Development of a miniature STM holder for study of electronic conductance of metal nanowires in UHV–TEM

A new miniature scanning tunneling microscope (STM) holder was developed in order to simultaneously investigate electronic conductance and structure of nanowires in an ultra high-vacuum electron microscope (UHV–TEM). A thin gold wire held between the STM tip and substrate stage of the specimen holder was stretched to form a suspended gold nanowire. The new TEM–STM system allowed us to measure electronic conductance at intervals of 20 ms, and to record high-resolution TEM images on videotape at 30 fps. Suspended gold nanowires formed from [1 1 0] oriented electrodes were well-elongated. In contrast, [1 0 0] and [1 1 1] electrodes produced nanowires with short necks. Electronic conductance was found to change as nanowire structure changed, with conductance quantization in units of 2e2/h, where e is the electron charge and h is Planck’s constant, only being exhibited for well-elongated nanowires.