Nanoestruturas de GaN crescidas pelas técnicas de epitaxia por magnetron sputtering e epitaxia por feixe molecular

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Annealing effects of sapphire substrate on properties of ZnO films grown by magnetron sputtering

The annealing effects of sapphire substrates on the quality of epitaxial ZnO films grown by dc reactive magnetron sputtering were studied. The atomic steps formed on (0001) sapphire (alpha-Al2O3) substrates surface by annealing at high temperature were analyzed by atomic force microscopy. Their influence on the growth of ZnO films was examined by X-ray diffraction and photoluminescence measurements. Experimental results indicate that the film quality is strongly affected by annealing treatment of the sapphire substrate surface. The optimum annealing temperature of sapphire substrates for ZnO grown by magnetron sputtering is 1400 degrees C for 1 h in air.

Surface plasmon enhanced ultraviolet emission from ZnO films deposited on Ag/Si(001) by magnetron sputtering

The ZnO films were grown on Ag/Si(001) substrates by sputtering Ag and ZnO targets successively in a pure Ar ambient. A significant enhancement of ZnO ultraviolet emission and a reduction of its full width of half maximum have been observed while introducing a 100 nm Ag interlayer between ZnO film and Si substrate. Furthermore, a complete suppression of the defect related visible emission was also found for the ZnO/Ag/Si sample. This improved optical performance of ZnO is attributed to the resonant coupling between Ag surface plasmon and ultraviolet emission of ZnO. (c) 2007 American Institute of Physics.

Magnetron sputtering growth of InAs0.3Sb0.7 films on (100) GaAs substrates: Strong effect of growth conditions on film structure

The growth of highly lattice-mismatched InAs0.3Sb0.7 films on (100) GaAs Substrates by magnetron Sputtering has been investigated and even epitaxial lnAs(0.3)Sb(0.7) films have been successfully obtained. A strong effect of the growth conditions on the film structure was observed, revealing that there was a growth mechanism transition from three-dimensional nucleation growth to epitaxial layer-by-layer growth mode when increasing the substrate temperature. A qualitative explanation for that transition was proposed and the critical conditions for the epitaxial layer-by-layer growth mode were also discussed. (c) 2005 Elsevier B.V. All rights reserved.

Preparação e caracterização óptica de filmes nanocristalinos de GaAs:H depositados por RF magnetron sputtering

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Influência da temperatura e do tipo de substrato em filmes de GaN depositados por magnetron sputtering reativo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo das propriedades ópticas e vibracionais de filmes de GaN dopados com Mn elaborados por RF Magnetron Sputtering Reativo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Inductively coupled plasma-assisted RF magnetron sputtering deposition of boron-doped microcrystalline Si films

An innovative custom-designed inductively coupled plasma-assisted RF magnetron sputtering deposition system has been developed to synthesize B-doped microcrystalline silicon thin films using a pure boron sputtering target in a reactive silane and argon gas mixture. Films were deposited using different boron target powers ranging from 0 to 350 W at a substrate temperature of 250 °C. The effect of the boron target power on the structural and electrical properties of the synthesized films was extensively investigated using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and Hall-effect system. It is shown that, with an initial increase of the boron target power from 0 to 300 W, the structural and electrical properties of the B-doped microcrystalline films are improved. However, when the target power is increased too much (e.g. to 350 W), these properties become slightly worse. The variation of the structural and electrical properties of the synthesized B-doped microcrystalline thin films is related to the incorporation of boron atoms during the crystallization and doping of silicon in the inductively coupled plasma-based process. This work is particularly relevant to the microcrystalline silicon-based p-i-n junction solar cells.

Inductively coupled plasma-assisted RF magnetron sputtering deposition of highly uniform SiC nanoislanded films

A new deposition technique-inductively coupled plasma-assisted RF magnetron sputtering has been developed to fabricate SiC nanoislanded films. In this system, the plasma production and magnetron sputtering can be controlled independently during the discharge. The deposited SiC nanoislanded films are highly uniform, have excellent stoichiometry, have a typical size of 10-45 nm, and contain small (∼ 6 nm) cubic SiC nanocrystallites embedded in an amorphous SiC matrix.

RF magnetron sputtering deposition of bioactive Ca-P-based coatings on Ti-6Al-4V alloy

RF magnetron concurrent sputtering of Hydroxyapatite and Ti forming functionally graded calcium phosphate-based composite bioactive films on Ti-6Al-4V orthopedic alloy is reported. Calcium oxide phosphate (4CaO•P2O5) is the main crystalline phase. In vitro cell culturing tests suggest outstanding biocompatibility of the Ca-P-Ti films. Images of the plasma-enhanced sputtering processes and cell culturing are presented and discussed.

