Search results for "Epitaxy"
showing 10 items of 287 documents
LPE growth and study of the Ce3+ incorporation in LuAlO3:Ce single crystalline film scintillators
2019
This work reports the results of the optical and electron paramagnetic resonance (EPR) investigation of the Ce3+ incorporation in single crystalline film (SCF) scintillators of Ce-doped LuAlO3 perovskite, grown by the liquid phase epitaxy method onto YAlO3 substrates using a PbO–B2O3 flux. The absorption, luminescence and EPR spectra showed the presence of the main Ce3+ center type (CeLu) corresponding to the location of Ce3+ ions in the twelve-fold coordinated cuboctahedral positions of the LuAlO3 host. Also the dimer CeLu–CeLu centers were found in the EPR spectra of the LuAP:Ce SCFs. No EPR spectrum of the Ce3+ ions located in the octahedral positions of Al3+ cations has been detected in…
XRD and micro Raman characterization of epitaxial Bi-2201, Bi-2212 and Bi-2223 thin films
1997
Copyright (c) 1997 Elsevier Science B.V. All rights reserved. Micro Raman characterization is performed on high quality thin films of Bi 2 Sr 2 CuO 6+x (2201), Bi 2 Sr 2 CaCu 2 O 8+x (2212), Bi 2 Sr 2 Ca 2 Cu 3 O 10+x (2223) made by dc-sputtering. Single crystal X-ray measurements reveal the full epitaxy of the films, which allows for polarized Raman spectra to be obtained.
Temperature and substrate influence on the structure of TiN O thin films grown by low pressure metal organic chemical vapour deposition
2000
Abstract This paper presents the growth and characterization of titanium oxinitride (TiN x O y ) films grown by low pressure metal organic chemical vapour deposition (LP-MOCVD). The film nitrogen content, obtained by Rutherford backscattering spectroscopy (RBS), increases as the growth temperature increases (from 23 at.% at 450°C to 46 at.% at 750°C). Below 550°C, the films do not show any X-ray diffraction pattern. Above 550°C, the deposited films present the (111) and (200) TiN textures. Films deposited on (100) Si exhibit a 2 θ shift to higher Bragg angles, depending on the N/O ratio. These shifts are explained by using a substitutional oxygen model. Moreover, the atomic structure of suc…
Interfacial disorder of graphene grown at high temperatures on 4H-SiC(000-1)
2016
This paper presents an investigation of the morphological and structural properties of graphene (Gr) grown on SiC(000-1) by thermal treatments at high temperatures (from 1850 to 1950 °C) in Ar at atmospheric pressure. Atomic force microscopy and micro-Raman spectroscopy showed that the grown Gr films are laterally inhomogeneous in the number of layers, and that regions with different stacking-type (coupled or decoupled Gr films) can coexist in the same sample. Scanning transmission electron microscopy and electron energy loss spectroscopy shoed that a nm-thick C-Si-O amorphous layer is present at the interface between Gr and SiC. Basing on these structural results, the mechanisms of Gr grow…
Spontaneous intercalation of Ga and In bilayers during plasma-assisted molecular beam epitaxy growth of GaN on graphene on SiC
2019
The formation of a self-limited metallic bilayer is reported during the growth of GaN by plasma-assisted molecular beam epitaxy on graphene on (0001) SiC. Depending on growth conditions, this layer may consist of either Ga or In, which gets intercalated between graphene and the SiC surface. Diffusion of metal atoms is eased by steps at SiC surface and N plasma induced defects in the graphene layer. Energetically favorable wetting of the (0001) SiC surface by Ga or In is tentatively assigned to the breaking of covalent bonds between (0001) SiC surface and carbon buffer layer. As a consequence, graphene doping and local strain/doping fluctuations decrease. Furthermore, the presence of a metal…
Cathodoluminescence and structural studies of nitrided 3D gallium structures grown by MOCVD
2009
Abstract Cathodoluminescence (CL) spectrum imaging and grazing incidence X-ray diffraction (GIXRD) are employed to investigate nitride three-dimensional (3D) gallium structures. The metallic precursors are naturally obtained on a large variety of substrates by metal-organic chemical vapor deposition (CVD) with different shape/size controlled by the growth conditions, especially the temperature. These 3D metallic structures are subsequently exposed to a nitridation process in a conventional CVD reactor to form GaN nanocrystals, as confirmed by GIXRD measurements. CL spectroscopy shows visible light emission (2.5–2.8 eV) excited from the GaN in the 3D structures.
Ferroelectric Behavior in Epitaxial Films of Relaxor PbMg1/3Nb2/3O3
2004
The nonlinear dielectric response of epitaxial thin films of relaxor ferroelectric PbMg1/3Nb2/3O3 was experimentally studied using digital Fourier analysis. Change from glass-like to ferroelectric behavior was detected in a broad temperature range, at relatively low ac and/or dc electric fields, and at a time scale of seconds. The presence of interfaces and peculiar microstructure of thin films are suggested to determine such a specific behavior.
Thin film preparation of the low charge carrier density Kondo system CeSb
1999
Abstract We report the thin film preparation of CeSb by means of molecular beam epitaxy (MBE) onto sapphire (1 1 −2 0) substrates. Above a substrate temperature of about 300°C CeSb crystallizes in (0 0 1) orientation. The growth mode of the films changes from a fiber textured to an epitaxial mode for deposition temperatures above 900°C. Although the specific resistivity is enhanced the characteristic energy scales, like the Kondo temperature TK and the magnetic ordering temperature TN, are not changed significantly.
Theoretical investigation of the platinum substrate influence on BaTiO 3 thin film polarisation
2019
Density functional theory calculations are performed to study the out-of-plane polarisation in BaTiO3 (BTO) thin films epitaxially grown on platinum. Prior to any polarisation calculation, the stability of the Pt(001)/BaTiO3(001) structure is thoroughly discussed. In particular, the nature of the Pt/BTO and BTO/vacuum interfaces is characterised. The growth of BTO is shown to start with a TiO2 layer while the nature of the surface termination does not broadly modify the stability. Therefore both upper terminations are considered when describing the ferroelectric behaviour in Pt/BTO interfaces. The geometric and electronic effects of the substrate on the polarisation are investigated. To iso…
Electronic properties of *-oriented thin films
2007
Abstract To perform high precision measurements of the transport anisotropy, epitaxial, a *-oriented thin films of UPd 2 Al 3 have been prepared on LaAlO 3 (1 1 0) substrates. The critical temperature T c ≈ 1.75 K and the upper critical field B c 2 ≈ 3 T are comparable to typical bulk values. In contrast to UNi 2 Al 3 , we observed only a weak anisotropy in directional resistivity measurements, especially no dependence of the superconducting transition temperature on the direction of the applied current. Hall effect measurements show two characteristic minima at T = 16 K ≈ T N and T ≈ 6 K , which corresponds to features seen in earlier measurements on c *-oriented films.