Cinar Demir - Academia.edu (original) (raw)

Papers by Cinar Demir

Radiation Effects and Defects in Solids, 2017

ABSTRACT Gallium Selenide (GaSe) thin films were grown by the electrochemical deposition (ECD) te... more ABSTRACT Gallium Selenide (GaSe) thin films were grown by the electrochemical deposition (ECD) technique on Indium tin oxide (ITO) and p-Si (100) substrates. The Electron paramagnetic resonance (EPR) spectrum of GaSe thin films’ growth on ITO was recorded at room temperature. According to EPR results, the g value of an EPR signal obtained for GaSe deposited on ITO is 2.0012 ± 0.0005. In/GaSe/p-Si heterojunction was irradiated with high-energy (6 MeV) and low-dose (1.53 × 1010 e− cm−2) electrons. The ideality factor of the In/GaSe/p-Si device was calculated as 1.24 and barrier height was determined as 0.82 eV from I–V measurements before irradiation. Acceptor concentration, built-in potential and barrier height of the In/GaSe/p-Si device were also obtained as 0.72 × 1014 cm−3, 0.65 eV and 0.97 eV from C–V measurements, respectively. After irradiation, the ideality factor n and barrier height Φb values of the In/GaSe/p-Si device were calculated as 1.55 and 0.781 eV, respectively. Acceptor concentration, the built-in potential and barrier height values of the In/GaSe/p-Si device have also shown a decrease after 6 MeV electron irradiation. This change in heterojunction device parameters shows that current transport does not obey thermionic emission, and thus tunneling could be active due to the defects formed by irradiation at the In–GaSe interface.

Current Applied Physics, 2019

In this study, nanostructured indium selenide (InSe) thin films were deposited on Indium tin oxid... more In this study, nanostructured indium selenide (InSe) thin films were deposited on Indium tin oxide (ITO)-coated glass substrate using electrochemical deposition (ECD) from aqueous solution containing In(SO 4) 3 .H 2 O and SeO 2. The effects of deposition potential (−0.70 to −1.35 V), time (30-3600 s), temperature (25-80°C) and pH (2.58 for A samples; 2 for B samples and 1.45 for C samples) on growth of the InSe thin films were examined in terms of their structural, morphological and optical properties. X-ray diffraction (XRD) analysis confirmed that the InSe thin films are in polycrystalline structure. It was found that the values of grain size decreased and the full width half maximum (FWHM) values increased with the increasing deposition potential. According to the absorption measurements, optical properties of the thin films varied with changes in deposition conditions. Based on the atomic force microscopy (AFM) and the scanning electron microscopy (SEM) images, surface morphology of the thin films was influenced by deposition potential and pH of the electrolyte, and nonhomogeneous depositions distributed across the entire surface were observed. In addition, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectroscopy (FT-IR) analyses were used to further examine crystal quality, vibration, chemical binding conditions, In/Se orientation and structure of the prepared InSe thin films. When Raman results are examined, the B12 sample shows a more intensity and narrow peak at 248 cm −1. XPS measurements sowed that A6 sample exhibited more growth in low potential for a long time and better film stoichiometry compared to the other three samples. Also, FT-IR studies prove the presence of InSe. According to the results, the film did not form at low temperatures and short times. However, the film formation began with the increasing deposition temperature and time at the low potential value of −0.730 V. But, it is clear that a high quality film can be obtained in cathodic potential with −1.3 V and shorter deposition time with 300 s at room temperature respectively. Overall results showed that the high quality thin films can be obtained by the ECD technique. However, deposition conditions must be sensitively adjusted to control morphology of the electrodeposited nanoparticles.

Radiation Effects and Defects in Solids, 2016

Mn-doped p-InSe semiconductor crystals were grown by Bridgman-Stockbarger technique. The crystals... more Mn-doped p-InSe semiconductor crystals were grown by Bridgman-Stockbarger technique. The crystals were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fabricated Sn/InSe:Mn Schottky diodes. The current-voltage (I-V) and capacitance-voltage (C-V) measurements of diodes were investigated to determine the response of devices to electron irradiation with 9 MeV energy and 1.2 × 10 10 e − cm −2 dose. After irradiation, the ideality factor and barrier height of the Sn/InSe:Mn Schottky diode were determined as 1.66 and 0.85 eV, respectively. Before irradiation, they were determined as 1.37 and 0.90 eV, respectively. It has been concluded that the radiation with high energy may contribute to form defects at the interface of the Sn/InSe:Mn device.

