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We have synthesized ZnO tubes, without any catalyst, on Al2O3 (001) substrates by metal organic chemical vapor deposition (MOCVD) at different growth temperatures, pressures and Zn-O ratios. The results confirm that the growth temperature, reactor pressure and Zn-O ratio play important roles in the formation of hexagonal ZnO tubes. Scanning electron microscopy (SEM) images indicated that, at a growth temperature of 500 °C, reactor pressure of 75 Torr and Zn-O ratio of 10/75 are an appropriate condition to obtain hexagonal and well-aligned ZnO tubes. High-resolution, double crystal XRD analysis shows a symmetric ω-scan rocking curve, with a full width at half maximum (FWHM) of 1.1°. It confirms the ZnO tubes have highly c-axis orientation on Al2O3 substrate. Subsequently, room temperature photoluminescence (PL) studies confirm that the enhancement of UV emissions from ZnO tubes is due to increasing Zn-O ratios.

This paper discusses the development of a reactive sputtering process for the deposition of epitaxially grown AlN films on Si(111) using a technology suitable for 8" substrates. X-ray diffraction (XRD) and rocking curves (RC) are used to determine the crystalline orientation. The influence of substrate temperature, target-substrate distance and target voltage on the full width at half maximum (FWHM) of the RC is investigated. The film deposition was performed on Si(111) wafers and on AlN-on-Si(111) templates prepared by metal organic chemical vapor deposition (MOCVD). Based on the sixfold symmetry identifiable in the pole figure of the AlN(302) plane reflections, oriented in-plane film growth on Si(111) was verified for the process. Best oriented films sputtered directly on Si(111) achieved for 500 nm AlN films featured a RC-FWHM of 0.93° of AlN(100) and 0.77° of AlN(002). Root mean square roughness (RMS) of the samples varied between 2.3 nm and 2.8 nm. The deposition rate was between 70 nm/min and 100 nm/min. Films deposited onto the MOCVD templates grew maintaining the crystalline quality of the MOCVD substrate, verified by the FWHM of the RC of in-plane and out-of-plane reflections.

Mild heating of the Zn(C5F6HO2)(2)center dot 2H(2)O center dot CH3(OCH2CH2)(2)OCH3 precursor allowed MOCVD deposition of ZnO films, in a low-pressure horizontal hot-wall reactor, on ITO substrates. The ZnO films were subsequently implanted with Sb ions. XRD measurements provided evidence that they consist of hexagonal, (002) and (101) oriented, crystals. UV-vis spectra showed that the transmittance of these films in the visible region is about 90%. The Sb implanted ZnO film showed a current-voltage characteristic that resembles that of a rectifying diode. This study represents the first example of Sb-implantation in ZnO films obtained by MOCVD.

WOS: 000400536000016, In this study we report the VIII ratio effects on growth, structural, optical and doping characteristics of low growth rate (similar to 1 angstrom/s) heteroepitaxial Metal Organic Chemical Vapor Deposition (MOCVD) grown In(x)A(1-x)As layers, a part of Quantum Cascade Laser (QCL) structures, on InP substrate. Especially photoluminescence (PL) properties of InAlAs-InP interface show strong dependence on AsH3 overpressure. We have shown that the VIII ratio with fixed metalorganic precursor flow is a crucial parameter on In In(x)A(1-x)As layers to have a good material quality in terms of crystallinity, optical and electrical characteristics with and without doping. (C) 2017 Elsevier Ltd. All rights reserved., Republic of Turkey, Ministry of Science, Industry and Technology-SANTEZ program [0573.STZ.2013-2]; TUBITAK PhD Program fellowship [BIDEB-2211], This study was partially supported by Republic of Turkey, Ministry of Science, Industry and Technology-SANTEZ program under grant number 0573.STZ.2013-2. Ilkay Demir acknowledges the support through TUBITAK PhD Program fellowship BIDEB-2211 Grant. The authors thank Ms. A. Alev Kizilbulut from ERMAKSAN Optoelectronics for PL measurements.

InN thin films are grown on GaN/sapphire substrates with varying the nitrogen plasma power in plasma assisted molecular beam epitaxy (PA-MBE) system. In order to evaluate the effect of nitrogen plasma power on the different properties of the InN films, several characterization viz, x-ray diffraction, atomic force microscopy, photoluminescence measurement, infra-red spectroscopy and Hall measurement were performed. Two interesting phenomena observed from the measurements are described in this paper. Firstly, it is found from both the photoluminescence and infrared spectroscopy that only by varying the nitrogen plasma power (thus the BIN ratio), one can fine tune the optical absorption edge, i.e., the effective band gap of InN from similar to 0.72 eV to similar to 0.77 eV. Secondly, it is inferred that the film grown with stoichiometric condition (III/V similar to 1) exhibits the best structural and electrical properties. (C) 2016 Elsevier Ltd. All rights reserved.

