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Öğe Analysis of current conduction mechanism in CZTSSe/n-Si structure(Springer, 2018) Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Güllü, Hasan Hüseyin; Çolako?lu, Tahir; Yıldız, Dilber Esra; Parlak, MehmetIn this study, Cu2ZnSn(S,Se)(4) (CZTSSe) thin films were deposited by the single step thermal evaporation process using the sintered powder of CZTSSe on soda lime glass (SLG) and Si wafer substrates. The structural, optical, and electrical properties of deposited films were investigated. Current-voltage (I-V) in the temperature range of 250-350 K, capacitance-voltage(C-V) and conductance-voltage (G/w-V) measurements at room temperature were carried out to determine electrical properties of CZTSSe/n-Si structure. The forward bias I-V analysis based on thermionic emission (TE) showed barrier height inhomogeneity at the interface and thus, the conduction mechanism was modeled under the assumption of Gaussian distribution of barrier height. The mean barrier height and standard deviation at zero bias were obtained as 1.27 eV and 0.18 V, respectively. Moreover, Richardson constant was obtained as 120.46 A cm(-2) K-2 via modified Richardson plot and the density of interface states (D-it) profile was determined using the data obtained from forward bias I-V measurements. In addition, by the results of frequency dependent C-V measurements, characteristics of the interface state density were calculated applying high-low frequency capacitance (C-HF - C-LF) and Hill-Coleman methods.Öğe Characterization of Cu-rich and Zn-poor Cu2ZnSnS4 single crystal grown by vertical Bridgman technique(Elsevier B.V., 2021) Peksu, Elif; Terlemezoğlu, Makbule; Parlak, Mehmet; Karaağaç, HakanTo date, although a number of studies have focused on understanding the fundamental properties of Cu-poor/Zn-rich Cu2ZnSnS4 (CZTS) single crystals, little attention has been paid to investigate the physical properties of those with a Cu-rich / Zn-poor chemical composition. Therefore, in this study, the structural and electrical properties of Cu-rich/Zn-poor CZTS single crystal grown by the Bridgman technique have been studied in order to fill this gap in literature. XRD and Raman findings confirm the growth of CZTS single crystal having a kesterite phase without secondary phases. Hall and temperature dependent conductivity measurements reveal the presence of VCu and CuZn antisite point defects in CZTS during the growth stage with thermal activation energies of 15 meV and ?100 meV, respectively. Hall mobility, resistivity and hole carrier concentration values at room temperature were found to be 1.2 cm2/V.s, 16.2 ?.cm and 3.1 × 1017 cm?3, respectively. © 2021 Elsevier B.V.Öğe Characterization of one-step deposited Cu2ZnSnS4 thin films derived from a single crystalline powder(Pergamon-Elsevier Science Ltd, 2019) Peksu, Elif; Terlemezoğlu, Makbule; Parlak, Mehmet; Karaağaç, HakanIn this paper, Cu-deficient and Zn-rich Cu2ZnSnS4 (CZTS) single crystals were successfully grown by Bridgman technique. Following the investigation of structural and photo-electrical properties of the grown CZTS crystal, the powder extracted from it was evaporated through electron-beam technique for the fabrication of CZTS thin films by one-step deposition. Compositional analysis revealed that CZTS thin films were obtained with a composition stoichiometry very close to that measured for the crystal powder. Detailed XRD and Raman analyses have shown that the as-grown CZTS films have an amorphous matrix and then transform into a polycrystalline form with a monophase kesterite phase having (112) oriented plane direction following the post-annealing process at 500 degrees C. The optical band gap was found to be 1.50 eV for the CZTS film annealed 500 degrees C. The conducted photo-electrical measurements revealed that CZTS thin films have good sensitivity to the visible light, which is essential for an absorber layer in the solar cell device structure. The room temperature values of conductivity, mobility and hole carrier concentration of the films annealed at 500 degrees C were determined as similar to 5.1 x 10(-4) (Omega cm)(-1), 1.22 cm(2)/V s and 2.6 x 10(15) cm(-3), respectively. