Zhongyi Hua

A new transparent conductive thin film In2O3:Mo

Abstract A new high quality transparent conductive thin film In2O3:Mo (IMO) was prepared by conventional thermal reactive evaporation at the substrate temperature of approximately 350°C. From X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis of IMO films, it was confirmed that Mo6+ substituted In3+ without changing the cubic bixbyite structure of In2O3 and there were no new compounds in IMO as well. One atom of dopant contributes with more electrons to the electrical conductivity and at the same carrier concentration there is fewer dopant in IMO than in other doped oxides. So, the IMO film exhibits simultaneously higher values of Hall mobility, electric conductivity, visible light transmittance, infrared reflectance and plasma wavelength. An electrical resistivity as low as 1.7×10−4 Ω cm was obtained, while the infrared reflectance above 4 μm and the average total visible light transmittance of the IMO film plus the glass substrate were both over 80%, and the plasma wavelength was at approximately 2.2 μm. IMO is more suitable for the energy efficient windows used in cold climates or even for optoelectronic device applications.

Molybdenum-doped indium oxide transparent conductive thin films

We developed a novel transparent conductive film, molybdenum-doped indium oxide (IMO). Using normal thermal reactive evaporation without any special treatments, IMO films have been prepared on normal glass microscope slides at about 350 °C with electrical resistivity of 1.7×10−4 Ω cm, mobility over 100 cm2 V−1 s−1, and an average spectral transmittance in the visible region over 80%. From x-ray photoelectron spectroscopy and x-ray diffraction spectra of the IMO films, it is confirmed that the lattice of IMO is the same as that of In2O3 of cubic bixbyite structure, Mo6+ substitutes for In3+ in In2O3, and there are no new compounds in IMO. The valence difference of 3 between Mo6+ and In3+ is of great advantage to the IMO film with high conductivity and high transparency simultaneously.

Preparation and electrical/optical bistable property of potassium tetracyanoquinodimethane thin films

Potassium tetracyanoquinodimethane (K(TCNQ)) thin films were prepared using physical vapor deposition combined with solid state chemical replacement reaction. Reversible electrical bistable behavior at or even above room temperature was observed; and, the optical bistable property of K(TCNQ) film was observed.

The role of the silver intermediate layer in the YBa2Cu3O7−x/Ag/ In2O3/Si system

Abstract Superconducting YBa 2 Cu 3 O 7− x (YBCO) thin films were deposited on Si(111) substrates with a conductive intermediate layer of Ag In 2 O 3 . In 2 O 3 was prepared by the d.c. magnetron method and a silver thin film was evaporated on the In 2 O 3 /Si(111). The YBCO thin films were deposited by d.c. magnetron sputtering. The conductive In 2 O 3 thin film was used to minimize the interdiffusion between silicon and the YBCO superconducting material. The silver thin film improves the zero-resistance temperature, transition temperature width, and the critical current density of the superconducting YBCO film in the YBCO/In 2 O 3 /Si system. Films of YBCO on the Ag/In 2 O 3 /Si substrate have zero resistance at 85 K and a critical current density of 2.0 x 10 3 A cm −2 at 77 K. The XRD spectrum indicates that the superconducting thin films have a preferential c axis oriented structure. Auger electron spectroscopy depth profiling was used to analyse the interfaces.

Depositing In2O3 films as conductive buffer layers for high temperature YBa2Cu3O7−x superconducting thin films on silicon

Abstract By depositing a conductive buffer layer of In 2 O 3 , we have been able to prepare superconducting YBa 2 Cu 3 O 7− x on silicon by d.c. magnetron sputtering. The buffer layer sputtered by the reactive d.c. magnetron method was used to minimize the interdiffusion between silicon and the superconductor. The typical as-deposited superconducting thin film, without subsequent high temperature annealing, has a T c onset at 96 K with zero resistance at 81 K. X-ray diffraction data indicate that the films have a preferential c axis oriented structure. Depth profiling by Auger electron spectroscopy has been employed to study the diffusion and structural variation near the interfaces.

A new storage material for rewritable blue-light DVD

A category of new photochromatic storage material has been found suitable for rewritable digital video disc (DVD). The ratio of transmissivity before and after the write-in process is 3:1 at /spl lambda/=450 nm (blue) and 2:7 at /spl lambda/=650 nm (red), with a transition time of 2-3 ns. The number of write-erase cycles is about 1,000.

A high-Tc SQUID for measuring susceptibility of high-Tc superconductive thin films

Abstract A variable-temperature susceptometer (VTS) using a Y Ba Cu O RF-SQUID has been made for testing weak magnetization of high-Tc superconductive thin films. The temperature of the sample chamber can be varied from 77 K to room temperature. A solenoid of normal metal has been used to supply a magnetic field up to 0.1 T. A double-hole RF-SQUID made of Y Ba Cu O bulk material working at 19 MHz has a flux resolution of5×10−4φ0/Hz1/2(20–200Hz) at 77 K. The magnetic moment re resolution of the VTS is 1.3 × 10−6 emu. Susceptibility versus temperature curves of Y Ba Cu O and Gd Ba Cu O films have been obtained.

Research on the structure of Ag-TCNQ thin films for information storage

The structure and the electrical bistable properties of vacuum deposited thin films of Ag-TCNQ (7,7,8,8- Tetracyanoquinodimethane) complex have been investigated. The characteristics of obtained films under different preparation conditions have been compared. The optical transmission spectra and the x-ray diffraction measurements were conducted to analyze the structure and the thermal stability of the films. The atomic force microscope was used to examine the morphology and grain size of the films. The corresponding electrical switching property was measured upon the Ag-TCNQ films with different combined sandwich- shaped electrodes. The results how that the films can have very stable switching properties. The switching time between high and low impedance states is about 10 ns, and the switching voltage is around 4.0 V. The film preparation parameters and different layered structure have an important influence on the characteristic of the films. The switching mechanism was discussed.