大面積單層二硫化鉬合成與鑑定

Abstract

近年來，石墨烯獨特的物理特性重新引起科學家對非有機二維材料電性與光性的興趣。過渡金屬硫族化合物(TMDCs)單一層中是由強共價鍵鍵結，然而層與層之間則是靠較弱的凡德瓦力鍵結，因此可剝離成二維單層結構。雖然過渡金屬硫族化合物已被研究幾十年以上，但最近在奈米尺度下對此材料的特性表徵和元件製作讓科學家重新看到此種層狀二維材料在微電子與光電領域發展的機會。作為典型的代表，二硫化鉬(MoS2)可應用在電晶體、光感測器與發光元件上。因為將層數削減至單層，二硫化鉬能隙將由非直接能隙轉變為直接能隙。然而，尚無有效合成高品質大面積單層二硫化鉬的技術。在這裡，我們使用三氧化鉬(MoO3)與硫(S)做為前驅物，藉由化學氣相沉積法(CVD)在藍寶石基板上成長大面積單層二硫化鉬(約2cmⅹ2cm)。並利用多種光譜與顯微鏡技術鑑定CVD合成二硫化鉬為高結晶、高品質。最後以CVD合成單層二硫化鉬為基底，製作電雙層電晶體，得以知道CVD合成單層二硫化鉬為n型半導體且電子遷移率最高約為8.11 cm2/ Vs。

The remarkable properties of graphene have renewed interest in inorganic, two-dimensional materials with unique electronic and optical attributes. Transition metal dichalcogenides (TMDCs) are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into two-dimensional layers of single unit cell thickness. Although TMDCs have been studied for decades, recent advances in nanoscale materials characterization and device fabrication have opened up new opportunities for two-dimensional layers of thin TMDCs in nanoelectronics and optoelectronics. MoS2, as a typical example, have sizable bandgaps that change from indirect to direct in single layers, allowing applications such as transistors, photodetectors and electroluminescent devices. However, the synthetic approach to obtain high-quality and large-area MoS2 atomic thin layers is still rare. In this contribution, CVD is adopted to synthesize high-quality and large-area MoS2 monolayers (about 2cmⅹ2cm) directly on sapphire substrates using MoO3 and S powders as the reactants. Spectroscopic and microscopic results reveal that the synthesized MoS2 layers are high-quality. The top-gated field-effect transistors based on CVD MoS2 monolayers using ionic liquid as the dielectrics exhibit n-type semiconductor behaviour, where the electron mobility values is up to 8.11 cm2/ Vs respectively.