고품질 이황화 몰리브덴 성장 및 이를 이용한 소자 응용 연구

Abstract

Atomically thin two-dimensional (2D) layered semiconducting transition metal dichalcogenides, such as molybdenum disulfide (MoS2), have recently emerged as a family of 2D materials because single and few-layered MoS2 exhibits novel properties that are distinctly different from those of graphene. Whereas graphene is a gapless materials, MoS2 shows the thickness dependent bandgap tunability property ranging from bulk form indirect bandgap of 1.2 eV to direct bandgap of 1.8 eV in single layered MoS2. Within the layers, atoms are held together by covalent bonds, while neighbouring layers are weakly bound together by van der Waals interactions. Preparing MoS2 atomic thin layers have been proposed to several method, including scotch tape assisted mechanical exfoliation, physical vapor deposition, solution exfoliation, thermolysis of a precursor containing Mo and S atoms, sulfurization of molybdenum oxide. Recently, MoS2 atomic thin film layers have been fabricated to field effect transistors which exhibit excellent on/off current ratio 107-108 and a high photoresponsivity. These properties allow for their applications in nanoelectronic and optoelectronic devices on both conventional and flexible substrate. This is possible for most basic application where light converted into a current. In the case of photodetectors, the photoresponsivity are very important. However, it is very difficult to obtain the desired uniformity and repeatability of the film thickness and the geometry from the chemical vapor deposition (CVD). Also, the photoresponsivity of previously reported MoS2 thin film transistors is still substantially low. In this work, we describe a method of synthesize large-area and uniform CVD grown MoS2 film, with control over the size and number at predetermined locations. With controlling growth temperature with increase growth temperature, surface coverage with MoS2 triangular island is significantly improved due to an increase in density of nuclei. And fully continuous film is growth with the growth temperature reached to 800 ℃. To evaluate the electrical performance of MoS2 layer, back gated transistor were fabricated using transferred MoS2. It is comparable to that of CVD grown MoS2 base transistor. To improve photoresponsivity, surface plasmon(SP) is suggested with SP. Photo responsivity was improved by three times. The proposed growth of continuous film and fabrication strategy can be extended to any kind of 2D materials and enable the realization of electronic circuit and optical devices easily transferable to any other support.