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Öğe Characterization of Al/In:ZnO/p-Si photodiodes for various In doped level to ZnO interfacial layers(ELSEVIER SCIENCE SA, 2018) Yildirim, Murat; Kocyigit, AdemThe detection of the light by a device is so important for industrial applications such as energy harvesting, sensing and switching. For that aim, we have introduced various In doped (0%, 0.1%, 0.5% and 1.0%) nanostructure ZnO thin films which was prepared by the sol-gel spin coating technique as interfacial materials between the Al metal and p-type Si for investigation photodetection properties of the material. According to morphological results of the In doped ZnO thin films at AFM, undoped and In doped ZnO thin films formed as fiber like structures. The obtained optical band gap energy for undoped, 0.1%, 0.5% and 1.0% In doped ZnO thin films were determined as 3.293 eV, 3.283 eV, 3.272 eV and 3.263 eV, respectively. The Al/In:ZnO/p-Si devices were characterized with I-V and C-V measurements. The I-V data was acquired under various illumination conditions to see the response of the devices to the light. The I-V characteristics have revealed that the devices have high ideality factors and, their values usually increased with increasing In doping level, but the rectifying properties decreased. In addition, barrier heights and series resistance values decreased with increasing In doping level. Also, the device parameters were calculated via Cheung and Norde methods for accuracy of the results. The current transient measurements highlighted that In doping provided to increase of light response. The C-V measurements have imparted that the capacitance values are strong function of the frequency and voltage for various In doping level. The devices can be thought and improved as photodiode and photodetector applications in the industry. (C) 2018 Elsevier B.V. All rights reserved.Öğe A comparison of the electrical characteristics of TiO2/p-Si/Ag, GNR-TiO2/p-Si/Ag and MWCNT-TiO2/p-Si/Ag photodiodes(SPRINGER, 2019) Erdal, Mehmet Okan; Yildirim, Murat; Kocyigit, AdemThe TiO2/p-Si/Ag, graphene nanoparticles doped (GNR) TiO2/p-Si/Ag and multi-walled carbon nanotube (MWCNT) doped TiO2/p-Si/Ag photodiodes were fabricated by electro-spinning technique at the same experimental conditions, and their structural, morphological and electrical properties were compared for photodiode applications. XRD measurements were confirmed undoped, GNR and MWCNT doped TiO2 structures, and brookite phase of (121) preferred orientation TiO2 has been observed from XRD patterns. SEM images of the heterojunctions showed that undoped and doped TiO2 layer have homogenous surfaces. I-V measurements were performed for electrical characterization of the TiO2/p-Si/Ag, GNR-TiO2/p-Si/Ag and MWCNT-TiO2/p-Si/Ag photodiodes under dark and light illumination conditions at room temperatures. The results imparted that all heterojunctions have good rectifying and photodiode properties. Some heterojunction parameters such as ideality factor, barrier height, series resistance were calculated and discussed in details according to thermionic emission theory, Cheung and Norde techniques. The determined ideality factor values are 8.55, 9.70 and 8.99, and barrier height values are 0.75 eV, 0.74 eV and 0.73 eV for the TiO2/p-Si/Ag, GNR-TiO2/p-Si/Ag and MWCNT-TiO2/p-Si/Ag photodiodes, respectively. These heterojunctions can be considered and improved as photodiodes in industrial applications.Öğe Determination of contact parameters of Au/n-Ge schottky barrier diode with rubrene interlayer(GAZI UNIV, 2017) Yildirim, MuratElectrical characterization of an Au/n-Ge semiconductor Schottky diode with organic (rubrene) interface has been systematically carried out over a wide temperature range. In sample fabrication stage, first, the ohmic In contact has been performed on one surface of n-Ge wafer grown in direction of (100). Later, the other surface of the wafer has been coated with rubrene by spin-coating method and then the Schottky contact has been constituted on the organic material via thermal evaporation method. The current-voltage (I-V) characteristics of prepared Schottky diode has been measured at a temperature range of 150-300 K and it has been observed that the diode have a rather good rectification behavior at all temperature. By using the I-V characteristics, the idealite factor, barrier height and some other diode parameters have been calculated for all temperatures. These parameters have also been calculated by means of Cheung-Cheung method. Werner and Guttler's model has been employed to analyze the temperature dependence of barrier height and ideality factor at low temperatures. The standard deviation of the zero-bias barrier height was calculated as 120 mV and the voltage coefficients of the barrier height were determined as rho(z) = 0.184 and rho(3) = 0.232 mV. At high temperatures, the zero-bias barrier height decreases with increasing temperature because of the temperature dependence of semiconductor band gap. The non-linearity has been observed in the Richardson plot due to temperature dependence of the zero-bias barrier height. Richardson constant was determined by using different methods. Of the current-voltage analysis's has emerged an abnormal decrease of apparent barrier height and increase of ideality factor at low temperature. It is determined that these abnormalies result due to the barrier height inhomogeneities prevailing at the organic-semiconductor interface. As a result, homogeneities in Au/rubrene/n-Ge Schottky barrier diode can be successfully characterized by a Gaussian distribution.