Ti-Si-N films prepared by plasma-enhanced chemical vapor deposition

Ti-Si-N thin films were deposited on HSS substrates at 560°C using plasmaenhanced chemical vapor deposition. Feed gases used were TiCl₄, SiCl₄, N₂, and H₂. The composition of the films could be controlled well through adjustment of the mixing ratio of the chlorides in the feed gases. The Si content in the film varied in the range of O to 40 at. %. It was jbund that a small addition of Si to a TiN film improved the morphology significantlv, showing dense and glasslike structure. Also a much smootherand more homogeneous interface between thefilm and the substrate was obtained. The Ti-Si- N films containing 10–15 at. % Si showed the maximal microhardness value of about 6350 kgf/mm², much higher than that of TiN films.     

Magnetic characteristics of Fe4N epitaxial films grown by halide vapor phase deposition under atmospheric pressure

The thin films of Fe₄N, which were prepared by atmospheric pressure halide vapor phase deposition, were epitaxially grown on a MgO(100) substrate and have cubic structure with good crystallinity. The magnetic characteristics of Fe₄N epitaxial film show soft magnetic behavior under various temperatures and various external magnetic field directions. As the temperature is decreased, the saturation magnetization increases. Also, the magnetized behavior is observed when the magnetic field is applied parallel to the film plane. It was found that the magnetic moments of Fe₄N epitaxial film are facing parallel to the film plane.     

Crystal quality,electrical and optical properties of single crystal pyrite films prepared by chemical vapor deposition under atmospheric pressure

Crystal quality, electrical and optical properties of single crystal thin films of pyrite prepared by means of chemical vapor deposition under atmospheric pressure (AP-CVD) using FeCl₃ and CH₃CSNH₂ as starting materials have been studied by various analytical method. X-ray diffraction and pole figure measurements showed that the as-grown films are single crystal. It was found that the quality of the pyrite films grown on a Si(100) substrate is significantly dependent upon the ratio of CH₃CSNH₂:FeCl₃ used as source materials. Electrical conductivity and Hall mobility increases as the CH₃CSNH₂:FeCl₃ ratio is increased, while carrier concentration decreases. This is explained in term of the formation of sulphur vacancies. A decrease of the CH₃CSNH₂:FeCl₃ ratio causes the increase of sulphur defects in the pyrite film. This also increases the number of electrons being trapped by the defects, while their mobility is reduced because of the electron being scattering at the vacancies. Strong absorption occurs in the photon energy range higher than 1 eV, and then reaches plateau with an absorption coefficient of about $5\times {10}^4{\text{cm}}^{-1}$ at $E>2\text{eV}$.     

Evolution of crystalline structure in SnS thin films prepared by chemical deposition

Crystal structure and morphology undergo significant evolution in thin films of tin(II) sulfide prepared by chemical deposition, over a narrow interval of bath temperature of 20–40 °C, but has not been recognized in previous studies. The chemical bath is constituted using tin(II) chloride, triethanolamine, ammonia(aq.) and thioacetamide. At bath temperature of 20 °C, the deposition rate of the film is 10 nm/h; and at 24 h, a film of thickness 260 nm is obtained. This film is compact and with a predominantly cubic (Cub-) crystalline structure. At 40 °C, the deposition rate is 25 nm/h, and a film of 600 nm in thickness is deposited in 24 h. However, this film has evolved into vertically stacked platelets of orthorhombic (OR-) crystalline structure. The transition from compact-to-platelet morphology as well as from Cub-to-OR-crystalline structure is observed near a deposition temperature, 35 °C. The Cub-SnS has a characteristic high optical band gap, 1.67 eV (direct gap; forbidden transitions) with an electrical conductivity, 10⁻⁷(Ω cm)⁻¹; both properties being un-affected when films are heated at 300 °C in a nitrogen ambient. In OR-SnS, the band gap is 1.1 eV (indirect gap; allowed transitions). The electrical conductivity of such films is notably higher, 10⁻⁴ (Ω cm)⁻¹, which increases further by an order of magnitude when the films have been heated at 300 °C in nitrogen.     

Epitaxial growth of high purity cubic InN films on MgO substrates using HfN buffer layers by pulsed laser deposition

Cubic InN films have been grown on MgO substrates with HfN buffer layers by pulsed laser deposition (PLD). It has been found that the use of HfN (100) buffer layers allows us to grow cubic InN (100) films with an in-plane epitaxial relationship of [001]_InN//[001]_HfN//[001]_MgO. X-ray diffraction and electron back-scattered diffraction measurements have revealed that the phase purity of the cubic InN films was as high as 99%, which can be attributed to the use of HfN buffer layers and the enhanced surface migration of the film precursors by the use of PLD.     

