本論文探討二碲化鎢(WTe2)的磁阻以及相關物理特性。二碲化鎢的磁阻隨磁場增加而無飽和磁阻，具有許多研究潛力而受到高度重視，相關文獻提到二碲化鎢屬於第二類外爾半金屬，存在無質量且具有手性的外爾費米子，手性決定此粒子自旋方向與移動方向，具有此特性的粒子，無法以半古典的電子運動方程式來描述，因此出現負磁阻、量子震盪、拓樸絕緣體等特性。
本研究利用化學氣相沉積法合成WTe2單晶，以偏振拉曼光學分析技術，判斷其異向特性，再以電性四點量測系統，鑑定各種製程對於材料的影響，透過物理特性量測系統測量磁阻，判斷材料的局域化效應與溫度效應，並透過載子摻雜來改變材料物理特性，以獲得高磁阻元件及高溫巨磁阻之應用。

n this research, we study the extremely large magnetoresistance and related physical properties of the CVD-grown tungsten tellurides (WTe2). Recently, tungsten telluride is categorized into type II Weyl semimetals and its magnetoresistance is not saturated with the increase of magnetic field, which attract considerable attentions. In the Weyl semimetals, conduction carrier is a mass-free fermion with chirality and the chirality would determine the spin direction and the movement direction of the particle. Particle with these properties cannot be described by semi-classical equation of electron motion, which is correlated to some characteristics including negative magnetoresistance, quantum oscillation and topological insulator. Here we realize the CVD synthesis of the WTe2 and determine the crystalline orientation with polarization-resolved Raman spectroscopy. The WTe2 devices are fabricated with two representative process and further study their electrical properties with four-point measurements. Influence of temperature, carrier configurations on magnetoresistance and related properties of the WTe2 are studied and discussed.

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