Thermionic Vacuum Arc Technique Research Articles

Sn doped ZnO thin film deposition using thermionic vacuum arc technique

Sn doped ZnO thin films were prepared on glass, polyethylene terephthalate (PET) and silicon substrate make use of the thermionic vacuum arc technique and their structural, morphological, optical properties were investigated with various methods. The surface and microstructural properties of the Sn doped ZnO thin films were investigated by X-ray diffractometer, field emission scanning electron microscopy, atomic force microscopy, UV–visible spectroscopy, and Raman spectroscopy. According to the obtained results, all deposited films are in polycrystalline form with large crystallites. Due to larger crystallites on a deposited layer on glass and Si substrates, resistivity was found lower than deposited layer on PET substrate.

Investigation of the substrate effect for Zr doped ZnO thin film deposition by thermionic vacuum arc technique

ZnO is a fundamental wide band gap semiconductor. Especially, doped elements change the optical properties of the ZnO thin film, drastically. Doped ZnO semiconductor is a promising materials for the transparent conductive oxide layer. Especially, Zr doped ZnO is a potential material for the high performance TCO. In this paper, ZnO semiconductors were doped with Zr element and microstructural, surface and optical properties of the Zr doped ZnO thin films were investigated. Zr doped ZnO thin films were deposited thermionic vacuum arc (TVA) technique. TVA is a rapid and high vacuum deposition method. A glass, polyethylene terephthalate and Si wafer (111) were used as a substrate material. Zr doped ZnO thin films deposited by TVA technique and their substrate effect investigated. As a results, deposited thin films has a high transparency. The crystal orientation of the films are in polycrystal formation. Especially, substrate crystal orientation strongly change the crystal formation of the films. Substrate crystal structure can change the optical band gap, microstructural properties and deposited layer formation. According to the atomic force microscopy and field emission scanning electron microscopy measurements, all deposited layer shows homogeneous, compact and low roughness. The band values of the deposited thin film were approximately found as to be 3.1–3.4 eV. According to the results, Zr elements created more optical defect and shifted to the band gap value towards to blue region.

Investigation of the surface, morphological and optical properties of boron– doped ZnO thin films deposited by thermionic vacuum arc technique

In this study, boron—doped ZnO (ZnO:B) thin films have been deposited on amorphous glass and polyethylene terephthalate (PET) substrates by thermionic vacuum arc (TVA) technique. The surface, morphology, microstructure, optical properties, and chemical analysis of B doped ZnO thin films were investigated. To determine the subjected properties, atomic force microscopy (AFM), field emission electron microscopy (FESEM), x–ray diffraction (XRD), UV–Vis spectrophotometer, Raman and Fourier transform infrared spectroscopy measurements have been carried out. The thicknesses values of the films were measured as to be 50 nm and 60 nm on glass and PET substrates. XRD results show that polycrystalline nature of the deposited thin films on the PET substrate is higher than the deposited films on glass substrate. All films are in polycrystalline structure. The deposited thin films are including ZnO crystalline formations. According to the Scherrer’s formula, the crystallite sizes were calculated approximately 20 nm for ZnO crystallites. Atomic force microscopy and field emission electron microscopy images revealed the formation of fine—dispersed, homogeneous, uniform and granular structure on the surface of the films. Optical studies show that the average transmittance values of the ZnO:B films were obtained to be 62% and 83% on glass and PET substrates, respectively. The mean refractive index of the films also obtained as 1.69 and 1.65 on glass and PET substrate, respectively. In order to the Tauc’s relation and photoluminescence measurements, the optical band gap values of the boron doped films were found to be 3.2 and 3.3 eV on glass and PET substrates, respectively. Raman spectra are also support the boron doped ZnO structures deposited onto glass and PET substrate.

Photoelectrical properties of fabricated ZnS/Si heterojunction device using thermionic vacuum arc method

ZnS thin films have been successfully deposited with the same production parameters using thermionic vacuum arc technique on glass and silicon substrates. UV–Vis absorbance spectra and photoluminescence measurements were performed for the optical characterization of ZnS/glass thin film and ZnS/p-Si heterojunction device, respectively. The optical band gap is found approximately 3.78 eV. Further, electrical parameters of the device were determined for the current-voltage (I-V) measurements in dark and under illumination conditions. The open-circuit voltage and the short-circuit current values have been obtained related to illumination I-V measurements. Also, we have utilized photocurrent measurements to investigate the wavelength dependent to photosensitivity of the ZnS/p-Si heterojunction device.

