Tunable electrical resistivity of oxygen-deficient zinc oxide thin films

Abstract

Oxygen-deficient zinc oxide thin films were deposited by radio frequency magnetron sputtering with a sintered zinc oxide ceramic target under an atmosphere of manipulated sputtering gas pressure (SGP). Under the designed deposition conditions, all the prepared films were of hexagonal würtzite structure with c-axis as the preferential growth orientation. With increasing SGP, the film thickness, deposition rate, grain size and atomic ratio of O to Zn in the films initially increased and then decreased. Interestingly, when the SGP was low, the main defects in the films were oxygen vacancies; when it was high, the dominant defects were interstitial zinc; but when it was in a moderate value, the film composition might be relatively close to the stoichiometric ZnO, possessing the least number of defects. As a result, the electrical resistivity of the films first increased and then dropped down as the SGP increased.

High-performance varistors simply by hot-dipping zinc oxide thin films in Pr6O11: Influence of temperature

“…For comparison, the result on the as-deposited ZnO 0.81 film is also presented. The lattice constant of the as-deposited ZnO 0.81 thin film is 5.1668 Å, smaller than that of stoichiometric ZnO (5.2066 Å)20, implying that the applied ZnO 0.81 thin film is an oxygen-deficient one with lots of oxygen vacancies1121. However, after hot-dipping at the designed temperatures, the lattice constant for the samples increased, although all of them were still less than 5.2066 Å (more or less).…”

“…For details, please check them in refs 6 and 11. Then the as-deposited ZnO 0.81 thin film samples were buried in Pr 6 O 11 powder in a half-covered alumina crucible, and heated in a muffle furnace at a temperature of 300, 400, 500, 600, 700 and 800 °C, respectively, for an optimized time of 50 min (see Extended Data Fig.…”

“…X-ray photoelectron spectroscopy (XPS) analysis indicated that, only Zn 2p and O 1 s peaks could be detected in the applied oxygen deficient zinc oxide thin films, which had a composition of ZnO 0.81 611. After hot-dipping in Pr 6 O 11 powder at the designed conditions, the elemental composition and chemical state of the obtained samples were also examined by XPS.…”

“…Considering the afore-mentioned facts, to improve the performance of ZnO-Bi 2 O 3 based thin-film varistors, in our previous work, by radio frequency (RF) magnetron sputtering of a sintered zinc oxide ceramic target, oxygen-deficient zinc oxide thin films with tunable composition and electrical resistivity were deposited11, and through hot-dipping the obtained oxygen-deficient zinc oxide thin films in Bi 2 O 3 powder, highly nonlinear binary ZnO-Bi 2 O 3 thin-film varistors with an optimum nonlinear coefficient of 15.1 (basically being an equivalent to ZnO-based bulk ceramic varistors) were obtained, because the effective double Schottky barriers were well built up at the grain boundaries6. However, such thin-film varistors will still suffer from low high-temperature stability in applications, because at high temperature, the core oxygen-deficient zinc oxide films are easily oxidized and the shell Bi 2 O 3 thin films are highly volatile.…”

High‐performance varistors prepared by hot‐dipping tin oxide thin films in Sb2O3 powder: Influence of temperature

“…X‐ray photoelectron spectroscopy (XPS; Thermo Fisher, nonmonochromated Al K α radiation, photon energy 1486.7 eV, Waltham, MA, USA) was used to examine the films composition and elementally chemical state. For the XPS characterization, the correction of the energy shift of the samples was carried out by referencing it to the C 1s line (284.6 eV) . The electrochemical impedance spectra of the samples were recorded by an electrochemical workstation (CHI660E; Chenghua Instrument Company, China), and the impedance data were analyzed by the ZSimpWin software.…”