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Öğe A comparative photoluminescence study on Mn-Free GaAs/AlAs and Mn-containing Ga1-xMnxAs/AlAs quantum wells (QWs) grown on various orientations by MBE(Taylor & Francis Ltd, 2016) Gunes, M.; Erken, O.; Gumus, C.; Yalaz, E.; Pesen, E.; Ukelge, M. O.; Arpapay, B.Optical properties of diluted magnetic semiconductor Ga0.999Mn0.001As/AlAs quantum well structures grown on (1 0 0 ), (1 1 0), (3 1 1)B and (4 1 1)B by molecular beam epitaxy are reported. Temperature-dependent spectral photoluminescence (PL) measurement was performed at temperatures between 15 and 300K. The PL measurements showed that band gap of the alloy decreases with increasing lattice temperature regardless the growth orientations. S-shaped temperature dependence has been observed in the samples grown on (1 0 0), (3 1 1)B, (4 1 1)B orientations. PL emission energy is fitted with Varshni and Bose-Einstein Approximation to determine Debye temperature (beta), (Theta(E)) and thermal expansion coefficient (alpha), the exciton-phonon coupling strength (a(B)).Öğe A study of the electronic and physical properties of SnO2 thin films as a function of substrate temperature(Elsevier Sci Ltd, 2019) Erken, O.; Ozkendir, O. M.; Gunes, M.; Harputlu, E.; Ulutas, C.; Gumus, C.In this work, tin dioxide (SnO2) thin films were prepared at various substrate temperatures (380-440 degrees C, in steps of 20 degrees C) on glass substrates by the Spray Pyrolysis Method. X-ray Diffraction (XRD) measurements revealed that the SnO2 thin films were formed in a tetragonal crystallized structure. The electronic structure of the tin dioxide thin films that were prepared at several substrate temperatures were investigated with the collected X-ray Absorption Spectroscopy (XAS) data. The crystal structure analysis was also supported by the Extended X-ray Absorption Fine Structure (EXAFS) data analysis extracted from the X-ray Absorption Fine Structure (XAFS) data. Unstable crystal behaviors were detected in the samples due to metastable SnO structure formations as a result of phase transitions from the SnO to SnO2 structure during the annealing processes. Clear information on the atomic displacements in the samples as a picture of the crystal mechanism was obtained from the analysis of EXAFS data. The SnO2 thin films were found to exhibit high transmittance (average 90%) in the 400-1100 nm interval. The thickness of the SnO2 thin film (t) and refractive index (n) were calculated from transmittance spectra in the visible region using envelope method. The direct energy band gaps of the films obtained were 4.01-4.09 eV. Atomic force microscope (AFM) measurements were performed in order to investigate the surface roughness of the SnO2 thin films.Öğe Effect of molar concentration on the structural, linear and nonlinear optical properties of CuS (covellite) thin films(Elsevier Ltd, 2022) Habiboglu, C.; Erken, O.; Gunes, M.; Yilmaz, O.; Cevlik, H.C.; Ulutas, C.; Gumus, C.CuS thin films with various molar concentrations at 70 °C temperature were deposited by Chemical Bath Deposition. The effect of molar concentration on the structural, linear optic, nonlinear optic and morphological properties of CuS films were deeply investigated. X-ray diffraction (XRD) analysis exhibited that CuS films were formed in polycrystal structure and hexagonal phase. The fundamental optical parameters of films such as energy band gap, reflection and extinction coefficient were determined with the results of optical transmission and optical absorption by UV–vis spectrophotometer. The energy band gap values were reduced with increasing films thickness. Moreover, the dependence of the optical dielectric constants, loss tangent, optical conductivity, surface and volume energy loss function values on the molar concentrations were studied. Furthermore, the third order nonlinear optical susceptibility and nonlinear refractive index, which is considered to be the base of the first order optical susceptibility with nonlinear optical properties were discussed in detail. © 