Functional Semiconductor Micro and Nanotube Arrays
This process produces a new class of nanoscale building blocks based on III-V semiconductor tubes created by a strain-induced self-rolling mechanism from epitaxially grown heterojunction films that have been lithographically patterned and subsequent etching of an underlying sacrificial layer. Depending on the undercut extent, single or multi-wall tubes can be formed. Our research builds on this new nanotechnology paradigm.
The formation approach involves epitaxial growth (bottom-up) which determines the composition and thickness (thus diameter) of the rolling component and lithographic processing (top-down) which controls the length, position and shape of the final structure. Also, if the strain direction is reversed, when the compressively strained layer is placed on the top, the rolling direction goes downward.
These semiconductor nanotubes (SNT) can be transfer printed to another substrate with their alignment and integrity maintained, creating the potential of new 3-D nanoscale structures for heterogeneous integration.
These micro and nanotubes can be "functionalized" by epitaxially embedding active structures such as quantum wells, quantum dots, and 2D electron gas, as well incorporating polycrystalline and amorphorous layers in the tube wall. Further, the basic fabrication concept of strained induced self-rolling, analogous to the Japanese paper folding micro-origami technique, can be used to produce arrays of MEMS/NEMS components based on the use of multiple strained layers sandwiched by sacrificial layers and step by step lithography patterning to sequentially release parts of the structure in desired directions.
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