leone et al., Phys. Status Solidi RRL. 14, 1900535 (2020). (3) A. Moram and S. Zhang, J. Mater. Chem. A. 2, 6042–6050 (2014). (4) Wu et al., Acta Materialia. 76, 87–93 (2014). Fig. 1: Left: atomic resolution STEM-HAADF image showing bright Sc-bearing layers at variable distance. Right: EDS elemental distribution maps and integrated counts perpendicular the layers.

The effect of metal concentration and annealing temperature on the growth of ultrasmall metallic nanoparticles inside a silica matrix

Abstract text (incl. figure legends and references) The nanocomposites (NCs) comprising ultra-small metallic Nanoparticles (NPs) embedded in silica matrix are more stable over time than chemically grown NPs and have shown improved practical efficiency, leading to a wide range of applications in plasmonics, nano-photonics, bio-medical and catalysis due to Localized Surface Plasmon Resonance (LSPR) [1-2]. The stability of these ultra-small NPs (diameter &lt; 10 nm) is essential for high-temperature applications [3].The LSPR frequencies associated with NPs are strongly dependent on particle morphology and metal concentration, thus knowledge about the effect of metal concentration and the growth mechanisms of NPs at different annealing temperatures (ATs) are crucial to controlling the morphology of NPs for application purposes. We have prepared Ag-SiO2 NC thin films using the atom beam co-sputtering technique at two different metal concentrations [4]. The evolution of silver NPs inside the silica matrix was discussed in Ref [4] utilising UV-Visible spectroscopy and High-Resolution Transmission Electron Microscopy (HRTEM) up to the annealing temperature of 400 °C. This work is now extended to the high annealing temperature of 900 °C. At each AT, HRTEM pictures, diffraction patterns, and STEM images are acquired to closely monitor the growth process of Ag NPs. A similar temperature-dependent growth investigation is also performed on Au and Au-Ag alloy NPs embedded in silica surrounds. For Ag-SiO2 NC, UV-Visible absorption spectra show a red shifting in the LSPR peak position, indicating the increase in the size of NPs with ATs. A quantum model simulation is combined with absorption results to estimate the size of the NPs at different ATs, suggesting the size of NPs is increasing. The morphological changes in NPs with ATs are monitored by HRTEM. We observed that the majority of the NPs are spherical in shape and remain in quantum size or ultra-small size regime (diameter &lt; 10 nm). The diameter of the NPs varies from ~5 nm to 6.5 nm when the temperature rises from RT to 800 °C. However, exponential growth is observed at 900 °C. We observed that these ultra-small NPs have shown excellent stability up to the temperature of 800 °C, hence suitable for high-temperature applications. Similar primary results are observed for Au and Au-Ag alloy NCs, however, their detailed analysis is still ongoing. Based on the results, a three-stage mechanism is proposed to understand the process of nucleation and growth of the silica-embedded Ag NPs. References: [1] Campos, A., Troc, N., Cottancin, E., Pellarin, M., Weissker, H. C., Lermé, J.,&amp; Hillenkamp, M. Nature Physics 2019, 15, 275-280. [2] Amendola, V., Pilot, R., Frasconi, M., Marago, OM. Iati, MA. Jour. of Phy.: Cond. Mat. 2017, 29, 203002. [3] Goodman, E.D., Carlson, E.Z., Dietze, E.M., Tahsini, N., Johnson, A., Aitbekova, A., Taylor, T.N., Plessow, P.N. and Cargnello, M., Nanoscale 13(2), 930-938 (2021) [4] Jatav, Hemant, Ambuj Mishra, and D. Kabiraj. Materials Today: Proceedings 57 (2022): 234-238.

Dimensionality-controlled interface properties in infinite-layer nickelate superlattices

