An Introduction to the Helium Ion Microscope - John Notte
From Katie Gentilello
Although conceived 50 years ago, the helium ion microscope has only recently been realized as a commercial product. Now with several of these instruments deployed at scientific institutions around the globe, new applications are being discovered. The technology relies upon a source of helium ions that is just a few angstroms in size. Once created, the helium ions are accelerated, scanned and focused onto any desired sample. Although similar to the traditional SEM or gallium FIB, the unique ion source makes it possible to create a focused probe size as small as 0.25 nm. As the ions strike the sample, they produce photons, secondary electrons, secondary ions, and backscattered helium atoms. The detection rate of these products can be used to generate high resolution images with novel contrast mechanisms. A careful analysis of the properties of the products (such as the energy and angle) can reveal information about the sample’s material composition. Alternatively, the well controlled helium ion beam can be used for altering materials at the nanometer scale using gas assisted deposition and etching, or by the patterning of resists.