Shrinkage and expansion mechanisms of SiO2 elliptical membrane nanopores

20 nm SiO2 elliptical membrane nanopores with various thicknesses were directly formed in situ by using a focused electron beam with transmission electron microscopy (TEM). The shrinkage and the expansion behaviors of the SiO2 ellipse nanopores with different thicknesses were attributed to variations in their geometries, in particular their curvatures. The geometric mechanisms of elliptical nanopores with various thicknesses fabricated utilizing a SiO2 membrane with a thickness gradient by using an electron beam irradiation are described on the basis of TEM images, which depend on the electron beam irradiation time.