Controllable silicon nano-grass formation using a hydrogenation assisted deep reactive ion etching

Highly controllable silicon nano-grass formation is reported based on a hydrogen assisted reactive ion etching method in desirable shapes and locations. By controlling the etching parameters, one can achieve grass-free high aspect ratio vertical or three-dimensional structures on silicon substrates. On the other hand, one can program the etching procedure to arrive at grass-full surfaces and structures in pre-designed features and in desired places. The improved wetting properties of the grass-full surfaces have been investigated. In addition, the grass-full surface has been used to entrap kidney cells. Aspect ratios of the order of 40–50 and features of the size of 250 nm can be achieved.