Şadan Korkmaz

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.

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.

ANTIREFLECTIVE COATING ON POLYETHYLENE TEREPHTHALATE BY THERMIONIC VACUUM ARC

Transparent polyethylene terephthalate (PET) substrates were coated with SiO2 and ZrO2 using thermionic vacuum arc (TVA) method for the first time. The melting point of PET is approximately 260°C. Transmittances, thickness, reflectance, and refractive indices of coated PET samples were measured by ultraviolet—visible spectrophotometer and interferometry to characterize their optical properties. Additionally, scanning electron microscopy, energy dispersive X-ray spectroscopy, and atomic force microscopy were used to characterize the coated PET surface morphologies. Our results show that the SiO2- and ZrO2-coated PET samples had lower reflection when the TVA method was used; so, they show antireflective (AR) properties. Moreover, the coating homogeneity and surface roughness are proper for multi-layer AR coatings.

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.

Atomic transport properties of liquid alkaline earth metals: a comparison of scaling laws proposed for diffusion and viscosity

Certain atomic transport and surface properties of liquid alkaline earth metals are reported. The diffusion and viscosity coefficient of liquid Mg, Ca, Sr and Ba metals are calculated using scaling laws which express the possible relationship between the excess entropy and transport properties of liquids. The excess entropies are computed by the two body approximation. As the input pseudopotential, the individual version of the electron–ion potential proposed by Fioalhais and coworkers which was originally developed for the solid state is used. Static structure factors are derived from the solution of the Ornstein-Zernike integral equation with Rogers–Young closure. From present investigations, it is shown that these scaling laws lead to a good estimation for the diffusion and viscosity coefficients of liquid alkaline earth metals.

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.

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.

Nanostructured vanadium carbide thin films produced by RF magnetron sputtering

In this paper, nanostructured vanadium carbide thin films were deposited on glass substrates and their optical and surface properties were analyzed. All produced samples were transparent in the optical region. Refractive index values were calculated using the Drude model. According to contact angle measurements of the coated surfaces, the samples show high wettability. The surface free energies of the samples were found to be very similar. The influence of the nitrogen content in the buffer gas mixture was determined; it was concluded that the microstructure, refractive index, surface morphology, surface free energy, and thickness of thin films can change in response to the nitrogen concentration of the radio frequency (RF) buffer gas.