Pencil-shaped silicon nanowires (SiNWs) were synthesized by colloidal lithography and inductively coupled plasma reactive ion etching for photovoltaic application. Light reflectance of below 10% could be obtained by the asymmetric pencil-shaped SiNW array. The pencil-shaped SiNW structure and properties were investigated and compared with metal catalyzed electroless etching (MCEE) and nanoimprinted SiNWs. Single-junction solar cells consisting of pencil-shaped n-SiNW substrates and p-Si shell layer grown by chemical vapor deposition were fabricated. A combination of two-step H2 annealing and back surface field formation was applied to improve the solar cell properties. Good crystal quality and surface of pencil-shaped SiNWs provided an excellent solar cell junction interface. The great light trapping of the pencil-shaped SiNW solar cell could enhance the conversion efficiency by more than 0.6% compared to the solar cells using MCEE and nanoimprinted SiNWs.

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Blue light emitting diodes (LEDs) have been fabricated with InGaN/GaN well layers (QWs) on micro-patterned sapphire substrate (PSS). Low pressure growth of GaN layer on PSS effectively reduces the density of edge dislocations. The growth of InGaN/GaN MQWs on PSS as compared to conventional sapphire substrate (CSS) improves the internal quantum efficiency (IQE) from 50 to 56%. The higher thermal barrier for luminescence thermal quenching ensures of more e-h pair recombination at the quantum wells and improves the IQE. The light extraction efficiency (h extr ) from the LEDs is enhanced with use of PSS substrate and nanopores generation on the ITO p-contact. This would be attributed to the improvement in the quality of GaN film through reduction of threading dislocations and scattering of light from the sidewalls of the patterned sapphire.

A novel and efficient method to produce surface enhanced Raman scattering (SERS)-active nanogaps was developed by double-step Au film depositions and subsequent thermal annealings. The obtained nanostructure comprises metallic sea, islands, and in particular gaps between the sea and islands whose width can be automatically adjusted <10 nm, which is difficult to be achieved by the conventional single-step metal deposition and annealing. The nanogap structure gave an increased enhancement factor up to the order of 10 9 , whereas conventional vacant sea and Au island structure exhibited 10 7 . The SERS-active performances are supported by increased localized surface plasmon at the nanogaps.