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Article Citation - WoS: 14Citation - Scopus: 14Temperature Dependence of Electrical Properties in In/Cu2< Diodes(indian Acad Sciences, 2019) Gullu, H. H.; Yildiz, D. E.; Surucu, O. Bayrakli; Terlemezoglu, M.; Parlak, M.Cu2ZnSnTe4 (CZTTe) thin films with In metal contact were deposited by thermal evaporation on monocrystalline n-type Si wafers with Ag ohmic contact to investigate the device characteristics of an In/CZTTe/Si/Ag diode. The variation in electrical characteristics of the diode was analysed by carrying out current-voltage (I-V) measurements in the temperature range of 220-360 K. The forward bias I-V behaviour was modelled according to the thermionic emission (TE) theory to obtain main diode parameters. In addition, the experimental data were detailed by taking into account the presence of an interfacial layer and possible dominant current transport mechanisms were studied under analysis of ideality factor, n. Strong effects of temperature were observed on zero-bias barrier height (Phi(B0)) and n values due to barrier height inhomogeneity at the interface. The anomaly observed in the analysis of TE was modelled by Gaussian distribution (GD) of barrier heights with 0.844 eV mean barrier height and 0.132 V standard deviation. According to the Tung's theoretical approach, a linear correlation between Phi(B0) and n cannot be satisfied, and thus the modified Richardson plot was used to determine Richardson constant (A*). As a result, A* was calculated approximately as 120.6 A cm(-2) K-2 very close to the theoretical value for n-Si. In addition, the effects of series resistance (R-s) by estimating from Cheng's function and density of surface states (N-ss) by taking the bias dependence of effective barrier height, were discussed.Article Citation - WoS: 5Citation - Scopus: 5Dielectric and photo-dielectric properties of TlGaSeS crystals(indian Acad Sciences, 2014) Qasrawi, A. F.; Abu-Zaid, Samah F.; Ghanameh, Salam A.; Gasanly, N. M.The room temperature, dark and photo-dielectric properties of the novel crystals TlGaSeS are investigated in the frequency, intensity and biasing voltage having ranges of similar to 1-120 MHz, 14-40 klux and 0-1 V, respectively. The crystals are observed to exhibit a dark high frequency effective dielectric constant value of similar to 10.65 x 10(3) with a quality factor of similar to 8.84 x 10(4) at similar to 120 MHz. The dielectric spectra showed sharp resonance-antiresonance peaks in the frequency range of similar to 25-250 kHz. When photoexcited, pronounced increase in the dielectric constant and in the quality factor values with increasing illumination intensity are observed. Signal amplification up to similar to 33% with improved signal quality up to similar to 29% is attainable via photoexcitation. On the other hand, the illuminated capacitance voltage characteristics of the crystals reflected a downward shift in the voltage biasing and in the built-in voltage of the device that is associated with increase in the uncompensated carrier density. The increase in the dielectric constant with increasing illumination intensity is ascribed to the decrease in the crystal's resistance as a result of increased free carrier density. The light sensitivity of the crystals, the improved dielectric properties and the lower biasing voltage obtained via photoexcitation and the well-enhanced signal quality factor of the crystals make them promising candidates for optical communication systems.Article Citation - WoS: 8Citation - Scopus: 9Investigation of Electrical Properties of In/Znin2< Diode(indian Acad Sciences, 2019) Gullu, H. H.In/ZnIn2Te4/n-Si/Ag diode structure was fabricated by the thermal deposition of a ZnIn2Te4 thin film on n-Si wafer substrate with Ag metal back contact. The structural characteristics of the film were investigated in terms of composition, X-ray diffraction and topographic measurements. The diode structure was completed by evaporating In metal on the film surface as a top contact. The diode parameters as saturation current, barrier height, ideality factor and series resistance values were determined from the semi-logarithmic forward bias current-voltage characteristics of the diode. According to the assumption of the thermionic emission model, the ideality factor was found higher than unity and it was also observed that the barrier height and ideality factor showed a temperature-dependent profile resulting from the non-ideality in the current-voltage behaviour of the diode. As a result, the model was modified by considering inhomogeneous barrier formation and Gaussian distribution was expected to be dominant on 1.37 eV mean barrier height with a deviation of 0.18. In addition, the voltage dependence of these Gaussian diode parameters was investigated. The forward and reverse bias capacitance and conductance measurements showed that there was a slight change in capacitance values with frequency whereas the conductance values decreased with increase in frequency. In addition to the current-voltage analysis, the distribution of density of interface states and the values of series resistance were evaluated as a function of bias voltage and frequency.Article Citation - WoS: 12Citation - Scopus: 14Coating of Titanium Implants With Boron Nitride by