Journal of Instrumentation, 2016

In this work we fabricated detectors based on semi-insulating GaAs and studied their electrical p... more In this work we fabricated detectors based on semi-insulating GaAs and studied their electrical properties (current-voltage characteristics, galvanomagnetic measurements) after irradiation with 5 MeV electrons from a linear accelerator up to a dose of 104 kGy. A series of detectors were prepared using Ti/Pt/Au Schottky contact with 1 mm diameter. The thickness of the base material was about 230 μm. A whole area Ni/AuGe/Au ohmic contact was evaporated on the back side. For galvanomagnetic measurements we used three samples from the same wafer. All samples were irradiated by a pulse beam of 5 MeV electrons using the linear accelerator in 11 steps, where the accumulative dose increased from 1 kGy up to 104 kGy. Also different dose rates (20, 40 and 80 kGy/h) were applied to the samples. After each irradiation step we performed electrical measurement of each sample. We analyze the electron Hall mobility, resistivity, electron Hall concentration, breakdown voltage and reverse current of samples before and after irradiation using different dose rates.

2019 IEEE Regional Symposium on Micro and Nanoelectronics (RSM), 2019

Electrochemical deposition method has been widely used due to its advantages in stoichiometry con... more Electrochemical deposition method has been widely used due to its advantages in stoichiometry control, large area growth, easy to form nano-structures, being low coast, possible formation of homogeneous thin films. In this study, Cu2ZnSnS4 (CZTS) thin films were deposited on ITO substrates by using single step electrodeposition method. CZTS absorber layers have been tried to be obtained at four different pH values of 4.70, 5.10, 5.70 and 6.23. Trisodium citrate was used as a complexing agent for co-electrodeposition. CZTS thin films were annealed for recrystallization in stoichiometric kesterite structure after deposition at 580 °C in sulfur powder and N2 atmosphere for 60 min. The structural, morphological and optical properties of CZTS thin films have been investigated by using X-ray diffraction (XRD), optical absorption techniques, scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy measurements. Diffraction peaks observed at 28.53°, 37.02°, 47.33°, 56.17°, 69.23° and 76.44° correspond to diffraction of (112), (202), (220), (312), (008) and (332) planes of CZTS films deposited in solution with pH 5.7, respectively. Thin films grown at other pH values, there are peaks observed from the secondary phases. CZTS films grown at pH: 5.7 has shown three Raman modes with a strong peak at 326 cm−1 and two weak peaks at 284 cm−1 and 367 cm−1, which are not visible in other films. These peaks are due to the kesterite CZTS structure present in CZTS films and well compatible with CZTS Raman peaks.

Radiation Effects and Defects in Solids, 2017

ABSTRACT Gallium Selenide (GaSe) thin films were grown by the electrochemical deposition (ECD) te... more ABSTRACT Gallium Selenide (GaSe) thin films were grown by the electrochemical deposition (ECD) technique on Indium tin oxide (ITO) and p-Si (100) substrates. The Electron paramagnetic resonance (EPR) spectrum of GaSe thin films’ growth on ITO was recorded at room temperature. According to EPR results, the g value of an EPR signal obtained for GaSe deposited on ITO is 2.0012 ± 0.0005. In/GaSe/p-Si heterojunction was irradiated with high-energy (6 MeV) and low-dose (1.53 × 1010 e− cm−2) electrons. The ideality factor of the In/GaSe/p-Si device was calculated as 1.24 and barrier height was determined as 0.82 eV from I–V measurements before irradiation. Acceptor concentration, built-in potential and barrier height of the In/GaSe/p-Si device were also obtained as 0.72 × 1014 cm−3, 0.65 eV and 0.97 eV from C–V measurements, respectively. After irradiation, the ideality factor n and barrier height Φb values of the In/GaSe/p-Si device were calculated as 1.55 and 0.781 eV, respectively. Acceptor concentration, the built-in potential and barrier height values of the In/GaSe/p-Si device have also shown a decrease after 6 MeV electron irradiation. This change in heterojunction device parameters shows that current transport does not obey thermionic emission, and thus tunneling could be active due to the defects formed by irradiation at the In–GaSe interface.

