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Member, Materials Science Institute
B.A., Rutgers University, 1978. Ph.D., Cornell University, 1983 (Michel J. Sienko). Postdoctoral: Cornell University, 1983–84 (M. J. Sienko). Honors and Awards: Henry Rutgers Undergraduate Research Scholar, 1977–78; Office of Naval Research Young Investigator Award, 1987–90. At Oregon since 1986.
Research Interests:
Dave Johnson’s research group focuses its efforts on developing kinetically-controlled approaches to the synthesis of new solid-state materials and correlating physical properties with structure and bonding. We have pioneered the use of modulated elemental reactants as a means to control the kinetics of solid-state reactions and understand the structural evolution that occurs at reacting interfaces.
The key feature of modulated elemental reactants is the ability of the researcher to control composition on the Ångstrom-length scale. These reactants are prepared in computer-controlled ultrahigh vacuum deposition chambers, which allows the composition, the elemental layer sequence, and the total film thickness to be easily varied. If the initial layer thicknesses are above a critical thickness, interfacial nucleation is observed. If the layer thicknesses in the modulated reactant are below a critical value, initial interdiffusion of the superlattice reactant results in an amorphous reaction intermediate, thus avoiding stable binary compounds as reaction intermediates. Nucleation is the rate-limiting step, which can be controlled using the overall composition and “seeding”. This approach permits us to prepare new binary and ternary compounds that are only kinetically stable with respect to disproportionation into more stable binary compounds.
By preparing more complicated elementally-modulated reactants, we can prepare crystalline superlattices consisting of intergrowths of two compounds. The diffraction patterns of these superlattices are striking, with as many as 130 (00l) diffraction lines. This synthesis approach yields unit cell control over the thickness of the layers in the resulting superlattice unit cell. This new synthesis approach has resulted in a new “thin film metallurgy” in which heterostructures and superlattices are prepared with a high degree of coherency, orientation and alignment between component layers. We anticipate unexpected atomic-bonding, phase transformations, interface-related processes, mechanical and electrical properties that can be systematically examined as a function of superlattice length scales. This synthesis approach permits new compounds to be prepared which are inaccessible via other synthetic approaches.
Our group also routinely characterizes the structure and electrical and magnetic properties of the new compounds we prepare. The correlation of structural information with physical properties provides important insight for applications as diverse as new magnetic materials with designed hysteresis loops; new themoelectrics with designed nanostructure; and graded materials for joining dissimilar materials. We are also exploring adhesion and hardness of coatings; strength and fracture mode in metal matrix composites; and performance enhancements found in nanocrystalline materials. There are unlimited systems to investigate. We have several new projects, including: preparing complex oxides using a variety of deposition approaches; preparing interwoven dichalcogenides designed to be correlated electron systems; synthesizing kinetically-stable new thermoelectrics; and understanding and controlling interfacial phase formation of silicides and germanides of interest to the semiconductor industry. The nature of this research encourages professional development and fosters technical and problem-solving skills. By combining these skills with internships in academia, industry, and opportunities abroad, my students excel in their careers!
Research in the Johnson Lab is Supported by: The National Science Foundation, The Office of Naval Research, and the National Renewable Energy Laboratory.
Selected Publications:
109. J M. Jensen, A. B. Oelkers, R. Toivola, David C. Johnson, J.W. Elam and S. M. George, "X-ray Reflectivity Characterization of ZnO/Al2203 Multilayers prepared by Atomic Layer Deposition" Chemistry of Materials, 14 (2002) 2276-2282.
110. Polly A. Berseth, Thomas A. Hughes, Robert Schneidmiller, Arwyn Smalley and David C. Johnson, "Low Temperature Synthesis Using Modulated Elemental Reactants: A New Metastable Ternary Compound NixMoSe2" Solid State Science 4 (2002) 717-722.
111. Joshua R. Williams, Mark Johnson and David C. Johnson, 'Suppression of Binary Nucleation in Amorphous La-Fe-Sb Mixtures" Journal of the American Chemical Society. 123(12) (2003) 3589-3592.
112. Joshua R. Williams, Mark Johnson and David C. Johnson, "Synthesis of Crystalline Superlattices Using the Modulated Elemental Reactant Method" Journal of the American Chemical Society, 12(34) (2003) 10335-10341.
113. Jacob M. Jensen, Sochetra Ly, Xavier Kyablue, and David C. Johnson, "Selective Preparation of Nickel Silicides and Germanides Using Multilayer Reactants," Mat. Res. Soc. Symp. Proc. 2002, 755 (Solid State Chemisry of Inorganic Materials IV), 393-397.
114. Jacob M. Jensen, Sochetra Ly, Xavier Kyablue and David C. Johnson, "Length scale dependent variation of the first nucleated phase in nickel-silicon multilayers", Journal of Applied Physics, 94(2), (2003) 1252-1257.
115. Fred. R. Harris, Stacey Standridge, Carolyn Feik and David C. Johnson, "Design and Synthesis of [(Bi2Te3)x(TiTe2)y] Superlattices", Angewandte Chemie, International Edition 42(43), (2003) 5296-5299.
116. Jacob M. Jensen, Sochetra Ly and David C. Johnson, "Low Temperature Preparation of High Temperaure Nickel Germanides Using Multilayer Reactants." Chemistry of Materials, 15(22) (2003) 4200-4204.
117. Arwyn L. E. Smalley, Seok Kim and David C. Johnson, "Effects of Composition and Annealing on the Electrical Properties of CoSb3" Chemistry of Materials, 15(20) (2003) 3847-3851.
118. Arwyn L. E. Smalley, Michael L. Jespersen, David C. Johnson, "The Synthesis and Structural Evolution of RuSb3, a New Metastable Skutterudite Compound" Inorganic Chemistry, 43(8) (2004) 2486-2490.
To Contact Dr. Johnson:
Phone: 541-346-4612
davej@uoregon.edu
WEBMASTER
lynde@uoregon.edu