International audience; In the present study, we investigate different surface pretreatments and their influence on a subsequent surface metallization. A direct liquid injection metalorganic CVD (DLI-MOCVD) process is presented for the low temperature metallization of composites, ultimately aiming at the surface unctionalization of 3D parts. The process involves the organometallic precursor Cu(I) hexafluoroacetylacetonate 2-methyl-1-hexene-3-yne (hfac)Cu(MHY). We determine chemical kinetics of the global deposition reaction and show the improvement of the adhesion of the Cu films by applying surface pretreatments that etch and/or activate the surface before deposition. To this purpose, gas phase and wet chemical processes are used. Gas phase pretreatments consist either in the use of a remote microwave plasma, an in situ UV oxidation, or in the deposition of acrylic acid/ethylene plasma buffer layer by using an atmospheric pressure cold plasma jet. The liquid phase pretreatment is based on a commercial series of solutions that includes swelling, oxidation, and neutralization steps. The adhesive strength of the Cu films on poly-epoxy and on carbon fiber/poly-epoxy composite surfaces is specifically investigated by scratch and cross-cut testing, and is correlatedwith topographical, chemical, and energetic characteristics of the surfaces prior deposition, investigated by interferometry, X-ray photoelectron spectroscopy and wettability measurements through the sessile drop method. Pretreatments result in surface functionalization and topographical changes which significantly increase the surface energy and improve the wettability. In some cases the induced modification of the microstructure of the Cu films is found to be eneficial to the electrical resistivity.

WOS: 000391905300075, We report the growth of high quality InGaAs/InAlAs quantum cascade laser (QCL) structure which composed of superlattices (SLs) and the effects of interruption time between each layer of the SL structure. Inserting an interruption delay during the growth dramatically effects the quality of the SL as indicated by crystallinity, interface sharpness and optical properties. The results show that an increase in interruption time up to a certain value makes sharper interfaces and improves optical and structural properties, but, beyond that value, overall quality starts to degrade. The composition and the growth rate of each single thin layer are determined by using high resolution X-ray diffraction (HRXRD) measurements. (C) 2016 Elsevier Ltd. All rights reserved., Republic of Turkey, Ministry of Science, Industry and Technology-SANTEZ program [0573.STZ.2013-2]; TUBITAK PhD Program fellowship [BIDEB-2211, 1649B031100137]; Republic of Turkey, Ministry of Science, Industry and Technology-SANTEZ program [0573.STZ.2013-2]; TUBITAK PhD Program fellowship [BIDEB-2211, 1649B031100137], This study was partially supported by Republic of Turkey, Ministry of Science, Industry and Technology-SANTEZ program under grant number 0573.STZ.2013-2. Ilkay Demir acknowledges the support through TUBITAK PhD Program fellowship BIDEB-2211 Grant-1649B031100137. The authors thank Ms. A. Alev Kizilbulut from ERMAKSAN Optoelectronics for PL measurements.

AlGaN/AlN layers were grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. The AlN buffer thickness was varied from 400 nm to 800 nm. The AlGaN layer thickness was 1000 nm. The crystalline quality, thickness and composition of AlGaN were determined using high resolution X-ray diffraction (HRXRD). The threading dislocation density (TDD) was found to decrease with increase of AlN layer thickness. Reciprocal space mapping (RSM) was used to estimate the strain and relaxation between AlGaN and AlN. The optical properties of AlGaN layers were investigated by temperature dependent photoluminescence (PL). PL intensities of AlGaN layers increases with increasing the AlN thickness. The surface morphology of AlGaN was studied by atomic force microscopy (AFM). Root mean square (RMS) roughness values were found to be decreased while increase of AlN thickness.

International audience; This work presents the synthesis and the characterization of hybrid material thin films obtained by the combination of two processes. The electrochemical grafting of organic layers made of carboxyphenyl moieties is carried out from the reduction of a diazonium salt on tin dioxide (SnO2) thin films previously deposited on Si substrates by metal organic chemical vapor deposition (MOCVD). Since the MOCVD experimental parameters impact the crystal growth of the SnO2 layer (i.e. its morphology and its texturation), various electrochemical grafting models can occur, producing different hybrid materials. In order to evidence the efficiency of the electrochemical grafting of the carboxyphenyl moieties, X-ray Photoelectron Spectroscopy (XPS) is used to characterize the first nanometers in depth of the synthesized hybrid material layer. Then three electrochemical grafting models are proposed.

Li4Ti5O12 is well known to be a safe and efficient anode material for Li-ion batteries. A metal-organic chemical vapor deposition process has been developed for the synthesis of Li4Ti5O12 thin film anodes on planar and 3D substrates. The influences of various deposition parameters, including precursor flow rates and post-annealing temperatures, have been investigated by material and electrochemical analyses. Li4Ti5O12 thin films deposited at the optimized process parameters showed a high crystallinity and high electrochemical activity. A reversible storage capacity of 151 mAh/g was achieved at a current of 0.5 C, corresponding to 86.3% of the theoretical specific capacity of Li4Ti5O12. Up to almost 600 cycles, the electrodes showed no significant capacity loss. Furthermore, the deposited thin film anodes also showed excellent rate performance. Compared to the storage capacity at 0.5 C, 93% of the capacity was maintained at 10 C. Thin films were also deposited on highly structured substrates to investigate the uniformity and electrochemical performance. With the same footprint area, the 3D Li4Ti5O12 film anode showed a 2.5 times higher storage capacity than planar electrode.

