New Method Developed to Isolate Atomic Sheets and Create New MaterialsNew exfoliation method makes l
New Method Developed to Isolate Atomic Sheets and Create New MaterialsNew exfoliation method makes large-area atomically thin layers that can be stacked in any desired order and orientation to generate a whole new class of artificial materials; opens the door to new research and commercialization.Two-dimensional materials from layered van der Waals (vdW) crystals hold great promise for electronic, optoelectronic, and quantum devices, but making/manufacturing them has been limited by the lack of high-throughput techniques for exfoliating single-crystal monolayers with sufficient size and high quality. Columbia University researchers reported yesterday (February 21, 2020) in Science that they have invented a new method—using ultraflat gold films—to disassemble vdW single crystals layer by layer into monolayers with near-unity yield and with dimensions limited only by bulk crystal sizes.The monolayers generated using this technique have the same high quality as those created by conventional “Scotch tape” exfoliation, but are roughly a million times larger. The monolayers can be assembled into macroscopic artificial structures, with properties not easily created in conventionally grown bulk crystals. For instance, layers of molybdenum disulfide can be aligned with each other so that the resulting stack lacks mirror-symmetry and as a result demonstrates strongly nonlinear optical response, where it absorbs red light and emits ultraviolet light, a process known as second harmonic generation.Read more. -- source link
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