Yue Zhao

The grain boundary related p-type conductivity in ZnO films prepared by ultrasonic spray pyrolysis

Intrinsic p-type ZnO thin film was fabricated on sapphire substrate by ultrasonic spray pyrolysis, the p-type ZnO film is achieved using O2 as the carrier gas, with a resistivity of 2.18 Ω cm−1, a carrier concentration of 1.10×1016 cm−3, and a high Hall mobility of 261 cm2/V s. The scanning capacitance microscopy images and annealing the p-type ZnO indicate that the absorbed oxygen in the grain boundary (GB) aroused the p-type conductivity, and the high Hall mobility of the p-type ZnO film own to the quasi-two-dimensional hole gas, which was induced by the negatively charged interface states in the GBs.

Characterization of Ag doped P-type ZnO thin films prepared by electrostatic-enhanced ultrasonic spray pyrolysis

In this paper, the structure, electrical and optical properties and stabilities of Ag doped p-type ZnO thin films, prepared by electrostatic-enhanced ultrasonic spray pyrolysis were investigated. XRD and Hall data analyses indicated that the resistivity of 4at. % Ag doped p-type ZnO was low, without Ag2O phase separation. The optical transmission spectra illustrated that optical band gaps decreases with the gradual increase of Ag dopant. Moreover, ZnO: Ag films placed for 10 days still showed p-type, but the optical transmittance decreased, suggesting that AgZn in the ZnO: Ag thin films captured electrons to generate Agi, which reunited to be Ag nano-particles and decreased the optical transmittance of ZnO: Ag.

Sensitivity to NO2 of ZnO Film Prepared by Electrostatic-Enhanced Ultrasonic Spray Pyrolysis

The NO2-sensing properties of the ZnO films prepared by EUSP were investigated. Effect of substrate temperature on the NO2-sensing properties of ZnO films showed that the powder-like ZnO film deposited at 550°C was more sensitive to NO2, and the film illustrated good response-restoration property. Besides, the influence of doping amount on the NO2-sensing properties of the ZnO films at 260°C showed that the ZnO:Al film with the Al content of 0.4mol% presented the best sensitivity, and the ZnO: 3mol % Ag exhibited the highest NO2 sensitivity. The dynamic response tests indicated that the ZnO: Al film was of the highest sensitivity to NO2, and the sensitivity of ZnO: Ag film was lowest.

The study of the CdS film and the carrier transport characteristics of CdS/CuInS 2 pn junction

Cadmium sulfide (CdS) films were grown by chemical-bath deposition (CBD). Some films were annealed at 300 °C in N2 atmosphere for 30 min. The diffraction peaks related to the (111) crystal plane of wurtzite CdS phase appeared in as prepared CdS films. After annealing, the diffraction peaks related to (220) and (311) crystal planes of wurtzite CdS phase came out. Meanwhile, the roughness, the crystallite sizes and the Cd/S ratio of annealed CdS films increased, which might be due to the volatilization of S element. Furthermore, the absolute values of photocurrent of different CdS films may be related to the interaction between the electron and the intrinsic defects in CdS film and the absorption capacity for incident light. Moreover, the I-V characteristics for all FTO/CdS/CuInS2/Mo hetero-junctions exhibited successful rectifying characteristic, and the corresponding electrical parameters may be attributed to the thickness of CdS films and the intrinsic defects in p-n junction.Graphical abstractThe figure is the photocurrent-time curves of CdS thin films prepared by different time.

Passivation Effect and Stability of Diamond-Like Carbon Film on CdZnTe Devices

Leakage currents of a CdZnTe (CZT) detector are desired to be as low as possible for a better signal-to-noise ratio in the acquisition of x-ray/gamma-ray spectra. Surface passivation plays a major role in reduction of the surface leakage current and thereby improves the detector performance. In this paper, diamond-like carbon (DLC) film has been introduced as the passivation layer for a CZT detector. Passivation effect and stability of the DLC film on CZT devices have been investigated by the Raman spectrum, x-ray photoelectron spectroscopy (XPS), atomicforce microscopy (AFM) and current–voltage characteristic. High-quality DLC films were effectively fabricated on CZT devices measured by the Raman spectrum. The XPS in-depth profiling of CZT passivated with DLC film demonstrated that no interface reaction occurred, and DLC effectively prevented the oxidation reaction to produce the state Te4+ in Te3d spectra. Moreover, the surface leakage current evidently dropped after the DLC film passivation. In addition, properties of the DLC films with different thickness were investigated. It was shown that the effect of this passivation over stability with time is not perfect and an optimum thickness of the DLC film is proposed for reaching the best stability for CZT devices.