AlGaN/GaN heterostructures with different thicknesses of AlN interlayer (AlN-IL) were grown by metal organic chemical vapour deposition (MOCVD) system. The results obtained from atomic force microscopy revealed that, surface roughness decreases with increase in the interlayer thickness. Scanning electron microscopy and transmission electron microscopy images portrayed good interfaces between AlGaN/GaN heterostructures containing AlN as the IL. From the high-resolution X-ray diffraction data, the aluminium composition was estimated as 21–24%, and the AlGaN layer thicknesses were found to be 22–26 nm in the AlGaN layers using the epitaxy smooth fit software. Using reciprocal space mapping, the strain between AlGaN and GaN layers scanned along (1 0 5) plane were analyzed for the AlGaN/GaN heterostructures. Photoluminescence (PL) spectroscopy revealed a significant shift in the AlGaN peaks for samples both in the presence and absence of AlN-IL. Time resolved photoluminescence results exhibit dominate decay time in AlGaN/GaN heterostructures samples containing AlN-IL of around 3 nm thick. It is to be noted that, mobility increased from 1246 to 2000 cm2/volt-sec due to the presence of AlN-IL at 300 K.

International audience; Deposition inside a cavity with a narrow neck, i.e. a hollow body, is a challenge, in particular for the supply and the evacuation of the reactive phase and of the effluents through the same entrance. High gradients (pressure, velocity, species concentrations) and important convective mechanisms related to the impacting jet of the gaseous phase on the bottom inner wall of the cavity are created in that region. Given the increasing number of experimental parameters,modeling helps efficient process optimization with better understanding of physical and chemical phenomena occurring inside the hollow body. This study presents a numerical modeling using the CFD code Fluent to simulate a direct liquid injection metal organic chemical vapor deposition of amorphous alumina coatings from aluminum tri-isopropoxide (ATI) on the inner walls of a glass bottle. The model is used to predict local profiles of gas velocity, temperature and species concentrations into the reactor as well as local growth rate based on an apparent heterogeneous kinetic law of ATI decomposition. Comparison with experimental thickness profiles allows validating the model and leads to a better insight in the phenomena which impact film thickness inhomogeneity along the inner surface. The model contributes to the improvement of the reactor configuration by increasing the distance between nozzle and bottle and the outlet section of the nozzle.

3rd group element nitride based semiconductor compounds are widely used in various optical and electronic devices. One problem in the fabrication of GaN based device heterostructures is the synthesis of p conductivity epitaxial layers. Magnesium is a typical doping impurity for GaN. The choice of optimum doping and thermal activation conditions is of utmost importance for the synthesis of low-Ohmic p-GaN epitaxial layers. The effect of thermal annealing of GaN:Mg layers on acceptor impurity activation has been investigated. Hole concentration increased and mobility decreased with an increase in thermal annealing temperature. The sample annealed at 1000 °C demonstrated the lowest value of resistivity. Rapid thermal annealing (annealing with high heating speed) considerably improved the efficiency of Mg activation in the GaN layers. The optimum time of annealing at 1000 °C has been determined. The hole concentration increased by up to 4 times compared to specimens after conventional annealing.

International audience; Functional properties of tin doped indium oxide (ITO) layers grown by MOCVD from different indium and tin precursors are investigated. Selected indium precursors are In(acac)3, In(tmhd)3 and InMe2OtBu, and tin precursors are DBTDA and Sn(acac)2. ITO layers are optically and electrically characterized to determine the better doping conditions. Differences in electrical properties of ITO layers are found when using InMe2OtBu, as compared to In(acac)3 and to In(tmhd)3. The best films present a resistivity of 2.5 × 10−4 Ω cm and a transmittance higher than 84% for high deposition temperatures (T ⩾ 600 °C). The nature of tin precursors modifies the optimal doping at which these characteristics are achieved. When doped by DBTDA optimal doping is 8 at.%, therefore close to the solubility limit of tin in In2O3 matrix; but when using Sn(acac)2, or In(acac)3/DBTDA combination, best functional characteristics are obtained for the maximal doping content obtained, i.e. 2.5 at.%. For optimized conditions, the resistivity decreases when deposition temperature increases except when using the couple InMe2OtBu/DBTDA without oxygen addition during deposition. For this combination of precursors a resistivity of 1 × 10−3 Ω cm is obtained at a deposition temperature of 350 °C and remains constant up to 600 °C. Only the films obtained from InMe2OtBu/DBTDA are crystalline state at a deposition temperature of 350 °C.

Epitaxial nickel oxide (NiO) thin films have been grown by Metal Organic Chemical Vapor Deposition on AlGaN/GaN heterostructures. Critical growth parameters have been studied in order to optimize the deposition process of NiO films suitable for applications in GaN-based devices. In particular, a second generation precursor has been used as nickel source, namely the N,N,N′,N′-tetramethylethylenediamine adduct of nickel bis 2-thenoyl-trifluoroacetonate, using different deposition temperatures and oxygen flow values. Optimized operative conditions allowed the growth of epitaxial thin films which exhibited a permittivity of 11.7, close to the bulk value. The electrical characterization of the obtained epitaxial films pointed out to promising dielectric properties for AlGaN/GaN transistor technology.

