Quanjie Jia

The point defect structure and its transformation in As-implanted ZnO crystals

The point defect structure of As-implanted ZnO crystals was investigated using diffuse x-ray scattering and spectroscopic methods. A dynamic picture regarding the defect structure transformation was revealed. The defect type, size and combination state experienced obvious changes during annealing. Before annealing the point defects distributed isolatedly and coexisted with dislocation loops. After annealing, As-O disappeared and other point defects either aggregated into large clusters or formed defect complexes including As-Zn-2V(Zn) whose ionization energy was measured and which was discerned as the main origin of p-type conductivity.

Surface roughness exponent and non-designed cap layer in PbZr0.53Ti0.47O3/La1.85Sr0.15CuO4 bilayers

The surface and interface roughness and roughness exponent of PbZr0.53Ti0.47O3 (PZT)/La1.85Sr0.15CuO4 bilayers deposited on SrTiO3 (001) substrates by rf/dc magnetron sputtering have been measured by x-ray reflectivity and diffuse-scattering methods. We have found that the surface roughness increases and the roughness exponent decreases with the increase of the thickness of the PZT layers; and that there exist non-designed cap layers on the upper surfaces of the PZT layers. The growth character of the bilayer films is discussed.

Positron Beam Characterization of Silica Thin Films with Structurally Ordered Porosity

Well-ordered 2-dimensional (2D) hexagonal and 3-dimensional (3D) cubic mesoporous silicon oxide thin films prepared using triblock Poly(ethylene oxide)-Poly(Propylene oxide)-Poly(ethylene oxide) copolymer species (P123, F127) as the structure-directing agents, are studied by positron beam analysis in parallel with X-ray reflection measurements. It is observed that in the two films with equivalent porosity and pore size (normal to the film surface direction), the shape of mesopores considerably affects positron annihilation behavior. The narrowed positron annihilation Doppler broadening in the 2D hexagonal mesoporous film may suggest a higher positronium formation probability there, owing to a larger effective open volume area originated from the extension of pore channels parallel to the film substrate.

Effect of strain on the transport and magnetoresistance properties of La0.8Ca0.2MnO3 epitaxial thin films

The true residual stress in La0.8Ca0.2MnO3 (LCMO) thin films of various thicknesses deposited on STO substrates under the same deposition conditions was measured quantitatively by x-ray diffraction sin2ψ method. The truly strain-induced effect on the transport and magnetoresistance (MR) properties of LCMO films was investigated. The in-plane residual stress (σ11) in the LCMO film is tensile, while the out-of-plane one (σ33) is compressive. Moreover, the value of σ33 is larger than that of σ11. With increasing film thickness, the crystalline unit cell of the LCMO film reduces; also both the in- and out-of-plane components of the residual stress in the LCMO film decrease. It was found that the resistivity, TMI and MR strongly depend on the in-plane tensile stress σ11 (or/and the out-of-plane stress σ33). With the increase in the in-plane stress σ11 (or/and the out-of-plane stress σ33), the values of resistivity and MR increase, while TMI decreases. The truly strain-induced effect on the transport and magnetoresistance properties of LCMO film is discussed briefly.

Direct preparation and microstructure investigation of p -type transparent conducting Ga-doped SnO 2 thin films

Transparent p -type conducting Ga-doped SnO 2 thin films were prepared using reactive rf-magnetron sputtering. Good p -type conduction was directly realized without the need of postdeposition annealing. The p -type conductivity was found to be very sensitive to the growth condition and process, suggesting that the carrier behavior is strongly related to the fine microstructure of the films. The microstructures of the films were characterized using synchrotron X-ray diffraction and specular reflectivity techniques. The valence state of the Ga dopant was measured from X-ray photoelectron spectra to explain the origin of net holes presented in the films.

Study of the microstructures and the strain of PbZr0.53Ti0.47O3/La1.85Sr0.15CuO4 integrated films

A series of PbZr0.53Ti0.47O3 (PZT)/La1.85Sr0.15CuO4 (LSCO) integrated films were grown on SrTiO3 (STO)(001) substrates by DC/RF magnetron sputtering method. The film thickness of the PZT changes from 500 to 9000 Angstrom, while that of the LSCO is kept at 1000 Angstrom. The microstructures of interface and surface of the bilayer film have been investigated by small-angle X-ray reflection, high-resolution X-ray diffraction (XRD) using synchrotron radiation, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM images show island-like growth of the PZT layers with the particle size changing from 0.1 to 0.4 mu m, while the thickness of the PZT layer increased from 500 to 9000 Angstrom. The Full width at half maximums (FWHMs) of diffraction peak of the PZT layers are dramatically larger than that of LSCO layers, and the internal strains of the PZT layers are larger than that of LSCO films by an order. This indicated that the crystal perfection of the LSCO layers are better compared with PZT layers, and we attribute this to the different growth molds for PZT and LSCO films. However, no grand strain transition layers were found either in the PZT/LSCO or in the LSCO/PZT interfaces