A scanning tunnelling microscope (STM) was designed and built. Atomic resolution was achieved. Research was carried out into zeolite topography and spectroscopy at atomic scale. Preliminary results include data on the local forces between the scanning tip and the zeolite surface.
A commercially available STM was used to study fullerene molecules. Examination of the growth of Buckminster fullerene (C60) on lamellar substrates revealed triangular structures.
Several computational techniques have been developed to account for the 3-dimensional character of electron tunnelling in simplified models of scanning tunnelling microscopy.
An ultra high vacuum scanning tunnelling microscope (STM) has been developed which yields atomic resolution. Software to control the system has been written. A preparation chamber with an airlock has been constructed, and a transportable ultra high vacuum container (vacuum suitcase) has been developed to carry samples between the low energy ion implanter and the STM. The vacuum suitcase has complex specimen handling facilities, industry viewport, wobblesticks and transfer canes.
The STM has been used to study copper surfaces irradiated with low energy helium ions. Small rounded features were observed and the nature of their formation is discussed.
The result of depositing copper by low energy ion beam deposition on graphite was studied. The expitaxial copper film quality was poor.
Scanning tunnelling microscopy (STM) has been used to investigate the relation between the structural quality and the electronic properties of thin metal films. The STM system (Nanoscope II) is reliable and permits the inspection of surface topography to within a few arc minutes.
The surface topography of thin gold films has been linked to the preparation conditions. For deposition at liquid nitrogen temperature the films are polycrystalline with a grain size of about 15 nm. Deposition at room temperature increases the lateral size of the grains. At 250 C, the gold films show the formation of micron sized crystallites on which atomically flat regions can be observed.
The quality of fine gold lines (width 30 nm) grown on silicon oxide (SiO2) substrates has been probed. Lines evaporated in a residual atmosphere of oxygen or helium have a more homogeneous film structure and are frees of holes than those evaporated in vacuo.
STM has also been used for lithography. Narrow gold lines were fabricated by developing locally a thin resist layer with STM. Local field evaporation of atoms at the edges of terraces on high temperature superconductor films has been used to modify the characteristic topography of yttrium barium copper oxide (YBa2Cu307).
STM in an ultra high vacuum (10E-10 mbar) has been used to determine the fractal surface structure of a rough gold surface, and to investigate erosion of an iron film surface by an ion beam.
The present twinning project aims at helping the participating laboratories to develop a common capability in Scanning Tunneling Microscopy, Scanning Tunneling Spectrocopy and Atomic Force
Microscopy. In the first phase of the project, the mechanical and electronic components will be realized and assembled in a coordinated effort. In the exploitation phase, the instrument will be used to investigate 1) the effects of ion-beam deposition and implantation on the topography of surfaces; 2) the surface structure during thin film growth and 3) surface electronic states of semiconductors under laser illumination.
Funding SchemeCSC - Cost-sharing contracts
3000 Louvain / Leuven