Nanosized palladium layers on silicon (100) substrates were obtained employing MOCVD method under VUV and thermal stimulations in hydrogen medium, with the use of Pd(hfaс) 2 as a precursor. The deposition temperature under thermal stimulation amounted to 230 °C, whereas with the VUV (145 nm) stimulation this value was equal to 100 °C, within the time interval ranging from 1 to 30 min. With the use of monochromatic null ellipsometry and scanning electron microscopy techniques, initial stages of palladium nanolayer growth were studied. It has been established that the growth of Pd films exhibits a pronounced cyclical character. The analysis of electron microscopy images of growing film surfaces was based on the Voronoi–Delaunay method with the introduction of parameters such as peak, valley and minimum spanning tree (MST). It was demonstrated that the parameters used directly reflect the process of film growth, whereby two stages of the process have been distinguished.

The interest in the Ge doped Sb–Te chalcogenide alloy is mainly related to phase change memory applications. In view of phase change device scaling and reduction of programming energy, Sb–Te nanowires (NWs) become an attractive option. In this work, in order to investigate their potential transferability to industrial implementation, the self-assembly of Sb 2 Te 3 NWs and Ge–Sb–Te NWs with Ge content in the range of 1–13% (Ge doping) was studied by coupling the advantages of MOCVD and the Vapour–Liquid–Solid (VLS) mechanism. The results show the structural and compositional gradual changes occurring from pure Sb 2 Te 3 NWs to the previously reported, stoichiometric Ge 1 Sb 2 Te 4 NWs [ [12] M. Longo et al., Nano Lett., 12 (2012) 1509]. The typical diameter of the obtained NWs resulted to be 50 nm, with lengths up to 3 μm. The typology of Au catalyst nanoislands influenced both the NW morphology and the Ge incorporation during the VLS self-assembly; the Ge metalorganic precursor partial pressure affected the NW morphology and their structure. Finally, TEM observations revealed that defect-free, monocrystalline Sb 2 Te 3 and Ge-doped Sb–Te phase change NWs could be obtained.

Complexes with acetylacetone Sc(acac)3, dipivaloylmethane Sc(thd)3, 2,2,6,6–tetramethyl-4-fluoro-3,5-heptanedione Sc(tfhd)3, pivaloyltrifluoroacetone Sc(ptac)3, trifluoroacetylacetone Sc(tfac)3, and hexafluoroacetylacetone Sc(hfac)3 were synthesized, purified and identified by elemental analysis, m.p., IR and NMR spectroscopy, and mass spectrometry. The thermal behaviour of the synthesized compounds in the solid state was investigated by the method of difference-scanning calorimetry in vacuum. As a result the thermodynamic characteristics of the melting processes were determined. The temperature dependences of saturated and unsaturated vapour pressure of complexes under study were measured by static method with membrane-gauge manometers. The average molecular weight of gas calculated from the experimental data on unsaturated vapours using ideal gas law was close to the molecular weight of monomer for all investigated compounds. Decomposition temperatures of compounds under study were defined as the temperature above that pressure changes became irreversible. The information about melting and decomposition processes were taken into account at measuring saturated vapour pressure of complexes. The row of volatility Sc(hfac)3 > Sc(ptac)3 > Sc(tfac)3 > Sc(thd)3 ≥ Sc(tfhd)3 > Sc(acac)3 was determined from the p–T dependences obtained. Above information about thermal behaviour of complexes enabled one to use it as a guide for CVD experiments aimed at achieving oxide films with high optical properties. Precursor chosen for film deposition was Sc(thd)3 The Sc2O3 film deposition conditions were following: the gas-carrier rate 1 l/h, He gas-reagent rate 10 l/h, total pressure 10 Torr, evaporator temperature 105-110С, substrate temperature 450- 650С, substrate Si(100). Ellipsometry was applied to characterize the film thickness and refractive index. The morphology and the composition of the films were determined with XPS and SEM.

New volatile heteroleptic copper(II) complexes having beta-ketoiminate (O,N) and diketonate (O,O) ligands in one molecule were tested as precursors for LPCVD of copper films. Saturated vapor pressure was measured and compared for new compounds Cu(ki)(hfa) and Cu(dpk)(hfa), where ki = pentane-2-imino-4-onato, hfa = 1,1,1,5,5,5-hexafluoro-pentane- 2,4-dionato, dpk= 2,2,6,6-tetramethyl-3-iminoheptane-5-onato. The precursors are air stable and non hygroscopic compounds with long shelf life. It was demonstrated that copper metal films can be selectively deposited on metallic surfaces in the presence of hydrogen as a gas-reactant at temperatures of 250, 300, 350 °C and pressure of 20 Torr. Si(100), SiO2 (melted quartz), stainless steel, and Cu, Al, RuO2, Ru and Ta sublayers on Si(100) were tested as substrate materials. Deposited films were analyzed and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Dimethylgold(III) complexes with S,S donor ligands having AuC 2 S 2 coordination core are compared as precursors for gold MOCVD. Three of them are liquids, the fourth one is low-melting compound. They are non-sensitive to air and light, stable under storage, do not require special handling conditions, and show a good volatility and sufficient vaporization stability. Based on monitoring of the gas phase during the programmed heating of the compound vapor in vacuum, in hydrogen and in oxygen presence, the information concerning stability of the precursor in the gas phase and gaseous products of thermolysis was obtained. It was established that decomposition mechanism in the presence of the studied gas- reactants changed in comparison with vacuum only for diethyldithiocarbamate complex. MOCVD experiments have been performed within the temperature range 210-300 o C with and without hydrogen or oxygen. The films obtained in hydrogen presence were more thick indicating higher growth rate. Effect of gas-reactant on the morphology of the films deposited is discussed.

