Research of Surface Science Group
How do electronics behave in nanoscale traps?
We want to use high-time resolution, femtosecond laser probes and high-energy resolution photoemission to probe the dynamics, transport, and energetics of electrons in the extraordinarily small features at the surface of a prefect single crystal. These traps use self-assembly to form very regular arrays of features on a surface, say Pt or Si, and then use the discontinuities in surface potentials to confine the electrons on a length scale much smaller than the Debroglie wavelength in the crystal. We have shown that neighboring surface features can interact and form delocalized surface bands. Or that surface dynamics depends on the surface confinement of electrons.
Our collaborators in this work are Peter Johnson and Tony Valla at Brookhaven National Laboratory, who have a set of superb occupied surface probes on Beamline U, Andrea Locatteli at the ELETTRA Laboratory in Italy, and Peter Sutteris 's group at the Brookhaven Center for Nanofunction materials.
How does light move electrons and break bonds at the surface of Oxides and Semiconductors?
Light and semiconductors are combined in some of the most important electronic devices. But in fact very little is known about the atomic or molecular level effects of light at the interfaces of these devices. In this area, we explore the ejection of light across the molecular layers that form the interfaces in organic devices such OLEDs or solar cells. We wish to understand how electronics can tunnel from a contact metal into the surface molecules or how molecules react when they capture such an electron. We do this work using powerful ultravacuum tools such as time of flight mass spectrometers or Auger electron emission. We initiate the processes using pulsed ultraviolet lasers. Related work on optical processes in nanoscale oxide quantum dots has been carried out in collaboration with Dr. Hrbek at Brookhaven National Laboratory. There we make use of many powerful probes available in their Nanocenter for Functional Nanomaterials.
Can we grow precise atomically defined layers of functional oxides?
New advances in electronic and optical devices increasingly rely on our ability to grown ultrathin ultraprecise layers. These layers must have their thickness known to within one atomic layer and have clearly defined composition. They also should be conformal to nanoscale changes in the substrate topography. In this area, we use the most advanced surface science tools to grow and probe nanoscale films using atomic layer deposition or epitaxy. In the recent past we have examined growth of II-VI materials and currently we are examining the growth of precise high-dielectric materials.