Silicon shows unique electrochemical properties in solutions containing hydrofluoric acid.[1±4] Cylindrical holes electrochemically formed in silicon in these solutions have recently attracted much attention due to their possible applications in photonic crystals, [5] micromachining, [6] etc. These nanoholes are generated in the <100> direction at those positions where small pits were preformed by photolithography. [7,8] Here we report that, without using an electrochemical method, cylindrical nanoholes can be generated by immersing silicon wafers loaded with Ag nanoparticles in a solution containing hydrofluoric acid and hydrogen peroxide. We have been studying the chemical etching of silicon for making an antireflective surface structure (textured structure) in order to increase the efficiency of multi-crystalline Si solar cells. [9] In the course of this study, we found that the use of Ag nanoparticles as a catalyst is especially effective for making the textured structure. We also found that the catalysis by Ag nanoparticles results in the formation of cylindrical nanoholes in single-crystalline Si wafers when the treatment is continued for a longer time. During the process, the Ag particles gradually sink into the silicon, forming nanoholes as deep as 500 lm and with diameters of about 50 nm. Figure 1 shows a scanning electron microscope (SEM) image of Ag particles deposited on the surface of a p-type Si(100) wafer by electroless plating (see Experimental).[10]The sizes of the particles are mostly between 30 nm and 100 nm. There was no significant difference between the p-type and n-type wafers in densities and size distributions of the deposited Ag particles. In addition, the (100) and (111) orientations did not affect the Ag deposition. Other metal particles were also deposited on Si wafers from solutions containing metal ions, such as Pt, Pd, and Cu.After the deposition of these metal particles, the Si wafers were etched in a mixed solution of 10 % HF and 30 % H 2 O 2 (10:1 v/v) for 30 min in the dark at room temperature. The etched surface of the Si wafers was covered with a microporous Si layer. The microporous Si layer became as thick as 3 lm when Pt particles were used as the catalyst, and showed orange photoluminescence under UV irradiation at 265 nm. Since Pt has a strong catalytic activity in the reduction of hydrogen peroxide, [11] it is assumed that valence-band electrons in Si are drawn through the Si/metal interface as hydrogen peroxide is reduced. As a result, positively charged holes are generated in the Si, leading to the formation of a microporous

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Nanotechnology V 1505Boring Deep Cylindrical Nanoholes in Silicon Using Silver Nanoparticles as a Catalyst. -Cylindrical nanoholes in Si are generated by immersing Si wafers loaded with Ag nanoparticles in a solution containing HF and H2O2. The depth of the holes reaches 500 µm after etching for 10 h. The position of the holes can be controlled by the loading position of the Ag particles. The method is expected to be useful for making new electronic and optical devices. -(TSUJINO, K.; MATSUMURA*, M.; Adv. Mater. (Weinheim, Ger.) 17 (2005) 8, 1045-1047; Res. Cent. Solar Eng. Chem.

We report and discuss UV patterning technology of nanoLED with ultra‐high‐resolution. Additionally, we also report on the performances of the ultra‐high‐resolution nanoLED panel for ARJVR by UV patterning technology.

Hydrogen evolved continuously when Si͑111͒ wafers with atomically flat and hydrogen-terminated surfaces were immersed in aqueous 40% NH 4 F solution or oxygen-free water. The evolution of hydrogen was attributed to oxidative dissolution of silicon into the liquids. Although the dissolution rates were rather slow, the process could be sensitively traced by measuring the amount of hydrogen evolved. The rate of the hydrogen evolution was nearly proportional to the step densities existing on the Si͑111͒ surface, suggesting that silicon dissolves from the step edges. On the basis of the rates of hydrogen evolution and the densities of steps, we determined the receding speeds of the monohydride steps to be about 39 and 7.5 nm min −1 in 40% NH 4 F solution and in oxygen-free water, respectively, at room temperature. Continuous hydrogen evolution was also observed when atomically flat Si͑111͒ wafers with dihydride steps were exposed to an inert gas containing water vapor.