Room temperature pulsed laser deposition of Si x C thin films in different compositions

Amorphous silicon–carbon alloy films in different compositions were prepared by pulsed laser deposition from two-component targets containing pure silicon and carbon parts. The silicon–carbon ratio in the films was varied by adjusting the number of laser shots on the constituent silicon and carbon targets. The composition, optical properties, thickness, and bonding structure of the films were determined by backscattering spectrometry, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy, respectively. Backscattering spectrometry data were used to determine the deposition rate of silicon and carbon. This enabled the calculation of the number of the shots onto each target to reach a predefined composition. As the film composition changed from carbon to silicon, it was shown that the microscopic and macroscopic properties of the films also changed from a diamond-like carbon phase to an amorphous silicon phase via graphite- and silicon-carbide-like composite.     

Manufacturing of Sputtering Composite Targets Containing Phases of Co<Subscript>2</Subscript>FeSi or Co<Subscript>2</Subscript>MnSi Heusler Alloy

The paper presents a method for manufacturing mechanically strong sputtering composite targets containing the phase of the Co₂FeSi or Co₂MnSi Heusler alloy of the stoichiometric composition, which can be used for fabrication of spin electronic devices by high-frequency magnetron deposition and pulsed laser deposition of thin films.     

Study of graded Ni-Ti shape memory alloy film growth on Si(100) substrate

In-situ X-ray diffraction (XRD) was employed to study the effect of the deliberate change of the Ti/Ni ratio during the deposition of Ni-Ti films. Thus, graded films were deposited exhibiting distinctive composition and crystalline structure along the growth direction. The as-sputtered films were ex-situ characterized by Auger electron spectroscopy (AES), cross-sectional transmission electron microscopy (XTEM), and electrical resistivity (ER) measurements (during thermal cycling). In this paper results are presented concerning a film (thickness of ≈ 420 nm) with a Ti-rich composition in the central part (ranging from 50 to ≈60 at. %) and near-equiatomic composition in the extremities, following four distinct deposition periods (different Ti target powers). During the initial deposition step (near-equiatomic composition) the Ni-Ti B2 phase starts by stacking onto (h00) planes on the naturally oxidized Si(100) substrate due to the presence of the native Si oxide (2–3 nm). The increase of the power of the Ti target in the second and third steps induced the precipitation of Ti₂Ni. When stopping the Ti co-sputtering, Ti₂Ni dissolves and, thus, plays the role of a Ti reservoir for the formation of B2 phase now preferentially stacking onto (110) with the system approaching again the equiatomic composition. The ex-situ study of the morphology of the interface has shown the presence of NiSi₂ silicides (A-NiSi₂ and B-NiSi₂), Ti₄Ni₄Si₇, Ti₂Ni and a non-identified phase constituted by Ni, Ti and Si, most likely amorphous. During thermal cycling, ER measurements revealed phase transitions associated with the B2, R-phase and B19^′ phases. These type of studies allow the identification of intermediate states during deposition and annealing, and the correlation with the final structure of the film, being useful for the optimisation of the deposition parameters in order to fabricate films with a two-way reversible actuation. PACS 81.15.Cd; 61.10.Nz; 68.55.Jk     

Temperature effect on photolytic deposition of platinum ohmic contacts and schottky diodes

An argon laser is used to induce Laser Chemical Vapor Deposition (LCVD) of platinum using platinum bihexafluoroacetyl-acetonate as precursor. The process can be photolytic or pyrolytic depending on the laser power used. These processes are studied by recording the laser light transmitted through of deposit and substrate. Photolytic deposition takes place either in the adsorbed phase or in the gaseous phase depending on the temperature induced by radiation absorption. The induced-temperature calculation using a model developed by us confirms the experimental results obtained. The influence of the substrate base temperature and the precursor product vapour pressure confirms photolytic deposition from the adsorbed phase for low powers and from the vapour phase onwards for high powers. The deposits obtained present a typical 96% Pt composition and its use in Schottky diode manufacture permit obtaining devices with good characteristics in spite of experimental limitations.     

Formation and stability of Al-Mn quasicrystalline thin films prepared by high temperature successive deposition

This article reviews the results on the formation of i-QC thin films prepared by high-temperature successive deposition in the Al-Mn system and the metastable quasicrystalline Al₄Mn and crystalline Al₆Mn phase transformation in detail. Experimental evidence is given for the location of the solid-phase reaction. New data concerning the effects of preparation parameters (temperature, Mn deposition rate, composition) on the formation processes are reported. The phase formation and transformation processes are described by the combination of thermodynamic and kinetic factors.     