The study of metal enhanced fluorescence property of Ag/ZnO composite structure

In this paper, Ag nanoparticles were successfully prepared by chemical reduction, and then Ag/ZnO composite particles were successfully prepared and deposited onto glass substrates to form Ag/ZnO thin films. Hereafter, the structure, the morphology and the metal enhanced fluorescence (MEF) property of Ag nanoparticles and ZnO/Ag composite particles were studied by XRD, SEM, EDS, TEM, UV-vis absorption and fluorescence (FL) spectrometer. The results showed that the average size of Ag nanoparticles increased with the increase of prepared time. Moreover, ZnO layer consisted of polycrystalline structure and amorphous interface layer, but nano-Ag particle was polycrystalline structure. Annealing process was carried out to investigate the influence of annealing process parameters on MEF property of Ag/ZnO composite structure. Due to annealing treatment, the amorphous component of Ag/ZnO thin films was reduced, which might improve the density of Ag/ZnO thin films and the diameter of composite particles. Furthermore, FL enhancement phenomenon of fluorescein isothiocyanate (FITC) molecules might be attributed to the joint influence of the roughness and the density of these films and the average diameter of composite particles.

The Optical Properties and the Structure of CuInS2 Thin Films Deposited by Oblique Angle Deposition Technique

The oblique angle deposition (OAD) technique was used to deposit copper indium disulfide (CuInS2) films onto glass substrates by a vacuum thermal evaporation method. The powder source used in this work was obtained from the crushed CuInS2 polycrystalline ingot grown by Vertical Bridgeman method. In order to study the influences of depositing angle on the optical property and the structure of the CuInS2 films, the depositing angle θ was varied from 10° to 70° with a 30° gradient. These films were characterized by SEM, XRD and UV-Vis spectrophotometer. The results showed that the optical property and the structure of the films were closely related to the depositing angle θ. When the depositing angle θ increased, the band gap increased and the intensity of (112) characteristic peak of the CuInS2 films decreased.

The Influence of Oblique Deposited Angle on Metal Enhanced Fluorescence Property of Ag and Ag/ZnO Core-Shell Structure

In this paper, the Ag nanoparticles were successfully prepared by oblique evaporation method, and then the ZnO shell layer was coated on surface of silver particles using wet chemical method. Hereafter, the structure, the morphology and the metal enhanced fluorescence (MEF) property of the Ag and the Ag/ZnO core-shell particles were studied by XRD,SEM,TEM and fluorescence (FL) spectra. From the XRD patterns and the SEM,TEM images, the Ag nanocolumn and the Ag/ZnO composite were successful obtained. Furthermore, the density of Ag nanocolumnar structure decreased with the increase of depositing angle. This phenomenon could be attributed to the surface diffusion function and the shading effect, As the result of the FL spectra, the MEF performance of the Ag/ZnO composite was more prominent than that of Ag nanocolumn, due to the quenching effect. Moreover, the MEF performance of the Ag/ZnO composite depended on the deposited angle, firstly increasing and then decreasing with the tilt angle of Ag/ZnO core-shell structure. The mechanism of fluorescence enhancement would be due to the surface plasmon resonance of Ag surface and the change in photonic mode density and/or reduction in self-quenching of fluorophores for ZnO nanostructure.

The Preparation and Optical Properties of Ag/ZnO Composite Materials

A simple, two-step fabrication technique was presented to prepare the Ag/ZnO hybrid nanostructures using silver nitrate and zinc nitrate. Silver particles were synthesized by chemical reduction method and the ZnO layer was coated on the surface of silver using wet chemical method. The microstructure, the composition and the optical properties of the obtained materials were further characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence (FL) spectroscopy. The results showed that the silver and zinc oxide composite had been successful prepared. The intensity of fluorescence showed an enhancement of R6G (dye) indicate that ZnO shell had an improvement on the silver metal enhance fluorescence.

Growth of ZnO Nanostructures on Metal-Filled Porous Silicons

Abstract The growth of zinc oxide (ZnO) nanostructures on Au-, Cu- and Zn-filled (111) and (100) porous silicons (PSs) has been investigated. The results indicate that the ZnO nanostructures grown on Au-filled (111) PS are possessed of rod-shapes with hexagonal end faces, those on the Cu-filled (100) or (111) PS are possessed of belt-shapes or rod-shapes, and those on the Zn-filled (100) or (111) PS are possessed of wire-shapes. The ZnO growth on the Au- and Cu-filled PS are mainly along c-axis orientation, while its growth on the Zn-filled PS are mainly along [ 01 1 ¯ 0 ] orientation, and it possesses a single crystal hexagonal structure without dislocations and stacking faults. In addition, the green emission intensity of the ZnO grown on Zn-filled PS caused by oxygen vacancies of the ZnO is weaker than that of the ZnO grown on Au (Cu)-filled PS,. It could be concluded that the ZnO grown on Zn-filled PS produces a better quality. After annealing in air, the positions of the green emission peaks do not vary, while the intensities are weakened.