Traditional sample preparation supports for electron microscopy have usually been thin films of amorphous or holey carbon stretched over a metallic grid. More recently introduced formats include organic polymers over metallic grids or silicon nitride and silicon oxide membranes over silicon frames. Here, the application of a nanofabricated silicon membrane technology as a novel sample preparation support for electron microscopy is described. These new supports offer several unique characteristics, including nanoscale thickness and pores, which may improve imaging and analysis of materials and biological molecules.
Recently developed technology permits the fabrication of pure silicon membranes that are among the world's thinnest materials—only 5 to 15 nm thick. See Striemer et al., Nature (2007) 445: 749-751 for more details. These silicon membranes are also among the world's first membrane technologies to offer nanoscale pores of 5 to 50 nm. This combination of characteristics is unique and not shared by the materials currently employed as sample supports. Moreover, it suggests that these silicon membranes could overcome many of the problems associated with current generation materials. For example, the holes of lacey and holey carbon grids (1-5 micron diameter) are incompatible with the size of most nanotubes and nanoparticles (2-40 nm). Obtaining background-free images of the entire nanostructure is rarely possible with this incompatible combination of sizes. Another significant issue is the inability to vigorously plasma clean samples on carbon grids. In some cases, this inability to remove organic contaminants can prevent high-resolution imaging of samples.