Investigation of the structural, surface, optical and electrical properties of the Indium doped CuxO thin films deposited by a thermionic vacuum arc

In this study, investigation of some physical properties of In-doped CuxO thin films onto amorphous glass substrates were done. The thin films were depsoied by thermionic vacuum arc technique (TVA). TVA technique gives a thin film with lower precursor impurity according to the other chemical and physical depsoition methods. The microstructural properties of the produced thin films was determined by x-ray diffraction device (XRD). The thickness values were measured as to be 30 nm and 60 nm, respectively. The miller indices of the thin films’ crystalline planes were determined as to be Cu (111), CuO ( 12), CuInO2 (107) and Cu2O (200), Cu (111), CuO ( 12), CuO ( 02), CuInO2 (015) for sample C1 and C2, respectively. The produced In-doped CuO thin films are in polycrystalline structure. The surface properties of produced In doped CuO thin films were determined by using an atomic force microscope (AFM) and field emission scanning electron microscope (FESEM) tools. The optical properties of the In doped CuO thin films were determined by UV–vis spectrophotometer, interferometer, and photoluminescence devices. p-type semiconductor thin film was obtained by TVA depsoition.

The investigation of the Cr doped ZnO thin films deposited by thermionic vacuum arc technique

Cr doped ZnO thin films were prepared onto glass and polyethylene terephthalate (PET) substrates using thermionic vacuum arc. XRD patterns show the polycrystalline nature of the films. Cr, Zn, ZnO and Cr2O3 were detected in the layers. The mean crystallite sizes of the films were calculated about 20 nm for the films onto glass and PET substrates. The maximum dislocation density and internal strain values of the films are calculated. According to the optical analysis, the average transmittance and reflectance of the films were found to be approximately 53% and 16% for glass and PET substrates, respectively. The mean refractive index of the layer decreased to 2.15 from 2.38 for the PET substrate. The band gap values of the Cr-doped ZnO thin films were determined as 3.10 and 3.13 eV for glass and PET substrates.

Investigation of the optical properties of the indium-doped ZnO thin films deposited by a thermionic vacuum arc

In this paper, the investigation of optical properties of an indium-doped ZnO (IZO) thin films deposited on glass and polyethylene terephthalate (PET) by thermionic vacuum arc technique were done. Also, the surface, structural and electrical properties of deposited films were studied by an atomic force microscopy (AFM), field emission electron microscopy (FESEM), X-ray diffraction (XRD), ultraviolet-visible (UV–vis) spectrophotometer, interferometer and Hall effect system. Using a Filmetrics F20 thin film measurement system, the thickness values of the deposited IZO thin films were obtained as to be 110nm and 190nm on glass and PET substrates, respectively. All IZO films are in a polycrystalline structure. The estimated mean crystallite size values were recorded as 29.34nm and 28.17nm on the glass and PET substrates, respectively. The surface images of the FESEM analysis show growth of granular structure on the surface and the results are in good agreement with AFM results. Using UV–vis spectrophotometer and interferometer, the refractive index, reflectance, transmittance, absorbance and optical band gap of the deposited films were determined. The calculated optical band gap values of the films are obtained as to 3.64eV and 3.55eV for glass and PET substrate, respectively. The electrical measurements show that sheet resistance is dependence on the substrate materials.

Transparent nano layered Li3PO4 coatings on bare and ITO coated glass by thermionic vacuum arc method

In this paper, Li3PO4 (LPO) thin films were coated onto bare and indium tin oxide (ITO) coated glass substrates by thermionic vacuum arc technique. The structural, surface, and optical properties of the LPO films were investigated. The properties of the deposited films were analyzed using an X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, UV–Vis spectrophotometer, and interferometer tools. The miller indices of the crystalline planes of the ITO coated samples were determined as to be (222), (123), (400), (420), (440), (622), and (444). The (200), (121), (112), (301), and (410) miller indices for the crystalline planes were detected for the LPO layers deposited directly on glass. The grain sizes, the microstrain, the lattice strain values, the dislocation density and the number of crystallite per unit area were estimated for LPO layer. The transparency values of the produced Li3PO4/glass (sample S1) and Li3PO4/ITO/glass (sample S2) structures were relatively high 87 and 90% for bare and ITO coated glass substrate, respectively. The reflection values of the coated samples onto bare and ITO coated glass were approximately as 0.05 and 0.06 at 550 nm, respectively.

