Search results for "Epitaxy"
showing 10 items of 287 documents
MOVPE growth of Ga 3D structures for fabrication of GaN materials
2004
Abstract This paper presents the growth and characterization of metallic gallium three-dimensional (3D) structures and preliminary results of their transformation into GaN-like structures. The structures were grown by metal-organic vapour phase epitaxy (MOVPE), using trimethyl gallium as gallium precursor on silicon (1 0 0). The growth temperature was between 550°C and 750°C. Interesting and new metallic structures were obtained with our growth parameters: balloon (montgolfier-like structure) and cauliflower-like. These metallic structures can grow up perpendicular to the substrate surface and have diameters between 0.1 and 5 μm, depending on the growth conditions. Moreover, selective metal…
Single Photon Emission from Site-Controlled InAs Quantum Dots Grown on GaAs(001) Patterned Substrates
2009
5 páginas, 5 figuras.
Effects of the Buffer Layers on the Performances of (Al,Ga)N Ultraviolet Photodetectors
2004
The fabrication of (Al,Ga)N-based metal–semiconductor–metal (MSM) photovoltaic detectors requires the growth of high-quality (Al,Ga)N films. Inserting a low-temperature deposited buffer layer enables the growth of an epitaxial layer with a reduced density of defects. Two structures using GaN and AlN buffer layers have been deposited by low-pressure metalorganic chemical vapor deposition and used to fabricate MSM interdigitated detectors. The devices have been characterized to investigate the effects of the buffer layers on the detector performances.
Seed layer technique for high quality epitaxial manganite films
2016
We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening tempera…
Faceting and structural anisotropy of nanopatterned CdO(110) layers
2005
CdO(110) layers with a self-organized surface structure have been grown on (10math0) sapphire (m plane) substrates by metal-organic vapor phase epitaxy. The epitaxial relationships between layer and substrate have been determined and a crystallographic model that accounts for the CdO in-plane orientation, which results in a reduced lattice mismatch when the CdO[001] direction is perpendicular to the sapphire c axis, has been proposed. Although the measured lattice parameters indicate that the layers are almost fully relaxed, an anisotropic mosaicity is detected with symmetrical rocking curves attaining minimum values when measured along the CdO[math10] direction. The layer morphology consis…
X-ray multiple diffraction in the characterization of TiNO and TiO2 thin films grown on Si(001)
2006
Abstract TiO 2 and TiN x O y thin films grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) on top of Si(0 0 1) substrate were characterized by X-ray multiple diffraction. X-ray reflectivity analysis of TiO 2 [1 1 0] and TiNO[1 0 0] polycrystalline layers allowed to determine the growth rate (−80 A/min) of TiO 2 and (−40 A/min) of TiNO films. X-ray multiple diffraction through the Renninger scans, i.e., ϕ -scans for (0 0 2)Si substrate primary reflection is used as a non-conventional method to obtain the substrate lattice parameter distortion due to the thin film conventional deposition, from where the information on film strain type is obtained.
Evidence of hexagonal WO3 structure stabilization on mica substrate
2009
International audience; WO3 nanorods are grown by a simple vapor deposition method on a mica substrate and characterized by Selected Area Electron Diffraction and Energy Dispersive X-rays Spectroscopy. Experimental results show the clear evidence of an unexpected WO3 hexagonal structure as well as an epitaxial growth on the mica substrate. Besides, potassium is evidenced inside the nanorods. It is thus deduced that a metastable WO3 hexagonal phase is stabilized by epitaxy through a tungsten bronze interlayer having same hexagonal structure.
Temperature Effects on the Phonon Spectrum in YBa2Cu3O7 Single Crystals and Thin Films
1989
We have performed a detailed investigation of the temperature dependence of the 385cm-1 phonon in single crystals and thin films of the YBa2Cu3O7 superconductor by means of Raman spectroscopy. In the single crystal the frequency of this phonon shows a downshift of about 5 cm-1 on passing the superconducting transition from above, which is referred to a strong electron-phonon interaction in the superconductor. The shift of the phonon in thin epitaxial films on MgO or SrTiO3 substrates is only about 2.5 cm-1. This difference may be a result of a structural transition in the single crystal which is possibly suppressed in the films because of the epitaxy. The electron-phonon interaction is also…
Dopant radial inhomogeneity in Mg-doped GaN nanowires
2018
International audience; Using atom probe tomography, it is demonstrated that Mg doping of GaN nanowires grown by Molecular Beam Epitaxy results in a marked radial inhomogeneity, namely a higher Mg content in the periphery of the nanowires. This spatial inhomogeneity is attributed to a preferential incorporation of Mg through the m-plane sidewalls of nanowires and is related to the formation of a Mg-rich surface which is stabilized by hydrogen. This is further supported by Raman spectroscopy experiments which give evidence of Mg-H complexes in the doped nanowires. A Mg doping mechanism such as this, specific to nanowires, may lead to higher levels of Mg doping than in layers, boosting the po…
CVD elaboration and in situ characterization of barium silicate thin films.
2010
International audience; This study is concerned with the elaboration of barium silicate thin films by metal organic chemical vapor deposition (MOCVD) and in situ characterization by X-ray photoemission spectroscopy (XPS) with an apparatus connected to the deposition reactor. The difficulty to find an efficient metal organic precursor for barium is described. After characterizations of the selected reactant, Ba(TMHD)2tetraglyme, the development of an original specific vapor delivering source which allows reactant sublimation in the CVD reactor was performed. In the most optimized cases, including use of oxygen introduction during the deposition, barium silicate films were obtained. Moreover,…