Investigation of Structural Properties of Gradient -Porosity Porous Silicon Layer Produced by Laser- Assisted Etching

Laser-assisted etching process with a step-gradient illumination intensity of 630nm laser wavelength was conducted to produce high porosity and minimum thickness of gradient ? porosity porous silicon layer (GPSi). The structural properties were studied with the aid of scanning electron microscopy. The porous surface consisted of complex network of deep and shallow cylindrical pores. The x-ray investigation of the gradient-porosity porous silicon revealed a conversion of the native orientation of silicon wafer from (100) to poly - crystalline phase with new (101, 002, 111 and 211) orientations having nanocrystallite sizes of 15, 15.7, 20 and 15 nm respectively.