| AVS 61st International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | Sarun Atiganyanun, University of New Mexico |
| Authors: | M. Zhou, University of New Mexico S. Atiganyanun, University of New Mexico S. Ghosh, University of New Mexico J. Chavez, University of New Mexico S.E. Han, University of New Mexico S.M. Han, University of New Mexico |
| Correspondent: | Click to Email |
Photonic crystals give rise to a variety of applications such as absorbers, waveguides, and light filters. One of the common examples is an inverse opal structure made of semiconductors. This structure, unlike its counterpart opal structure, exhibits a complete photonic band gap. In this study, we investigate a low-cost and scalable fabrication of an inverse opal structure via self-assembly of colloidal silica microspheres and Ge molecular beam epitaxial (MBE) back filling, followed by buffered HF etching. First, silica microspheres are functionalized with allyltrimethoxysilane and dispersed in chloroform. Langmuir-Blodgett (LB) method is then used to self-assemble silica microspheres with a diameter of ~800 nm onto Si(100) substrates. By optimizing the pulling speed of the substrate and surface pressure within the trough, a hexagonally closed-packed opal structure is achieved. Scanning electron microscopy (SEM) images have shown domain size of the monolayer assembly to be approximately 10 µm by 10 µm. By repeating LB coating for n times, an n-multilayer assembly is formed, creating an opal template structure. After assembling silica microspheres on Si substrates, Ge MBE is used to back fill the voids between microspheres. The effusion cell temperature ranges from 1150 to 1000ºC, which corresponds to the Ge flux of 6.44*1014 to 1.83*1013 Ge atoms/cm2-sec, respectively. When the substrate temperature is held constant at 580ºC, the SEM characterization shows that the low Ge flux at 1000ºC reduces random nucleation on top of the microspheres by approximately one order of magnitude compared to the high Ge flux at 1150ºC. Following the backfill, the silica microspheres are removed by immersing the substrate in a buffered HF solution, creating a single-crystalline Ge inverse opal structure. In this presentation, we will further discuss the optimization of Ge flux and substrate temperature, examination of crystal quality of Ge by X-ray diffraction and Ge/Si interface by transmission electron microscopy, and the structure’s optical properties with Fourier transform infrared spectroscopy.