Ph.D. Stanford, 1985
The research in my group is concerned with the properties of novel solid materials, especially thin film superconducting and magnetic materials. A particular focus is on thermodynamic properties of thin films and (most recently) nanoscale biological systems; we have taken advantage of Si micromachining technology to develop a micro/nano-calorimeter (patent pending) capable of measuring sub-microgram quantities of material at temperatures from 1K to at least 250C. We are also involved with the materials science of the effects of vapor-deposition growth on the structure of thin film amorphous and crystalline materials; in the growth temperature regime where atomic mobility is large at the surface, but bulk mobility is negligible, we have shown that surface equilibrium states dominate the properties of the film, producing for example uniaxial anisotropy in cubic and amorphous materials. Current projects include studies of perpendicular anisotropy and magnetoresistance in amorphous magnetic materials, perpendicular anisotropy and surface-induced clustering in chemically-disordered epitaxial thin films such as CoPt3, the superconducting, magnetic, and normal state properties of doped C60 and related fullerene alloys and compounds, and development of instrumentation for nano-calorimetry. We interact strongly with other members of the condensed matter group, particularly in the areas of magnetic, superconducting, and other highly correlated electron materials.
Selected Publications:
Surface-to-Surface Segregation During Growth of Polycrystalline Thin Films. Hellman, Appl. Phys. Lett. 51 , 948 (1987).
Surface-induced Ordering: A Model for Vapor-deposition Growth of Amorphous Materials. Hellman, Appl. Phys. Lett. 64 , 1947 (1994).
Thin Film Microcalorimeter for Heat Capacity Measurements from 1.5 to 800 K. D. W. Denlinger, E. N. Abarra, Kimberly Allen, P. W. Rooney, S. K. Watson, and F.Hellman , Rev. Sci. Instrum., 65 , 946 (1994).
Evidence of a Surface-Mediated Magnetically-Induced Miscibility Gap in Vapor-Deposited CoPt3. P.W. Rooney, A. L. Shapiro, M. Q. Tran, and F. Hellman, Phys. Rev. Lett. 75, 1843 (1995). 75 , 1843 (1995).
Heat Capacity Measurements of Anti-Ferromagnetic Superlattices. E. N. Abarra, K. Takano, A. E. Berkowitz, and F. Hellman, Submitted to Phys. Rev. Lett.
Destruction of Superconductivity in a Narrow-band Metal, K3C60. Susan Watson, Kimberly Allen, D. W. Denlinger, and F. Hellman Submitted to Phys. Rev. Lett.