Influence of deposition pressure on hydrogenated amorphous carbon films prepared by d.c.‐pulse plasma chemical vapor deposition

Hydrogenated amorphous carbon films (a‐C : H) were prepared by d.c.‐pulse plasma chemical vapor deposition using CH₄ and H₂ gases. The microstructure and hardness of the resulting films were investigated at different deposition pressures (6, 8, 11, 15, and 20 Pa). The growth rate increased sharply from 3.2 to 10.3 nm/min with increasing the pressure from 6 to 20 Pa. According to Raman spectra, XPS, and Fourier transform infrared analysis, the films deposited at the pressure of 6 and 8 Pa have high sp³ content and show typical diamond‐like character. However, the microstructures and bond configuration of the films deposited at 11, 15, and 20 Pa have high sp² content and favored fullerene‐like nanostructure. The hardness and sp² content were shown to reach their minimum values simultaneously at a deposition pressure of 8 Pa and then increased continuously. The film with fullerene‐like nanostructure obtained at 20 Pa displays a high Raman I_D/I_G ratio (~1.6), and low XPS C 1s binding energy (284.4 eV). The microstructural analysis indicates that the films are composed of a hard and locally dense fullerene‐like network, i.e. a predominantly sp²‐bonded material. The rigidity of the films is basically provided by a matrix of dispersed cross‐linked sp² sites. Copyright © 2012 John Wiley & Sons, Ltd.     

Alloys prepared by plasma-enhanced chemical vapor deposition (PECVD)

Three different techniques for the deposition of thin metal alloy films by plasma-enhanced chemical vapor deposition are described. These are the joint vaporization of a mixture of precursors, the use of separate sources connected directly to the reactor, and finally, the use of several reservoirs arranged in series. Various organometallics have been used as precursors to prepare combinations of Fe/Co and Au/Pt/Pd.     

Titanium arsenide films from the atmospheric pressure chemical vapour deposition of tetrakisdimethylamidotitanium and tert-butylarsine

Thin films of titanium arsenide have been deposited from the atmospheric pressure chemical vapour deposition (APCVD) of [Ti(NMe(2))(4)] and (t)BuAsH(2) at substrate temperatures between 350-550 °C. Highly reflective, silver coloured films were obtained which showed borderline metallic-semiconductor resistivities. The titanium arsenide films were analyzed by scanning electron microscopy (SEM), Raman spectroscopy, wavelength dispersive analysis of X-rays (WDX), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The films showed variable titanium to arsenic ratios but at substrate temperatures of 500 and 550 °C films with a 1 : 1 ratio of Ti : As, consistent with the composition TiAs, were deposited. Powder XRD showed that all of the films were crystalline and consistent with the formation of TiAs. Both nitrogen and carbon contamination of the films were negligible.     

Characterization of iron catalysts prepared by chemical vapor deposition on nonzeolitic supports

Chemical vapor deposition (CVD) of FeCl3 has been used to deposit Fe3+ ions on the surface of sulfated zirconia (SZ) and silica-alumina (SA). Upon exposure to FeCl3 vapor most Br?nsted acid sites and silanol groups are replaced by Fe, as evidenced by IR. With SZ the concentration of the acid sites and thus the retention of Fe increase with the sulfate loading up to approximately 45% of a monolayer, followed by an abrupt decrease at higher loadings. This indicates condensation of sulfate groups to polysulfates, which is in line with a lower number of Br?nsted sites per sulfate. Release of HCl due to the reaction of Br?nsted sites with FeCl3 peaks at 85 degrees C for SZ but only at 345 degrees C for SA. After replacing Cl- by OH- and calcining, the materials were tested as De-NOx catalysts and characterized by temperature-programmed reduction (TPR) with H2 or CO. Mononuclear and dinuclear oxo-ions of Fe coexist with Fe oxide particles in calcined Fe/SA, resulting in a low selectivity for NOx reduction. During reduction of Fe/SA up to 800 degrees C, a significant fraction of the Fe forms a chemical compound with SA, possibly an aluminate. In Fe/SZ the Fe dramatically increases the reducibility of the sulfate groups, from 57% partial reduction to SO2 in the absence of Fe, to 90% deep reduction to S2- ions in its presence. Formation of Fe sulfide is indicated by the enhanced sulfur retention upon reduction. Fe/SZ is active for NOx reduction with isobutane. Catalysts with low Fe content that are prepared by controlled sublimation are superior to those prepared by impregnation. At 450 degrees C and GHSV = 30,000 h(-1), 65% of NOx is reduced to N2 in excess O2.     

