Photoluminescence from Ge-SiO_2 thin films and its mechanism

Ge-SiO2 thin films were deposited on p-type Si substrates using the radio frequency (rf) magnetron sputtering technique with a Ge-SiO2 composite target. Films were annealed in N2 ambience for 30 min at 300℃-1000℃ with an interval of 100℃. Through the X-ray diffraction, the average size of Ge nanocrystals (nc-Ge) was determined. They increased from 3.9 to 6.1 nm with increasing annealing temperature in the range of 600℃-1000℃. Under ultraviolet excitation, all samples emit a strong violet band centered at 396 nm. With the formation of nc-Ge, the samples exhibit another emission of orange band with the peak at 580 nm and its intensity increases with the increasing size of nc-Ge.The peak positions of two bands do not shift obviously. Experimental data indicate that the violet band comes from GeO defect and the orange band originates mainly from the luminescence centers at the interface between the nc-Ge and SiO2 matrix.

Ge-SiO2 thin films were deposited on p-type Si substrates using the radio frequency (rf) magnetron sputtering technique with a Ge-SiO2 composite target. Films were annealed in N2 ambience for 30 min at 300℃-1000℃ with an interval of 100C. Through the X-ray diffraction, the average size of Ge nanocrystals (nc-Ge) was determined. They increased from 3.9 to 6.1 nm with increasing annealing temperature in the range of 600℃-1000℃. Under ultraviolet excitation, all samples emit a strong violet band centered at 396 nm. With the formation of nc-Ge, the samples exhibit another emission of orange band with the peak at 580 nm and its intensity increases with the increasing size of nc-Ge.The peak positions of two bands do not shift obviously. Experimental data indicate that the violet band conies from GeO defect and the orange band originates mainly from the luminescence centers at the interface between the nc-Ge and matrix.