Güllü, Hasan Hüseyin

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Profile URL
https://hdl.handle.net/20.500.14411/8052
Name Variants
Gullu,H.H.
H.,Güllü
H.H.Güllü
G., Hasan Huseyin
Güllü, Hasan Hüseyin
H., Gullu
G.,Hasan Huseyin
H.H.Gullu
Hasan Hüseyin, Güllü
G.,Hasan Hüseyin
Hasan Huseyin, Gullu
Gullu, Hasan Huseyin
Güllü,H.H.
Gullu, H. H.
Gullu, Hasan H.
Job Title
Doktor Öğretim Üyesi
Email Address
hasan.gullu@atilim.edu.tr
Main Affiliation
Department of Electrical & Electronics Engineering
Status
Former Staff
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2

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14

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17

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5

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16

PEACE, JUSTICE AND STRONG INSTITUTIONS
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8

DECENT WORK AND ECONOMIC GROWTH
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4

QUALITY EDUCATION
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6

CLEAN WATER AND SANITATION
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7

AFFORDABLE AND CLEAN ENERGY
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5

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10

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11

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9

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Scholarly Output

55

Articles

52

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7/0

Supervised MSc Theses

1

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0

WoS Citation Count

877

Scopus Citation Count

899

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16

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16

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WoS Citations per Publication

15.95

Scopus Citations per Publication

16.35

Open Access Source

8

Supervised Theses

1

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JournalCount
Journal of Materials Science: Materials in Electronics16
Physica B: Condensed Matter7
Bulletin of Materials Science3
Materials Science in Semiconductor Processing3
Optik3
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Has files: falseSubject: Thin films

Scholarly Output Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Structural and Optical Properties of Thermally Evaporated Ga-In Thin Films
    (World Scientific Publ Co Pte Ltd, 2014) Isik, Mehmet; Gullu, Hasan Huseyin
    In this paper, structural and optical properties of Ga-In-Se (GIS) thin films deposited by thermal evaporation technique have been investigated. The effect of annealing was also studied for samples annealed at temperatures between 300 degrees C and 500 degrees C. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy have been used for structural characterization. It was reported that increase of annealing temperature results with better crystallization and chemical composition of the films were almost same. Optical properties of the films were studied by transmission measurements in the wavelength range of 320-1100 nm. The direct bandgap transitions with energies in the range of 1.52 eV and 1.65 eV were revealed for the investigated GIS films. Photon energy dependence of absorption coefficient showed that there exist three distinct transition regions for films annealed at 400 degrees C and 500 degrees C. The quasicubic model was applied for these transitions to calculate crystal-field splitting and spin-orbit splitting energy values.
  • Thumbnail Image
    Article
    Citation - WoS: 3
    Citation - Scopus: 6
    Structural and Optical Properties of Thermally Evaporated Cu-Ga (cgs) Thin Films
    (Elsevier, 2018) Gullu, H. H.; Isik, M.; Gasanly, N. M.
    The structural and optical properties of thermally evaporated Cu-Ga-S (CGS) thin films were investigated by Xray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM) and optical transmittance measurements. The effect of annealing temperature on the results of applied techniques was also studied in the present paper. EDS results revealed that each of the elements, Cu, Ga and S are presented in the films and Cu and Ga concentration increases whereas S concentration decreases within the films as annealing temperature is increased. XRD pattern exhibited four diffraction peaks which are well-matched with those of tetragonal CuGaS2 compound. AFM images were recorded to get knowledge about the surface morphology and roughness of deposited thin films. Transmittance measurements were applied in the wavelength region of 300-1000 nm. Analyses of the absorption coefficient derived from transmittance data resulted in presence of three distinct transition regions in each thin films with direct transition type. Crystal-field and spin-orbit splitting energies existing due to valence band splitting were also calculated using quasicubic model.
  • Thumbnail Image
    Article
    Citation - WoS: 10
    Citation - Scopus: 10
    Temperature Dependent Band Gap in Sns2x< (x=0.5) Thin Films
    (Elsevier Sci Ltd, 2020) Delice, S.; Isik, M.; Gullu, H. H.; Terlemezoglu, M.; Surucu, O. Bayrakli; Gasanly, N. M.; Parlak, M.
    Structural 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 x 10(-4) eV K-1, respectively.
  • Thumbnail Image
    Article
    Citation - WoS: 10
    Citation - Scopus: 10
    Temperature Effects on Optical Characteristics of Cdse Thin Films
    (Elsevier Sci Ltd, 2021) Gullu, H. H.; Isik, M.; Surucu, O.; Gasanly, N. M.; Parlak, M.
    CdSe is one of the significant members of II-VI type semiconducting family and it has a wide range of technological applications in which optoelectronic devices take a special position. The present paper reports the structural and optical characteristics of thermally evaporated CdSe thin films. XRD pattern exhibited preferential orientation along (111) plane while atomic composition analyses resulted in the ratio of Cd/Se as closer to 1.0. Temperature-dependent band gap characteristics of CdSe thin films were investigated for the first time by carrying out transmission experiments in the 10-300 K range. The analyses showed that direct band gap energy of the compound decreases from 1.750 (at 10 K) to 1.705 eV (at 300 K). Varshni model was successfully applied to the temperature-band gap energy dependency and various optical constants were determined. Raman spectrum of CdSe thin films was also presented to understand the vibrational characteristics of the compound. The present paper would provide worthwhile data to researchers especially studying on optoelectronic device applications of CdSe thin films.