ZnO-CuO core-shell heterojunction nanowires for optoelectronic applications

Abstract

Nowadays, core-shell nanowires have attracted a great scientific interest due to their unique physical properties and advanced functionalities leading to applications in optoelectronic area [1]. Combining ZnO, an n type semiconductor with a band gap of 3.3 eV [2] and CuO, an p type semiconductor with a band gap of 1.2 eV [3], into core-shell radial heterojunction nanowires, a type II heterojunction alignment can be acquired, with a good control of the separation and recombination of the charge carriers at the interface between the two semiconductors. In this context, the ZnO-CuO core-shell heterojunction nanowire arrays were synthesized by thermal oxidation in air and radiofrequency magnetron sputtering (Figure 1). The ZnO-CuO core-shell nanowire arrays were investigated by the morphological, structural, optical, compositional and surface chemistry point of views. In order to assessed their optoelectronic properties, individual ZnO-CuO core-shell nanowires were contacted using photolithography, electron beam lithography and thin film deposition techniques. Exhibiting a rectifying behavior (Figure 2), typical for n-p diodes, these single ZnO-CuO core-shell nanowires can be used in UV photodetectors applications, such as radiation detection, air purification, advanced communications etc.