Yudu - Nanotimes June/July 2011

nanotimes News in Brief

11-06/07 :: June/July 2011

Silicon Nanowires // Nanowires Show a Dramatic Increase in Efficiency and Sensitivity With a Simple Coating

y applying a coating to individual silicon nano- wires, U.S. researchers at Harvard and Berkeley

have significantly improved the materials‘ efficiency and sensitivity.

“Nanowires have the potential to offer high energy conversion at low cost, yet their limited efficiency has held them back,” says Kenneth Crozier, Associ- ate Professor of Electrical Engineering at the Harvard School of Engineering and Applied Sciences (SEAS). With their latest work, Crozier and his colleagues demonstrated what could be promising solution. Making fine-precision measurements on single na- nowires coated with an amorphous silicon layer, the team showed a dramatic reduction in the surface re- combination. Surface passivation has long been used to promote efficiency in silicon chips. Until now, surface passivation of nanowires has been explored far less.

The creation of the coating that passivated the sur- faces of the nanowires was a happy accident. During preparation of a batch of single-crystal silicon nano- wires, the scientists conjecture, the small gold parti- cles used to grow the nanowires became depleted. As a result, they think, the amorphous silicon coating was simply deposited onto the individual wires.

Instead of abandoning the batch, Crozier and his team decided to test it. Scanning photocurrent studies indicated, astoundingly, almost a hundred- fold reduction in surface recombination. Overall, the coated wires boasted a 90-fold increase in photosen- sitivity compared to uncoated ones.

Yaping Dan, Kwanyong Seo, Kuniharu Takei, Jhim H. Meza, Ali Javey, Kenneth B. Crozier: Dramatic Reduction of Sur- face Recombination by in Situ Surface Passivation of Silicon Nanowires, In: NANO Letters, Vol. 11(2011), Issue 6, June 8, 2011, Pages 2527-2532, DOI:10.1021/nl201179n: http://dx.doi.org/10.1021/nl201179n