Investigating the Role of the annealing temperature on some properties of nanoporous porous silicon wafers

Abstract

In this research, four wafers of bulk silicon with dimensions (2x2 cm2) were prepared. These wafers were treated with hydrofluoric acid in order to convert bulk silicon into porous silicon. This was done using the photo electrochemical method, where the slices had a resistivity of (0.02 ohm. cm) and a directionality of (110) and their majority carriers were electrons. A hydrofluoric solution was used at a concentration of (9:4) with ethanol and a lamp with a power of (500 watts). After producing the porous silicon, the samples were thermally treated at (400, 500, and 600) degrees Celsius for half an hour. Through the surface topographic examinations obtained from the Atomic Force Microscope (AFM), it was found that the increase in annealing temperatures reduced the porosity and decreased the thickness of the porous layer. This in turn has a direct effect if these samples are used as gas sensors or light detectors. As for the visual examination, luminescence was used to find energy gap and identifying the extent to which it is affected by thermal treatment. It was found that the energy gap increases with increasing thermal treatment temperatures.