Current Applied Physics, 2019

In this study, nanostructured indium selenide (InSe) thin films were deposited on Indium tin oxid... more In this study, nanostructured indium selenide (InSe) thin films were deposited on Indium tin oxide (ITO)-coated glass substrate using electrochemical deposition (ECD) from aqueous solution containing In(SO 4) 3 .H 2 O and SeO 2. The effects of deposition potential (−0.70 to −1.35 V), time (30-3600 s), temperature (25-80°C) and pH (2.58 for A samples; 2 for B samples and 1.45 for C samples) on growth of the InSe thin films were examined in terms of their structural, morphological and optical properties. X-ray diffraction (XRD) analysis confirmed that the InSe thin films are in polycrystalline structure. It was found that the values of grain size decreased and the full width half maximum (FWHM) values increased with the increasing deposition potential. According to the absorption measurements, optical properties of the thin films varied with changes in deposition conditions. Based on the atomic force microscopy (AFM) and the scanning electron microscopy (SEM) images, surface morphology of the thin films was influenced by deposition potential and pH of the electrolyte, and nonhomogeneous depositions distributed across the entire surface were observed. In addition, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectroscopy (FT-IR) analyses were used to further examine crystal quality, vibration, chemical binding conditions, In/Se orientation and structure of the prepared InSe thin films. When Raman results are examined, the B12 sample shows a more intensity and narrow peak at 248 cm −1. XPS measurements sowed that A6 sample exhibited more growth in low potential for a long time and better film stoichiometry compared to the other three samples. Also, FT-IR studies prove the presence of InSe. According to the results, the film did not form at low temperatures and short times. However, the film formation began with the increasing deposition temperature and time at the low potential value of −0.730 V. But, it is clear that a high quality film can be obtained in cathodic potential with −1.3 V and shorter deposition time with 300 s at room temperature respectively. Overall results showed that the high quality thin films can be obtained by the ECD technique. However, deposition conditions must be sensitively adjusted to control morphology of the electrodeposited nanoparticles.

Radiation Effects and Defects in Solids, 2016

Mn-doped p-InSe semiconductor crystals were grown by Bridgman-Stockbarger technique. The crystals... more Mn-doped p-InSe semiconductor crystals were grown by Bridgman-Stockbarger technique. The crystals were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fabricated Sn/InSe:Mn Schottky diodes. The current-voltage (I-V) and capacitance-voltage (C-V) measurements of diodes were investigated to determine the response of devices to electron irradiation with 9 MeV energy and 1.2 × 10 10 e − cm −2 dose. After irradiation, the ideality factor and barrier height of the Sn/InSe:Mn Schottky diode were determined as 1.66 and 0.85 eV, respectively. Before irradiation, they were determined as 1.37 and 0.90 eV, respectively. It has been concluded that the radiation with high energy may contribute to form defects at the interface of the Sn/InSe:Mn device.

Journal of Instrumentation, 2016

In this work we fabricated detectors based on semi-insulating GaAs and studied their electrical p... more In this work we fabricated detectors based on semi-insulating GaAs and studied their electrical properties (current-voltage characteristics, galvanomagnetic measurements) after irradiation with 5 MeV electrons from a linear accelerator up to a dose of 104 kGy. A series of detectors were prepared using Ti/Pt/Au Schottky contact with 1 mm diameter. The thickness of the base material was about 230 μm. A whole area Ni/AuGe/Au ohmic contact was evaporated on the back side. For galvanomagnetic measurements we used three samples from the same wafer. All samples were irradiated by a pulse beam of 5 MeV electrons using the linear accelerator in 11 steps, where the accumulative dose increased from 1 kGy up to 104 kGy. Also different dose rates (20, 40 and 80 kGy/h) were applied to the samples. After each irradiation step we performed electrical measurement of each sample. We analyze the electron Hall mobility, resistivity, electron Hall concentration, breakdown voltage and reverse current of samples before and after irradiation using different dose rates.

2019 IEEE Regional Symposium on Micro and Nanoelectronics (RSM), 2019

Electrochemical deposition method has been widely used due to its advantages in stoichiometry con... more Electrochemical deposition method has been widely used due to its advantages in stoichiometry control, large area growth, easy to form nano-structures, being low coast, possible formation of homogeneous thin films. In this study, Cu2ZnSnS4 (CZTS) thin films were deposited on ITO substrates by using single step electrodeposition method. CZTS absorber layers have been tried to be obtained at four different pH values of 4.70, 5.10, 5.70 and 6.23. Trisodium citrate was used as a complexing agent for co-electrodeposition. CZTS thin films were annealed for recrystallization in stoichiometric kesterite structure after deposition at 580 °C in sulfur powder and N2 atmosphere for 60 min. The structural, morphological and optical properties of CZTS thin films have been investigated by using X-ray diffraction (XRD), optical absorption techniques, scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy measurements. Diffraction peaks observed at 28.53°, 37.02°, 47.33°, 56.17°, 69.23° and 76.44° correspond to diffraction of (112), (202), (220), (312), (008) and (332) planes of CZTS films deposited in solution with pH 5.7, respectively. Thin films grown at other pH values, there are peaks observed from the secondary phases. CZTS films grown at pH: 5.7 has shown three Raman modes with a strong peak at 326 cm−1 and two weak peaks at 284 cm−1 and 367 cm−1, which are not visible in other films. These peaks are due to the kesterite CZTS structure present in CZTS films and well compatible with CZTS Raman peaks.