Status of the technology in sensitive and fast-response detection of the mid-infrared radiation with devices based on variable gap HgCdTe heterostructures working without cryocooling. Recent efforts were concentrated on performance approaching fundamental limits for whole 2-13 μm range, the extension of useful spectral range above 13 μm and sub-nanosecond response time and.

Zinc oxide (ZnO) nanowire (NW) arrays were grown on Si (100) substrate by metal-organic chemical vapor deposition (MOCVD) via Zn[TMHD]2 as precursor. Here we adopted two different procedures to grow ZnO NWs namely, colloid and sputtered Au pre-deposition on Si (100) substrate. Comparative studies based on the morphology and growth behavior of ZnO NWs were performed. The grown ZnO NWs were characterized by field-emission scanning electron microscopy (FE-SEM), Atomic Force Microscopy (AFM), Co-focal laser scanning microscopy (CLSM), and Raman spectroscopy.

In this article we summarize our results on the fabrication process of the Ni-Cr-W biaxially textured tape, which is non-magnetic at 77 K. The deposition processes of the buffer and HTS layers by reel-to-reel MOCVD technology are described as well. The HTS wire is finished with reel-to-reel depositions of the silver protective layer by magnetron sputtering and copper stabilizing layer by electroplating. Sharp cubic texture with in-plane and out-of-plane misorientation below 7 degrees and low surface roughness (Ra < 5 nm on 5*5 μm2 area) have been achieved on reel-to-reel processed metallic tapes. The texture characteristics of the MgO buffer layer (ΔωRD = 6.0̊, ΔωTD = 9.0̊, ΔφTRUE = 5.2̊) have been found to be very close to those of the textured substrate tape. Using this structure with additional buffer layers we have succeeded in growing superconducting YBCO coatings with Ic (77 K, s.f.) values higher than 120 A per cm of the tape width at the HTS layer thickness of about 1 μm.

By controlling the deposition parameters of low pressure chemical vapor deposition (LPCVD) grown ZnO transparent conductive oxide (TCO), we show that it is possible to achieve a switch of crystallographic orientations and to obtain novel surface nanotexture. The new layers are (0 0 0 2) oriented and exhibit light scattering at larger angles than state-of-the-art TCO used in thin film silicon solar cells. This property translates into a strong enhancement of the top amorphous cell current in micromorph tandem devices. (C) 2010 Elsevier B.V. All rights reserved.

The Metalorganic Chemical Vapor Deposition process was adopted for the first time to grow GeTe nanowires (NWs) on SiO(2)/Si substrates. The growth occurred in the presence of Au as metal catalyst species on the SiO(2). Morphological, structural and compositional investigations were carried out on the obtained GeTe NWs. Local structural and chemical analyses were also performed on single nanostructures by High Resolution and Analytical Transmission Electron Microscopy. The NWs exhibited random orientations with respect to the substrate surface plane. The typical diameter of the NWs was in the range of 40-60 nm and their lengths up to 4 mu m. The structural measurements showed that both cubic and rhombohedral crystalline phases of GeTe are present in the grown structures. The compositional analyses, either performed on large area or on single nanostructures, yielded Ge(0.45)Te(0.55) composition on average; transmission electron microscopy observations revealed that nanowires with diameter

International audience; Titanium oxynitride coatings were deposited on various substrates by an original atmospheric pressure metal organic chemical vapor deposition (MOCVD) process using titanium tetra-iso-propoxide as titanium and oxygen precursors and hydrazine as a nitrogen source. The films composition was monitored by controlling the N2H4 mole fraction in the initial reactive gas phase. The variation of the N content in the films results in significant changes in morphological, structural and mechanical properties. When a large excess of the nitrogen source is used the resulting film contains ca 17 at % of nitrogen and forms dense and amorphous TiOxNy films. Growth rates of these amorphous TiO1.5N0.5 coatings as high as 14 μm/h were obtained under atmospheric pressure. The influence of the deposition conditions on the morphology, the structure, the composition and the growth rate of the films is presented. For the particular conditions leading to the growth of amorphous TiO1.5N0.5 coatings, first studies on the mechanical properties of samples grown on stainless steel have revealed a high hardness, a low friction coefficient, and a good wear resistance in unlubricated sliding experiments against alumina which make them very attractive as protective metallurgical coatings.