Rf-Magnetron Sputtering(indian Acad Sciences, 2016) Gokmenoglu, Ceren; Ozmeric, Nurdan; Cakal, Gaye; Dokmetas, Nihan; Ergene, Cansu; Kaftanoglu, BilginSurface modification is necessary for titanium implants since it is unable to induce bone apposition. The beneficial effects of boron on bone formation, composition and physical properties make it suitable as a coating material. In the present study, surface properties of boron nitride (BN) coating on titanium implants were evaluated. Twenty-four implants and 12 abutments were coated with BN by RF-magnetron sputtering system. ATR-FTIR measurements were conducted to assess surface chemistry and morphology of BN-coated implants. Adhesion tests were performed by CSM nanoscratch test device to determine adhesion of BN to titanium surface. Surface profilometry and atomic force microscopy (AFM) was used to evaluate surface roughness. Mean roughness values were calculated. Contact angle measurements were done for evaluation of wettability. Surface characterization of coated implants was repeated after RF power of the system was increased and voltage values were changed to evaluate if these settings have an impact on coating quality. Three different voltage values were used for this purpose. Hexagonal-BN was determined in FTIR spectra. RF-coating technique provided adequate adherence of BN coatings to the titanium surface. A uniform BN coating layer was formed on the titanium implants with no deformation on the titanium surface. Similar roughness values were maintained after BN coating procedure. Before coating, the contact angles of the implants were in between 63(ay) and 79(ay), whereas BN coated implants' contact angles ranged between 46(ay) and 67(ay). BN-coated implant surfaces still have hydrophilic characteristics. The change in voltage values seemed to affect the surface coating characteristics. Especially, the phase of the BN coating was different when different voltages were used. According to our results, BN coating can be sufficiently performed on pretreated implant surfaces and the characteristics of BN coated surfaces can be changed with the change in parameters of RF-magnetron sputtering system.Article Citation - WoS: 5Citation - Scopus: 5Influence of Layer on the Electrical Properties of Au/N-4h Sic Diodes(indian Acad Sciences, 2018) Yigiterol, Fatih; Gullu, Hasan H.; Yildiz, Esra D.In this study, the effect of insulator layer on the electrical characteristics of Au/n-4H SiC diode was investigated. The current-voltage (), capacitance-voltage () and conductance-voltage () measurements were carried out at room temperature condition. Under thermionic emission model, electrical parameters as zero-bias barrier height (), ideality factor (n), interface states (), and series () and shunt () resistances were estimated from forward bias analyses. The values of n and were about 1.305 and 0.796 eV for metal-semiconductor (MS) rectifying diode, and 3.142 and 0.713 eV for metal-insulator-semiconductor (MIS) diode with the insertion of layer, respectively. Since the values of n were greater than the unity, the fabricated diodes showed non-ideal behaviour. The energy distribution profile of of the diodes was calculated by taking into account of the bias dependence of the effective barrier height () and . The obtained values with are almost one order of magnitude lower than those without for two diodes. According to Cheung's model, were calculated and these values were found in increasing behaviour with the contribution of insulator layer. In addition, the plot behaviours with linear dependence between ln() vs. indicated that the dominant conduction mechanism in the reverse bias region was Schottky effect for both MS and MIS diodes. In the room temperature measurements, different from the results of MIS diode, the values of C for MS diode was observed in decreasing behaviour from ideality with crossing the certain forward bias voltage point ( ). The decrease in the negative capacitance corresponds to the increase of G / w.Article Citation - WoS: 13Citation - Scopus: 13Thermally Assisted Variable Range Hopping in Tl4s3< Crystal(indian Acad Sciences, 2015) Ziqan, Abdelhalim M.; Qasrawi, A. F.; Mohammad, Abdulftah H.; Gasanly, N. M.In this study, a modified model for the application of the thermionic and hopping current conduction mechanisms in the presence of continuous mixed conduction is investigated, discussed, experimented and simulated. It is observed that there exists a contribution from the hopping conductivity to the total conduction even at temperature ranges where the thermionic emission is mainly dominant. The contribution weight of a specific mechanism at particular temperature range is estimated. In addition, a modification to the Mott's variable range hopping (VRH) transport parameters like density of localized state near the Fermi level, the average hopping range and the hopping energy in the presence of mixed conduction mechanism is also reported. This new approach corrects the evaluated electrical parameters that are necessary for the construction of electronic devices like absorption layers in solar cells. This proposed model is also used to explain the conduction mechanism and investigate the electrical conduction thermionic and Mott's VRH parameters in Tl4S3Se crystals and in CuAlO2 thin films.
