The surface wetting behavior of the Si nanostructures was also analyzed by the water contact angle measurement. Methods Figure 1 shows a schematic illustration of the process procedures for fabricating Si nanostructures on a single-side-polished Si substrate (p-type (100), 1 to 30 Ω cm, approximately 25 × 25 mm2) by MaCE with spin-coated Ag mesh patterns . Details of the spin-coated Ag ink and explanation of the experimental process can be found in the literature . In this work,
an aqueous solution containing HNO3 (70%), HF (50%), and DI water was utilized. The HNO3 was used as an oxidant to selectively oxidize the Si underneath the Ag mesh patterns by providing positive holes (h+) into Si instead of H2O2 and AgNO3, which have been widely explored for Si MaCE [12–18]. In order Vorinostat selleck chemicals llc to produce Si nanostructures with reasonable height, the etching time was fixed as 450 s because nanostructures with extremely tall height can be bunched together and may be mechanically unstable [4, 13]. To investigate the influence of the concentration of etch solution on the morphologies and optical properties of the fabricated
Si nanostructures, the quantity of target etchant was adjusted while fixing the quantity of other etchants and the etching temperature (23°C). The effect of etching temperature on the morphologies and optical properties of the resulting Si nanostructures was investigated with a fixed quantity of HNO3, HF, and DI water. All variables for the Si MaCE process were carefully adjusted to obtain a suitable etching rate and morphology for solar cell applications . After the Si MaCE process, the residual Ag was completely removed by immersing the samples in a wet etchant containing KI, I2, and DI water (KI/I2/DI = 1 g:1 g:40 ml) for 5 s at room temperature without any
change in the shape of Si nanostructures; this was followed by rinsing with DI water and drying with N2 jet. Figure 1 The process steps to fabricate Si nanostructures using spin-coated Ag ink and by subsequent MaCE. Gefitinib mouse Results and discussion Figure 2 shows the influence of HNO3 concentration on the morphologies and antireflection properties of the produced Si nanostructures. The HNO3 concentration was adjusted from 10% to 22% in an aqueous solution, which was composed of HF and DI water with a fixed volume ratio (1:20 v/v), by pouring in additional HNO3. The field-emission scanning electron microscope (FE-SEM, S-4700, Hitachi, Ltd., Tokyo, Japan) images clearly reveal that the average height of the Si nanostructures increases from 96 ± 14 to 695 ± 47 nm and the etching rate of Si nanostructures increases from 12.8 to 92.7 nm/min by increasing the HNO3 concentration.