The electrical, elemental, optical, and surface properties of Si-doped ZnO thin films prepared by thermionic vacuum arc

The purpose of this work is to study the properties of Si-doped ZnO (SZO) thin films, which were prepared using the non-reactive thermionic vacuum arc technique. The analysis of the elemental, optical, and surface properties of ZnO:Si thin films was carried out using energy dispersive x-ray spectroscopy, UV–VIS spectrophotometry, atomic force microscopy, and scanning electron microscopy, respectively. The current–voltage measurement was employed in order to study the electrical properties of the films. The effect of Si doping on the physical properties of ZnO films was investigated. The film thicknesses were measured as 55 and 35 nm for glass and PET substrates, respectively. It was clearly observed from the x-ray diffraction results that the Si and ZnO peaks were present in the coated SZO films for all samples. The morphological studies showed that the deposited surfaces are homogenous, dense, and have a uniform surface, with the existence of some cracks only on the glass substrate. The elemental composition has confirmed the existence of Zn, Si, and O elements within the prepared films. Using a UV–VIS spectrophotometer, the optical parameters such as transmittance, absorbance, refractive index, and reflectance were calculated. It should be noted that the transparency and refractive indices obtained from the measurements decrease with increasing Si concentration. The obtained optical bandgap values using transmittance spectra were determined to be 3.74 and 3.84 eV for the glass and PET substrates, respectively. An increase in the bandgap results demonstrates that the Si doping concentration is comparable to the pure ZnO thin films. The current versus voltage curves revealed the ohmic nature of the films. Subsequently, the development and fabrication of excellent transparent conducting electrodes enabled the appropriate use of Si-doped ZnO thin films.

The characteristics of ZnS/Si heterojunction diode fabricated by thermionic vacuum arc

ZnS/p-Si heterojunction diode has been successfully fabricated by depositing the ZnS thin films on p-type Si substrates using thermionic vacuum arc technique (TVA). The structural analysis was performed with X-ray diffraction (XRD) and Atomic force microscopy (AFM). The results revealed that ZnS thin film demonstrates nano-crystalline behavior with very smooth and homogeneous surface properties. The type was determined as n-type and the carrier concentration was found approximately 3.1 × 1017 cm−3 of the ZnS thin film by means of Hall Effect measurement. The dark current-voltage (I-V) and the capacitance-voltage (C-V) measurements with different frequencies were performed to determine the characteristics of the ZnS/p-Si heterojunction diode at room temperature. I-V results show that the diode has a good rectifying characteristic with excellent rectification ratio. The electrical parameters of the diode have been obtained by using current transport mechanism. It was found that the barrier height calculated from dark I-V measurements is in good agreement with the value obtained from C-V measurements at a frequency of 1.5 MHz. The series resistance and the built in potential of the fabricated diode were calculated as 3.6 kΩ and 0.7 V using Cheung and Cheung's equation and C-V measurement, respectively. The low cost and effective film production method were utilized to fabrication of heterojunction diode and to investigate characteristics.

Investigation of the some physical properties of Ge-doped ZnO thin films deposited by thermionic vacuum arc technique

We exhibit the first nano-crystalline Ge–ZnO thin films deposited on glass and PET substrates by a thermionic vacuum arc technique. The effect of Ge doping on the structural, morphological and optical properties of ZnO:Ge films were investigated. An X-ray diffraction (XRD), atomic force microscopy, field emission scanning electron microscopy (FESEM) and UV–Vis spectrophotometer were used for the analysis. XRD patterns show the polycrystalline structure of the films in the range of 20°–80°. The roughness value for the ZnO:Ge on PET substrate was increased due to agglomeration of the grains. The results are in a good agreement with the FESEM images. Using Filmetrics F20 tool, the thickness values of the deposited thin films were obtained as 60 and 80 nm on glass and PET substrates, respectively. The optical properties of the films such as transmittance, absorbance, refractive index, and reflectance were determined. The band gap values were obtained as to be 3.43 and 3.38 eV glass and PET substrates, respectively. It was found that band gap variation of ZnO is very small with Ge doping.

