Controlled growth and properties of p-type cuprous oxide films by plasma-enhanced atomic layer deposition at low temperature

Abstract

Various copper oxide films were successfully grown by plasma-enhanced atomic layer deposition (PEALD) at a low temperature of 100 degrees C. X-ray diffraction analysis of the films indicated that phase-controlled deposition of CuOx phases (0 <= x< 1) was possible by controlling the number of Cu deposition steps during one PEALD cycle with a fixed oxidation step. When Cu deposition was executed in one step, an amorphous CuOx (x=0.9) film with a smooth surface (RMS roughness of 0.97 nm) was obtained. On the other hand, when the number of Cu deposition steps was increased to three, a CuOx (x=0.6) thin film with a polycrystalline phase (grain size: 25 nm) was obtained. The as-deposited CuO0.6 film showed p-type conductivity (Hall mobility similar to 37 cm(2)/V.s and hole concentration similar to 5.4 x 10(14) cm(-3)). Moreover, p-type CuO0.6/n-type ZnO heterojunction diodes fabricated on a flexible polyethylene terephthalate substrate exhibited electrical rectification with a threshold voltage of 1.2 V.