Abstract text (incl. figure legends and references)

Zinc oxide is well-known for its non-linear current-voltage (I‑V) characteristics and its respective application as varistor (variable resistor) ceramic.¹ The varistor effect itself is attributed to dopant-induced electrostatic potential barriers at ZnO grain boundaries.^1,2 In case of so‑called piezotronic materials, semiconducting and piezoelectric properties are combined in order to tune such potential barriers. Therefore, ZnO – featuring piezoelectricity as well as intrinsic semiconduction – has received renewed scientific interest as piezotronic material and is considered to hold a large potential for the development of novel devices, such as strain-triggered transistors, diodes or sensors.^3,4 However, the dopant-related formation of varistor-type potential barriers in ZnO as well as the related semiconducting properties are still not completely elucidated, in particular, against the background of novel piezotronic applications, which imply conditions different from the established polycrystalline ZnO varistor ceramics. In the presented study, ZnO bicrystals with (0001) inversion boundaries were analyzed using atomic resolution (S)TEM methods, with a special focus on orientation and dopant segregation.^5,6 In doing so, different synthesis methods were applied and their effect on the interface properties was investigated. Based on the TEM findings and corresponding I-V measurements, a distinct correlation between interface coherency, degree of segregation and degree of non-linearity was observed. Since this correlation is attributed to basic principles of segregation and interfacial properties, the presented results are not only seen as a valuable contribution to the field of piezotronics and varistor ceramics, but also as adaptable for other material systems.

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