Fluorescence study of silicon fabricated by nanosecond pulse laser

Abstract

ABSTRACT Some ~20Pm wide slots have been fabricated on Si (100) using a homebuilt 355nm nanosecond pulse laser micromachining system. The slots were characterized by fluorescence microscopy, local spectroscopy and scanning electron microscopy. A kind of microstructure like porous silicon was formed in the fabrication zone. Strong photoluminescence emission from the fabricated zone in the wavelength range between 450nm and 700nm has been detected. Furthermore, a strong decay of the PL intensity has been observed as a function of irradiation time for excitation with wavelength between 400nm and 440nm. The analysis of elemental composition in the fabrication zone shows that the fluorescence emission is in relationship with Oxygen distribution and the modified structure. Keywords: Fluorescence, porous silicon, micromachining, nanosecond pulse laser 1. INTRODUCTION Porous silicon (PS) has raised a lot of interest in the field of optoelectronics applications since the discovery of efficient visible photoluminescence (PL) at room temperature [1]. Many methods of electrochemistry and photochemistry, such as anodical etching, magnetron sputtering, laser breakdown of silane and laser ablation, have been used to produce PS in the past researches [2-4]. Some strategies to improve the PL emission efficiency like band gap engineering and quantum confinement in low-dimensional structures have been purposed [5-6]. Because of noncontact fabrication, high efficiency and high compatibility with silicon processing technology, laser fabrication become a simple and better choice to create PL emission structure on silicon compared with other methods. In order to prepare PL emission structure based on silicon, investigate the interaction between nanosecond pulse laser and silicon wafer, and reveal the reason of PL emission at fabricated zone, we designed a micromachining system based on 355nm nanosecond pulse laser and did some experiments on fabricated silicon with the help of fluorescence microscope and scanning electron microscope (SEM).