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Construction of self-assembled vertical nanoflakes on CZTSSe thin films(Institute of Physics Publishing, 2019) Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Çolako?lu, Tahir; Abak, Musa Kurtuluş; Güllü, Hasan Hüseyin; Erçelebi, Çiğdem; Parlak, MehmetCu2ZnSn(S, Se)4 (CZTSSe) is a promising alternative absorber material to achieve high power conversion efficiencies, besides its property of involving low-cost and earth-abundant elements when compared to Cu(In, Ga)Se2 (CIGS) and cadmium telluride (CdTe), to be used in solar cell technology. In this study, a novel fabrication technique was developed by utilizing RF sputtering deposition of CZTSSe thin films having a surface decorated with self-assembled nanoflakes. The formation of nanoflakes was investigated by detailed spectroscopic method of analysis in the effect of each stacked layer deposition in an optimized sequence and the size of nanoflakes by an accurate control of sputtering process including film thickness. Moreover, the effects of substrate temperature on the formation of nanoflakes on the film surface were discussed at a fixed deposition route. One of the main advantages arising from the film surface with self-assembled nanoflakes is the efficient light trapping which decreases the surface reflectance. As a result of the detailed production and characterization studies, it was observed that there was a possibility of repeatable and controllable fabrication sequence for the preparation of CZTSSe thin films with self-textured surfaces yielding low surface reflectance. © 2018 IOP Publishing Ltd.Öğe CZTSSe thin films fabricated by single step deposition for superstrate solar cell applications(Springer New York LLC, 2019) Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Doğru Balbaşı, Çiğdem; Güllü, Hasan Hüseyin; Çiftpınar, Hande; Erçelebi, Çiğdem; Parlak, MehmetThe focus of this study is the characterization of Cu2ZnSn(S,Se)4 (CZTSSe) thin films and fabrication of CZTSSe solar cell in superstrate configuration. In this work, superstrate-type configuration of glass/ITO/CdS/CZTSSe/Au was entirely fabricated by totally vacuum-based process. CZTSSe absorber layers were grown by RF magnetron sputtering technique using stacked layer procedure. SnS, CuSe and ZnSe solid targets were used as precursors and no additional step like the selenization process was applied. The structural and morphological properties of deposited CZTSSe layers were analyzed using X-ray diffraction (XRD), Raman scattering, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analysis (EDS) measurements. The optical and electrical properties of the CZTSSe thin films were investigated by UV–Vis spectroscopy, Hall-Effect and photoconductivity measurements. In addition, the device performance of the fabricated superstrate solar cell was examined. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Öğe Deposition of CZTSe thin films and illumination effects on the device properties of Ag/n-Si/p-CZTSe/In heterostructure(Elsevier Science Sa, 2017) Bayraklı Sürücü, Özge; Terlemezoğlu, Makbule; Güllü, H. H.; Parlak, MehmetCharacterization of Cu2ZnSnSe4 (CZTSe) thin films deposited by thermal evaporation sequentially from the pure elemental sources and in-situ post annealing was carried out at 400 C under Se evaporation atmosphere. Another annealing process was applied in nitrogen atmosphere at 450 degrees C to get poly-crystalline monophase CZTSe film structure. XRD analysis together with Raman spectroscopy was used to determine the structural properties. Spectral optical absorption coefficient evaluated from transmission data showed the band gap value of 1.49 eV for annealed film. Electrical measurements indicated that CZTSe thin films have p-type semiconductor behavior with the carrier density and mobility values of 10(-19) cm(-3) and 0.70 cm(2)/(V.s). Illumination effects on the device properties of Ag/n-Si/p-CZTSe/In heterostructure were investigated by analyzing current-voltage(I-V) and frequency dependent capacitance-voltage(C-V) data. Under the illumination, Ag/n-Si/p-CZTSe/In heterostructure showed photodiode behavior having V-oc value of 100 mV and I-sc value of 27.5 mu A. With the illumination, series resistances (R-s), diode ideality factor (n) and barrier height (Phi(b)) decreased and shunt resistance (R-sh) increased. Capacitance value at lower frequency decreased due to the illumination effect. (C) 2017 Elsevier B.V. All rights reserved.