Suat Pat

Optical and Surface Characteristics of Mg-Doped GaAs Nanocrystalline Thin Film Deposited by Thermionic Vacuum Arc Technique

Magnesium (Mg) is the most promising p-type dopant for gallium arsenide (GaAs) semiconductor technology. Mg-doped GaAs nanocrystalline thin film has been deposited at room temperature by the thermionic vacuum arc technique, a rapid deposition method for production of doped GaAs material. The microstructure and surface and optical properties of the deposited sample were investigated by x-ray diffraction analysis, scanning electron microscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, ultraviolet–visible spectrophotometry, and interferometry. The crystalline direction of the deposited sample was determined to be (220) plane and (331) plane at 44.53° and 72.30°, respectively. The Mg-doped GaAs nanocrystalline sample showed high transmittance.

Electrically conductive and optically transparent polyethylene terephthalate films coated with gold and silver by thermionic vacuum arc

This study shows the morphology, physical, mechanical, and optical properties of conductive and transparent Ag and Au coated on polyethylene terephthalate (PET) by thermionic vacuum arc (TVA). Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) were used for the morphology investigation. To determine the mechanical and physical properties, hardness, scratch resistance, adhesion tests, and friction coefficient were measured. Friction coefficients were determined to be 0.141, 0.233, and 0.245 for uncoated PET, Gold (Au)-coated PET and Silver (Ag)-coated PET, respectively. Electrical resistivity measurements were performed using the two-probe technique. Au was 40 Ω and Ag 7 Ω versus uncoated PET, which is nonconductive with electrical surface resistance value in the order of 1014—1018Ω. The Au- and Ag-coated PETs reflectance was approximately 50% at 550 nm. Transmittance values of the Au- and Ag-coated PET films were approximately 70% and 20% at 550 nm.

Diamond-like carbon coated on polyethylene terephthalate by Thermionic Vacuum Arc

Diamond-like carbon (DLC) coatings were deposited on transparent polyethylene terephthalate (PET) using a thermionic vacuum arc (TVA) method. The TVA method parameters used to produce DLC coating and the volt—ampere characteristic during the plasma ignition were determined with 22 A of filament current. The crystal orientations and surface morphology of the deposited DLC thin films were investigated using X-ray diffractometer and atomic force microscopy. Reflectance and refractive indices of DLC-coated PET were analyzed by interferometry. According to experimental measurement, DLC-coated thin film was polycrystalline with (1 1 1) and (1 1 0) preferred orientations. Refractive indices were approximately 2.60 in the visible range. DLC-coated PET reflection is close to the PET substrate in the infrared region. According to Fresnel equation, the DLC-coated PET reflection decreased from 19.25% to 10% at 632 nm due to local coating agglomeration. Surface hardness increased to from 2.77 to 10 GPa with DLC coating.

The influence of voltage applied between the electrodes on optical and morphological properties of the InGaN thin films grown by thermionic vacuum arc

The aim of this research is to investigate the optical and morphological properties of the InGaN thin films deposited onto amorphous glass substrates in two separate experiments with two different voltages applied between the electrodes, i.e. 500 and 600 V by means of the thermionic vacuum arc technique. This technique is original for thin film deposition and it enables thin film production in a very short period of time. The optical and morphological properties of the films were investigated by using field emission scanning electron microscope, atomic force microscope, spectroscopic ellipsometer, reflectometer, spectrophotometer, and optical tensiometer. Optical properties were also supported by empirical relations. The deposition rates were calculated as 3 and 3.3 nm/sec for 500 and 600 V, respectively. The increase in the voltage also increased the refractive index, grain size, root mean square roughness and surface free energy. According to the results of the wetting experiments, InGaN samples were low-wettable, also known as hydrophobic.

Optical, morphological properties and surface energy of the transparent Li4Ti5O12 (LTO) thin film as anode material for secondary type batteries

LTO thin film was deposited for the first time on a glass microscope slide (MS) by RF magnetron sputtering technology. This method has been suitable for preparation of high-quality thin films. The surface properties of the produced film were determined by atomic force microscope (AFM). The surface of the produced film appeared smooth and homogeneous. LTO coated on MS had compact structure and low roughness. A UV–vis spectrophotometer was used to determine intensity of light passing through the samples. Thus, according to the results obtained the produced film was highly transparent. The refractive index of the LTO thin film was presented in a low MSE value by spectroscopic ellipsometry (SE) and it was about 1.5. The optical band gap (E g) was determined by the Tauc method. The produced LTO thin film exhibited a wide band gap semiconductor property with a band gap energy of about 2.95 eV. Finally, the surface free energy of the LTO thin film was calculated from the contact angle measurements using the Lewis acid-base, OWRK/Fowkes, Wu and Zisman methods.

Optical and surface properties of optically transparent Li3 PO4 solid electrolyte layer for transparent solid batteries.