金属离子掺杂对TiO2/白云母纳米复合材料中TiO2的颗粒形态及相组成的影响

采用化学液相沉积法制备了系列未掺杂和掺杂不同金属离子的TiO2白云母纳米复合材料.利用扫描电子显微镜(SEM),x射线衍射(XRD)对其TiO2薄膜的TiO2颗粒形态和相组成进行了详细研究.结果表明,TiO2颗粒在15—50nm之间;除球形颗粒外,掺杂Mn2+,Zn2+的样品中还出现有金红石柱状颗粒.TiO2薄膜中相组成以锐钛矿、金红石共存为特征;掺杂金属离子对TiO2相组成的影响取决于金属离子的离子半径、电荷及配位体特征. 关键词： 金属离子掺杂 TiO2 颗粒形态 相组成     

Photocatalytic activity of nanostructured TiO2 films produced by supersonic cluster beam deposition

The photocatalytic activity of thin, nanostructured films of titanium dioxide, synthesized by supersonic cluster beam deposition (SCBD) from the gas phase, has been investigated employing the photodegradation of salicylic acid as test reaction. Because of the low deposition energy, the so-deposited highly porous TiO₂ films are composed of nanoparticles maintaining their original properties in the film, which can be fully controlled by tuning the deposition and post-deposition treatment conditions. A systematic investigation on the evolution of light absorption properties and photoactivity of the films in relation to their morphology, determined by AFM analysis, and phase composition, determined by Raman spectroscopy, has been performed. The absorption and photocatalytic activity of the nanostructured films in the visible region could be enhanced either through post-deposition annealing treatment in ammonia containing atmosphere or employing mild oxidation conditions, followed by annealing in N₂ at 600 °C.     

YGdBCO/YBCO+BaHfO3 复合超导层的制备

采用脉冲激光沉积和化学溶液沉积相结合制备超导薄膜. 在物理法制备的 YGdBCO 薄膜上实现化学法YBCO+BHO 的同质外延生长. 利用 X 射线衍射和扫描电镜对复合薄膜的相组成、 织构和形貌进行了表征. 结果表明, 采用化学溶液沉积可以在 YGdBCO 层上制备出高性能的 YBCO+BHO 薄膜. 复合薄膜具有良好表面形貌和锐利织构, 而且复合薄膜在77 K、1 T 的磁场下J c 为0.3 MA/cm2 , 最大钉扎力达到3 GN/m3 .     

Temperature dependences of optical properties,chemical composition,structure,and laser damage in Ta2O5 films

Ta2O5 films are prepared by e-beam evaporation with varied deposition temperatures,annealing temperatures,and annealing times.The effects of temperature on the optical properties,chemical composition,structure,and laserinduced damage threshold(LIDT) are systematically investigated.The results show that the increase of deposition temperature decreases the film transmittance slightly,yet annealing below 923 K is beneficial for the transmittance.The XRD analysis reveals that the film is in the amorphous phase when annealed below 873 K and in thehexagonal phase when annealed at 1073 K.While an interesting near-crystalline phase is found when annealed at 923 K.The LIDT increases with the deposition temperature increasing,whereas it increases firstly and then decreases as the annealing temperature increases.In addition,the increase of the annealing time from 4 h to 12 h is favourable to improving the LIDT,which is mainly due to the improvement of the O/Ta ratio.The highest LIDT film is obtained when annealed at 923 K,owing to the lowest density of defect.     

Formation of ultrathin iron magnetic films on the silicon vicinal surface

Physics of the Solid State - The phase composition, electronic structure, and magnetic properties of ultrathin layers of iron and iron silicides formed upon deposition of 1- to 25-Å-thick Fe...     

Electrophoretic deposition of PVA coated hydroxyapatite on 316L stainless steel

Polyvinyl alcohol (PVA) coated hydroxyapatite was deposited onto a 316L stainless steel substrate by electrophoretic deposition. Deposition was carried out in a methanol suspension at pH 5.5 using a graphite rod as an anode. Parameters such as PVA concentration, deposition voltage and time were optimized to achieve a homogeneous, crack-free adhesive coating. Techniques such as X-ray diffraction and Fourier transform infrared spectroscopy were used to study the phase composition of the coated materials and the stability of hydroxyapatite in the presence of PVA.     

Production of nanocrystalline silicon layers using the plasma enhanced chemical vapor deposition from the gas phase of silicon tetrafluoride

The production of silicon layers using plasma enhanced chemical vapor deposition in the mixture of silicon tetrafluoride and hydrogen is reported. The samples have been analyzed by X-ray diffraction, Raman spectroscopy, and secondary ion mass spectrometry. The phase composition of the layers is nanocrystalline silicon with the crystalline-domain sizes from 3 to 9 nm in dependence of the conditions of the process. The samples are characterized by intense photoluminescence at room temperature.     

Phase composition of Ti-C Films obtained under the technological conditions of diamond formation at a carbon content of above 50 at. %

The phase composition of Ti-C films (with the carbon content varying from 50 to 100 at. %) is studied by electron diffraction. The films are obtained by C and Ti ion sputtering followed by vapor deposition in the regime of the lowest possible supersaturation. It is found that the condensation in a certain proportion of components leads to the formation of a TiC₂ compound, which has the bcc lattice with a period of 0.294 nm. When the carbon content is increased above 64 at. %, a transition to the diamond phase is observed.     

