| dc.description.abstract | Porous silicon has high surface area and adsorption property with good compatibility with semiconductor fabrication, which can be applied to many advanced technology, such as lithium-ion batteries, biological and chemical sensors, and surface texturization in photovoltaic cells. It also has low thermal conductivity compared to bulk silicon, which is favorable as thermal insulation or thermoelectric materials. Numerous methods have been developed to fabricate porous silicon, such as dry etching, electrochemical etching, and metal-assisted chemical etching, The metal-assisted chemical etching is relatively simple and cost-effective, in which a thin layer of noble metal, served as a catalyst, is deposited on the smaple surface and then immersed in a mixed solution containing hydrofluoric acid and oxidant. Numerous studies have shown the fabrication of various nanostructures with different catalyst metal. However, the study on the effects of catalyst layer morphology is very rare.
In this work we use platinum as catalyst, due to its faster etching rate and better stability in disolution. The Pt film is thermal annealed to form nanoparticles flowed by the metal-assisted chemical etching to investigate its effects to the etching results. First we compared the size and distribution of nanoparticles in different annealing conditions with various atmospheres, annealing time, temperature, and platinum thickness. Then we observe the etching profiles using scanning electron microscopy. In the results, we found there are negligible effects in annealing time and atmospheric gases in high annealing temperature. And the higher the Pt thickness result the higher the nanoparticles size. In etching results, the etching rates are the same for various sizes of nanoparticles. The number density of nanoparticles is a key for structure morphology. Higher number density tends to form porous structures with some etching at the top of the structures, while lower number density tends to form columnar structures without etching at the top of the structures.
| en_US |