These enhanced optical and electrical properties indicated a potential application selleck compound for the highly efficient quantum dot solar cells. Methods The
fabrication of the 3D Si-ND array was based on bio-template and NB processes. Figure 1 schematically illustrates the fabrication flow, which started with (Figure 1a) a 2-nm-thick SiC film and 4-nm-thick poly-Si being deposited alternately four times on the n-doped Si substrate using a high-vacuum sputtering system and electron beam evaporation. Then a 3-nm-thick SiO2 layer was fabricated as a surface oxide (called NBO-SiO2 after this) by the NB oxidation process we developed at a low temperature of 300°C . Figure 1b has a 2D array of bio-template molecules (Listeria-Dps) that was deposited on the surface of the NBO-SiO2. Figure 1c shows the
bio-template protein shell that was removed by annealing it in an oxygen atmosphere to obtain a 2D array of iron cores as a uniform mask for the etching process. Figure 1d shows the etching process that was carried out with nitrogen trifluoride gas/hydrogen radical treatment (NF3 treatment) to remove the surface SiO2, which was carried out with NB etching to remove the poly-Si. Here we performed a one-step etching and found a well-aligned vertical etching profile due to high etching selectivity between the iron cores and etched material and the low selectivity of 1.3 between Si and SiC. The etching process has been AZD6094 price detailed elsewhere [17–19]. Figure 1e CFTRinh-172 shows that the iron cores were then removed by HCl wet cleaning, and then the remaining surface SiO2 was removed by NF3 treatment. Figure 1f shows that the SiC was deposited between pillars, which were stacked Si-NDs, by the sputtering system. The diameter, space between NDs, and average ND center-to-ND center distance corresponded to 6.4, 2.3, and 8.7 nm in the structure. The size
distribution of the Si-NDs was less than 10% for all samples [19, 21]. We prepared three types of Si-ND arrangements, as seen in Figure 2: separated Si-NDs as a single QD, a 2D array selleck chemicals llc of Si-NDs as a 2D QDSL, and a 3D array of Si-NDs as a 3D QDSL. The electrical conductivity and optical absorption in QDSLs were methodically, experimentally, and theoretically investigated with these samples to study the effect of wave function coupling between QDs. Figure 1 Schematic of the fabrication flow for 3D array of Si-NDs with SiC interlayer. (a) Deposition of 2-nm-thick SiC, 4-nm-thick poly-Si, and 3-nm-thick SiO2 layers. (b) Arrangement of 2D array of bio-template molecules on the surface. (c) Removal of bio-template protein shell by annealing in oxygen atmosphere. (d) NF3 treatment to remove surface SiO2 and NB etching to remove surface multilayers of poly-Si and SiC. (e) Removal of iron cores with HCl and NF3 treatment to etch remaining surface SiO2. (f) SiC deposition on Si-NDs. Figure 2 Schematics of the three types of Si-ND arrangements.