It is essential to investigate the light-scattering
properties of SiNW arrays in order to understand their high optical confinement. In this study, Salubrinal we have investigated the optical properties of SiNW arrays prepared by MAE. Since the SiNW arrays prepared by this method are deposited on silicon substrates, it is difficult to measure the optical properties of SiNW arrays in isolation from the substrate. To remove the effect of the substrate, the SiNW arrays were peeled from the substrate. We present experimentally determined angular distribution functions (ADFs) [20] of the transmittance of SiNW arrays composed of SiNWs of different lengths. The effects of light scattering were also investigated. Methods The PRN1371 mw silver nanoparticles were fabricated by electroless silver plating. Si wafers (p-type, (100), 2 to 10 Ω·cm) were immersed in a silver coating solution composed of 0.015 M AgNO3 and 4.8 M HF for 1 min to cover the surface with silver nanoparticles. The size of the silver nanoparticles appears in the range of 20 to 60 nm. The silver nanoparticle-coated Si wafers were placed in GSK126 cost an etching solution composed of 4.8
M HF and 0.15 M H2O2 at room temperature. The length of the resulting SiNW arrays was controlled by the etching time. In this time, the etching time was varied from 5 to 10 min. After etching, the wafers were dipped in a HNO3 aqueous solution for 10 min to remove all remaining silver nanoparticles. The wafers were then immersed in a 5% HF solution to remove the oxide layer. After preparation of the SiNW arrays, polydimethylsiloxane (PDMS) solution MTMR9 [21] was spin-coated on the arrays at 200 rpm and baked at 150°C. The transmittance of the 2-mm-thick PDMS coating was more than 90% in the range from 400 to 1,100 nm and exhibited a refractive index of about 1.4. The SiNW arrays thus embedded in the PDMS coating were mechanically peeled from the substrate
with a razor blade. The optical properties of the peeled SiNW arrays were measured by an ultraviolet–visible-near-infrared spectrophotometer (Shimadzu Solid Spec-3700, Kyoto, Japan). The spectrophotometer was equipped with a unit for measurement of the ADF as illustrated in Figure 1. The ADF defines the intensity distribution of scattered light as a function of the angle at which the scattered light propagates. The wavelength of the incident light was varied from 400 to 1,500 nm. The detector was moved from 0° to 90° in 5° increments. The structure of the SiNW arrays before and after they were peeled from the substrate was characterized by field emission scanning electron microscopy using a JEOL JSM-7001F instrument (Akishima-shi, Japan). The length of SiNW arrays after peeling off was determined by a scanning electron microscopy (SEM) image. Figure 1 Schematic diagram of an angle-resolved scattering measurement.