Öğe Determination of current transport characteristics in Au-Cu/CuO/n-Si Schottky diodes(Elsevier B.V., 2019) Bayraklı Sürücü, Özge; Güllü, Hasan Hüseyin; Terlemezoğlu, Makbule; Yıldız, D. E.; Parlak, MehmetIn this study, the material properties of CuO thin films fabricated by sputtering technique and electrical properties of CuO/n-Si structure were reported. Temperature-dependent current-voltage (I-V) measurement was carried out to determine the detail electrical characteristics of this structure. The anomaly in thermionic emission (TE) model related to barrier height inhomogeneity at the interface was obtained from the forward bias I-V analysis. The current transport mechanism at the junction was determined under the assumption of TE with Gaussian distribution of barrier height. In this analysis, standard deviation and mean zero bias barrier height were evaluated as 0.176 and 1.48 eV, respectively. Depending on the change in the diode parameters with temperature, Richardson constant was recalculated as 110.20 Acm?2K?2 with the help of modified Richardson plot. In addition, density of states at the interface were determined by using the forward bias I-V results. © 2019 Elsevier B.V.Öğe Electrical characterization of CdZnTe/Si diode structure(Springer, 2020) Balbasi, C.D.; Terlemezoğlu, Makbule; Güllü, H. H.; Yıldız, D. E.; Parlak, MehmetTemperature-dependent current-voltage (I- V) , and frequency dependent capacitance-voltage (C- V) and conductance-voltage (G- V) measurements were performed in order to analyze characteristics of CdZnTe/Si structure. Obtained profiles enable us to understand the different characteristics of the diode structure such as the carrier conduction mechanism and the nature of the interfacial layer. Over the temperature range between 220 and 340 K, taking consideration of the disparity in the forward-biased current, the diode parameters such as saturation current (I) , zero-bias barrier height (? B) and ideality factor (n) have been obtained. The barrier height increased (0.53 to 0.80 eV) while the ideality factor decreased (4.63 to 2.79) with increasing temperature from 220 to 340 K, indicating an improvement in the junction characteristics at high temperatures. Due to the inhomogeneity in barrier height, the conduction mechanism was investigated by Gaussian distribution analysis. Hence, the mean zero-bias barrier height (? ¯ B) and zero-bias standard deviation (?) were calculated as 1.31 eV and 0.18, respectively. Moreover, for holes in p-type Si, Richardson constant was found to be 32.09 A cm?2 K?2 via modified Richardson plot. Using the capacitance-voltage (C- V) and conductance-voltage (G- V) characteristics, series resistance (Rs) and density of interfacial traps (Dit) have been also investigated in detail. A decreasing trend for Rs and Dit profiles with increasing frequency was observed due to the impurities at the CdZnTe/Si interface and interfacial layer between the front metal contact and CdZnTe film. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Öğe Fabrication of CdSeXTe1-x thin films by sequential growth using double sources(Elsevier, 2021) Demir, M.; Güllü, H. H.; Terlemezoğlu, Makbule; Parlak, MehmetCdSexTe(1-x) (CST) ternary thin films were fabricated by stacking thermally evaporated CdSe and electron beam evaporated CdTe layers. The final structure was achieved in a stoichiometric form of approximately Cd:Se:Te = 50:25:25. The post-annealing processes at 300, 400, and 450 degrees C were applied to trigger the compound formation of CST thin films. The X-ray diffraction (XRD) profiles revealed that CdTe and CdSe have major peaks at 23.9 degrees and 25.5 degrees corresponds to (111) direction in cubic zinc-blend structure. Raman modes of CdTe were observed at 140 and 168 cm(-1), while Raman modes of CdSe films were detected at 208 and 417 cm(-1). The post-annealing process was found to be an effective method in order to combine both diffraction peaks and the vibrational modes of CdTe and CdSe, consequently to form CST ternary alloy. Transmission spectroscopy analysis revealed that CST films have direct band gap value of 1.6 eV.Öğe Frequency effect on electrical and dielectric characteristics of In/Cu 2 ZnSnTe 4 /Si/Ag diode structure(Springer New York LLC, 2019) Güllü, H. H.; Bayraklı Sürücü, Özge; Terlemezoğlu, Makbule; Yıldız, D. E.; Parlak, MehmetIn/Cu 2 ZnSnTe 4 /Si/Ag diode structure was fabricated by sputtering Cu 2 ZnSnTe 4 (CZTTe) thin film layer on the Si layer with In front contact. The frequency dependent room temperature capacitance and conductance measurements were carried out to obtain detailed information of its electrical characteristics. Admittance spectra of the diode exhibited strong frequency dependence and the obtained values showed decreasing behavior with the increase in the applied frequency. The effect of interfacial film layer with series resistance values and density of interface states were investigated by taking into consideration of non-ideal electrical