Hydrothermal Atomic Force Microscope (HAFM)

Support: U.S. Department of Energy, Basic Energy Sciences, Geosciences

In collaboration with Dr. Kevin Knauss and Carl Boro at Lawrence Livermore National Lab, we have developed a contact atomic force microscope capable of imaging in aqueous solution at up to 12 bars and 150 C. Publications related to the HAFM include:

Jordan, J., Higgins, S.R., Eggleston, C.M., Swapp, S.M., Janney, D. and Knauss, K. (1998) Acidic dissolution of plagioclase. In Situ observations by hydrothermal scanning force microscopy. Geochimica et Cosmochimica Acta (in press).

Eggleston, C.M., Higgins, S.R. and Maurice, P.A. (1998) New Views of Environmental Surfaces from Scanning Probe Microscopy. Environmental Science and Technology 32, 456A-459A.

Higgins, S.R., Jordan, G., Eggleston, C.M. and Knauss, K. (1998) Dissolution kinetics of the barium sulfate (001) surface by hydrothermal atomic force microscopy. Langmuir 14(18), 4967-4971.

Higgins, S.R., Eggleston, C.M., Knauss, K. and Boro, C. (1998) A novel new high-temperature and pressure atomic force microscope. Reviews of Scientific Instruments 69(8), 2994-2998.

Figure 1 below gives an image of an early version of the HAFM. Figure 2 is an image of barite (001) (BaSO4) dissolving in water at 125 C. The arrows indicate "unbounded" steps that retreat at a rate far faster than "bounded" steps within etch pits. The difference in step motion for "bounded" and "unbounded" steps is attributed to the fact that "unbounded" steps do not require a double-kink nucleation step in order to retreat, where as "bounded" steps do require double-kink nucleation in order to retreat.

Below the still figures is a movie version of the barite dissolution sequence.

Figure 1: Image of an early version of the HAFM Figure 2: Barite dissovling at 125 C: