| Time：1131030 (Wed.) 14:20~16:20 Speaker：Prof.林俊良(Lin, Chun-Liang) 國立陽明交通大學電子物理學系/Department of Electrophysics, National Yang Ming Chiao Tung University Title：How can STM help next-generation semiconductor Industry? Abstract： Current semiconductor industry is facing a limit of scaling. Thus, it is urgent to find a new type of material to replace Si for next-generation semiconductor devices. Two-dimensional (2D) materials, especially those with a proper band gap provide a solution to this problem since the thickness of monolayer 2D materials can be reduced to only few atoms. However, to fabricate a field effect transistor (FET) based on 2D materials is still faced a lot of problems such as low carrier mobilities, low on currents, and high contact resistance. Scanning tunneling microscopy (STM) is a powerful method to reveal both the geometry and electronic structure down to atomic scale. It is widely used to study 2D materials including graphene, silicene, and transition metal dichalcogenides (TMDs). In this presentation, I will introduce several examples of 2D materials and devices studied by STM. First, for the issue in the channel of FET, the defect induced mobility modulation in FET devices fabricated by MoS2 is visualized by STM. It is clear that the mobility of FET made by MoS2 is correlated to the density of defects on the surface [1]. Therefore, a feasible method to sufficiently reduce defects on surface is necessary. A two-step approach, including Ar+ bombardment and annealing, can reduce surface defects by more than 99%. Defect density < 1.0 × 1010 cm–2 is achieved, which cannot be done solely with annealing [2]. Second, for the issue in the contact and gate of FET, a bandgap engineering technique for two monolayer materials, MoS2 and PtTe2, with the tunneling current as a control parameter is demonstrated [3]. The bandgap of monolayer MoS2 decreases logarithmically by the increasing tunneling current. Monolayer PtTe2, by contrast, exhibits a much stronger gap reduction, and a reversible semiconductor-to-metal transition occurs at a moderate tunneling current. This demonstration also means that the metal electrodes can interact monolayer TMD with different manners. [1] Chen et al., Appl. Phys. Lett. 121, 151601 (2022). [ 2] Chen et al., ACS Appl. Mater. Interfaces, 15, 12, (2023). [3] Lin et al., ACS Nano 16, 14918–14924 (2022) Place：B101, Gongguan Campus, NTNU |
