Browsing by Author "Yilmaz, I."

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Open Access
Donor-acceptor pair recombination in AgIn5S8 single crystals
(American Institute of Physics, 1999-03-15) Gasanly, N. M.; Serpengüzel, A.; Aydınlı, Atilla; Gürlü, O.; Yilmaz, I.
Photoluminescence (PL) spectra of AgIn5S8 single crystals were investigated in the 1.44-1.91 eV energy region and in the 10-170 K temperature range. The PL band was observed to be centered at 1.65 eV at 10 K and an excitation intensity of 0.97 W cm(-2). The redshift of this band with increasing temperature and with decreasing excitation intensity was observed. To explain the observed PL behavior, we propose that the emission is due to radiative recombination of a donor-acceptor pair, with an electron occupying a donor level located at 0.06 eV below the conduction band, and a hole occupying an acceptor level located at 0.32 eV above the valence band. (C) 1999 American Institute of Physics.
Open Access
Long-range ordered vertical III-nitride nano-cylinder arrays: Via plasma-assisted atomic layer deposition
(Royal Society of Chemistry, 2018) Haider A.; Deminskyi, P.; Yılmaz, Mehmet; Elmabruk, K.; Yilmaz, I.; Bıyıklı, Necmi
In this work, we demonstrate vertical GaN, AlN, and InN hollow nano-cylindrical arrays (HNCs) grown on Si substrates using anodized aluminum oxide (AAO) membrane templated lowerature plasma-assisted atomic layer deposition (PA-ALD). III-Nitride HNCs have been characterized for their structural, chemical, surface, and optical properties. The material properties of nanostructured III-nitride materials have been compared with the thin-film counterparts which were also grown using PA-ALD. Our results revealed that long-range ordered arrays of III nitride HNCs were successfully integrated on Si substrates and possess hexagonal polycrystalline wurtzite crystalline structure. Such long-range ordered wafer-scale III-nitride nanostructures might be potentially used in piezotronic sensing, energy harvesting, resistive memory, flexible and wearable electronics, III-nitride photovoltaics, and (photo)catalysis.
Open Access
Low-temperature photoluminescence spectra of layered semiconductor TlGaS2
(Pergamon Press, 1998) Gasanly, N. M.; Aydınlı, Atilla; Bek, A.; Yilmaz, I.
Photoluminescence (PL) spectra of TlGaS2 layered single crystals were studied in the wavelength region 500-860 nm and in the temperature range 9.5-293 K. We observed a total of three PL bands centered at 568 nm (2.183 eV, A-band), 718 nm (1.727 eV, B-band) and 780 nm (1.590 eV, C-band) at various temperatures. We have also studied the variations of the A- and B-band intensities vs excitation laser density in the range from 7 × 10-2 to 9 W cm-2. The A- and B-bands were found to be due to radiative transitions from the deep donor levels located at 0.362 and 0.738 eV below the bottom of the conduction band to the shallow acceptor levels at 0.005 and 0.085 eV located above the top of the valence band, respectively. The proposed energy-level diagram permits us to interpret the recombination processes in TlGaS2 layered single crystals. © 1997 Elsevier Science Ltd.
Open Access
Temperature dependence of the Raman-active phonon frequencies in indium sulfide
(Pergamon Press, 1999) Gasanly, N. M.; Özkan, H.; Aydınlı, Atilla; Yilmaz, I.
The temperature dependence of the Raman-active mode frequencies in indium sulfide was measured in the range from 10 to 300 K. The analysis of the temperature dependence of the A g intralayer optical modes show that Raman frequency shift results from the change of harmonic frequency with volume expansion and anharmonic coupling to phonons of other branches. The pure-temperature contribution (phonon-phonon coupling) is due to three- and four-phonon processes.