characteristics of the diode. The distribution profile of the interface states was extracted by Hill-Coleman and high–low frequency capacitance methods. As a function of frequency, they were in proportionality with the inverse of applied frequency. Dielectric constant and dielectric loss parameters were calculated from the maximum value of the diode capacitance at the strong accumulation region. The loss tangent showed a characteristic peak behavior at each frequency. Based on the time-dependent response of the interfacial charges to the applied ac field, the values of ac electrical conductivity and complex electric modulus were calculated and discussed as a function of frequency and bias voltage. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Öğe Growth and Characterization of Stoichiometric Cu2ZnSnS4 Crystal Using Vertical Bridgman Technique(John Wiley and Sons Inc, 2022) Peksu, Elif; Terlemezoğlu, Makbule; Parlak, Mehmet; Karaağaç, HakanStoichiometric Cu2ZnSnS4 (CZTS) single phase crystals are successfully grown in a single-zone vertical furnace by Bridgman technique. X-ray diffraction (XRD) and Raman spectroscopy measurements are employed to investigate the structural properties of the grown crystals, which verifies the formation of mono-phase CZTS crystals with kesterite structure. The energy-dispersive X-ray analysis (EDS) indicates the growth of CZTS single phase crystals with a nearly stoichiometric chemical composition. The carrier concentration, mobility, and resistivity of the crystals are determined from Hall Effect measurements. At room temperature, the respective values are found to be 4.0 × 1015 cm?3, 1.0 cm2 Vs?1, and 1540 ? cm. The activation energies for the acceptor levels are also determined using the temperature-dependent hole concentration measurement. CuZn-antisite originated acceptor level with activation energies of ?121 meV is identified in a nearly stoichiometric kesterite structure. © 2021 Wiley-VCH GmbHÖğe Illumination and voltage effects on the forward and reverse bias current-voltage (I-V) characteristics in In/In2S3/p-Si photodiodes(Springer, 2021) Yükseltürk, Esra; Sürücü, Özge; Terlemezoğlu, Makbule; Parlak, Mehmet; Altındal, ŞemsettinThe illumination and voltage effects on the I-V measurements of the fabricated In/In2S3/p-Si photodiode were investigated in dark and under various illumination intensities (20–100 mW/cm2) between ± 2 V. Two linear regions in the forward-bias ln(I)-V plots were observed. The value of diode ideality factor (n) had an increasing trend with increasing illumination intensity while the barrier height (?Bo) had a decreasing trend due to the increase of photocurrent. The photodiode properties were also investigated, and the value of linear-dynamic value range (LDR) was found to be 20.56 dB. The photoresponse (Iph/Idark), the photoresponsivity (R), and specific detectivity (D*) of the photodiode were calculated as a function of the illumination. The open-circuit voltage (Voc) and short-current (Isc) were found to be 0.36 V and 2.87 mA under 100 mW.cm?2 illumination intensity, respectively. The possible conduction mechanisms (CMs) were investigated using the forward ln(I)-V and reverse ln(I)-V0.5 plots. The energy-dependent surface states (Nss) profile was extracted from the positive I-V data by considering voltage-dependent barrier height (BH) and ideality factor (n) in dark and illumination at 100 mW/cm2. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Öğe Investigation of band gap energy versus temperature for SnS2 thin films grown by RF-magnetron sputtering(Elsevier B.V., 2020) Işık, M.; Güllü, H. H.; Terlemezoğlu, Makbule; Surucu, O.B.; Parlak, Mehmet; Gasanly, Nizami MamedSnS2 thin films grown by magnetron sputtering technique were characterized by structurally and optically in the present work. Crystalline parameters, atomic compositions, and surface characteristics of SnS2 thin films were presented according to results of applied structural techniques. Optical studies of SnS2 thin films were accomplished by Raman spectroscopy and transmission methods. Raman spectrum exhibited two modes around 198 and 320 cm?1. Transmittance data obtained for various temperatures between 10 and 300 K were analyzed to reveal various optical characteristics like band gap energy, variation rate of gap energy with temperature, average phonon energy, gap energy at absolute zero. Band gap energy of SnS2 thin films were reported as 2.18 and 2.22 eV at 300 and 10 K, respectively. The temperature-band gap energy dependency was analyzed taking into account the Varshni and O'Donnell-Chen models. © 2020 Elsevier B.V.