The formation of the metal dot pattern on the silicon substrate can be explained by the mechanism of displacement plating, as demonstrated in the case of copper in our previous work [26]. In this work, the electroless deposition of Ag on a silicon substrate

could be achieved in a AgNO3/HF solution selleck chemicals llc by the predominant dissolution of SiO2, which is produced by the localized anodization of the silicon substrate underneath the barrier layer of the upper alumina mask, and the subsequent dissolution of silicon to supply electrons for Ag deposition. On the basis of the present method, it must be noted that noble metal nanodot arrays can be formed directly and spontaneously on a silicon substrate over a large area without any dry process such as sputtering. Moreover, in principle, there is no limit to the deposition area that can be patterned because it is not necessary to use special vacuum equipment. Although the controllability of Ag deposition needs to be click here improved further, the proposed pattern transfer is suitable for the large-scale production of ordered noble metal dot pattern on a silicon substrate. Metal-assisted CHIR-99021 chemical structure chemical etching of silicon using patterned metal dot arrays After the formation of Ag dot arrays on the silicon substrate, the specimens were immersed in a solution of HF and H2O2 to form silicon nanohole arrays by metal-assisted chemical etching. Figure 5 shows SEM images of the etched silicon

surface using the patterned Ag catalyst. The silicon nanoholes obtained HSP90 were arranged hexagonally over the entire area of the specimen. When

Ag nanoparticles deposited randomly without the use of mask were applied as a catalyst, the regularity of arrangement of silicon nanoholes was extremely low [29, 30]. In this work, the periodicity of the silicon nanohole arrays was approximately 100 nm, corresponding to that of the Ag dot arrays used as the catalyst and that of the pores in porous alumina used as the initial mask. Ag particles, which were detected as circular bright spots, were observed inside holes in the silicon substrate, as shown in Figure 5a. The diameter of the holes observed in Figure 5a coincided with the sizes of the deposited Ag particles. These results indicate that chemical etching occurred one-to-one only at the Ag/silicon interface and proceeded anisotropically perpendicular to the substrate, i.e., in the <100> direction as shown in the inset of Figure 5a. The area of contact between the alumina mask and the underlying silicon substrate remains as a rim of the silicon nanohole at the surface of silicon. Figure 5 SEM images of Si nanohole arrays fabricated by Ag-assisted chemical etching. SEM images of Si nanohole arrays fabricated by Ag-assisted chemical etching in 5 mol dm-3 HF – 1 mol dm-3 H2O2 solution for (a) 20 s, (b) 30 s, and (c) 1 min. (d) Silicon nanohole arrays formed in 10 mol dm-3 HF – 1 mol dm-3 H2O2 solution for 1 min. (a) top and (b-d) cross-sectional SEM images.