Structure, bonding state and in-vitro study of Ca–P–Ti film deposited on Ti6Al4V by RF magnetron sputtering

Experimental investigation of functionally graded calcium phosphate-based bio-active films on Ti-6A1-4V orthopaedic alloy prepared in an RF magnetron sputtering plasma reactor is reported. The technique involves concurrent sputtering of Hydroxyapatite (HA) and Ti targets, which results in remarkably enhanced adhesion of the film to the substrate and stability of the interface. The films have been characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XPS data show that the films are composed of O, Ca, P and Ti, and reveal the formation of O=P groups and hybridization of O-Ca-P. The XRD pattern shows that the Ca-P thin films are of crystalline calcium oxide phosphate (4CaO·P2O5) with preferred orientation varying with processing parameters. High-resolution optical emission spectra show that the emission of CaO is dominant. The CaO, PO and CaPO species are strongly influenced by deposition conditions. The introduction of Ti element during deposition provides a stable interface between bio-inert substrates Ti-6A1-4V and bioactive HA coating. In-vitro cell culturing tests suggest excellent biocompatibility of the Ca-P-Ti films.

Electrical and structural properties of zirconia thin films prepared by reactive magnetron sputtering

Thin films of ZrO2 were prepared by reactive magnetron sputtering. Annealing of the films exhibited a drastic change in the properties due to improved crystallinity and packing density. The root mean square roughness of the sample observed from atomic force microscope is about 5.75 nm which is comparable to the average grain size of the thin film which is about 6 nm obtained from X-ray diffraction. The film annealed at 873 K exhibits an optical band gap of around 4.83 eV and shows +4 oxidation state of zirconium indicating fully oxidized zirconium, whereas higher annealing temperatures lead to oxygen deficiency in the films and this is reflected in their properties. A discontinuity in the imaginary part of the AC conductivity was observed in the frequency range of tens of thousands of Hz, where as, the real part does not show such behavior.

dc reactive magnetron sputtering of titanium‐structural and optical characterization of TiO2 films

This paper deals with the reactive sputtering of titanium in an argon and oxygen mixture. The variation in cathode potential as a function of oxygen partial pressure has been explained in terms of cathode poisoning effects. The titania films deposited during this process have been studied for their structural and optical characteristics. The effect of substrate temperature (from 25 to 400 °C) and annealing (from 250 to 700 °C) on the packing density, refractive index, extinction coefficient, and crystallinity has been investigated. The refractive index varied from 2.24 to 2.46 and extinction coefficient from 2.6 × 10-3 to 10.4× 10-3 at 500 nm as the substrate temperature increased from 25 to 400 °C. The refractive index increased from 2.19 to 2.35 and extinction coefficient changed from 3.2× 10-3 to 11.6 × 10-3 at 500 nm as the annealing temperature was increased from 250 to 700 °C. Anatase and rutile phases have been observed in the films deposited at 400 °C substrate temperature and annealed at 300 °C. The changes in the optical constants at higher substrate temperature have been attributed to an increase in packing density, oxygen content, and crystallinity of the films.

Effect of substrate temperature on the properties of ZrO2 films prepared by d.c. reactive magnetron sputtering

Studies of ZrO2 films prepared by d.c. reactive magnetron sputtering are described. The effects of substrate temperature on the packing density, refractive index, extinction coefficient and crystallinity phase have been investigated in the temperature range 25–450 °C. The refractive index varied from 1.84 to 1.95 and extinction coefficient from 2 × 10−3 to 9.6 × 10−3. This was explained on the basis of an increase in packing density from 0.686 to 0.813. The change in packing density has been attributed to a decrease in the oxygen condensation at higher temperatures. Annealing results in a decrease in refractive index and increase in extinction coefficient. The films deposited at 150 °C showed a monoclinic phase which transforms to a tetragonal phase at higher substrate temperatures.

Rapid thermal processed thin films of niobium pentoxide (Nb2 O5) deposited by reactive magnetron sputtering

Niobium pentoxide thin films have been deposited on silicon and platinum-coated silicon substrates by reactive magnetron sputtering. The as-deposited films were amorphous and showed good electrical properties in terms of a dielectric permittivity of about 30, and leakage current density of 10(-6) A cm(-2) al a field of 120 kV cm(-1). A rapid thermal annealing process at 800 degrees C further increased the dielectric constant to 90 and increased the leakage current density to 5 x 10(-6) A cm(-2). The current-voltage characteristics observed at low and high fields suggested a combination of phenomena at different regimes of applied electric field. The capacitance-voltage characteristics performed in the metal-insulator-semiconductor configuration indicated good electronic interfaces with a nominal trap density of 4.5 x 10(12) cm(-2) eV(-1), which is consistent with the behavior observed with conventional dielectrics such as SiO2 on silicon surfaces.