Trapping centres and their distributions in as-grown TlGaSeS layered single
crystals were studied using thermally stimulated current (TSC) measurements.
The investigations were performed in the temperature range of 10&ndash / 160 K with
various heating rates between 0.6&ndash / 1.2 K/s. Experimental evidence has been
found for the presence of three electrons trapping centres with activation
energies 12, 20, and 49 meV and one hole trapping centre located at 12 meV.
Their capture cross-sections and concentrations were also determined. It is
concluded that in these centres retrapping is negligible as confirmed by the good
agreement between the experimental results and the theoretical predictions of
the model that assumes slow retrapping.
The optical properties of TlGaSeS layered single crystals have been investigated
by measuring the transmission and the reflection in the wavelength region
between 400 and 1100 nm. The optical indirect transitions with a band gap
energy of 2.27 eV and direct transitions with a band gap energy of 2.58 eV were
found by analyzing the absorption data at room temperature. The rate of change
v
of the indirect band gap with temperature was determined from the transmission
measurements in the temperature range of 10&ndash / 300 K. The oscillator and the
dispersion energies, the oscillator strength, and the zero-frequency refractive
index were also reported. The parameters of monoclinic unit cell and the
chemical composition of TlGaSes crystals were found by X-ray powder
diffraction and energy dispersive spectroscopic analysis, respectively.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/3/12611866/index.pdf |
| Date | 01 July 2010 |
| Creators | Nasser, Hisham |
| Contributors | Hasanli, Nizami |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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