Papers by Keyword: CVD

Abstract: 3C-SiC films have been grown on [100] n-doped Si substrates in a horizontal cold wall CVD reactor. Without the use of plasma enhancement, the precursors silane and propane are used to deposit silicon carbide films at T < 1200°C. The structure of the grown films has been investigated via FESEM, XRD and Raman spectroscopy. It has been found that the growth rates are between 200 and 300 nm/h. Additionally, structural analysis give evidence of polycrystalline phases. Reasons for that could be insufficient cracking of the precursors and homogenous nucleation of Si species in the gas phase.

Abstract: Experimental results presented in this contribution demonstrate that adding HCl to the SiC CVD process is not only an efficient way to suppress the Aluminum memory effect but may also be considered as a powerful tool for fine tuning of intentional Al incorporation in 3C-SiC and 4H-SiC thin films. The approach is easy to implement and seems more reliable than changing TMA bubbling/dilution parameters during the growth. An ad-hoc phenomenological model is proposed to explain the correlation between the HCl supply and Al incorporation.

Abstract: Combination of high energy radiation and chemical vapour deposition in the grafting process for the synthesis of metal adsorbent was investigated. Radiation-induced grafting of glycidyl methacrylate onto kenaf fiber was performed in vapour phase to develop adsorbent for removal of aluminum from aqueous solution. Morphological changes of cross-section kenaf fiber was observed via scanning electron microscope and the thickness of co-monomer in the final graft co-polymer was determined. The comparison in cross-section morphology between ungrafted kenaf fibers and grafted kenaf fiber shows approximately 3.88 [μm] thick of additional grafted layer. The functionalization of the grafted fiber using imidazole was calculated grametrically and verified by elemental analysis. Imidazole has proven to be effective on the adsorption of aluminum ion. It was found that the adsorbent could remove more than 99% aluminum with the highest adsorption capacity of 4.93 [mg/g] at pH 4 and 60 minutes reaction time.

Abstract: Synthesize of Boron Nitride nanowires were made by utilizing Austenitic hardened steel AISI 316 with a nitriding layer of 15–16 μm thickness. Deposition experiments at deferent substrate temperatures for BN Nanowires productions were carried out with the help of a blended gas stage depositing handle procedure (PVD and CVD). Chemical composition and crystallinity along with the average grain size for BN phases was investigated by using XRD test and FTIR spectrum. The SEM images was used to examine the surface topography. Finally theoretical investigations computations were performed by thickness useful hypothesis (DFT) in Gaussian 09 bundle. According to our results, the impact of the depositing temperature on the chemical composition and the structure should be pointed out as the major effect for the higher deposition rate that leads to thicker and more dense BN surface film, where the more uniform BN Nanostructures wires with a regular diameter of 20 nm and average grain size of ~18nm was compelled through novel materializing crystalline stages causing grain size to rise with increasing deposition temperature to specific level.

Abstract: Chemical vapour deposited HfN can be utilised as a component of multilayer systems in protective coatings on cutting tools. In this study, related AlHfN coatings were synthesized through a reaction of metallic hafnium and aluminium with HCl gas forming gaseous HfCl₄ and AlCl₃, which were subsequently transported into a heated coating reactor. Via high temperatures and separately introduced NH₃ and N₂ as reaction gases, AlHfN coatings were deposited on hardmetal inserts. By varying the ratio between AlCl₃ and HfCl₄, compositionally different AlHfN coatings were examined. Additionally, surface morphology, composition as well as crystalline phases of the obtained coatings were analysed by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Finally, the microstructure of the cross section of a coating was investigated via transmission electron microscopy. The observations revealed a great impact of the gas composition on the morphology and crystal structures of the coatings. Within the layer, the growth of columnar microstructures was detected. Additionally, the formation of an amorphous HfN intermediate layer between the substrate and the AlHfN with a thickness of approximately 2 nm was found.

