Manfred H. Jericho Professor Scanning Probe Microscopy and Condensed Matter Physics B.Sc., Dalhousie University (1959) M.Sc., Dalhousie University (1960) Ph.D., Cambridge University (1963) Office Phone: (902)494-2316 Email: manfred.jericho@dal.ca

     Many novel ways of examining the structure of surfaces have recently been developed. Of particular interest are the Scanning Tunneling (STM) and the Atomic Force (AFM) microscopes. In the STM a sharp needle is positioned within a few atomic diameters above a conducting surface. When voltage is applied between needle and sample, and the needle is scanned over the surface, the resulting variations in the tunneling current that flows between needle-tip and sample surface are used to compose a topographic image of the sample surface. Atom resolved images of surfaces can be obtained in this way. Our research group has constructed an STM that can examine surfaces in an ultra-high vacuum and at temperatures ranging from 400 K to ~20 K. The tunneling current is sensitive to the details of the electronic structure of surfaces. We are using the STM to study this electronic structure by examining the current-voltage characteristics of the tunneling process at different locations (including different atomic sites) on surfaces. A variety of materials permit the inclusion of guest atoms in the lattice structure of a host material. We are examining, with atomic resolution, the resulting changes in the arrangement of atoms at the surface as well as the formation of new superlattice structures at different temperatures. Imaging and the manipulation of guest atoms at the sample surface is also an important part of the program.
     When the sample is not electrically conducting, surfaces can be studied with the AFM. In this instrument a sharp tip attached to a cantilever spring is used as the surface probe. With the help of computers, the vertical deflections of the cantilever are transformed into topographic images of the surface. Measurements are also possible with the sample and cantilever immersed in water. One aim of our research is to study biological material and soft interfaces under proper physiological conditions. A unique feature of the AFM is its ability to manipulate material that has been deposited on the substrate surface. A major program is thus concerned with the measurement of the elastic properties of fibers, membranes, and even whole bac- teria. The AFM is a high sensitivity force sensor and other projects attempt to use the AFM to measure as well as understand theoretically long and short-range forces between biological surfaces immersed in electrolytes.

Selected publications

• W. Xu, P.J. Mulhern, B.L. Blackford, M.H. Jericho, M. Firtel, and T.J. Beveridge "Modeling and measuring elastic properties of an Archael surface, the sheath of Methanospirillum hungatei, and the implication for methane production" J. of Bacteriology 178 (1996) 3106-3112.
• W. Xu, P.J. Mulhern, B.L. Blackford, M.H. Jericho, and I. Templeton "A new atomic force microscopy technique for the measurement of the elastic properties of biological materials" Scanning Microscopy 8 (1994) 499-506.
• B.L. Blackford, C.S. Arnold, P.J. Mulhern, and M.H. Jericho "A scanning tunneling microscope study of a palladium sphere in hydrogen gas: Expansion and surface topology" J. Appl. Phys. 76 (1994) 4054-4060.
• D. Maclean, A.M. Simpson, and M.H. Jericho "Static Young's modulus obtained by dilatometry on TaS3 in the drifting charge-density-wave state" Phys. Rev. B 46 (1992) 12117-12120.
• P. Mulhern, T. Hubbard, C.S. Arnold, B.L. Blackford, and M.H. Jericho "A scanning force microscope with a fiber-optic-interferometer displacement sensor" Rev. Sci. Instrum. 62 (1991)1280.

Updated 18 July 1997