Photoluminescent silicon quantum dots in core/shell configuration: synthesis by lowtemperature and spontaneous plasma processing

Abstract

Quantum confinement in zero-dimensional silicon nanocrystals (nC) in the quantum dot (QD)configuration has triggered a tremendous interest in nanostructured device technology.However, the formation of Si-QDs eventually proceeds through multi-step routes and involveshigh temperature processing that impedes preferred device configuration. The present workdemonstrates the formation of nC-Si QDs of controlled size, density and distributionthrough one-step and spontaneous plasma processing, at a low substrate temperature (300 °C) compatible for device fabrication. Direct growth ofnC-Si/SiOx core/shellquantum dots embedded in the a-Si matrix, 6.4–3.7 nm in diameter and with number density in therange ∼ 6 × 109–1 × 1011 cm − 2 has been accomplished, following a novel route where He dilution toSiH4 in RF plasma CVD has been found instrumental. On gradual reduction in the sizeof QDs, splitting of the energy bands widens the optical band gap and inducesvisible photoluminescence that appears controllable by tuning the size anddensity of the dots. This low temperature and spontaneous plasma processing ofnC-Si/SiOx core/shell QDs that exhibit the quantum size effect in photoluminescence is being reportedfor the first time.