Structural properties of porous silicon obtained with laser photoetching assisted by computerized numeric control

Abstract

This study presents the preparation of porous silicon (PS) using the photoetching technique. The light source was a laser with a 405 nm wavelength. Hydrofluoric acid, hydrogen peroxide, and ethanol were used in the process. An approach to forming PS in a selected area was also studied, in which a computational control of the laser movement was developed. A laser allows for the formation of PS in short period of time using n-type crystalline silicon (c-Si) as a substrate. Photosynthesized PS shows similar characteristics (physical and chemical) to anodized PS. Raman scattering showed a broadening of the peak centered at 525 cm−1, this behavior is related to the formation of PS. Micro-Fourier transform infrared spectroscopy showed bands related to Si-H wagging and SiH2 bending vibrations, these types of bonds were generated during the porosification process. The morphologic characteristics were defined by scanning electron microscopy (SEM) and revealed that the porous structures depend on the potency of the laser used. The topography of the surface confirms PS formation. SEM analysis demonstrated that pores with diameters of 60 and 300 nm can be obtained. Energy-dispersive x-ray spectroscopy showed an increase in oxygen in the PS due to the oxidation process following photoetching. The x-ray diffraction showed that this type of etching eliminates the induced tension in the c-Si grain edges due to PS formation.