Control of optical bandgap energy and optical absorption coefficient by geometric parameters in sub-10 nm silicon-nanodisc array structure

• Published in: Nanotechnology 2012-02, Vol.23 (6), p.065302-1-6
• Main Authors: Budiman, Mohd Fairuz, Hu, Weiguo, Igarashi, Makoto, Tsukamoto, Rikako, Isoda, Taiga, Itoh, Kohei M, Yamashita, Ichiro, Murayama, Akihiro, Okada, Yoshitaka, Samukawa, Seiji
• Format: Article
• Language: English
• Subjects: Absorption coefficient; Arrays; Banded structure; Etching; Iron oxides; Quantum dots; Silicon; Wavefunctions
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/23/6/065302

A sub-10 nm, high-density, periodic silicon-nanodisc (Si-ND) array has been fabricated using a new top-down process, which involves a 2D array bio-template etching mask made of Listeria-Dps with a 4.5 nm diameter iron oxide core and damage-free neutral-beam etching (Si-ND diameter: 6.4 nm). An Si-ND array with an SiO2 matrix demonstrated more controllable optical bandgap energy due to the fine tunability of the Si-ND thickness and diameter. Unlike the case of shrinking Si-ND thickness, the case of shrinking Si-ND diameter simultaneously increased the optical absorption coefficient and the optical bandgap energy. The optical absorption coefficient became higher due to the decrease in the center-to-center distance of NDs to enhance wavefunction coupling. This means that our 6 nm diameter Si-ND structure can satisfy the strict requirements of optical bandgap energy control and high absorption coefficient for achieving realistic Si quantum dot solar cells.