UBC Theses and Dissertations
Fabrication and Raman study of twisted stacked few layer black phosphorus Fang, Tao
Two-dimensional black phosphorus (BP) has attracted much interest as a promising semiconductor with a tunable direct bandgap of 0.3-2 eV, depending on its thickness. However, BP-based heterostructures, such as van der Waals junctions, and their interlayer couplings have not been well studied. In this work, we first provided a new“film-based” transfer method, which can be used to transfer BP to specific positions. This is a very convenient transfer method for BP, since commonly used dry transfer and wet transfer methods do not work well for BP. Based on this new method, we successfully fabricated twisted stacked few layer BP with different twist angles (7 to 90 degrees) and thicknesses (10 -30 nm). Raman measurements revealed an “abnormal blue shift” for the twisted few-layer BP. Density functional theory (DFT) calculations by Teren Liu provided an explanation for this phenomenon in terms of changes in charge distributions. Based on the calculated charge distributions, we propose that the interlayer coupling in BP is not just through van der Waals interactions. Other interactions, such as weak valence bond, may exist in this system.
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