In this thesis, in order to study the structural, optical and electrical transport properties of
Tl2In2S3Se, TlInSeS and Tl2In2SSe3 crystals, X-ray diffraction (XRD), energy dispersive
spectroscopic analysis (EDSA), transmission, reflection, photoluminescence (PL), thermally
stimulated current (TSC) and photoconductivity decay (PC) measurements were carried out.
Lattice parameters and atomic composition of these crystals were determined from XRD and
EDSA experiments, respectively. By the help of transmission and reflection experiments,
the room temperature absorption data were analyzed and it was revealed the coexistence of
indirect and direct band gap energies of the studied crystals. Moreover, the refractive index
dispersion parameters - oscillator energies, dispersion energies, oscillator strengths, oscillator
wavelengths and zero-frequency refractive indexes were determined. Temperature-dependent
transmission measurements made it possible to find the rate of change of indirect band gaps
with temperature, absolute zero values of the band gap energies and Debye temperatures of
these crystals. From the analysis of the transmission and reflection measurements, it was
established that, there is a decrease in the values of indirect and direct band gaps energies and
an increase in zero-frequency refractive indexes with increasing of selenium content.
PL measurements were carried out to obtain the detailed information about recombination
levels in crystals studied. The behavior of PL spectra were investigated as a function of
laser excitation intensity and temperature. The variation of the spectra with laser excitation
intensity and temperature suggested that the observed emission bands in these crystals were
due to the donor-acceptor pair recombination.
TSC measurements were carried out with various heating rates at different illumination temperatures
to obtain information about trap levels in these crystals. The mean activation energies,
attempt-to-escape frequencies, concentrations and capture cross sections of the traps
were determined as a result of TSC spectra analysis. The analysis of experimental TSC curves
registered at different light illumination temperatures revealed the exponential trap distribution
in the studied crystals. From the analysis of PC measurements, carrier lifetimes were
obtained.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12613362/index.pdf |
| Date | 01 June 2011 |
| Creators | Guler, Ipek |
| Contributors | Hasanli, Nizami M. |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for METU campus |
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