Abstract text (incl. figure legends and references) The interface polarity plays a vital role in physical properties of oxide heterointerfaces since it can enforce the reconstruction of the electronic and atomic structure. A strong polar interface possibly exists in recently discovered nickelate superconductors and the superconductivity is absent in its bulk material, attracting increasing attentions on interface effects [1-4]. This motivated our investigation of the electronic and atomic structure at atomic scale at the interfaces of infinite-layer nickelates. Recently, we reported that advancedfour-dimensional scanning transmission electron microscopy (4D-STEM) technique can provide clear phase-contrast imaging of the oxygen sublattice [5]. Here, by employing 4D-STEM and atomic-resolution electron energy-loss spectroscopy (EELS), we systematically studied the oxygen distribution and atomic structure at the interface of infinite-layer NdNiO2 (NNO) and SrTiO3 (STO). Figure 1a shows an HAADF image of a 4NNO/2STO superlattice, where the STO and NNO layers can be easily identified due to their distinctly different mean inner potentials. It has been well accepted that the infinite layer of NNO can be synthesized by the topotactic reduction method. In order to understand the deintercalation process of oxygen ions and the variation of oxygen concentration in NNO layers, we acquired all oxygen positions by Gaussian fitting and then extracted the oxygen intensity map as displayed in Figure 1d. The corresponding intensity line profile of apical oxygen is presented in Figure 1e, identifying the reduction procedure about the local symmetry variations from octahedral to square planar. By calculating the white-line ratio, we obtained the valence variations of Ni and Ti ions across the interfaces as shown in Figure 2. The valence of Ti intermixed on Ni sites for the 4NNO/2STO superlattice tends to be 3+ while it almost maintains 4+ for the 8NNO/4STO superlattice (Figure 2c and 2f). The Ni valence varies between 1+ and 2+ since it depends on the extent of deintercalation of the apical oxygen in the NNO inner layer. An apparent gradient variation of Ni valence is visible in the NNO layer for the 8NNO/4STO superlattice. Furthermore, we will discuss the effects of elemental intermixing, cation distortion, and oxygen distribution as well as occupancy on the observed valence variations near the interfaces. References [1] D. F. Li, et al. Nature 2019, 572 (7771), 624-627. [2] B. H. Goodge, et al. arXiv:2201.03613, 2022. [3] B. Geisler et al. Phys. Rev. B 2020, 102 (2), 020502. [4] R. He et al. arXiv:2006.00656, 2020. [5] C. Yang et al. Nano Lett. 2021, 21 (21), 9138-9145. [6] This project has received funding from the European Union"s Horizon 2020 research and innovation programme under Grant Agreement 823717 – ESTEEM3. Figure 1 Atomic structure of a 4NNO/2STO superlattice. (a) An overview HAADF image of a 4NNO/2STO superlattice. (b) An enlarged HAADF image and (c) the iCoM image obtained in the region marked by a yellow dashed box in (a). (d) The oxygen intensity map calculated from the oxygen columns in (c). (e) The extracted intensity line profile of apical oxygen columns from the white dashed line marked in (d). Figure 2 Valence variations of Ni and Ti ions in 4NNO/2STO and 8NNO/4STO superlattices. HAADF images of (a) the 4NNO/2STO superlattice and (d) the 8NNO/4STO superlattice. (b) Ni L3/L2 intensity ratio and (c) Ti L3/L2 intensity ratio of the 4NNO/2STO superlattice. (e) Ni L3/L2 intensity ratio and (f) Ti L3/L2 intensity ratio of the 8NNO/4STO superlattice. The references of Ni3+ and Ni1+ valences are from our NdNiO3 and NdNiO2 samples, respectively. The Ni2+ reference is from a NiO film in the Gatan EELS database. The Ti4+ reference is from our SrTiO3 sample.

Atomic-scale investigation of nickelate-based perovskite superlattices

Abstract text (incl. figure legends and references) Nickelate-perovskite heterostructures offer outstanding oppportunities to design technologically relevant structures with functionalities such as unconventional magnetic, electric, catalytic features and even the possibility of superconductivity [1]. The wide variety of fuctional properties stems from the strong hybridisation between the Ni d and oxygen p orbitals. Targetted manipulation of the oxygen environment of the Ni can be realised by structural distortions, which are associated with the deformation or rotations of oxygen octahedra of the perovkites [2]. Superlattices consisting of dissimilar perovskite-oxides offer several tuning parameters for direct control over the octahedral network. Besides the epitaxial strain, spatial confinement, octahedral connectivity and symmetry mismatch at the heterointerfaces can alter the crystal structure and induce sizable changes in the electronic properties. However, targetted design of properties through the orbital-lattice interaction is impeded by poor understanding of the heterostructuring parameters on the structure and their resultant effect on the orbital response. In order to disentagle the effects of heterostructuring parameters and understand the underlaying mechanisms, atomic scale investigation of the oxygen octahedral network is necessary. In this work, we investigated structural and transport properties of LaNiO3/LaGaO3 (LNO/LGO) superlattices (SLs). SLs with stacking sequences of LNO/LGO: 8/4, 4/4, and 4/8 pseudocubic unit cell were grown on (001) SrTiO3 substrate by pulsed-laser deposition. Cross-sectional HRTEM specimens were prepared by focused ion beam. Negative-spherical-aberration imaging was used to resolve the oxygen atomic columns using Cs-corrected HRTEM (FEI TITAN) operated at an electron accelerating voltage of 300 kV. Electrical transport measurements were performed in van-der-Pauw geometry. The results revealed, that the three stacking sequences of LNO/LGO stabilised different non-equilibrium states of the LNO. Within the LNO layers, we found significant variation in octahedral rotations and distortions in the vicinity of the LGO-LNO interface and away from the interface. We explained these results based on the varying contribution degree of epitaxial strain and spatial confinement by LGO on the structure evolution. The relative thickness ratio of the components also has an influence on the "strength" of the interfacial octahedral connectivity determining different structural distortions under the same epitaxial-strain condition. Thus the contribution of octahedral connectivity to epitaxial strain became tunable. Associated tunability of the electronic properties was comfirmed by transport measurements. The results show, that superlattices are effective platforms to optimize perovskite nickelate functionalities and manipulate the material properties in a controllable way. Acknowledgements We are grateful for financial support from DFG 323667265. We gratefully acknowledge Manuel Mundszinger for TEM sample preparation. [1] S. Catalano, M. Gibert, J. Fowlie, J. Íñiguez, J.-M. Tricone, and J. Kreisel, Rep. Prog. Phys., 2018 [2] J.M. Rondinelli, S.J. May, and J.W. Freeland, MRS Bulletin, 2012

