Scanning Tunneling Microscopy of Manganites

We have built a scanning tunneling microscope (STM) which employs a mechanical coarse approach mechanism. We have tested the mechanical and electronic components of the system and calibrated the piezoelectric scanning mechanism by imaging highly ordered pyrolytic graphite (HOPG) at room temperature. Atomic resolution HOPG images were obtained when the STM was placed inside a vibration isolated liquid helium dewar. We have also scanned single crystals and thin-films of hole-doped manganese oxides (manganites) and obtained images on the scale of about 100 nm to about 10 nm. After obtaining satisfactory images at room temperature, we will cool the apparatus first down to liquid nitrogen temperature (77 K) and then down to liquid helium temperature (4.2 K) to investigate micrometer and nanometer scale phase separation in manganites.