Agglomeration in Porous Silicon Prepared from Si-Nanowires Structures

Abstract

Silicon nanowires (SiNW’s) arrays prepared by electroless etching method are attractive due to their significant light absorption properties across the visible spectrum [1]. Typical silicon nanowires grown by electroless etching is shown in Figure 1a. Following this preparation of silicon nanowires, these samples are etched in an electrolytic HF and ethanol solution to produce porous silicon quantum confined structures. Mechanical behavior of materials at nanoscale is different due to their quantum confinement effect. When porous silicon nano-structures are prepared from SiNWs obtained through electroless process, they may have a tendency to become thin. Ultimately these nano-structures may collapse and form bunches on the surface [2], as shown in Figure 1b. However, bunched silicon nanowires structures may be desirable in some applications but may not be for some others. In order to avoid bunching of SiNWs, it may be necessary to reduce the surface tension during the growth of nanowires [3]. (a) (b) Fig 1. Cross-section images of silicon nanowires (a) grown by electroless etching, (b) Porous silicon structures prepared from SiNWs. SiNW’s were grown by eletroless etching in a solution of hydrofluoric acid (HF) and silver nitrate (AgNO3) at room temperature [4]. The prepared nanowires were then etched in an electrolytic solution containing HF and ethanol to make porous Si quantum confined structures. Reflectance and photoluminescence studies are performed on this structures Figure 1