Influence of the precursor anion on the photoluminescence properties of ZnO.

ZnO nanorod arrays were synthesized by hydrothermal method with two different zinc salts as precursors: zinc acetate and zinc nitrate. Different anions in solution distinctly influence the intrinsic defects in ZnO nanostructures, resulting in different photoluminescence properties. The defects induced by precursors were systematically studied by photoluminescence spectroscopy, X-ray photoelectron spectrometer and electron paramagnetic resonance. The results show that zinc acetate precursor mainly introduces zinc vacancy to the lattice while ZnO nanorods obtained from zinc nitrate contain more interstitial oxygen.

Surface charge transfer doping of monolayer molybdenum disulfide by black phosphorus quantum dots.

Monolayer molybdenum disulfide (MoS2), consisting of covalently bonded S-Mo-S sandwiched layers, has high carrier mobility and a direct bandgap of 1.8 eV, offering properties for electronic and optoelectronic devices with high performance. Usually, it is essential to modulate the carrier concentrations and conductivities of monolayer MoS2 for practical applications. In this paper, black phosphorus (BP) quantum dots (QDs) were synthesized by a liquid exfoliation method successfully, and have a diameter of ∼5 nm as confirmed with a transmission electron microscope (TEM). BP QDs were utilized to decorate monolayer MoS2 grown by chemical vapor deposition (CVD). The Raman and PL spectra of the BP QD/MoS2 hybrid structure clearly indicate that BP QDs are an effective n-type doping scheme for monolayer MoS2. Back-gated monolayer MoS2 transistors were fabricated and show an improved source-drain current after BP QD modifications. A high electron concentration of ∼5.39 × 1012 cm-2 in monolayer MoS2 was achieved, which is beneficial for designing FETs and photodetector devices with novel functions.

Control of the threshold voltage in ZnO nanobelt field-effect transistors by using MoO x thin film.

We report on the feasible control of the threshold voltage (V th) in ultra-thin ZnO nanobelt FETs by using substoichiometric molybdenum trioxide (MoO x , x < 3) either as a modification layer on the surface of ZnO nanobelts or as electrodes instead of the widely used Ti/Au. ZnO nanobelt FETs using Ti/Au as the electrodes usually exhibit a negative threshold voltage, indicating n-channel depletion mode behavior, whereas ZnO FETs with MoO x /Au electrodes instead of Ti/Au show a positive shift of threshold voltage, exhibiting an n-channel type enhancement mode, which can be explained by a high Schottky barrier created at the interface of MoO x and the ZnO channel. In contrast, the decoration on the surface of ZnO channel by MoO x significantly increases the zero-bias conductivity and electron carrier concentration, and then negatively shifts the threshold voltage. We propose that MoO x thin film may play a passivation effect role, much more so than the doping effect role, due to the large amount of adsorbed species on as-grown ZnO nanobelts, especially oxygen species.