Nanostructure Growth on Surfaces

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Variable Temperature Omicron STM

In Scanning Tunneling Microscopy (STM) a very sharp tip is moved close to the sample and a small voltage is applied across the two. This causes electrons to tunnel through the vacuum between the two electrodes. The tunneling current depends exponentially upon the height of the tip above the sample giving the STM atomic resolution.

Low Temperature Omicron STM

An Omicron Low Temperature STM (LTSTM) that can reach 4 K was purchased and installed in 2014. Both the sample and the tip are cooled down to low temperatures. This increases stability and minimizes drift allowing higher resolution of spectra in scanning tunneling spectroscopy (STS). The left picture shows the preparation chamber in front and the LTSTM towering in back. The right picture shows the actual STM stage after being unpacked.

High resolution LEED (SPA-LEED)

Low Energy Electron Diffraction (LEED) electrons with energy (usually between 30 and 200 eV) are directed on the surface. In conventional LEED the electrons diffract off the surface, excite a phosphor screen and generate a diffraction pattern. In SPA-LEED specially designed electron optics that minimize the beam divergence measure the shape of the diffracted spot with wavevector resolution 10-times that of conventional LEED.