⼆硒化鎢-⼆硒化鉬平⾯異質結於掃描式穿隧電⼦顯微鏡之能帶對齊研究

Abstract

當⼆維石墨烯被發現後，由於高載子移動率、優秀的熱導率、可撓性、不錯的轉移移電導……等有趣的性質，吸引了科學界不少的注意。但能帶隙的缺乏以及為了打開能帶隙而提升的製程難度，不利於場效電晶體的發展。此時，⼆維過渡⾦屬⼆硫族化物的發現，無疑開啟了另⼀道大門，特別是部分的⼆維過渡⾦屬⼆硫族化物擁有適當的能帶隙和電流開關比。 本論⽂中，使⽤掃描式穿隧電⼦顯微鏡研究單層⼆硒化鎢-⼆硒化鉬平⾯異質結在高配向性熱分解⽯墨基板的介⾯幾何性質和電性。藉由莫列波紋分析出⼆硒化鎢-⼆硒化鉬平⾯異質結與高配向性熱分解⽯墨之間的⾓度約為七度。透過⼆硒化鎢-⼆硒化鉬平面異質結的能帶對齊，可以得知⼆硒化鎢和⼆硒化鉬的能隙分別為 2.04 eV 和 2.16 eV；導帶和價帶偏移約為 0.26 eV和 0.37 eV；⼆硒化鎢和⼆硒化鉬的過渡帶約為 3.58 nm；於過渡帶的內建電場約為 7.7x10^7V/m。這些性質替光電⼦和電⼦裝置開啟了進⼀步研究的⼤⾨。

Graphene has catched a lot of attention since it was proved to be two-dimensional material. It has plenty of intresting properties such as high carrier mobility, superier thermal conductivity, fexibility, transconductances, and so on. The lack of bandgap and complex preparation to open the bandgap of graphene make it less attractive when the two-dimensional transition metal dichalcogenides (2-d TMDCs) was discovered. Some of the TMDCs are semiconductor and has suitable bandgap which would influence the on-o↵ ratio in field effect transistor (FET). We would reveal the band alignment of single layer WSe2-MoSe2 lateral heterojunction on highly oriented pyrolytic graphite (HOPG), and the band width in the WSe2-MoSe2 boundary by scanning tunneling microscopy. The moir´e pattern of TMDCs denotes that there is an angle around 7 between layers. The band offset and the built-in electric field are calculated. The bandgaps of WSe2 and MoSe2 are 2.04 eV and 2.16 eV. The band o↵set of conduction band and valence band are 0.26 eV and 0.37 eV. At the heterojunction boundary, we observed a transition width up to 3.58 nm with a built-in electric field of about 7.7x107 V/m. These properties expand the field of photonic and electrical devices.