Microphotoluminescence and Microphotoreflectance Analyses of Laser Rapid-Thermal-Annealed Surface With Buried Si Nanocrystals

The optical properties of a SiO_x film rapid-thermal-annealed (RTA) by CO₂ laser are primarily investigated. The microphotoluminescence (mu-PL) and high-resolution transmission electron microscopy (HRTEM) analyses indicate that the precipitation of random-oriented Si nanocrystals can be initiated when laser intensity (P_laser) is larger than 4.5 kW/cm². At P_laser of 6kW/cm², the Si nanocrystal exhibits a largest diameter of 8 nm and a highest density of 4.5times10¹⁶ cm^-3, which emits strong PL at 790-825 nm. The microphotoreflectance of the CO₂ laser RTA SiO_x film reveals a volume density product dependent refractive index increasing from 1.57 to 1.87 as P_laser increases from 1.5 to 7.5 kW/cm². Nonetheless, the laser ablation of the SiO_x film occurs with a linear ablation slope of 35 nm/kW/cm² at beyond 7.5 kW/cm², which terminates the enlargement of Si nanocrystals, degrades the near-infrared PL, and slightly reduces the refractive index of the CO ₂ laser RTA SiO_x film