利用化學氣相沉積法成長之大面積二維晶體及其異質結構

Abstract

本論文利用化學氣相沉積法 (CVD) 成長大面積二硫化鉬薄膜與異質結構。利用不同前導物質克數控制二硫化鉬層數雙層到五層，並分別以穿透式電子顯微鏡確認薄膜層數。接著以金/鈦為電極經熱退火後製備出多層二硫化鉬電晶體其載子遷移率可達0.31 cm2V-1S-1，開關電流比可達1.45 #westeur024# 105。相同化學氣相沉積法也用來成長大面積、可控制層數的二硫化鉬/石墨烯異質結構，穿透式電子顯微鏡剖面圖證明異質結構的存在與層數，在二硫化鉬/石墨烯異質結構電晶體中，我們觀察到照光後石墨烯通道因電子注入造成費米能階改變的現象。最後，我們以化學氣相沉積法成長石墨烯於二硫化鉬上並成功製備出石墨烯/二硫化鉬/石墨烯雙層異質結構，接著以穿透式電子顯微鏡確認此結構。本論文以化學氣相沉積法成功直接成長出二硫化鉬/石墨烯異質結構，為未來二維材料異質結構提供了可行的道路。

In this thesis, we have demonstrated large-area 2-D crystals and their hetero-structures grown by the chemical vapor deposition technique (CVD). By using different precursor amounts, 2- to 5- layer MoS2 films are prepared, which are confired by crossectional high-resolution transmission electron microscope (HRTEM) measurements. By using Ti/Au as the contact metal and following annealing procedure, field-effect transistors are fabricated by using the multi-layer MoS2 films. Enhanced field-effect mobility 0.31 cm2V-1S-1 and high ON/OFF ratio 1.45 #westeur024# 105 are extracted from the MoS2 transistors. By using the same CVD growth technique, uniform large-size MoS2/graphene hetero-structures fabricated directly on sapphire substrates are demonstrated with good layer-number controllability. The HRTEM images provide the direct evidences of layer numbers of MoS2/graphene hetero-structures. Photo-excited electron induced Fermi level shift of the graphene channel are observed on the single MoS2/graphene hetero-structure transistors. Furthermore, double hetero-structures of graphene/MoS2/graphene are achieved by CVD fabrication of graphene layers on top of the MoS2, as confirmed by the cross-sectional HRTEM. These results have paved the possibility of epitaxially grown multi-hetero-structures for practical applications.