碲化鍺化合物添加雜質之第一原理研究

Abstract

能源議題是人類社會面對的一個重大課題，而現今的能源大部分取得自燃燒化石燃料，其中又有約 80% 的能量會以廢氣伴隨著廢熱的形式排到環境。熱電材料是一個能夠將熱能轉成電能的材料，有望收集那些原本不可回收的廢熱，所以被廣泛研究。 本論文利用第一原理研究碲化鍺 (GeTe) 這個熱電材料的晶格結構與電子結構。我們會著重於探討立方 (cubic) 碲化鍺，並以菱形 (rhombohedral) 碲化鍺為輔助，敘述碲化鍺的物理性質。我們會討論鍺空缺 (Ge vacancy)，銻取代 (Sb Substitution)，和鎢取代 (W Substitution) 對碲化鍺的影響。

The energy issue is a big topic in the human society. Most of our energy comes from fossil fuels. We burn those fossil fuels to support all kinds of human activities. However, around 80% of industrial waste heat is released as heated gas. Thermoelectric materials, believed to be the solution to energy issue, are solid-state energy converters converting waste heat into electrical power. We use first-principles calculations to investigate the crystal structure and band structure of GeTe, which is a thermoelectric material. The cubic phase of GeTe will be mainly focused, while the rhombohedral phase is presented as a reference. We consider the cases with Ge vacancies, Sb substitution, and W substitution located on the Ge-sublattice. Then we will provide a theoretical analysis on how they affect the GeTe properties.