Jian Fu Tang

In-situ post-annealing technique for improving piezoelectricity and ferroelectricity of Li-doped ZnO thin films prepared by radio frequency magnetron sputtering system

Li-doped zinc oxide (L0.03Z0.97O) thin films are deposited onto Pt/Ti/SiO2/Si substrates via the radio frequency magnetron sputtering method. The structure evolution with annealing temperature of the predominantly (002)-oriented Li-doped ZnO (LZO) films after in-situ post-annealing process is determined. The largest values of the piezoelectric coefficient (d33) and the remnant polarization (Pr) (22.85 pm/V and 0.655 μC/cm2, respectively) are obtained for LZO films post-annealed at 600 °C, which can be attributed to the predominant (002)-oriented crystalline structure, the release of intrinsic residual compressive stress, and less non-lattice oxygen.

UV-Ozone Process for Film Densification of Solution-Processed InGaZnO Thin-Film Transistors

The effects of ultraviolet (UV)-ozone treatment on solution-processed amorphous InGaZnO (IGZO) thin-film transistors (TFTs) grown using the sol-gel method are investigated. The UV-ozone-treated TFT devices showed an improved field-effect mobility of 1.52 cm²·V^-1·s^-1 and a subthreshold slope (S) of 0.42 V/dec compared to those of IGZO TFT devices with only thermal annealing (0.75 cm²·V^-1·s^-1 and 0.84 V/dec, respectively). The enhancement of the UV-ozone-treated TFTs is mostly attributed to the increased film packing density, higher Al S/D electrodes adhesion properties, reduced oxygen-related defects, and less electron trapping of the IGZO thin films, which improved the TFT performance and bias stress stability.

Multi-step resistive switching behavior of Li-doped ZnO resistance random access memory device controlled by compliance current

The multi-step resistive switching (RS) behavior of a unipolar Pt/Li0.06Zn0.94O/Pt resistive random access memory (RRAM) device is investigated. It is found that the RRAM device exhibits normal, 2-, 3-, and 4-step RESET behaviors under different compliance currents. The transport mechanism within the device is investigated by means of current-voltage curves, in-situ transmission electron microscopy, and electrochemical impedance spectroscopy. It is shown that the ion transport mechanism is dominated by Ohmic behavior under low electric fields and the Poole-Frenkel emission effect (normal RS behavior) or Li+ ion diffusion (2-, 3-, and 4-step RESET behaviors) under high electric fields.

Effects of various hybrid nanostructures on antireflective performance of poly-Si solar cells

In this study, a hybrid nanostructure comprising ZnO nanorods embedded in polymethylmethacrylate (PMMA) was developed for use as an antireflection (AR) coating. The fabrication process includes the etching of PMMA as an alternative to conventional photolithographic methods. This approach enables rapid, large-scale production at low cost with minimal pollution. The PMMA serves to protect the ZnO nanorods against external damage, while the O2 plasma treatment provides a modified surface profile to reduce reflectance. X-ray diffractometer (XRD) measurements and TEM results confirm that the resulting crystal structures are pure ZnO with good crystallinity. This paper compares three hybrid nanostructures (flat film, columnar, and conical) as antireflective layers. The application of poly-Si solar cells with the proposed AR layer was shown to improve cell efficiency by enhancing short-circuit current density.

Dependence of seed layer thickness on sensitivity of nano-ZnO cholesterol biosensor

The anemone-like ZnO nanostructures have been synthesized by hydrothermal method and were further adsorbed immobilized cholesterol oxidase (ChOx) as a nano-biosensor. In this study, the sensitivity of biosensor were improved by varying the thickness of the ZnO seed layer. The SEM analysis showed changes in thickness of seed layer will not affect the morphologies of anemone-like ZnO nanostructures. The X-ray Diffraction patterns showed that the (002) plane of anemone-like ZnO grown on various thickness of the seed layer was more prouded than other crystal plane. Abioelectrode (ChOx/ZnO/ITO/glass) grown on the 30nm of ZnO seed layer with high sensitivity of 57.533μAmM-1cm-2 (1.488 μA (mg/dl) -1cm-2), a wide sensitive range from 25 to 500 mg/dl. It is concluded that the thinner sputtered ZnO seed layer for growing anemone-like ZnO nanostructure can effectively improve the sensitivity of the ZnO biosensor.

Effects of multilayer buffer on structural properties of ZnO nanostructures grown using a solvothermal method

This paper reports on a solvothermal method used in the fabrication of vertically aligned two-dimensional (2D) ZnO nanowall networks and one-dimensional (1D) ZnO nanorods with overlapping structures. The introduction of an Al thin film as a doping source was shown to alter the morphology from rods to walls. The proposed multilayer buffer results in the formation of two types of nanostructure (nanowalls and rods) and also increased the length to which the nanorods grow at the same time. Analysis based on transmission electron microscopy (TEM) and selected area electron diffraction (SAED) led us to formulate a possible growth mechanism and elucidate the optical properties of the ZnO nanostructures.

Synthesis High Sensivity ZnO Cholesterol Biosensor with One Dimensional Nanostructures

Chelosterol ZnO biosensors were synthesized by hydrothermal method with predeposited ALD-ZnO seed layers. The ZnO nanostructures were examined by SEM, XRD, AFM, respectively. The XRD is used to analyze the crystal structures of ZnO seed layers that were grown by ALD process, then using SEM and AFM to analysis the surface morphologies of them. Growing of one dimensional ZnO nanostructures on seed layer of 10nm thickness, reveals high sensitivity of 3.15 uA (mg/dl)-1cm-2(121.96 uAmM-1cm-2) and low Km value of 29mM in 25-100mg/dl cholesterol concentration range. The response time could be as low as 10seconds. In the study, it is found that increasing the aspect ratio of ZnO one dimensional nanostructure also increases the sensitivity and expends the linear measureable range of detecting cholesterol in solution. The thickness of seed layer has a significant influence on sensitivity for one dimensional nano ZnO cholesterol biosensor.