Öğe Investigation of carrier transport mechanisms in the Cu-Zn-Se based hetero-structure grown by sputtering technique(Canadian Science Publishing, Nrc Research Press, 2018) Güllü, H. H.; Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Yıldız, D. E.; Parlak, MehmetIn this paper, we present results of the electrical characterization of n-Si/p-Cu-Zn-Se hetero-structure. Sputtered film was found in Se-rich behavior with tetragonal polycrystalline nature along with (112) preferred orientation. The band gap energy for direct optical transitions was obtained as 2.65 eV. The results of the conductivity measurements indicated p-type behavior and carrier transport mechanism was modelled according to thermionic emission theory. Detailed electrical characterization of this structure was carried out with the help of temperature-dependent current-voltage measurements in the temperature range of 220-360 K, room temperature, and frequency-dependent capacitance-voltage and conductance-voltage measurements. The anomaly in current-voltage characteristics was related to barrier height inhomogeneity at the interface and modified by the assumption of Gaussian distribution of barrier height, in which mean barrier height and standard deviation at zero bias were found as 2.11 and 0.24 eV, respectively. Moreover, Richardson constant value was determined as 141.95 Acm(-2)K(-2) by means of modified Richardson plot.Öğe Investigation of electrical characteristics of Ag/ZnO/Si sandwich structure(Springer New York LLC, 2019) Güllü, H. H.; Bayraklı Sürücü, Özge; Terlemezoğlu, Makbule; Yıldız, D. E.; Parlak, MehmetIn this study, temperature-dependent current–voltage (I–V), frequency-dependent capacitance–voltage (C–V) and conductance–voltage (G/ ?- V) measurements are carried out for the electrical characterization of a zinc oxide (ZnO) thin film-based diode. The sandwich structure in the form of Ag/ZnO/Si/Al is investigated at temperatures between 220 and 360 K and in the frequency region of 1 kHz–1 MHz. ZnO thin film layer is deposited on a p-Si wafer substrate as a transparent conductive oxide layer by taking into consideration possible electronic applications with intrinsic attractive material properties. At each temperature step, the I–V curves showed about two orders of magnitude rectifying behavior and, according to the Schottky diode relation, the saturation current, zero-bias barrier height and ideality factor were extracted as a function of the temperature. In the case of non-ideal diode characteristics due to the inhomogeneties in the diode as observed from the characteristics of the calculated parameters, effective barrier height values are evaluated. In addition, based on the existence of the interface layer, density of interface states in the band gap region and parasitic resistances were determined by the capacitance measurements. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Öğe Investigation of precursor sequence and post-annealing effects on the properties of Cu2SnZnSe4 thin films deposited by the elemental thermal evaporation(Iop Publishing Ltd, 2017) Bayraklı Sürücü, Özge; Terlemezoğlu, Makbule; Güllü, H. H.; Parlak, MehmetCu2ZnSnSe4 (CZTSe) thin films were deposited onto soda lime glass substrates by thermal evaporation using the pure elemental sources. The influence of the sequential deposition order of Zn and Sn precursor layers for different evaporation cycles were investigated. In situ annealing at 400 degrees C under Se evaporation was applied to promote conversion of precursor layers to quaternary compound structure and additionally, subsequent post-annealing processes under nitrogen atmosphere at 450 degrees C was carried out to improve the crystalline behavior. The analyses concluded that the substrate temperature kept at 400 degrees C during selenization was not adequate to form homogenous CZTSe structure and as a result of post-annealing treatment, the polycrystalline quaternary CZTSe film structure was obtained. Structural analysis showed that in comparison with the initial Sn precursor layer, the growth process starting with Zn was found to be the preferable method to form better crystalline CZTSe structure. Furthermore, the stacking layer order and annealing processes showed the important effect on the stoichiometry and surface morphology of the films. The optical band gap energies were around 1.10 eV and also from Tauc plots, 1.40 eV was observed due to the admixture of secondary phases. The room temperature resistivity values and hole carrier densities were obtained around 10(-2) Omega cm and 1019 cm(-3), respectively. The mobility values of the samples were found in between 0.51 and 0.75 cm(2) V-1 s(-1).