Effect of annealing and hydrogen plasma treatment on the luminescence and persistent photoconductivity of polycrystalline ZnO films

Abstract

Photoluminescence (PL) and electrical properties of boron doped zinc oxide (ZnO) thin films, deposited by metalorganic chemical vapour deposition on a glass substrate, were investigated. The effects of annealing in air, as well as the influence of the radiofrequency—plasma treatment in hydrogen atmosphere, on the PL and electrical conductivity of the ZnO films were studied. A correlation between photoluminescence and electrical properties during annealing was observed. Hydrogen plasma treatment causes an increase in the carrier mobility and concentration and results in a very intensive near band edge emission (NBE). It was found that defects responsible for the dramatic increase in the intensity of NBE band in the hydrogen-treated ZnO films are hydrogen-related complexes formed near or at the surface of the samples. The intensity of NBE in hydrogen-treated samples decreases after aging in the dark, and, conversely, the NBE intensity increases under UV light illumination. This effect is fully reversible and depends on the gas atmosphere during the UV exposure and subsequent aging. It was proposed that the NBE band in the ZnO films annealed in the air and treated in hydrogen plasma emerges due to O-H complexes forming at zinc vacancy sites, n(O-H)-VZn.

Crystallization of ZnO thin films via thermal dissipation annealing method for high-performance UV photodetector with ultrahigh response speed

“…Figure 6a shows the photoluminescence (PL) spectra of the ZnO thin films after various annealing methods and all PL spectra consisted of sharp and broad emissions in the UV and visible regions, respectively. In general, the sharp and strong emission observed in the UV region is referred to as a near-band-edge (NBE) emission and is attributed to the recombination of free excitons, whereas the weak and broad emission observed in the visible region is referred to as a deep-level (DL) emission and is ascribed to defects in the ZnO lattice, such as zinc vacancies, oxygen vacancies, interstitial zinc, and interstitial oxygen [22][23][24][25][26] . As shown in Fig.…”

Tailoring the Surface Functionalities of Radio Frequency Magnetron-Sputtered ZnO Thin Films by Ar/NH3 Gas Mixture Surface-Wave Plasmas

“…Similar blue shifts of NBE emission have been observed in the nitrogen-doped ZnO thin films 45 or ZnO thin films grown by metal−organic chemical−vapor deposition after annealing 46 and so on. Furthermore, many reports present the enhancement of the NBE emission intensity by NH 3 plasma treatment, 47 H 2 plasma treatment, 48 and O 2 plasma treatment after annealing. 49 Here, we briefly describe the relation between the NBE emission peak and the strain of the ZnO thin films treated by the Ar/NH 3 gas mixture SWPs.…”

Effect of Hydrogen Plasma Treatment on the Sensitivity of ZnO Based Electrochemical Non-Enzymatic Biosensor

“…The thermal treatment and hydrogen plasma treatment of zinc oxide semiconductor materials are common methods for changing their physicochemical properties [ 40 , 41 , 42 ]. Negatively charged oxygen forms adsorbed on the ZnO grain boundaries play the role of electron capture centers and form potential energy barriers, thereby reducing the Hall mobility and concentration of free carriers.…”