Sarantopoulos, Christos Gleizes, Alain N. Maury, Francis 2nd International Symposium on Transparent Conducting Oxides OCT 22-26, 2008 Crete, GREECE Sp. Iss. SI; Photocatalytically active, N-doped TiO2 thin films were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) using titanium tetra-iso-propoxide (TTIP) as a precursor and NH3 as a reactive doping gas. We present the influence of the growth parameters (temperature, reactive gas phase composition) on the microstructural and physico-chemical characteristics of the films, as deduced from X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultra-violet and visible (UV/Vis) spectroscopy analysis. The N-doping level was controlled by the partial pressure ratio R=[NH3]/[TTIP] at the entrance of the reactor and by the substrate temperature. For R=2200, the N-doped TiO2 layers are transparent and exhibit significant visible light photocatalytic activity (PA) in a narrow growth temperature range (375-400 degrees C). The optimum N-doping level is approximately 0.8 at.%. However, the PA activity of these N-doped films, under UV light radiation, is lower than that of undoped TiO2 films of comparable thickness. (C) 2009 Elsevier B.V. All rights reserved.

International audience; The need of interconnect to separate fuel and oxidant gasses and connect individual cells into electrical series in a SOFC stack appears as one of the most important point in fuel cell technology. Due to their high electrical and thermal conductivities, thermal expansion compatibility with the other cell components and lowcost, ferritic stainless steels (FSS) are nowconsidered to be among the most promising candidate materials as interconnects in SOFC stacks. Despite the formation at 800 ◦C of a protective chromia Cr2O3 scale, it can transform in volatile chromium species, leading to the lost of its protectiveness and then the degradation of the fuel cell. A previous study demonstrated that in air, the application by metal organic chemical vapour deposition (MOCVD) of a nanometric layer of reactive element oxides (La2O3, Y2O3, Nd2O3) on FSS improved both the electrical conductivity and the oxidation resistance. The beneficial effect of this type of coating on FSS on oxidation resistance in H2/H2O (anode side) is not yet completely understood. So, the goal of this study is to apply reactive element oxide coating (La2O3, Y2O3, Nd2O3) on two FSS (a commercial, Crofer22APU, and a model, Fe30Cr) and to perform oxidation tests in H2/10%H2O. Kinetics was registered for 100 h at 800 ◦C and the corrosion products were characterized by SEM, EDX, TEM, SIMS and XRD.

International audience; Since a few years, a lot of research efforts have been devoted to InN, the least known of the semiconducting group-III nitrides. Most of the samples available today have been grown using the molecular beam epitaxy technique, and fewer using the metal organic vapor phase epitaxy (MOVPE) method. Whatever the method, the growth of InN is extremely challenging, in particular due to the fact that no lattice matched substrate is available. This paper present results on the improvement of the InN crystal quality in MOVPE. In particular, the use of carbon halides to enhance the lateral growth is demonstrated, leading to extremely smooth InN surfaces. A new process for the realization of InN nanostructures by recrystallization is presented, which allows to obtain a better crystal quality than direct MOVPE growth

Metal Organic Chemical Vapor Deposition of cubic stabilized zirconia was investigated by the addiction of the alkaline-earth oxides MgO and CaO. While Cp 2 ZrMe 2 [(Cp = –C 5 H 5 , Me = –CH 3 )] was used as precursor for ZrO 2 , two different Mg compounds were tested for the MgO deposition, namely bis-(η 5 -methylcyclopentadienyl)Mg(II) [(Mg(Cp-Me) 2 ] and bis-(2,2,6,6-tetramethyl-3,5-heptanedionate)(tetramethylethylenediamine)Mg(II) [Mg(tmhd) 2 ·tmeda]. Bis-(2,2,6,6-tetramethyl-3,5-heptanedionate)(triethyleneglycoldimethylether)Ca(II) [Ca(tmhd) 2 ·triglyme] was used for CaO growth. Depositions were carried out on fused quartz at 500 °C, yielding colorless and crack-free films well adherent to the substrates. A thorough characterization of their microstructure and chemical composition was obtained by the combined use of XRD (X-ray Diffraction), XPS (X-ray Photoelectron Spectroscopy) and EDXS (Energy Dispersive X-Ray Spectroscopy). The obtained results indicated a complete stabilization of zirconia in its cubic-fluorite phase when the magnesium and calcium content ranged from 12 to 30 at.% and from 17 to 38 at.%, respectively.

One of challenges in improving the performance and cost-effectiveness of solid oxide fuel cells (SOFCs) is the development of suitable interconnect materials. Recent researches have enabled to decrease the operating temperature of the SOFC from 1000 to 800 °C. Chromia forming alloys are then among the best candidates for interconnects. However, low electronic conductivity and volatility of chromium oxide scale need to be solved to improve interconnect performances. In the field of high temperature oxidation of metals, it is well known that the addition of reactive element into alloys or as thin film coatings, improves their oxidation resistance at high temperature. The elements of beginning of the lanthanide group and yttrium are the most efficient. The goal of this study is to make reactive element oxides (La 2 O 3 , Nd 2 O 3 and Y 2 O 3 ) coatings by metal organic chemical vapour deposition (MOCVD) on Crofer 22 APU, AL 453 and Haynes 230 in order to form perovskite oxides which present a good conductivity at high temperature. The coatings were analysed after 100 h ageing at 800 °C in air under atmospheric pressure by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analyses, X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Area-specific resistance (ASR) was measured in air for the same times and temperature, using a sandwich technique with Pt paste for electrical contacts between surfaces. The ASR values for the best coating were estimated to be limited to 0.035 Ω cm 2 , even after 40,000 h use.