Abstract: Diamond crystals are successfully synthesized by irradiating DC arc plasma jet to the substrate set in a methanol solution. It is the important procedure to preheat the substrate by inert Ar plasma jet before introducing the methanol solution gas to the plasma jet gun. The effects of two experimental conditions, the incident power and the substrates, are investigated. In the case of the Si substrate, cubic crystalline diamond grains of same size are synthesized at the plasma power of 470W. High speed hetero epitaxy is expected by using this method. In the case of the tungsten carbide substrate, diamond crystals and carbon nanotubes are simultaneously synthesized at the plasma power of 260W. The catalytic effect of Co binder in the substrate may cause the chemical reaction of the nanotube synthesis.

Abstract: In this work, we report the role of structure on electrochromic behavior of nickel oxide thin coatings deposited via chemical vapor deposition on ITO-coated glass in (EtCp)₂Ni–O₂–Ar and (EtCp)₂Ni–O₃–O₂–Ar reaction systems. The structure and chemical composition were analyzed and then correlated with electrochemical response and transmittance modulation when immersed in 1 M KOH electrolyte. The NiO exhibits an anodic coloration, reaching an optical density modulation of 0.66 between colored and bleached state at 550 nm, with a color efficiency of 30.7 cm²C^-1. Very fast switching between states was obtained, the coloration and bleaching time did not exceed 0.05 sec.

Abstract: Freestanding diamond foils are an exceptionally strong material. A major problem that prevents industrial use is their inherent brittleness. We here present a first approach to introduce metallic interlayers into a diamond matrix by brazing stacks of diamond foils. This represents a potential route to toughen the material. Laminates of two and four layers of diamond were produced from the same batch of diamond foils. A first attempt to approximate the bending strength of this new material was made using a Ball-on-three-Balls (B3B) setup. Substantially higher strength values were achieved for the laminates compared to the freestanding (monolithic) foil.

Abstract: Ternary transition metal nitrides are commonly used as protective coatings on cutting tools, owing to their excellent mechanical and wear properties. While AlTiN is a very well-studied material, little is known about AlZrN, in part due to the large miscibility gap in the phase diagram of AlN-ZrN. In this study, AlZrN thin films were prepared using chemical vapor deposition. By the reaction of metallic aluminum and zirconium with HCl gas under elevated temperature, AlCl₃ and ZrCl₄ were produced in situ and subsequently transported into a heated coating reactor with a carrier gas. Due to the high temperatures and the separately introduced mixture of NH₃ and N₂, AlZrN coatings were deposited. By varying the experimental conditions, such as the ratio between ZrCl₄ and AlCl₃, we studied the influence of these parameters on the coating thickness and morphology as well as the microstructure. Additionally, the impact of different sample positions in the coating reactor on the deposited coatings was investigated. Furthermore, the generated samples were characterized by scanning electron microscopy, energy dispersive x-ray spectroscopy and transmission electron microscopy.

Abstract: A promising two-dimensional material for applications in optoelectronic and photonics, MoS₂ is in focus since last decade. Its optical, structural and electronic properties are of practical importance along with its exciton dynamics. MoS₂ thin films were synthesized with Chemical Vapour Deposition (CVD) technique on Si/SiO₂ substrates. The thickness dependent regularities were controlled and examined to quantitatively control the film quality with thickness variation. Various characterization techniques were employed to investigate structural and morphological changes induced systematically to reveal the van der waal stacked layers of MoS₂ material. The In-plane characteristic mode E¹_2g and out of plane A_1g vibrational modes were detected in different configurations of film’s structure. Optical absorption spectra gave us information on photon energy with the absorbance; extrapolation of this curve gave optical bandgap (E_g) in the form of Tauc plot. These energies can be associated to interband electronic transitions in the Brillouin zone. The intrinsic excitonic response as a consequence of layer stacking and velly indexing can be attributed to this change in bandgap from 1.68 to 1.91 eV. Surface morphology of the as-grown films also provides better understanding of MoS₂ material with root mean square (RMS) roughness in the range of 1.32 to 3.85 nm.