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Abstract: A ZnO thin-film transistor (TFT) with an MgO insulator was fabricated on a silicon (100) substrate using a radiofrequency magnetron sputtering system. The MgO insulator was deposited using the same deposition system; the total pressure during the deposition process was maintained at 5 mTorr, and the oxygen percentage of O2/(Ar + O2) was set at 30%, 50%, or 70%. The process temperature was maintained at below 300 °C. The dielectric constant of the MgO thin layer was approximately 11.35 with an oxygen percentage of 70%. This ZnO TFT displayed enhanced transistor properties, with a field-effect mobility of 0.0235 cm2 V−1 s−1, an I ON/I OFF ratio of ∼105, and an SS value of 1.18 V decade−1; these properties were superior to those measured for the MgO insulators synthesized using oxygen percentages of 30% and 50%. [Copyright &y& Elsevier]

Abstract: Thermal annealing in NH3-ambient was carried out to form p-type ZnO films. The properties were examined by X-ray diffraction (XRD), Hall-effect measurement, photoluminescence (PL), and secondary ion mass spectrometry (SIMS). Electron concentrations in ZnO films were in the range of 1015–1017/cm3 with thermal annealing in NH3-ambient. The activation thermal annealing process was needed at 800 ∘C under N2-ambient to obtain p-type ZnO. The electrical properties of the p-type ZnO showed a hole concentration of 1.06×1016/cm3, a mobility of 15.8 cm2/V s, and a resistivity of 40.18 Ω cm. The N-doped ZnO films showed a strong photoluminescence peak at 3.306 eV at 13 K, which is closely related to neutral acceptor bound excitons of the p-type ZnO. The incorporation of nitrogen was confirmed in the SIMS spectra. [Copyright &y& Elsevier]

A polycrystalline MgZnO/ZnO bi-layer was deposited by using a RF co-magnetron sputtering method and the MgZnO/ZnO bi-layer TFTs were fabricated on the thermally oxidized silicon substrate. The performances with varying the thickness of ZnO layer were investigated. In this result, the MgZnO/ZnO bi-layer TFTs which the content of Mg is about 2.5 at % have shown the enhancement characteristics of high mobility (6.77–7.56 cm 2 V −1 s −1 ) and low sub-threshold swing (0.57–0.69 V decade −1 ) compare of the ZnO single layer TFT ( μ FE = 5.38 cm 2 V −1 s −1 ; S.S. = 0.86 V decade −1 ). Moreover, in the results of the positive bias stress, the ΔV on shift (4.8 V) of MgZnO/ZnO bi-layer is the 2 V lower than ZnO single layer TFT (ΔV on = 6.1 V). It reveals that the stability of the MgZnO/ZnO bi-layer TFT enhanced compared to that of the ZnO single layer TFT. [ABSTRACT FROM AUTHOR]

Abstract: Epitaxial ZnO/Mg0.1Zn0.9O (MZO) nano-scale multilayer thin films were prepared on Al2O3 (0001) substrates by pulsed laser deposition. The ZnO/MZO multilayer thin films were grown by stacking alternate layers of ZnO and Mg0.1Zn0.9O with a laser fluence, repetition rate, substrate temperature and oxygen partial pressure of 3J/cm2, 5Hz, 600°C and 3.8×10−7 Pa, respectively. The thickness of an individual ZnO layer was maintained at 3nm, whereas that of the MZO layers was varied from 3nm to 15nm. Cross-sectional transmission electron microscopy revealed alternating layers of bright and dark contrast, indicating the formation of a ZnO/MZO multilayer. X-ray diffraction results showed that multilayer thin films were epitaxially grown as a hexagonal wurzite phase with orientation relationship of . The 2θ value of the (0002) peak of the ZnO/MZO multilayer thin films increased from 34.30° to 34.71°, indicating that Mg is replaced with Zn in the hexagonal lattice in the MZO of ZnO/MZO multilayer. UV–visible spectroscopy showed a systematic increase in the band gap of the ZnO/MZO multilayer thin films from 3.34eV to 3.70eV with increasing MZO layer thickness, which suggests that the band gap energy of a ZnO/MZO multilayer thin film can be controlled by varying the thickness of each constituent layer. [Copyright &y& Elsevier]