In this study, optical and surface properties of the optically transparent Li3 PO4 solid electrolyte layer for transparent solid battery have been investigated for the first time. To determine the optical properties, transmittance, absorbance, reflection, refractive index spectra, and optical band gap were determined by UV-Vis spectrophotometer and optical interferometer. The surface property of the transparent Li3 PO4 solid electrolyte was analyzed using atomic force microscopy. One another important parameter is contact angle (CA) surface free energy (SFE). CA and SFE were determined by optical tensiometer. These values probably are a most important parameter for polymer and hybrid battery performance. For the best performance, value of CA should be low. As a result, solid electrolyte layer is a highly transparent and it has a high wettability. SCANNING 38:317-321, 2016.

ULTRA THIN CARBON FILMS DEPOSITED ON SrTiO3 SUBSTRATES BY THERMIONIC VACUUM ARC

Carbon thin films were obtained on strontium titanate (SrTiO3) substrates using the thermionic vacuum arc (TVA) method. TVA is a different, cheap and fast technology for thin film production. The films were produced with filament current of 22 amperes from a high purity graphite rod. The crystal structure and surface morphology of the thin films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. In this way, microstructural characterization, surface topography, nanomechanical properties (nanohardness and adhesion force) and reflective properties of the carbon thin films produced on SrTiO3 (100), (110) and (111) substrates were determined. Deposited carbon thin films on different orientated SrTiO3 substrates are in polycrystalline structures. Hardness of the carbon thin films has been measured in approximately 40 GPa. This hardness value is in the range of excellent hardness region. According to reflection analysis, the film is antireflective.

Study of Metal and Ceramic Thermionic Vacuum arc Discharges

The thermionic vacuum arc (TVA) is a new type of plasma source, which generates a pure metal and ceramic vapour plasma containing ions with a directed energy. TVA discharges can be ignited in high vacuum conditions between a heated cathode (electron gun) and an anode (tungsten crucible) containing the material. The accelerated electron beam, incident on the anode, heats the crucible, together with its contents, to a high temperature. After establishing a steady-state density of the evaporating anode material atoms, and when the voltage applied is high enough, a bright discharge is ignited between the electrodes. We generated silver and Al2O3 TVA discharges in order to compare the metal and ceramic TVA discharges. The electrical and optical characteristics of silver and Al2O3 TVA discharges were analysed. The TVA is also a new technique for the deposition of thin films. The film condenses on the sample from the plasma state of the vapour phase of the anode material, generated by a TVA. We deposited silver and Al2O3 thin films onto an aluminium substrate layer-by-layer using their TVA discharges, and produced micro and/or nano-layer Ag-Al2O3 composite samples. The composite samples using scanning electron microscopy was also analysed.

Morphological and optical comparison of the Si doped GaN thin film deposited onto the transparent substrates

The aim of this paper is to expand the body of knowledge about the silicon doped gallium nitride thin films deposited on different substrates. The physical properties of the Si doped GaN thin films deposited on the glass and polyethylene terephthalate substrates by thermionic vacuum arc which is plasma production technique were investigated. Thermionic vacuum arc method is a method of producing pure material plasma. The Si doped GaN thin films were analyzed using the following methods and the devices: atomic force microscopy, x-ray diffraction device, spectroscopic ellipsometer and energy dispersive x-ray spectroscopy detector. The produced Si doped GaN thin films are in the (113) orientation. The thicknesses and refractive index were determined by using Cauchy dispersion model. Surface morphologies of produced thin films are homogenous and low roughness. Our analysis showed that the thermionic vacuum arc method present important advantages for optical and industrial applications.

Non-Thermal Atmospheric Plasma: Can it Be Taken as a Common Solution for the Surface Treatment of Dental Materials?

This study aimed to evaluate the surface roughness and wetting properties of various dental prosthetic materials after different durations of non-thermal atmospheric plasma (NTAP) treatment. One hundred and sixty discs of titanium (Ti) (n:40), cobalt chromium (Co-Cr) (n:40), yttrium stabilized tetragonal zirconia polycrystals (Y-TZP) (n:40) and polymethylmethacrylate (PMMA) (n:40) materials were machined and smoothed with silicon carbide papers. The surface roughness was evaluated in a control group and in groups with different plasma exposure times [1-3-5 s]. The average surface roughness (Ra) and contact angle (CA) measurements were recorded via an atomic force microscope (AFM) and tensiometer, respectively. Surface changes were examined with a scanning electron microscope (SEM). Data were analyzed with two-way analysis of variance (ANOVA) and the Tukey HSD test α=0.05). According to the results, the NTAP surface treatment significantly affected the roughness and wettability properties (P < 0.05). SEM images reveal that more grooves were present in the NTAP groups. With an increase in the NTAP application time, an apparent increment was observed for Ra, except in the PMMA group, and a remarkable reduction in CA was observed in all groups. It is concluded that the NTAP technology could enhance the roughening and wetting performance of various dental materials.