Model of the formation of a polycrystalline $n$-ZnO/$p$-CuO heterojunction

A model of the formation of a heterojunction based on polycrystalline films of zinc and copper oxides is considered. Faces of the unit cells, between which epitaxial relations are fulfilled, are revealed on the basis of an analysis of the crystalline structure of the zinc and copper oxides. It is also shown that, in addition to fulfillment of the rule of epitaxial relations, the closeness of the values of the ionic radii for double-charged Cu$^{++}$ and Zn$^{++}$ ions makes it possible to form a polycrystalline heterojunction in a ZnO/CuO system.