A study on some physical properties of a Pb-doped GaAs thin film produced by thermionic vacuum arc

A 155 nm Pb-doped GaAs thin film was deposited on a glass substrate by means of the thermionic vacuum arc technique in 30 s using GaAs and Pb pellets as source materials. Tools and techniques such as an optical reflectometer, UV-VIS-NIR spectrophotometer, FESEM, EDX, AFM and optical tensiometer were employed to investigate the physical properties of the produced film. From the optical investigations, the refractive index at the wavelength of 632.8 nm and optical band gap of the film were found to be 4.03 and 1.13 eV respectively. It was observed that Pb doping increased the value of refractive index and decreased the band gap value. A uniform surface morphology with fine grain covering the entire surface was observed through the FESEM and AFM studies while 50–80 nm grain size and 2.22 nm root mean square roughness values were obtained. The EDX analysis confirmed the presence of Ga, As and Pb elements in the film. The wetting experiments revealed that the contact angle value was dependent on the liquid used. The surface free energy calculated with OWRK/Fowkes and Equation of State approaches were about 26 mN/m.

A new technique for transparent solid state Li3PO4 electrolyte layer growth: thermionic vacuum arc technique

In this research, a Li3PO4 electrolyte thin film was deposited on glass substrate under high vacuum condition by means of the thermionic vacuum arc (TVA) method. A new deposition mechanism for solid-state battery applications is presented. The physical properties of the produced sample were analyzed with X-ray diffraction device, spectrophotometer, interferometer, scanning electron microscope, and atomic force microscope. In order to understand the surface features of the thin film, AFM analysis was carried out by non-contact mode at ambient condition. The formation of microstructures were monitored clearly by the AFM device. The UV–Vis spectrophotometer result showed that produced film has a high transmittance in the visible region and near infrared region.

Beryllium layer response to ITER-like ELM plasma pulses in QSPA-Be

Material migration in ITER is expected to move beryllium (Be) eroded from the first wall primarily to the tungsten (W) divertor region and to magnetically shadowed areas of the wall itself. This paper is concerned with experimental study of Be layer response to ELM-like plasma pulses using the new QSPA-Be plasma gun (SRC RF TRINITI). The Be layers (1→50µm thick) are deposited on special castellated Be and W targets supplied by the ITER Organization using the Thermionic Vacuum Arc technique. Transient deuterium plasma pulses with duration ∼0.5ms were selected to provide absorbed energy densities on the plasma stream axis for a 30° target inclination of 0.2 and 0.5MJm−2, the first well below and the second near the Be melting point. This latter value is close to the prescribed maximum energy density for controlled ELMs on ITER. At 0.2MJm−2 on W, all Be layer thicknesses tested retain their integrity up to the maximum pulse number, except at local defects (flakes, holes and cracks) and on tile edges. At 0.5MJm−2 on W, Be layer melting and melt layer agglomeration are the main damage processes, they happen immediately in the first plasma impact. Melt layer movement was observed only near plasma facing edges. No significant melt splashing is observed in spite of high plasma pressure (higher than expected in ITER). Be layer of 10µm thick on Be target has higher resistance to plasma irradiation than 1 and 55µm, and retain their integrity up to the maximum pulse number at 0.2MJm−2. For 1µm and 55µm thick on Be target significant Be layer losses were observed at 0.2MJm−2.

Study of deuterium retention in Be-W coatings with distinct roughness profiles

Three batches of pure beryllium (Be), pure tungsten (W) and mixed Be:W (50:50) coatings were deposited by using the thermionic vacuum arc (TVA) technique. Different superficial roughness and morphologies were obtained by adjusting the bias voltages in the substrate holder. The coatings were irradiated afterwards with 15keV 2H+ ions up to a fluence of 5e17ion/cm2 with the purpose to investigate the influence of the roughness parameters on the retention of deuterium in Be-W deposits in the absence of other co-deposited impurities. Current densities lower than 0.2W/cm2 were used to avoid the release of deuterium induced by heating loads. The results of the experiment point to the negligible effect of rugosity on the retention behaviour under energetic ion bombardment.