Öğe Investigation of optical and device parameters of colloidal copper tungsten selenide ternary nanosheets(SPRINGER, 2018) Yildirim, Murat; Sarilmaz, Adem; Ozel, FarukHot injection synthesis route has been successfully applied for the preparation of high quality Cu2WSe4 (CWSe) nanosheets in order to determine their optical characterization and device parameters. Several techniques including XRD, SEM, TEM and SAED were used to characterize these nanosheets. These techniques confirmed that Cu2WSe4 nanosheets crystal shapes of synthesized are rectangular and square sheet and the average crystal size is between 20 and 40 nm. The spin coating technique was successfully used to deposit uniform of Cu2WSe4 thin film. Cu2WSe4 thin film has directly transition with a band gap of 1.64 eV. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple-Didomenico (WD) model. The single oscillator energy and the dispersion energy were estimated. Au/Cu2WSe4/n-Si structures was fabricated and its main electrical characteristics described by using current-voltage (I-V) methods. The forward and reverse bias current voltage (I-V) characteristics of Au/Cu2WSe4/n-Si at room temperature were studied to investigate its basic electrical parameters [i.e. saturation current (), ideality factor (), barrier height (), series ()]. Structural and optical mechanisms were discussed for future applications in optoelectronic devices.Öğe Investigation of optical framework of chalcostibite nanocrystal thin films: An insight into refractive index dispersion, optical band gap and single-oscillator parameters(ELSEVIER SCIENCE SA, 2017) Yildirim, Murat; Aljabour, Abdalaziz; Sarilmaz, Adem; Ozel, FarukHerein, we report the synthesis of chalcostibite ( CuSbS2) nanocrystals based on hot injection method and the characterization of CuSbS2 thin films by spin coating technique. The deposited films were subjected to the UV-Vis spectrophotometer, XRD, TEM and SAED for optical, structural, morphological and elemental analysis. XRD pattern showed that CuSbS2 nanocrystals have chalcostibite structures and SAED diffraction spots supported the XRD results. Different optical parameters like extinction coefficient, refractive index, real and imaginary parts of dielectric constant and surface and volume energy loss functions have been calculated applying single term Sellmeier dispersion relation and Wemple eDiDomenico single oscillator model. The obtained results are discussed in detail. The optical dispersion and dielectric properties of the CuSbS2 have been determined by the transmittance and reflectance modes in the range of 300-1600 nm. Thus, the CuSbS2 is transparent up to 40-45% in the visible range. The optical bandgap determined by the optical absorbance spectrum analysis showed that thin films possess direct bandgap of 1.86 eV. The calculated refractive index of thin film varies between 1.76 and 2.11 throughout the spectral region considered. The results presented here permit a better understanding of the properties of the chalcostibite nanocrystals which in turn result in the design of more efficient solar cells. (C) 2017 Elsevier B. V. All rights reserved.Öğe Investigation of structural, optical and dielectrical properties of Cu2WS4 thin film(SPRINGER, 2017) Yildirim, Murat; Ozel, Faruk; Sarilmaz, Adem; Aljabour, Abdalaziz; Patir, Imren HatayTernary I-Cu2WS4 were synthesized based on hot-injection process and their thin films are prepared by spin coating techniques at ambient temperature. The energy dispersive analysis of X-rays of the thin films confirmed that synthesized thin film is stoichiometric. Transmittance and reflectance have been used to determine the optical, dispersion and dielectric properties of the Cu2WS4 in the range of 200-2400 nm. The transparency of the Cu2WS4 is 40-45% in the visible range. Optical dispersion parameters have been calculated by using the single term Sellmeier dispersion relation and Wemple-DiDomenico single oscillator model. Several dispersion parameters were determined by the analysis of refractive index dispersion.Absorption coefficient (alpha), extinction coefficient (), the Urbach energy (), real and imaginary parts of dielectric constant (epsilon) and surface and volume energy loss function have been calculated. The optical bandgap determined by the optical absorbance spectrum analysis showed that thin films possess a direct bandgap of 1.74 eV.