Microscopic investigations of the indium nitride crystals with flower-like morphology grown by means of halide chemical vapour deposition under atmospheric pressure

Indium nitride prepared under atmospheric pressure using a halide chemical vapour deposition method has been examined by means of a variety of analytical techniques. From the scanning electron microscopic observations of the crystals deposited onto a Si(100) substrate, it was found that they have flower-like morphology. Based on the electron diffraction and X-ray photoelectron spectroscopic analyses, it was deduced that the flower-like InN crystals have a stoichiometry close to In:N=1:1. Transmission electron diffraction and selected area electron diffraction images showed that each petal and a style constituting the flower are of single crystals form with staggered hexagonal bipyramidal structure.     

Carbon-containing nano-titania prepared by chemical vapor deposition and its visible-light-responsive photocatalytic activity

Ultraviolet and visible-light-responsive titania was synthesized and employed in the NO_x photomineralization. A thermal decomposition reaction of titanium isopropoxide was carried out with a metal-organic chemical vapor deposition (MOCVD), enabling continuous production of TiO₂ nanoparticles. Carbon-containing titanium dioxide with the anatase phase prepared at 500 °C under nitrogen atmosphere exhibited high photocatalytic activity for NO oxidation under visible-light illumination. Experimental results indicate that up to 48% removal of NO_x can be achieved in a continuous flow type of reaction system under visible-light illumination (green LED). The chamber temperature in this MOCVD process plays an important role in lattice structure formation, and also affected TiO₂ carbon content. The carbonaceous species on the TiO₂ surface, shown by X-ray diffractometry (XRD), and Raman, UV–vis, and X-ray photoelectron spectroscopies (XPS), is important to the visible-light absorption and visible-light-catalytic mineralization of NO_x.     

A general atmospheric pressure chemical vapor deposition synthesis and crystallographic study of transition-metal sulfide one-dimensional nanostructures

A series of transition-metal sulfide one-dimensional (1D) nanostructures have been synthesized by means of a general atmospheric pressure, chemical vapor deposition (APCVD) strategy. Vapour-liquid-solid (VLS) and vapour-solid (VS) mechanisms, along with the results of SEM and TEM observations, were used to explain the formation of these nanostructures. The regularity of the growth in the direction of the hexagonal nanowire is explored; we find that it prefers to grow along (1 0 0), (1 1 0), or (0 0 x) directions owing to particular crystal structures. The adopted synthetic route was expected to provide abundant useful 1D building blocks for the research of mesoscopic physics and fabrication of nanoscale devices.     

Deposition of thin films and coatings by atmospheric pressure vapor plasma jet

An atmospheric pressure plasma jet generated by inductively coupled RF discharge and containing vapors of silicon compounds in argon-carrier gas was used to deposit a-Si∶H, a-Si∶(H, O), and a-SiC film. Rapid deposition up to 10 μm/min results from efficient material transport and is limited mainly by rates of surface reactions. Morphology, structure, and composition of deposits were studied.     

X-ray diffraction area mapping of preferred orientation and phase change in TiO2 thin films deposited by chemical vapor deposition

This paper reports on an investigation into the formation of TiO(2) thin films, whereby X-ray diffraction is used to map systematic changes in preferred orientation and phase observed throughout the films. The key to this strategy is the recording of X-ray diffraction patterns of specific and isolated areas of a substrate, ensuring this specificity by the use of a small X-ray sample illumination area (approximately 3-5 mm(2)). A map of the variation in film composition can then be built up by recording such diffraction patterns at regular intervals over the whole substrate. Two titania films will be presented, grown using atmospheric pressure chemical vapor deposition, at 450 and 600 degrees C, from TiCl(4) and ethyl-acetate precursors. The film grown at 450 degrees C showed a systematic change in preferred orientation, while the film grown at 600 degrees C was composed of a mixture of the rutile and anatase phases of TiO(2) with the ratio of these phases altering with position on the substrate. The results of physical property measurements and electron microscopy carried out on the films are also reported, conducted at locations identified by the X-ray diffraction mapping procedure as having different compositions, and hence different physical responses. We found that the photocatalytic activity and hydrophobicity were dependent on the rutile:anatase ratio at any given location on the film.     

