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    Analysis of mixed optical transitions in dilute magnetic AlAs/GaAs/ GaMnAs quantum wells grown on high substrate index by molecular beam epitaxy
    (Elsevier, 2023) Kerimova, Shemshat; Donmez, Omer; Gunes, Mustafa; Kuruoglu, Furkan; Aydin, Mustafa; Gumus, Cebrail; Erol, Ayse
    In this study, we report the influence of high-index substrate orientation on the optical properties of dilute Mn containing a single quantum well (QW) structure grown by molecular beam epitaxy (MBE). The electronic band structure of the samples is calculated with finite element methods (FEM). Photomodulated reflectance (PR) spectroscopy is employed to determine the optical transition energies at room temperature. PR experimental results are analyzed with the Third Derivative Functional Form (TDFF) signal function. TDFF fitting shows that the optical transition starts below the fundamental GaAs bandgap energy for the samples grown on (311) B and (411) B-oriented substrates. Comparing TDFF fitting and calculated optical transition energies with FEM show that the optical transition occurs in type-I and type-II as direct and indirect transitions, respectively. Type-I and -II optical transitions are addressed concerning the electronic band structure of the sample grown on oriented substrates.
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    Effect of Annealing Temperature on The physical Properties of Mn3O4 Thin Film Prepared by Chemical Bath Deposition
    (Esg, 2016) Ulutas, Cemal; Erken, Ozge; Gunes, Mustafa; Gumus, Cebrail
    In this study, Mn3O4 thin film was prepared by the chemical bath deposition (CBD) method on commercial microscope glass substrate deposited at 30 degrees C. The Mn3O4 film was annealed in an air atmosphere for an hour at temperatures 100 degrees C, 200 degrees C, 300 degrees C, 400 degrees C, 500 degrees C, respectively. The effect of annealing temperature on structural and optical properties such as optical constants of extinction coefficient (k), refractive index (n), the real (epsilon(1)) and imaginary (epsilon(2)) part of the dielectric constant and energy band gap (E-g) of the film were determined. The experimental characterization techniques included X-ray diffraction (XRD), UV-vis spectrophotometer and Hall effect measurement. XRD analysis showed that the film is grown in a polycrystalline structure in tetragonal phase. The conductivity of the film as a function of annealing temperature was measured as (1.32-6.65)x10(-6) (Omega cm)(-1).
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    Effect of annealing temperature on the physical properties of Mn3O4 thin film prepared by chemical bath deposition
    (Electrochemical Science Group, 2016) Ulutas, Cemal; Erken, Ozge; Gunes, Mustafa; Gumus, Cebrail
    In this study, Mn3O4 thin film was prepared by the chemical bath deposition (CBD) method on commercial microscope glass substrate deposited at 30° C. The Mn3O4 film was annealed in an air atmosphere for an hour at temperatures 100° C, 200° C, 300° C, 400° C, 500° C, respectively. The effect of annealing temperature on structural and optical properties such as optical constants of extinction coefficient (k), refractive index (n), the real (?1) and imaginary (?2) part of the dielectric constant and energy band gap (Eg) of the film were determined. The experimental characterization techniques included X-ray diffraction (XRD), UV-vis spectrophotometer and Hall effect measurement. XRD analysis showed that the film is grown in a polycrystalline structure in tetragonal phase. The conductivity of the film as a function of annealing temperature was measured as (1.32-6.65)×10-6 (?cm)-1. © 2016 The Authors.
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    Electronic transport in strained p-modulation Be-doped Ga0.8In0.2As/GaAs single quantum well
    (Taylor & Francis Ltd, 2014) Gunes, Mustafa; Gumus, Cebrail
    We report on the electronic transport properties of p-modulation Be-doped Ga0.8In0.2As/GaAs single quantum well. The experiments included the spectral photoluminescence between 8 and 300 K, and Hall effect measurements at temperatures between 14 and 300 K. The effect of strain which induces splitting of the valence band as light and heavy hole bands on transport is discussed. The calculated band alignment of the GaInAs sample using model-solid theory including strain effects indicates large conduction band discontinuities and a much smaller valance band discontinuity in GaInAs. The effect of the conduction and valance band discontinuity on the electronic transport properties is also discussed.
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    Physical properties of Cu2O thin films prepared by silar method
    (Pamukkale Univ, 2017) Ozaslan, Dogan; Gunes, Mustafa; Gumus, Cebrail
    Polycrystalline Cu2O thin films were obtained on glass substrates using by silar method at 70 degrees C. XRD analysis showed the films are a cubic structure and lattice parameters were calculated. The surface morphology of the films were imaged by FE-SEM (Field Emission Scanning Electron Microscope). In order to determine the optical properties of the Cu2O thin films UV/vis spectrophotometer was used. Optical transmittance (T%) values of the Cu2O films were determined in the wavelength range 300-1100 nm at room temperature. Semiconductor Cu20 of the thin films optical transmittance values were found to be 50-70% in the visible region. Energy band gap values (E-g) of the films were found to be 2.53-2.62 eV.
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    Structural and optical properties of diluted magnetic Ga1-xMnxAs-AlAs quantum wells grown on high-index GaAs planes
    (Indian Acad Sciences, 2017) Gunes, Mustafa; Gumus, Cebrail; Gobato, Yara Galvao; Henini, Mohamed
    We report on the structural and optical properties of Ga1-xMnxAs-AlAs quantum wells (QWs) with x = 0.1% grown by molecular beam epitaxy (MBE) on semi-insulating GaAs substrates with orientations (100), (110), (311)B and (411)B. Atomic force microscopy (AFM), X-ray diffraction (XRD) and photoluminescence (PL) techniques were used to investigate these QWs. AFM results have evidenced the formation of Mn-induced islands, which are randomly distributed on the surface. These islands tend to segregate for samples grown on (110) and (411)B planes, while no clear segregation was observed for samples grown on (100) and (311)B orientations. Results show that the PL line width increases with Mn segregation. XRD measurements were used to determine 2 theta, d and cell parameters.
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    Synthesis of Mn-doped ZnS Thin Films by Chemical Bath Deposition: Optical Properties in the Visible Region
    (Amer Inst Physics, 2017) Erken, Ozge; Gunes, Mustafa; Gumus, Cebrail
    Transparent ZnS: Mn thin films were produced by chemical bath deposition (CBD) technique at 80 degrees C for 4h, 6h and 8h durations. The optical properties such as optical transmittance (T %), reflectance (R %), extinction coefficient (k) and refractive index (n) were deeply investigated in terms of contribution ratio, wavelength and film thickness. The optical properties of ZnS: Mn thin films were determined by UV/vis spectrophotometer transmittance measurements in the range of lambda= 300-1100 nm. Optical transmittances of the films were found from 12% to 92% in the visible region. The refractive index (n) values for visible region were calculated as 1.34-5.09. However, film thicknesses were calculated between 50 and 901 nm by gravimetric analysis.