Application of a micromachine scanning tunnelling microscope (mu-STM) for vacuum tunnelling gap observation

This paper reports the observation of the vacuum tunnelling gap between two conductors of a scanning tunnelling microscope (STM), using a high-resolution transmission electron microscope (TEM). A micromachine scanning tunnelling microscope (mu-STM) is made on a 2.5 mm(2) chip, by an advanced ultra-large scale integrated circuit (ULSI) technology with a minimum dimension of 0.4 mu m and alignment accuracy of 0.1 mu m. The mu-STM is designed to fit into a TEM sample holder for direct observation of the tip apex, and the results demonstrate the possibility of analysing the tunnelling gap physics and material transport mechanisms at the tip apex.