Analysis of orientation fluctuation in fluids by small angle X-ray scattering

The small angle X-ray scattering of molecular fluids contains information on particular aspects of their orientational order. Examples are given for the case of the isotropic, nematic and cholesteric phases of mesogenic molecules. It is shown that the distribution of the molecular centers relative to the direction defined by the molecular long axes can be analysed by means of small angle X-ray scattering. An approximate expression for the circulation correlation function is given.     

Chemical vapor deposition growth of phase-selective inorganic lead halide perovskite films for sensitive photodetectors

Inorganic lead halide perovskites are attractive optoelectronic materials owing to their relative stability compared to organic cation alternatives.The chemical vapor deposition(CVD) method offers potential for high quality perovskite film growth.The deposition temperature is a critical parameter determining the film quality owing to the melting difference between the precursors.Here,perovskite films were deposited by the CVD method at various temperatures between 500-800℃.The perovskite phase converts from CsPb₂Br₅ to CsPbBr₃ gradually as the deposition temperature is increased.The grain size of the perovskite films also increases with temperature.The phase transition mechanism was clarified.The photoexcited state dynamics were investigated by spatially and temporally resolved fluorescence measurements.The perovskite film deposited under 750℃ condition is of the CsPbBr₃ phase,showing low trap-state density and large crystalline grain size.A photodetector based on perovskite films shows high photocurrent and an on/off ratio of ~2.5×10⁴.     

Fast growth of graphene on SiO2/Si substrates by atmospheric pressure chemical vapor deposition with floating metal catalysts

Graphene on dielectric substrates is essential for its electronic applications. Graphene is typically synthesized on the surface of metal and then transferred to an appropriate substrate for fabricating device applications. This post growth transfer process is detrimental to the quality and performance of the as-grown graphene. Therefore, direct growth of graphene films on dielectric substrates without any transfer process is highly desirable. However, fast growth of graphene on dielectric substrates remains challenging. Here, we demonstrate a transfer-free chemical vapor deposition (CVD) method to directly grow graphene films on dielectric substrates at fast growth rate using Cu as floating catalyst. A large area (centimeter level) graphene can be grown within 15 min using this CVD method, which is increased by 500 times compared to other direct CVD growth on dielectric substrate in the literatures. This research presents a significant progress in transfer-free growth of graphene and graphene device applications.     

Surface characterization of the SiOx films prepared by a remote atmospheric pressure plasma jet

The deposition rate and surface properties of SiO_x films were prepared and investigated using remote atmospheric pressure plasma (APP) jet. The APP, generated with low frequency power at 16 kHz, was fed with tetraethoxysilane (TEOS)/air gas mixture. After deposition, the SiO_x films were analyzed for chemical characteristics, elemental composition, surface morphology, and hardness. It was found that the deposition substrate temperature is the key factor to affect the deposition rate of remote APP chemical vapor deposition process. Fourier transform infrared (FTIR) spectra indicated that APP deposited SiO_x films are an inorganic feature. XPS examination revealed that the SiO_x films contained approximately 30% silicon, 58% oxygen and 12% carbon. Atomic forced microscopy (AFM) analysis results indicated a smooth surface of SiO_x films in deposition under higher substrate temperature. Also, pencil hardness tests indicated that the hardness of APP deposited SiO_x films was greatly improved with increasing substrate temperatures. Copyright © 2008 John Wiley & Sons, Ltd.     

Simultaneous growth of diamond and nanostructured graphite thin films by hot-filament chemical vapor deposition

Diamond and graphite films on silicon wafer were simultaneously synthesized at 850 °C without any additional catalyst. The synthesis was achieved in hot-filament chemical vapor deposition reactor by changing distance among filaments in traditional gas mixture. The inter-wire distance for diamond and graphite deposition was kept 5 and 15 mm, whereas kept constant from the substrate. The Raman spectroscopic analyses show that film deposited at 5 mm is good quality diamond and at 15 mm is nanostructured graphite and respective growths confirm by scanning auger electron microscopy. The scanning electron microscope results exhibit that black soot graphite is composed of needle-like nanostructures, whereas diamond with pyramidal featured structure. Transformation of diamond into graphite mainly attributes lacking in atomic hydrogen. The present study develops new trend in the field of carbon based coatings, where single substrate incorporate dual application can be utilized.