Equipment

LEEM/STM/XPS

Professor Chiang headed a campus collaboration which obtained an NSF instrumentation grant 1 and acquired the unique Advanced Surface Microscopy Facility, 2 which consists of an ultrahigh vacuum (UHV) low energy electron microscope (LEEM), a UHV scanning tunneling microscope (STM), and a surface analysis chamber with X-ray photoelectron spectroscopy (XPS), all installed in the same vacuum system with in situ sample transfer among the various instruments, sample preparation facilities, and two airlocks for rapid interchange of samples and tips (see diagram above). This unique facility enables the study of surface structures with STM, giving atomic resolution, field of view 100-10000Å, sample temperatures 150-1000K, at a rate of <1min./image, plus the real-time study at video rates (30 frames/sec) with LEEM, which enables imaging with resolution 100Å, field of view 1-50 microns, and sample temperatures from 150-1800K, together with information on the low energy electron diffraction (LEED) pattern of the surface. The LEEM permits real-time video imaging of the dynamical processes on surfaces, such as the motion of single height atomic steps, and the nucleation and growth of islands and overlayers on surfaces. The LEEM and STM give complementary information, in both spatial and temporal scales, on the growth and structures of adsorbed atoms, islands, and layers. Our instrumentation was the first in the world that allowed the use of both STM and LEEM to study an identical sample without removing it from the ultrahigh vacuum system. 1. NSF Grant DMR 95-12231, with matching funds from University of California, Davis. 2. C.L.H. Devlin, D. H. Futaba, A. Loui, J.D. Shine, and S. Chiang, A Unique Faciltiy for Surface Microscopy, Materials Science and Engineering B, 96, 215-220 (2002).