Education and Outreach :

1. Corrugated Chain Structure of In4Se3 (100) SurfaceJiandi Zhang, Florida International University, DMR 0346826 The density of states from (a) DFT-GGA calculations compared with (b) photoemission and (c) STM dI/dV spectra taken from the In4Se3 (100) surface. The photoemission experiments and theoretical calculations have been accomplished through the collaboration with Dowben’ s group at UNL. The crystal structure of In4Se3 (100) surface: (a) LEED image with the surface Brillouin zone, (b) a 36 36 nm2 STM image, and (c) a top view of schematic lattice structure. In4Se3 is characterized as a layered semiconductor, while the cleaved (100) surface of the single crystal compound appears a corrugated quasi-one-dimensional chain structure. We have studied both the surface lattice and electronic band structures. We discovered that, unlike these on other semiconductor surfaces such as Si(111), the quasi-1D In chains at the surface show nonmetallic behavior with an apparent energy gap although exhibit a large anisotropy in band structure. The strong bonding with Se atoms at subsurface layer prevents the metallicity of In chains at the surface. This study gains new insight into the surface electronic properties and the relationship to lattice structure of this useful semiconductor.

2. Corrugated Chain Structure of In4Se3 (100) SurfaceJiandi Zhang, Florida International University, DMR 0346826 Education and Outreach: There are two graduate students (En Cai and Melanie Klike) and one undergraduate student (Idaykis Rodriguez) involved in the highlighted research project. Several other undergraduate students have also participated in the research activities. Idaykis Rodrigues and Darwin Urbinaare two Hispanic students. Idaykis has just graduated and is going to be a new graduate student at FIU while Darwin is still working in the group. Besides, our group has participated in several education outreach activities through this funded program, especially the open house activities to local high-school students/teachers, research experience for high-school students/teachers and lectures to local public. Many of undergraduate students are recruited through these activities. Undergraduate student Darwin Urbina, who has been involved in the installation of new XPS/UPS system, is working on the calibration of the new electron energy analyzer in PI laboratory. Societal Impact: Tailoring complex materials for device applications will involve the preparation of surfaces, fabrication of thin films, superstructures and junctions. Knowledge of surface and interface properties as well as the effects derived by broken symmetry, quantum confinement and interface imperfection like defects is crucial if these devices are to be made to work at optimized functionality.