The fabricated pores were found to be stable at ambient conditions and in water. The pore-size tuning technique was further tested on holes fabricated using a different process. In agreement with Chen et al. 5 ,we find that a focused electron beam with a spot size of a few nanometres can be used to drill holes in thin free-standing SiO2 membranes,with an estimated thickness of about 10 nm (Fig. 3a). Figure 3b,c shows a pore that has been drilled using an electron-beam intensity above 1×108 Am–2 .Holes as small as 6 nm can be obtained,but this technique does not give full control at the nanometre scale because no images can be recorded during drilling
