Nanostructured Germanium Synthesized by High-Pressure Chemical Vapor Deposition in Mesoporous Silica Templates

Nanostructured semiconductors are interesting because of their varied electronic and optical properties compared to the bulk. Using ordered porous materials as templates is an appealing approach to prepare nanostructured materials. However, the very small pore sizes (< 10 nm) of many mesoporous silicas make traditional deposition methods for germanium difficult, resulting in aggregated particles or voids in the deposited material. To overcome this challenge, high-pressure chemical vapor deposition (HPCVD) has been used to deposit germanium within the pore network of KIT-5 mesoporous silica. This technique allows for smooth, continuous deposition within small, tortuous pore networks. Both crystalline and amorphous materials can be produced, expanding the applicability of the resulting materials for various uses. The resulting nanocrystalline germanium has 5-nm features derived from the parent KIT-5 and is the smallest templated material prepared using HPCVD to date. This work represents the first time a three-dimensional mesoporous silica, with features ≤ 5 nm, has been uniformly filled with a semiconductor.