1. Interface Structure for Graphene on SiC(000-1) Randall Feenstra, Carnegie-Mellon University, DMR 0856240 The interface of graphene on SiC(0001) is known to consist of a graphene-like "buffer" layer that acts as a template for subsequent layers of graphene. But on the SiC(000-1) surface prepared in vacuum, the interface is found to form a much different structure which does not act as a template for graphene formation. We have discovered that the (000-1) interface structure depends on the method of preparation, and under Si-rich conditions (5  10 -5 Torr disilane), an interface forms that is a graphene-like buffer layer. The discovery of this new (000-1) buffer layer provides a route for improved graphene quality on this surface. Color-coded map of graphene thickness on the surface, derived from electron reflectivity curves (intensity of reflected electrons vs. kinetic energy of electrons); white corresponds to the new "buffer layer" which is a graphene- like layer on the (000-1) surface, and blue corresponds to a single graphene layer on top of that buffer. B A C D

2. SEMITIP software package for computing fields and tunneling current for a tip near a semiconductor Randall Feenstra, Carnegie-Mellon University, DMR 0856240 Over the past decade, the PI and developed and posted software for computing electric fields and tunneling currents for a probe tip near a semi- conductor surface. Fully 3- dimensional geometries are allowed for the field distribution, and tunnel currents are computed either using the potential along the central axis (planar approximation) or using a plane wave expansion in a small region of space near the tunnel junction. A major upgrade of the software has been accomplished over the past year, and users world-wide are utilizing the programs for their own investigations. Electrostatic potential distribution for tip near semiconductor, with a quantum dot (gray) and surface charge to the left of the dot. Inset shows a computed conductance spectrum. http://www.andrew.cmu.edu/user/feenstra/semitip_v6/