An effect of rapid post-annealing temperature on the properties of cupric oxide thin films deposited by a remote plasma sputtering technique

Abstract

Traditional annealing has limitations of long-treatment time, excessive grain size and energy-intensive, inhibiting the quality and applications of the semiconductor thin films. Herein, an effect of rapid post-annealing (RPA) on the properties of cupric oxide (CuO) thin films deposited by a remote plasma sputtering technique was studied systemically. The chemical composition, microstructure, and the optoelectronic properties, including transmission, absorption, band gap, Urbach energy, carrier concentrations, and hall mobility, etc., were characterized by XRD, Raman, XPS, AFM, SEM TEM, optical transmission/absorption spectra and Hall measurements, correspondingly. The results reveal that the as-deposited and annealed (250, 350 and 450oC for 5 min) films all possess a single monoclinic CuO phase. All films possess compact nanostructures and the surface root-mean-square (RMS) roughness is around 1.5 nm because tiny and plain grains distribute uniformly within the films. The thermal annealing under higher temperature partially removes (or suppresses) the defects and this yields a broader bandgap for the CuO thin film, while the Urbach energy monotonous decreases with the increasing annealing temperature, signifying the minimizing disorder of the thin films. Meanwhile, the annealed CuO thin films possess decreased carrier concentration and enhanced hall mobility with increasing annealing temperature. For the 450oC-annealed CuO thin film, the carrier concentration is of 5.3 × 1015 cm−3 and the Hall mobility is of 2.3 cm2 V−1 s−1. This offers an essential material basis for photonic devices.