Nanostructured porous silicon films for terahertz optics.
A simple technique is reported to create 31 and 45 μm thick, graded-index Si films in the form of nanospirals on a Si substrate using a dynamic, oblique angle deposition technique. We show that the success in producing such a thick, nanostructured film without delamination from the Si substrate is primarily due to the nano-porous nature of the film which effectively eliminates the stress generated during growth. Effective refractive indices of 1.9 and 2.1 were extracted from the terahertz time-domain reflectivity data, which correspond to 57% and 51% porosity for the 31 and 45 μm thick films, respectively. The gradient of porosity through the film was modeled to describe quantitatively the terahertz reflectance data in the 0.2-2.0 THz regime.
Chemical Engineering Department, Rensselaer Polytechnic Institute, Troy, NY 12180, USA. rileym@rpi.edu
Michael
M
Riley
Albert
A
Redo-Sanchez
Panagiotis
P
Karampourniotis
Joel
J
Plawsky
Toh-Ming
TM
Lu