Growth of a textured quasicrystalline phase in Ti-Ni-Zr films prepared by pulsed laser deposition

The preparation in thin film form of the known icosahedral phase in Ti-Ni-Zr bulk alloys has been investigated as a function of substrate temperature. Films were deposited by pulsed laser deposition on sapphire substrates at temperatures ranging from room temperature to 350 °C. Morphological and structural modifications have been followed by grazing-incidence and θ–2θ X-ray diffraction, transmission electron diffraction and imaging. Chemical composition has been analyzed by electron probe microanalysis. The in-depth variation of composition has been studied by secondary neutral mass spectroscopy. We show that pulsed laser deposition at 275 °C makes the formation of a 1-μm-thick film of Ti-Ni-Zr quasicrystalline textured nanocrystallites possible. Received: 7 June 2001 / Accepted: 18 February 2002 / Published online: 3 June 2002 RID="*" ID="*"Corresponding author. Fax: +33-3/8357-6300, E-mail: brien@mines.u-nancy.fr     

纳米FePt颗粒:MgO多层复合薄膜的外延生长、微观结构与磁性研究

采用脉冲激光沉积法,在MgO(100)面上外延生长了FePt:MgO多层纳米复合薄膜,FePt成分为Fe48Pt52.FePt纳米颗粒周期性嵌埋于单晶MgO外延层中.原位反射式高能电子衍射分析结果表明,MgO外延层呈层状生长,而FePt纳米颗粒呈岛状生长.在整个FePt:MgO纳米复合薄膜的生长过程中,成功实现了层状-岛状生长模式的交替控制.高分辨透射电子显微镜分析结果表明,退火热处理后,结晶完整的L10-FePt纳米颗粒粒径约为5 nm,呈扁平六角形状,在MgO基底上形成逐层排列的纳米点阵.磁滞回线结果表明,退火后薄膜矫顽力增大,有序度提高,磁性增强.     

Magnetic properties and metastable states of Co-Ir films

The phase composition, crystal structure, and magnetic properties of Co_{1 ? x} Ir _x alloy films with x = 0.35–0.8 and fabricated by chemical deposition are studied. Saturation magnetization vs. composition and temperature, coercivity, and magnetization reversal of the films are investigated experimentally. It is shown that in the region of equiatomic composition, Co-Ir films have a two-phase hexagonal close-packed structure that alternates with disordered regions, producing halos in electron diffraction patterns.     

Parametric study of Al and Al2O3 ceramic coatings deposited by air plasma spray onto polymer substrate

Aluminum and ceramic (Al₂O₃) coatings were deposited onto the polymer substrate by air plasma spray (APS) to improve the mechanical properties of the polymer surface. The effect of spray parameters (current and spray distance in this paper) on the phase composition, microstructure and mechanical properties was investigated. Shear adhesion strength between the coatings and the substrates was also examined. The results indicate that the deposition parameters have a significant effect on the phase composition, microstructure and mechanical properties of as-spayed coatings. The maximum shear adhesion strength of the bond coats was 5.21 MPa with the current of 180 A and 190 mm spray distance.     

Magnetic and structural properties of nanocomposite Co-Ni-Cr-Al-Y-N thin films

The relation between structural and magnetic properties of Co-Ni-Cr-Al-Y-N thin films deposited by reactive r.f. magnetron sputtering was investigated. A marked change in the magnetic behaviour of the films with the different nitrogen partial pressure in the Ar/N₂ deposition atmosphere was observed and qualitatively explained in correlation with the phase composition. The nanocrystalline metal solid-solution obtained at low N₂ content and the nanocrystalline nitride/amorphous composite obtained at high N₂ content are not magnetic, whereas the amorphous phase produced for intermediate N₂ pressures behaves like a ferromagnetic semi-permanent material. The results demonstrate the possibility of modulating the magnetic properties of r.f. magnetron sputtered Co-Ni-Cr-Al-Y-N thin films, thus opening a new route for magnetic multilayer deposition. PACS 68.55.-a; 75.70.Ak; 75.75.+a; 85.70.-w     

Phase formation and control of morphology in sputtered Cu-In alloy layers

The dependence of structural properties and surface morphology of Cu-In alloy layers on the composition and sputtering deposition sequence were investigated by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The properties of the co-sputtered alloy layers changed abruptly around the composition boundary when the Cu/In ratio reached 1/2. This can be explained by the effective heat of formation (EHF) model, which has been used to predict the sequence of phase formation for metal diffusion couples. The use of a co-sputtered alloy layer with a high In concentration was not suitable for fabricating solar cells, because the film had a very rough morphology due to large In islands formed on the CuIn₂ phase. However, it was possible to minimize this phase by In sputtering followed by co-sputtering with a Cu/In ratio of 1 (Cu-In/In/Glass). This permitted the fabrication of a homogeneous Cu-In alloy layer, which was not possible through the simple co-sputtering.     

Evolution of properties in composite carbon films under thermal conditions and in the presence of a catalyst

The characteristics of composite carbon films are experimentally studied. The films are synthesized under concurrent conditions of the magnetron and plasmatron sputtering of molybdenum disilicide and polyphenyl methylsiloxane (PPMS 2/5). Automodulation of the elemental and phase composition is found and studied in the direction of film deposition onto the substrate. The stability of the automodulation parameters to subsequent high-temperature annealing is examined.