Growth and characterization of GaN thin film on Si substrate by thermionic vacuum arc (TVA)

Gallium nitride (GaN) is an attractive material with a wide-direct band gap (3.4 eV) and is one of the significant III-nitride materials, with many advantageous device applications such as high electron mobility transistors, lasers, sensors, LEDs, detectors, and solar cells, and has found applications in optoelectronic devices. GaN could also be useful for industrial research in the future. Chemical vapor deposition (CVD), molecular beam epitaxy (MBE), sputter, and pulsed laser deposition (PLD) are some of the methods used to fabricate GaN thin film. In this research, a GaN thin film grown on a silicon substrate using the thermionic vacuum arc (TVA) technique has been extensively studied. Fast deposition, short production time, homogeneity, and uniform nanostructure with low roughness can be seen as some of the merits of this method. The growth of the GaN was conducted at an operating pressure of , a plasma current and for a very short period of time of 40 s. For the characterization process, scanning electron microscopy (SEM) was conducted to determine the structure and surface morphology of the material. Energy dispersive x-ray spectroscopy (EDX) was used to comprehend the elemental analysis characterization of the film. X-ray diffraction (XRD) was used to analyze the structure of the film. Raman measurements were taken to investigate the phonon modes of the material. The morphological properties of the material were analyzed in detail by atomic force microscopy (AFM).

Influence of gaseous environments on beryllium–tungsten and tungsten surfaces investigated by XPS

Beryllium–tungsten and tungsten layers were deposited by thermionic vacuum arc technique in gaseous environments, in order to simulate the plasma–wall phenomena appearing during fusion device operation. In-depth x-ray photoelectron spectroscopy investigations highlighted the chemical changes on (Be-W) and W systems subjected to different plasma environments similar to a fusion device: deuterium, neon, helium, nitrogen, and oxygen. The metallic feature among oxides of beryllium can be detected only for deuterium and neon plasma atmosphere. Tungsten displays only the metallic contribution for the mentioned plasmas, deuterium, and neon. Full oxidation state of tungsten (W6+) is found in Be-W system for nitrogen and oxygen plasma environment deposition and for W system in oxygen atmosphere. Finally, the nitrogen atmosphere has a protective behavior by increasing the metallic feature followed by a decrease in the W oxidation state, from 19.7% for oxygen plasma to 31.5% for nitrogen plasma and 14.0% to 6.6%, respectively.

The substrate effect on Ge doped GaN thin films coated by thermionic vacuum arc

This study focuses on characterization and understanding of the substrate effect on Ge doped GaN thin films coated onto transparent substrates. The produced films were deposited onto unheated glass and unheated polyethylene terephthalate by using thermionic vacuum arc technique. Gallium nitride and germanium pellets were used in the thin film production. Reflectance, refractive index and thicknesses of Ge doped GaN thin films were measured by optical interferometer using Cauchy model for fitting. The transmittances were determined in the wavelength range between 200 and 1000 nm by using UV–Vis double beam spectrophotometer. The optical Tauc method was used to determine the band gap energies of produced thin films. Surface morphologies of produced thin films were characterized by atomic force microscopy and also field emission scanning electron microscopy. In conclusion, the substrate effect on the optical and morphological properties of the produced thin films was observed.

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.

Optical, structural, morphological and compositional characterization of a Co-doped GaAs semiconducting thin film produced by thermionic vacuum arc

A 80 nm 2 at% Co-doped GaAs thin film was deposited on a glass substrate under a high vacuum condition by means of the thermionic vacuum arc technique using GaAs and Co pellets as source materials. Tools and techniques such as an optical reflectometer, XRD, UV-VIS-NIR spectrophotometer, FESEM, EDX, and AFM were employed to investigate some of the physical properties of the produced film. From the optical investigations, the refractive index at 632.8 nm and optical band gap of the film were determined to be 3.60 and 1.42 eV respectively. XRD characterization indicated that the film contained GaAs and Co phases. A uniform surface morphology with fine grain covering the entire surface was observed through the FESEM and AFM studies, while 30 nm grain size and 2.72 nm root mean square roughness were obtained. The EDX analysis also confirmed the presence of Ga, As and Co in the film.