Metal-organic chemical vapour deposition (MOCVD) has been used to deposit crystalline films of cobalt metal with a strong crystalline texture. The process parameters were varied to control the grain size, while retaining this texture and a hexagonal habit. These films behave as typical ferromagnetic films, dominated by a balance between shape anisotropy and surface anisotropy, leading to in-plane remanence for films of thickness below 50 nm and a perpendicular component to the anisotropy for thicker films. The domain patterns studied by MFM reflect the in-plane magnetization for the thinner films and the perpendicular anisotropy in the thicker cases, leading to stripe domains. When the grain width is sufficient to support single domains under DC remanent conditions the shape of the magnetic domains is dominated by the grain size and morphology. This occurs for grains around 250 nm across or wider. Some of the largest grains can support a domain wall.

International audience; Nanocrystalline original Cr-based coatings were grown under atmospheric pressure by Direct Liquid Injection Metal Organic Chemical Vapor Deposition (DLI-MOCVD). The thin films were grown below 450 °C in a cold wall CVD reactor from solutions of Cr(CO)6 in toluene or THF injected and flash vaporized with or without NH3 addition prior to the deposition zone. Original nanocrystalline chromium oxycarbide and oxy-carbonitride phases were deposited on stainless steel substrates. The influence of injection parameters and conventional CVD conditions have been investigated on the main chemical, physical and structural characteristics of the coatings, as deduced from XRD, SEM, and EPMA analyses.

Dot array formation of zinc oxide (ZnO) along the linear single steps was demonstrated on sapphire substrates under near atmosphere pressure by metalorganic chemical vapor deposition (MOCVD). Sapphire substrates of ( 1 1 2 ¯ 0 ) , (0 0 0 1) and ( 1 1 ¯ 0 2 ) planes (A-plane, C-plane and R-plane, respectively) were employed as templates for manufacturing the nanostructures. For highly controlling dot array formation the substrates were prepared by annealing at 1000 °C for 3 h in air after chemical treatment. The step arrays were easily prepared on C-plane and R-plane sapphire. The linearly aligned ZnO nanodot arrays were formed on R-plane sapphire along the step edges over several ten micrometers. The result can be attributed to the smaller number of dangling bonds on R-plane than on A-plane and C-plane, enhancing the surface diffusion length. Sapphire can be a good template for manipulating II–VI semiconductor on it to form nanostructures even at near atmosphere pressure by a conventional MOCVD.

International audience; Cr-based coatings were grown under atmospheric pressure in different gaseous atmospheres (N2,H2, NH3) from the thermal decomposition of Cr(CO)6 at 300 °C in a cold-wall CVD reactor. Cr(CO)6 is a good candidate as precursor because of its low cost and its high volatility, which permits high flow rates. Original chromium oxycarbide and oxynitride coatings were deposited on steel. These phases were previously obtained by plasma-assisted CVD and low-pressure CVD, i.e., under nonequilibrium conditions. In the present work, the low deposition temperature likely accounts for their formation. We have investigated correlations between the growth conditions and their main chemical, structural and physical features. Preliminary results on the mechanical behavior of these Cr-based coatings are also reported.

We have investigated the effects of thermal annealing processes on Pr2O3/Pr-O-Si system grown using the metal organic chemical vapor deposition (MOCVD) technique from the Pr(tmhd)(3) [(H-tmhd = 2,2,6,6-tetramethylheptane-3,5-dione)] precursor. The influence of different atmospheres (Ar and O-2) during the annealing process has been investigated using transmission electron microscopy (TEM). The annealing processes have been carried out at two different temperatures, 800 and 900 degrees C, for 4 h. The praseodymium films have been found to be stable in argon atmosphere up to 800 degrees C whilst at 900 degrees C the film crystallization has been observed. On the other hand, in oxygen environment, evidence of crystallization processes has already been detected at 800 degrees C. The electron diffraction patterns of the crystallized films have shown some of the most intense reflections of the stoichiometric Pr8Si6O24 phase.

International audience; We demonstrate that the phonon frequencies that are reported in the literature for indium nitride (InN), films are all consistently correlated to the strain state of the material. Raman spectroscopy measurements and X-ray investigations of large size InN quantum dots grown on c-plane GaN are combined, which show these frequencies to experience a blue shift with increasing compression. The InN dots are weakly strained, most probably due to the formation of dislocations at the InN/GaN interface. We report the observation of a broad absorption in the 1.25 eV region that is typical of thin InN films. Such a feature we attribute to light absorption at the energy of the fundamental direct band gap of InN, while we attribute the low energy 650-800 meV photoluminescence to an extrinsic recombination process analogous to the processes that produce the blue band in AlN and the yellow band in GaN. (C) 2004 Elsevier B.V. All rights reserved.

