| I have studied the surface morphologies and electronic properties of GaAs, diamond, polyaniline and copper oxide. For these studies, I have built a scanning tunneling microscope (STM) for use in ultra high vacuum.;Molecular epitaxially grown GaAs(001) surfaces were studied using arsenic capping method. Depending on the procedure of capping, two sequences of reconstructed surface structures were observed as the surface composition changed upon annealing: one is c(4 x 4) to 1 x 1 and the other 2 x 4 to 4 x 1. STM images of 2 x 4 surface agreed with a unit cell which consists of three arsenic dimers and one missing dimer.;I have measured tip-surface distance dependent scanning tunneling spectroscopy (STS) from boron doped diamond. To reduce the onset voltage from 10 to 1 V, vertical position of the tip was lowered a few tens of nanometer. This suggests that the tip is in contact with the surface and acts as a stylus sensing a contact resistance varied by a point contact pressure.;STM images were taken from electropolymerized polyaniline thin film deposited on a gold electrode. Images taken at nucleation stages showed that the growth was inhomogeneous and the continuous film was formed through the merging of individual nuclei. STS results showed that the tunneling conductance increased with the electrochemical oxidation potential. In addition, the results of local tunneling spectroscopy supported that the insulator-to-metal transition occurred via electron percolation through metallic clusters, the average size of which was 300 A.;A thin layer of copper on a monolayer of alkyl thiol was studied. STM images of copper clusters showed an orientation which reflected the pseudohexagonal structure of the underlying organic film. STS results showed a rectifying I-V relation due to copper oxidation in air. |