Reproducibility and control of solid-state nanopore production by fast helium ion beam milling

Abstract text (incl. figure legends and references) Solid-state nanopores are of great interest for usage as an instrument for scalable and robust single-molecule measurements in life sciences. The nanopores are mechanically stable, and can withstand a wide range of environments, due to the materials used [1]. In order to further enhance the potential and usability of these nanopores, one of the main goals of our research is the fast and reliable fabrication. Measurements of analytes with nanopores are typically done using simple flow cells, which incorporate a membrane chip. The membrane includes a single nanopore, therefore it forms the only possible ion conduction path between two bath chambers with electrodes, allowing the measurement of single molecules passing through the pore. The usage and further research of the solid-state nanopores as an instrument, requires fast fabrication methods. So far, nanopores were produced with a Transmission Electron Microscope (TEM), which requires manual control over the electron beam. Additionally a very frequent vacuum transfer of the single sample chip after each milling step is necessary. Here we will present solid-state nanopores fabricated by a Helium Ion Microscope in silicon-nitride membranes. The HIM allows the etching of features smaller than 10 nm [2]. Furthermore, the depth of field is in the range of micrometres, which gives a better control over the aspect ratios of the pores. For high throughput production, this property is also useful, because the focus of the Helium Ion Beam does not need to be adjusted over a large field, which increases efficiency. We expect milling times 10-100x faster than TEM. Moreover, fast HIM scanning speeds allow low dwell times of the milling procedure (Fig. 3). Total dose each pore and dwell time - the time the Helium Ion Beam parks at one position - make up the precisely controllable parameters. The choice of these gives good control and reproducibility over the shapes of the pores, which was previously difficult to achieve by the fabrication using TEM. Precise measurements of the sizes of the pores were done using a TEM (Fig. 1, 2). Electron energy loss spectroscopy (EELS) allows the measurement of the thicknesses, therefore aspect ratios are precisely determinable. We will present results on the reproducibility of different aspect ratios and sizes of silicon nitride nanopores. Acknowledgements We thank Christoph Blattert (Hahn-Schickard, Villingen-Schwenningen, Germany) for provided silicon nitride membranes. This work is supported by the project TechPat nano (Translational platform for nanosensor-based medical diagnostics, funding code 35 4223.10/10). We acknowledge financial support from the State Ministry of Baden Wuerttemberg for Economic Affairs , Labour and Tourism. References Xue, L. et al., doi: 10.1038/s41578-020-0229-6 Shixuan He et al., doi: 10.1088/2631-7990/abc673 Figure 1. TEM (80kV) phase-contrast image of a nanopore array fabricated by HIM. Different total doses were applied from right to left (10 nC/µm² .. 100 nC/µm²) and the dwell time was varied from top to bottom (1µs .. 10µs). Figure 2. TEM (80kV) phase-contrast images of single nanopores, field of view 30 nm. With a dwell time of 1 µs, the total dose was varied from left to right: 40 nC/µm², 50 nC/µm², 100 nC/µm². Figure 3. Milling procedure done by HIM. Diameter d sets the geometry. Repeats of the spiral milling pattern from inside to outside are dependent on the total dose and dwell time.

PS 11
Poster session MS 4: Functional thin films

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Session chairs

Programm

PS 11Poster session MS 4: Functional thin films

Termin

Session chairs

Programm

PS 11
Poster session MS 4: Functional thin films