Flexible Electronics - Si Nanomembrane Devices on Plastic
Flexible circuits are often used as connectors in various applications where flexibility, space savings, or production constraints limit the serviceability of rigid circuit boards or hand wiring. In addition to cameras, a common application of flexible circuits is in computer keyboard manufacturing; most keyboards made today use flexible circuits for the switch matrix.
In the near future, flexible electronics will likely exist everywhere in our daily life, including cell phones, solar cells, displays and other electronic/optical detectors.
Silicon nanomembranes are good candidate fabrication materials for flexible electronics. Silicon is one of the most abundant materials on the earth, and has been used in most modern electronics. Our typical observation of bulk Si is that it is very rigid and a small force can cause it crack. However, once a Si sheet is thin enough, less than 500nm for example, the mechanical properties completely change. At this point, Si sheets become flexible, conformable, and stretchable. As shown in the images to the right. The membrane can be curved to very small radius of curvature without breaking.
We can release the nanomembrane from Silicon-on-insulator (SOI) and transfer it onto any substrate, for example, plastics. The adhesion is provided by a glue layer such as SU8. This transferred single crystal Si nanomemebrane can be used as the functional semiconductor which provides flexibility and high performance for electronic devices.
|Figure 1.The transparency of Si Nanomembranes is illustrated (top)
while a representative optical micrograph of a SiNM illustrates the
flexible nature of the membranes (bottom).
Author: Feng Chen
 Yuan, H. C., Z. Q. Ma, et al. "High-speed strained-single-crystal-silicon thin-film transistors on flexible polymers." Journal of Applied Physics 100, 013708 (2006).
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