2022 Elsevier LtdÖğe Effect of the deposition time on optical and electrical properties of semiconductor ZnS thin films prepared by chemical bath deposition(Natl Inst Science Communication-Niscair, 2017) Erken, O.; Gunes, M.; Ozaslan, D.; Gumus, C.Semiconductor ZnS thin films have been deposited by a chemical bath deposition (CBD) on a glass substrate at 80 degrees C with different deposition time (4, 6 and 8 h), The films have been further studied in order to determine the change in optical and electrical properties as a function of deposition time. The film thicknesses have been calculated between 210 - 1375 nm by using gravimetrical analysis. The optical properties of ZnS thin films have been determined by transmittance (%T) and absorbance (A) measurements by UV-Vis spectroscopy operated wavelength range between 300 and 1100 nm at room temperature. The optical transmittance values of ZnS thin films in the visible region of the electromagnetic spectrum have been found to be between 51-90%. The calculations indicate that the refractive index (n) in the visible region is between 1.40 and 2.45. The optical band gaps (E-g) of thin films have been calculated between 3.61-3.88 eV while the band edge sharpness values (B) are varied between 6.95 x 10(9)-8.96 x 10(10) eV/cm(2). The specific resistivity values (p) of the films are found to be between 1.08 x 10(5)-1.01 x 10(6) Omega.cm and exhibit an n-type conductivity by Hall measurement.Öğe Effect of the deposition time on optical and electrical properties of semiconductor ZnS thin films prepared by chemical bath deposition(National Institute of Science Communication and Information Resources (NISCAIR), 2017) Erken, O.; Gunes, M.; Ozaslan, D.; Gumus, C.Semiconductor ZnS thin films have been deposited by a chemical bath deposition (CBD) on a glass substrate at 80 °C with different deposition time (4, 6 and 8 h). The films have been further studied in order to determine the change in optical and electrical properties as a function of deposition time. The film thicknesses have been calculated between 210 - 1375 nm by using gravimetrical analysis. The optical properties of ZnS thin films have been determined by transmittance (%T) and absorbance (A) measurements by UV-Vis spectroscopy operated wavelength range between 300 and 1100 nm at room temperature. The optical transmittance values of ZnS thin films in the visible region of the electromagnetic spectrum have been found to be between 51-90%. The calculations indicate that the refractive index (n) in the visible region is between 1.40 and 2.45. The optical band gaps (Eg) of thin films have been calculated between 3.61-3.88 eV while the band edge sharpness values (B) are varied between 6.95 × 109-8.96 × 1010 eV/cm2. The specific resistivity values (p) of the films are found to be between 1.08 × 105-1.01 × 106 ?cm and exhibit an n-Type conductivity by Hall measurement.Öğe Investigation of properties the copper sulfide thin films prepared from different copper salts(Elsevier Gmbh, Urban & Fischer Verlag, 2018) Erken, O.; Gunes, M.; Kirmizigul, F.; Gumus, C.Copper sulfide (CuS) thin films were prepared on commercial glass substrates by Chemical Bath Deposition (CBD) method using solution of different copper salts at 50 degrees C temperature for seven hours. Different anions of copper salts that is crucial for the properties of the films affect the precipitation mechanism and growth rate. For this reason, the effect of the different copper salts on the properties of CuS thin films was investigated and discussed. The influence of the different copper salts in the chemical bath was determined by means of optical transmission of the thin films in the wavelength range of 400-1100 nm taken at room temperature. Next, using these data, the optical band gap values E-g, the extinction coefficient k, the refractive index n, and the real epsilon(1) and imaginary parts epsilon(2) of the dielectric constant were calculated. The crystallographic structure of CuS thin films were analyzed with an X-ray diffractometer (XRD). XRD analysis was revealed the polycrystalline and hexagonal phase of CuS thin films. The surface roughness of the films were measured by AFM. The surface roughness of the thin films was different despite the same deposition time.