Journal Article 2D materials field-effect transistors layered semiconductors 2D Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. anisotropy band engineering band structure modification black arsenic ferroelectrics gallium telluride laser-assisted doping nonvolatile memory oxygen chemisorption site selective transition metal dichalcogenide transition-metal dichalcogenides van der Waals epitaxy