AVS 53rd International Symposium
    Thin Film Wednesday Sessions
       Session TF-WeM

Paper TF-WeM2
Photonic Band Edge Engineering through Nano Coating of Cu Thin Film on 3D Photonic Crystals

Wednesday, November 15, 2006, 8:20 am, Room 2022

Session: Thin Films for Photovoltaics and Energy Applications
Presenter: D.-X. Ye, Rensselaer Polytechnic Institute
Authors: D.-X. Ye, Rensselaer Polytechnic Institute
Z.-P. Yang, Rensselaer Polytechnic Institute
J. Bur, Rensselaer Polytechnic Institute
S.Y. Lin, Rensselaer Polytechnic Institute
T.-M. Lu, Rensselaer Polytechnic Institute
Correspondent: Click to Email
Photonic crystals have extraordinary applications in illuminations, solar cells, and photovoltaic devices by redistributing the energy. At the edge of a photonic band gap, the photon group velocity approaches zero giving the coherent photon localization. Therefore, spontaneous emission near the photonic band edge can be totally suppressed. For energy applications, interesting photonic crystals are those with a band edge close to visible wavelengths. However, the band edge on this side is limited both by the fabrication methods and by the nature of the dielectric materials used. Here we present our strategy of breaking these limitations by conformal coating of Cu films using chemical vapor deposition (CVD). First, on pre-fabricated Si and W woodpile structures, 70 nm thick Cu was coated by CVD. Optical measurements showed that the photonic band edge is pushed from ~1500 nm to ~700 nm in these structures. Another class of photonic crystals is constructed using arrays of square nanosprings by oblique angle deposition technique. This technique was first used to fabricate the Si spring photonic crystals by M. J. Brett et al. However, the dimensions of the nanosprings cannot be maintained due to the fan-out growth. We designed a substrate rotation method to overcome this difficulty which is referred as swinging technique. In swinging technique, the substrate is rotated azimuthally back-and-forth within an angular range with a constant rotation speed. Uniform Si photonic structure can be fabricated without fan-out problem now. On the other hand, the other limitation of this technique prevents the geometry of the nanosprings to be optimized to achieve a large band gap. We solved this problem again by further Cu coating on Si nanosprings. The overall photonic crystal shows a complete band gap in the near infrared region. In summary, Cu coating on photonic crystals provides an easy path to modify the properties of photonic crystals.