Öğe Investigation on the electronic and physical properties of gamma-MnS films as a function of thickness(Elsevier Sci Ltd, 2022) Ulutas, C.; Erken, O.; Gunes, M.; Ozkendir, O. M.; Gumus, C.In this study, gamma-manganese sulphide (gamma-MnS) films were prepared at various thickness and deposition time at a temperature of 50 degrees C by Chemical Bath Deposition Method (CBD). The characterization of the gamma-MnS films were determined by using the following methods; X-ray Absorption Fine Structure Spectroscopy (XAFS), Xray diffraction (XRD), optical absorption, Field Emission-Scanning Electron Microscope (FE-SEM), Energy Dispersive X-ray analysis (EDX). The electronic interplay via the coupling between Mn 3d levels and S 2p levels was determined to build up strong molecular bonds containing broad band with hybrid pd levels at low energy levels. The results of the electronic structure analysis were also tested with the absorption spectroscopy calculations and high agreement is reported. XRD analysis revealed that the film deposited for 5 h had amorphous structure and turned to be crystal structure in hexagonal phase with deposition time 10, 15, 20 h due to increasing film thickness value. The optical band gap values were reduced from 3.86 eV to 3.10 eV with increasing film thickness. The average refractive index value of films at visible region were calculated between 1.55 and 2.81 as a function of increment in film thickness. The mobility and resistivity of the films were measured as 8.65-55.76 cm2/Vs and 3.10 x 105-2.39 x 106 omega cm, respectively, by Hall measurement.Öğe The effect of annealing temperature on the physical properties of Cu2O thin film deposited by SILAR method(Elsevier, 2020) Ozaslan, D.; Erken, O.; Gunes, M.; Gumus, C.Cu2O film was deposited on a glass substrate at 70 degrees C by the SILAR (Successive Ionic Layer Adsorption and Reaction) method. The Cu2O film was annealed in an air atmosphere at 100 degrees C, 300 degrees C, and 500 degrees C temperatures for 1 h and the effect of the annealing temperature on the physical properties was investigated. The phase-transition temperature that corresponds to the transformation from Cu2O to CuO was occurred at temperature of approximately 300 degrees C with annealing process. The energy band gap (E-g) was reduced from 2.57 eV to 1.91 eV with the increasing annealing temperature. Hall measurement revealed that the film showed p-type conductivity and the resistivity (rho) of Cu2O deposited at 70 degrees C and annealed 100 degrees C were calculated as 6.12 x 10(4) and 7.44 x 10(3 )Omega cm, respectively, while the film annealed at 300 degrees C and 500 degrees C the resistivity of CuO was found to be 8.23 x 10(3) and 5.11 x 10(2) Omega em, respectively.Öğe The effects of substrate on the physical properties of gamma-MnS thin films deposited by chemical bath deposition(Elsevier B.V., 2020) Ulutas, C.; Erken, O.; Gunes, M.; Gumus, C.Gamma-MnS thin films were deposited on glass and indium tin oxide (ITO) substrates at 40 °C temperature by Chemical Bath Deposition (CBD) method. XRD measurements revealed that the gamma-MnS films are polycrystalline in the wurtzite phases and show a preferential orientation along the c-axis. The grain size of the films that were deposited onto the glass and ITO were calculated as 327 nm and 189 nm, respectively. The energy band gap of the films deposited onto glass and ITO were also calculated as 3.56 eV, 3.74 eV, respectively. The refractive index of the gamma-MnS at the visible region (400–700 nm) were measured as 2.1 and 1.63 for the glass and ITO substrates, respectively. Hall measurement revealed that the gamma-MnS films showed n-type conductivity and the resistivity of the gamma-MnS films deposited on the glass and ITO substrates were measured as 7.1 × 105 ?cm, 3.04 × 102 ?cm, respectively. © 2020 Elsevier B.V.
