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Abstract: LiNbO3 (LNO) films were epitaxially grown on n-type GaN templates using pulsed laser deposition technique. The microstructures and electrical properties of the LNO/GaN heterostructure were characterized by x-ray diffraction, transmission electron microscope, and capacitance–voltage (C–V) measurements. The LNO films had two variants of grains rotated 60° in-plane to each other. The epitaxial relationship of the respective variants could be built as [10–10]LNO//[1–210]GaN and [1–100]LNO//[11–20]GaN via 30° in-plane rotation of the LNO film relative to the GaN layer. Interface analysis of the heterostructure demonstrated that two different epitaxial growth mechanisms vertical heteroepitaxy and lateral homoepitaxy, should happen at the interface of LNO/GaN. Counterclockwise C–V windows induced by the ferroelectric polarizations of LNO film could be observed clearly. The size of the window increased with increasing the sweep bias and a large window of 5.8V was achieved at ±15V. By solving Poisson and drift–diffusion equations, the physical mechanisms of the C–V characteristics were demonstrated. [Copyright &y& Elsevier]

Abstract: A series of metallic LaNiO3 (LNO) thin films were deposited on MgO (100) substrates by pulsed laser deposition (PLD) under the oxygen pressure of 20Pa at different substrate temperatures from 450 to 750°C. X-ray diffraction (XRD) was used to characterize the crystal structure of LNO films. θ–2θ scans of XRD indicate that LNO film deposited at a substrate temperature of 700°C has a high orientation of (l l 0). At other substrate temperatures, the LNO films have mixed phases of (l l 0) and (l 00). Furthermore, pole figure measurements show that LNO thin films, with the bicrystalline structure, were epitaxially deposited on MgO (100) substrates in the mode of LNO (110)//MgO (100) at 700°C. Reflection high-energy electric diffraction (RHEED) and atomic force microscopy (AFM) were also performed to investigate the microstructure of LNO films with the high (l l 0) orientation. RHEED patterns clearly confirm this epitaxial relationship. An atomically smooth surface of LNO films at 700°C was obtained. In addition, bicrystalline epitaxial LNO films, fabricated at 700°C, present a excellent conductivity with a lower electrical resistivity of 300μΩcm. Thus, the obtained results indicate that bicystalline epitaxial LNO films could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films. [Copyright &y& Elsevier]

Heteroepitaxial GaN films are grown on sapphire (0001) substrates using laser molecular beam epitaxy. The growth processes are in-situ monitored by reflection high energy electron diffraction. It is revealed that the growth mode of GaN transformed from three-dimensional (3D) island mode to two-dimensional (2D) layer-by-layer mode with the increase of thickness. This paper investigates the interfacial strain relaxation of GaN films by analysing their diffraction patterns. Calculation shows that the strain is completely relaxed when the thickness reaches 15 nm. The surface morphology evolution indicates that island merging and reduction of the island-edge barrier provide an effective way to make GaN films follow a 2D layer-by-layer growth mode. The 110-nm GaN films with a 2D growth mode have smooth regular hexagonal shapes. The X-ray diffraction indicates that thickness has a significant effect on the crystallized quality of GaN thin films. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS 2 ) thin films are deposited onto silicon (Si) substrates using magnetron sputtering technique. Raman spectra show that the out-of-plane vibration is preferentially excited for the film. X-ray diffraction patterns further illustrate that the deposited MoS 2 films have the preferential [100] orientation. These results demonstrate that the unit layers of S Mo S in the film are perpendicular to the substrate. This can supply high-speed paths for the transportation of the electron carriers along the out-of-plane orientation. Due to the unique vertically standing layered structure of the MoS 2 film, the fabricated MoS 2 /Si sensor device exhibits excellent hydrogen (H 2 ) sensing properties. The device performance can be featured by a high sensitivity (687.3% under 100.0 ppm H 2 ), high detection resolution (a 1.0-ppm level), as well as fast response and recovery, and good reversibility. The sensing mechanisms were discussed based on the microstructural characteristics of the MoS 2 film and the energy-band alignment near the MoS 2 /Si interface. The MoS 2 /Si heterojunctions proposed in this work might open new avenues for the development of future high-performance sensor devices. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional (3D) porous V2O5 and Fe0.1V2O5.15 thin films have been prepared by electrostatic spray deposition technique. X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy are employed to investigate the structures and valence states of the films. Galvanostatic cell cycling, cyclic voltammetry and impedance spectroscopy are used to characterize their electrochemical properties. The Fe0.1V2O5.15 thin film shows much better cycling performance than the non-doped V2O5 thin film. Fe3+ can act as a stabilizing agent in the layered V2O5 and increase the reversibility of the charge and discharge processes towards deeper depth of lithium insertion/extraction. The dissolution of the active material in the electrolyte can also be significantly suppressed in the Fe-doped sample. Nevertheless, the Fe-doping causes a slight decrease in lithium ion diffusion coefficient. [Copyright &y& Elsevier]