Precision Engineering of Semiconductor Nanostructures for Next Generation Electronic Devices

초록

Semiconductor materials provide exciting opportunities to fabricate high performnace devices for energy conversion, photonics, and sensing applications. Acquisition of ability to precisely control the crystal structure, geometry, or composition is necessary to realize the desired properties, especialy in highly confined nanoscale systems such as nanowires and 2D materials. Despite its crucial importance for robust control, fundamental and systematic studies on the relationship between process and nanostructure are still lacking. Our group has been focusing on the control of nanostructures of semiconductor materials ? e.g., 2D monolayer transition metal dichalcogenides (TMDs) and 1D nanowires. First, by measuring post-growth electron, raman microscopy, and photoluminescence spectroscopy, we confirm the strong correlation between precursor and carrier gas concentration in chemical vapor deposition (CVD) grown TMDs. Specifically, we use our custom-built furnace system optimized for CVD MoSe2 growth, enabling controlled gas flow rate and growth pressure. Controlling carrier gas flow rate and composition, we find a growth morphology of as-grown MoSe2 is significantly affected by the growth condition. Based on our observation, we propose a growth strategy to obtain a large area single crystalline monolayer epitaxy of 2D materials on substrate. In addition, using classic vapor-liquid-solid (VLS) growth mechanism of semiconductor nanowires, we show an importance of fundamental understanding of surface chemistry. By using an in situ or operando infrared spectroscopy, we confirm surface chemical species capable of affecting geometry and crystallinity of grown Si nanowire structures. These results ultimately provide the insights to control the nanostructures for broad photonic and electronic applications.