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High density of Sn quantum dots (QDs) have been grown epitaxially on Si(001) substrate by solid phase epitaxy (SPE).The dependences of morphology and crystallinity of Sn QDs on the Sn coverage,annealing temperature and time were investigated by atomic force microscopy (AFM) and x-my diffraction (XRD) respectively.The changes in microstructure of Sn QDs with various annealing conditions were studied by Raman and Fourier transform infrared (FTIR) spectra.AFM results showed high density of Sn QDs in small size were achieved under decreased deposition time,low annealing temperature and short annealing time respectively.Good crystallinity of Sn QDs was observed with XRD patterns.These β-Sn QDs were partially around with a SnO2 shell.Raman measurements on low temperature annealing sample present the existence of α-Sn QDs,which agrees with FTIR results.In addition,Raman spectra of α-Sn QDs show an upward shift of the Sn-Sn mode frequency (~22.8 cm-1) with α-Sn thin film due to the great residual strain existed in Sn QDs.