Characterization of Cd1-X ZnX Te single crystals

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2016

Tezin Dili: İngilizce

Öğrenci: BENGİSU YAŞAR

Danışman: YUNUS EREN KALAY

Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu

Özet:

Among all semiconductor materials CdZnTe (CZT) becomes prominent due to its high resistivity, elevated operating temperature with high atomic number. Significant improvements in the large area and low defect content CdZnTe crystals have led to widen the application areas. Accordingly, these crystals can be utilized as roomtemperature detectors in medical, industrial and nuclear applications. CZT detectors suffer from various crystallographic defects formed during crystal growth and postgrowth cooling processes. The control of defect formation during growth or postgrowth processes requires detailed characterization studies. In this respect, identification of mostly encountered defects such as dislocations, twins, stacking faults and second phase of tellurium with the help of advanced imaging techniques has been set to the main objective of this thesis. After CdZnTe ingots had been grown by modified Bridgman furnace, wafers slicing and processing were applied. The single crystallinity was ensured by X-ray diffraction (XRD) and electron back scattered diffraction (EBSD) methods. Various types of dislocations were able to be examined by scanning electron microscopy (SEM) and optical microscopy after appropriate etching techniques. In addition to the dislocations, hexagonal and triangular shape of tellurium inclusions were revealed. Besides of micron-scaled defects, nano-scaled defects were also captured and analyzed with the help of transmission electron microscopy (TEM). High-resolution electron microscopy (HRTEM) revealed linear defects along directions embedded in single crystalline matrix. There is still no consensus on designating such defects as they as classified both as Te precipitate, twins and stacking fault in the literature. In this respect, image simulations were applied for modelling coherent Te precipitates, twins and stacking faults and they were compared with the experimentally observed results.