Absorption and Raman scattering spectroscopies from semiconductor–glass composites

Semiconductor–glass composite films were fabricated using a dual gun RF magnetron sputtering technique. The semiconductor films are made sufficiently thin to form isolated clusters of reasonably uniform size, adjustable between 1.5 and 40 nm in diameter. The glass films are continuous and form a matrix around the isolated clusters. This structure produces semiconductor clusters whose electronic band structure is dominated by quantum confinement of the electron and hole wavefunctions. This work examines the effects of fabrication and heat treatments on the electronic band structure and LO-phonon properties of Si and Ge semiconductor clusters embedded in SiO2. Absorption measurements indicate a blue shift in energy with heat treatment as a result of quantum confinement effects. The evolution of the absorption shift as a function of both the amorphous and crystalline states is explored using Raman scattering spectroscopy.