Laboratory for Surface Analysis and Modification (LSAM)
The Laboratory for Surface Analysis and Modification (LSAM) has been set up within the Department of Physics at Baylor University since the Winter of 1997. The goal of the laboratory is (1) to establish a premier research program in the area of surface science and (2) to provide both undergraduates and graduates advanced learning opportunities in the forefront of contemporary surface science research. The main instrument in LSAM is the XSAM 800 Surface Analysis System (Kratos Analytical, Inc.), which is housed in two ultra-high vacuum (UHV) chambers. Several pumps are in operation to achieve the UHV pressure inside the chambers including one ion pump, three turbo molecular pumps, three mechanical oil pumps, and two sorption pumps, and under normal operation, the residual gas pressure is maintained in the 10-10 Torr range. For the studies which require high surface sensitivity, the UHV chambers are currently equipped with various analytical components as listed below.
- a 127 mm mean radius hemispherical energy analyzer for charged particles
- a dual anode X-ray gun (photon energies at either 1253.6 eV or 1486.8 eV)
- a high energy, high resolution electron gun (< 5 keV)
- a mini beam ion guns (< 5 keV)
- an A-DIDA ion gun (< 15 keV, Atomika)
- a quadrupole mass analyzer
- two scintillators
- a reverse-view Low Energy Electron Diffraction (LEED) optics
The combination of these tools allows one to carry out an investigation of complex surface and interface phenomena under a controlled and clean environment, and atomic, electronic, elemental and chemical information within the top 50 angstrom (+) of the surface is obtained. Several spectroscopic studies and information which the XSAM800 is capable of providing are summarized in Table I.
In addition, a number of auxiliary features and sample handling systems of the XSAM800 are available for its versatility: a multiple-motion (X-Y-Z-Θ-Φ) manipulator, a fast sample insertion mechanism, a heating & cooling stage, in situ sample fracture stage, and e-beam deposition chamber.
Table I. Surface Sensitive Probes Equipped to XSAM800 and Their Functions
|Angle Resolved X-ray Photoemission Spectroscopy (ARXPS)
|Occupied electronic structure; Detailed compositional & chemical analysis; Short-range surface atomic structure
|Scanning Auger Microprobe (SAM)
|Surface imaging; Elemental & chemical mapping of surface
|Auger Electron Spectroscopy (AES)
|Compositional & chemical analysis
|Ion Scattering Spectroscopy (ISS)
|Compositional analysis on the top surface layer; Short-range surface atomic structure; Depth Profiling
|Secondary Ion Mass Spectroscopy (SIMS)
|Chemical analysis with ultra-high sensitivity
|Reverse-view Low Energy Electron Diffraction optics (LEED)
|Analysis of long-range, periodic surface structures
Various electronics which power and monitor the analytical components are currently controlled using a DEC's Micro PDP11 computer. Typical experimental procedures from input setup to data acquisition to real time display are all automated. Also, for off-line data processing, software performing simple spectroscopic interpretation and data analysis is installed both on the PDP11 micro and a Pentium-based personal computers. To help understand and interpret experimental data, theoretical programs calculating electronic and structural properties of solids at highly sophisticated level are also available on the Baylor's DEC Alpha workstation. The WIEN97 (Vienna University of Technology), a density functional theory with a full potential linearized augmented plane wave method, has been appraised by some as one of the most accurate methods for the computation of the electronic structure of solids within density functional theory. It provides ab initio calculation of electronic properties as well as geometry optimization. For structural information, the SCAT program (Lawrence Berkeley National Laboratory), a curved-wave multiple-scattering calculation for photoelectron diffraction, is also available on both the DEC's Alpha workstation and a VAX computer. It allows one to simulate and study electron diffraction from various surfaces, thereby to accurately determine surface geometry corresponding the experimental data.
For more information about research in the LSAM, please Dr. Park.