Selective formation of ZnO nanodots grown by metalorganic chemical vapor deposition (MOCVD) was achieved on focused-ion beam (FIB)-nanopatterned SiO2 and Si substrates. The selective formation characteristics, dimension, and density of ZnO nanodots on FIB-nanopatterned substrates strongly depended on the FIB-patterning and MOCVD-growth conditions. The mechanism of the selective formation of ZnO nanodots on FIB-nanopatterned SiO2 substrates is attributed to a surfactant effect of the implanted Ga which leads to the formation of the preferred nucleation sites for the growth of ZnO nanodots, while that of ZnO nanodots on nanopatterned Si substrates is mainly considered in terms of the generation of surface atomic steps and kinks, which are created by Ga+ ion sputtering, on the patterned Si areas.

Optical, compositional, and structural properties of strontium bismuth tantalate (SBT) films deposited in a high throughput low-pressure chemical vapor deposition reactor using liquid metal-organic precursors were characterized using three non-destructive techniques, spectroscopic ellipsometry (SE), Rutherford backscattering spectrometry (RBS), and X-ray diffraction (XRD). The thicknesses and the refractive indices of the SBT layers were calculated with SE using different parametric dielectric function models. The samples were characterized with RBS using different tilt angles and probe ions to enhance the depth resolution and the mass separation. Comparison with SE measurements supports the results of Bahng et al. revealing an increasing refractive index (n) with increasing Bi/Sr ratio. The decreasing grain size measured by XRD was reflected as a decrease of n in the SE measurement. We show that RBS, XRD, and SE supply a wide range of information about the SBT layers, which can be used for qualification as well as for feedback to layer production. The results suggest that by SE, being used as in situ or in line characterization tool, the control of even complex MOCVD deposition looks feasible.

The new chloro(cyclopentadienyl)silanes Cp'SiHyCl3-y, (Cp' = Me4EtC5, y = 1: 1; Cp' = Me4C5H, y = 1: 2; y = 0: 3; Cp' = Me3C5H2, y = 1: 4 and pentachloro(cyclopentadienyl)disilanes Cp'Si2Cl5 (Cp' = Me5C5 5, Me4EtC5 6, Me4C5H 7, Me3C5H2 8, Me3SiC5H4 9) are synthesized in good yields via metathesis reactions. Treatment of 1-9 with LiAlH4 leads under CI-H exchange to the hydridosilyl compounds Cp'SiH3 (Cp' = Me4EtC5 10, Me4C5H 11, Me3C5H2 12) and to the hydridodisilanyl compounds Cp'Si2H5 (Cp' = Me5C5 13, Me4EtC5 14, Me4C5H 15, Me3C5H2 16, Me3SiC5H4 17). Complexes 1-17 are characterized by H-1, C-13, and Si-29-NMR spectroscopy, IR spectroscopy, mass spectrometry and CH-analysis. The structures of 6, 7 and 9 are determined by single-crystal X-ray diffraction analysis. Pyrolysis studies of the cyclopentadienylsilanes 10-12 and disilanes 13-17 show their suitability as precursors in the MOCVD process. (C) 2001 Elsevier Science B.V. All rights reserved.

The substrate orientation dependence of Zn incorporation on the nongrowing surface in the AsH 3 containing ambient was investigated using Zn δ-doped layers in GaAs grown by metal organic vapour-phase epitaxy (MOVPE). We found that the Zn δ-doping concentration significantly decreases with an increase of the (1 0 0) off-angle towards (1 1 1)B along the [0 1 1 ] direction. The Zn incorporation on the nongrowing As-terminated (1 1 1)B surface is negligible. A notable increase of the Zn incorporation was observed with increasing the (1 0 0) off-angle towards (1 1 1)A, while the maximum Zn δ-doping concentration was obtained on the (3 1 1)A surface. The Zn density decreases with a further increase in the (1 0 0) off-angle towards (1 1 1)A after (3 1 1)A. Based on the bonding configurations of the nongrowing surface, the possible mechanism of orientation effect on Zn incorporation is discussed.

We grew an InGaN/GaN-based light-emitting diode (LED) wafer by metal–organic chemical vapor deposition (MOCVD), fabricated devices by optical lithography, and successfully deposited ellipsoidal Ag nano-particles by way of e-beam lithography on top. The diodes exhibited good device performance, in which we expected an enhancement of the radiated intensity by the simulations and emission measurements. The obtained results showed the feasibility of plasmon-assisted LED emission enhancement. # 2007 Published by Elsevier B.V.

Modulation doped field effect transistors (MODFETs) with a p + -GaAs gate structure were fabricated from AlGaInP/ GaInAs/GaAs heterostructures for the first time. Self-aligned devices with a gate length of 0.7 μm exhibit drain currents of 330 mA mm –1 , transconductances of 200 mS mm –1 and very small gate currents below 50 nA even at gate-source voltages of – 5 V. Furthermore, large gate-drain diode breakdown voltages in excess of 30 V are observed. Short gatelength devices (0.3 μm) show a good r.f. performance with a current gain cut-off frequency of 60 GHz and a maximum frequency of oscillation of 140 GHz.