Electron-beam-induced damage in amorphous SiO2 and the direct fabrication of silicon nanostructures

摘要

We have investigated the behaviour of self-supporting amorphous SiO2 (a-SiO2) thin films under 100 keV electron-beam irradiation in a high-dose regime (10(7)-10(9) C m(-2)). Electron-energy-loss and energy-dispersive X-ray measurements show that oxygen is preferentially lost during the damage process which leaves the irradiated a-SiO2 oxygen deficient. The results are discussed in terms of previously reported models, which suggest that the mass loss from a-SiO2 is attributed to a combination of high-energy sputtering, surface desorption and volume-dissociated mechanisms. The oxygen can be totally removed from a-SiO2 layer 15 nm thick after a dosage of approximately 3 x 10(9) C m(-2) electrons. On the basis of the discovery of this effect we develop a controlled way of making nanostructures of silicon directly from a-SiO2. In particular, if a-SiO2 is irradiated with a highly intense electron beam of nanometre scale, then a column of silicon is formed, which can be as small as 2 nm in diameter. If the beam is moved in a straight line, then a thin plate of silicon is formed. These silicon nanostructures are formed directly under electron irradiation after a dose of 10(9) C m(-2) of 100 keV electrons and no resists or chemical development are required. [References: 37]