Enhanced Photodetection with Crystalline Si Nanoclusters

SiO nanodots were fabricated on a TiO₂ thin film using glancing angle deposition technique. The fabricated samples were annealed at 950 °C in open air configuration to obtain Si nanoclusters resulting from phase separation of SiO nanodots. Field Emission Gun Scanning electron microscopy and atomic force microscopy were used to examine the topography of the samples. The elemental composition of the samples was analyzed using energy dispersive X-ray mapping and their crystallinity was confirmed by analyzing the bandgap determined from the Tauc plots. The annealed samples show a broadband absorption which is about two folds in magnitude as compared to the as deposited (unannealed) samples. The photoluminescence spectra confirms the quantum confinement effect in the annealed samples. A photodetector was fabricated from an annealed sample by depositing gold contacts on top of it. This photodetector showed a two-fold increase in dark current and a 1.5-fold increase in light current compared to a photodetector made from the as-deposited SiO samples-which is due to the increased crystallinity in Si nanoclusters. Finally, the rise and fall times of the device were measured through a switching experiment.