Öğe Material and Si-based diode analyses of sputtered ZnTe thin films(Springer, 2020) Güllü, H. H.; Surucu, O.B.; Işık, M.; Terlemezoğlu, Makbule; Parlak, MehmetStructural, optical, and electrical properties ZnTe thin films grown by magnetron sputtering technique were studied by X-ray diffraction, atomic force microscopy, Raman spectroscopy, and electrical conductivity measurements. Structural analyses showed that ZnTe thin films grown on soda–lime glass substrates have a cubic crystalline structure. This crystalline nature of the films was also discussed in terms of Raman active modes. From atomic force microscopy images, the smooth and dense surface profile was observed. The conductivity of the film at room temperature was measured as 2.45 × 10?4 (? cm)?1 and the temperature dependency of conductivity showed Arrhenius behavior. The dark conductivity profile was modeled by thermionic emission mechanism and activation energies were extracted. In addition, the conductivity values indicated an increasing behavior with illumination intensity applied between 20 and 115 mW/cm2. The heterojunction diode was generated by sputtering ZnTe film on n-Si wafer substrate and the rectification behavior was evaluated to determine the main diode parameters. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.Öğe Temperature dependence of band gaps in sputtered SnSe thin films(Elsevier Ltd, 2019) Delice, S.; Işık, M.; Güllü, H. H.; Terlemezoğlu, Makbule; Bayraklı Sürücü, Özge; Parlak, Mehmet; Gasanly, Nizami MamedTemperature-dependent transmission experiments were performed for tin selenide (SnSe) thin films deposited by rf magnetron sputtering method in between 10 and 300 K and in the wavelength region of 400–1000 nm. Transmission spectra exhibited sharp decrease near the absorption edge around 900 nm. The transmittance spectra were analyzed using Tauc relation and first derivative spectroscopy techniques to get band gap energy of the SnSe thin films. Both of the applied methods resulted in existence of two band gaps with energies around 1.34 and 1.56 eV. The origin of these band gaps was investigated and it was assigned to the splitting of valence band into two bands due to spin-orbit interaction. Alteration of these band gap values due to varying sample temperature of the thin films were also explored in the study. It was seen that the gap energy values increased almost linearly with decreasing temperature as expected according to theoretical knowledge. © 2019 Elsevier LtdÖğe Temperature dependence of electrical properties in In/Cu 2 ZnSnTe 4 /Si/Ag diodes(Indian Academy of Sciences, 2019) Güllü, H. H.; Yıldız, D. E.; Bayraklı Sürücü, Özge; Terlemezoğlu, Makbule; Parlak, MehmetCu 2 ZnSnTe 4 (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 (? B 0 ) 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 ? B 0 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 120.6Acm-2K-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. © 2019, Indian Academy of Sciences.Öğe Temperature dependent band gap in SnS2xSe(2-2x) (x = 0.5) thin films(Elsevier Ltd, 2020) Delice, S.; Işık, M.; Güllü, H. H.; Terlemezoğlu, Makbule; Surucu, O.B.; Gasanly, Nizami Mamed; Parlak, MehmetStructural and optical properties of SnS2xSe(2-2x) thin films grown by magnetron sputtering method were investigated for composition of x = 0.5 (SnSSe) in the present study. X-ray diffraction, energy dispersive X-ray spectroscopy, atomic force microscopy and scanning electron microscopy methods were used for structural characterization while temperature-dependent transmission measurements carried out at various temperatures in between 10 and 300 K were accomplished for optical investigations. X-ray diffraction pattern of studied composition presented peaks at positions which are between those of SnSe2 and SnS2. Transmittance spectra recorded at all applied temperatures were analyzed using well-known Tauc relation. Analyses revealed the direct band gap energy value of SnSSe thin films as 1.75 eV at room temperature. Change of band gap energy as a response to varying temperature were discussed in the study by utilizing Varshni relation. It was shown that variation of gap energy values was well-matched with the Varshni's empirical formula. Energy band gap at absolute zero and rate of change of band gap with temperature were found to be 1.783 eV and ?2.1 × 10?4 eV K?1, respectively. © 2020 Elsevier Ltd
