Electron energy loss spectroscopy study of the formation process of Si nanocrystals in SiO2 due to electron stimulated desorption-decomposition

✍ Scribed by M Takeguchi; K Furuya; K Yoshihara

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 373 KB
• Volume: 30
• Category: Article
• ISSN: 0968-4328
• DOI: 10.1016/s0968-4328(99)00018-9

✦ Synopsis

It is well known that SiO 2 is decomposed to silicon and oxygen under irradiation by an electron beam. We have discovered that Si nanocrystals can be formed in SiO 2 thin films with a high-intensity convergent electron beam at high temperature. In the present work, we examined the formation process of Si nanocrystals by in situ electron energy loss spectroscopy in an ultrahigh-vacuum field-emission transmission electron microscope (UHV-FE-TEM). A sequence of time-resolved spectra showed that initial irradiation up to a dose of about 1 × 10 9 C/m 2 caused gradual reduction from SiO 2 to Si. At that time, no crystalline structures appeared in the TEM image. When the dose amounted to nearly 2 × 10 9 C/m 2 , the Si composition increased rapidly. Immediately after such an irradiation, the TEM image showed emergence of Si nanocrystals. These results suggest that some critical process, such as nucleation in Si crystal growth, exists in the formation of Si nanocrystals from SiO 2 .