# Formation of ZnO/CuO Heterostructures Based on Quasi-One-Dimensional Nanomaterials
## 1 Introduction
However, such nanolithography methods are mainly applied to create monolayer semiconductors and metal/metal oxide 2D patterns. In addition, their disadvantages are a relatively high cost and low productivity. The second approach makes use of the enlargement of the initial nuclei to one-dimensional nanostructures under the action of physicochemical forces. This occurs, for example, when using methods of gas-phase chemical synthesis, electrochemical deposition, crystallization from vapour or liquid phase, as well as template synthesis [32; 33]. The main obstacle to the wide practical application of this approach is that the synthesis of quasi-one-dimensional nanostructures involves the creation of specific growing conditions. In addition, there is a need for further removal of the substrate (template), usually by chemical etching, which can also have a negative impact on the quality of the obtained nanostructures. Therefore, currently, the focus is on developing reliable methods of obtaining such nanomaterials, including those, based on processes exploiting novel physical effects. A high-potential application of oxide materials is heterostructured solar power. Heterojunction solar cells or heterojunctions with intrinsic thin-layer solar cells are one fine example of such structures with high efficiency [34]. The characteristics of photodetector heterostructures can be improved by taking advantage of nanoheterojunctions. The defect-free junction of crystal lattices of the coupled materials is only possible when their type, orientation and period are the same. A special feature is the possibility of forming a polycrystalline heterojunction in a system of semiconductors belonging to different crystalline syngonies. For its implementation, it is sufficient that at least one of the faces of each lattice has close geometric parameters [35]. In [36] it has been shown that an important task at present is the development of technological methods ensuring the creation of n-ZnO/pCuO heterostructures formed on the basis of zinc oxide nanoobjects with arranged facets (10-10). The requirement of high surface area can be achieved by producing nanostructured layers in the form of both nanorods and nanowires. In [37] the possibilities of synthesis by pulse-periodic laser irradiation of arrays of quasi-one-dimensional ZnO nanostructures with varying micromorphology on metallic substrates were considered. The main distinguishing feature of this approach was the use of laser-induced vibrations to intensify diffusion processes in the solid phase of metallic materials as compared to the simple effects of laser beam heating. This identified physical effect has been explained by the synergy between thermal effects and vibrations in the range of sound and infrasound frequencies, leading to a non-stationary stress-strain state. By performing laser exposure on the pre-etching surface of Cu-Zn alloy, ZnO/CuO heterostructures based on ZnO nanowires were synthesized in [38]. The synthesized structures had a high surface area-to-volume ratio and good electrical contact between the oxide layer and the electrically conducting substrate. To effectively control the thermochemical processes, systems of laser beam shaping with free-form diffractive optics, which provide a predetermined spatial redistribution of energy, have been used [39]. Expanding the area of application of the advanced method of creating oxide heterostructures requires a detailed and comprehensive study of new possibilities used to form structures with improved physical properties. The principal objective of this article is to provide systematized information on the methods of fabrication and applications of CuO- and ZnO-based nanostructures, as well as features of the formation of ZnO/CuO heterostructures based on quasi-one-dimensional nanomaterials.