Prof. Christopher "Kit" Umbach

Undergraduate Lecturer/Program Coordinator, Dept. of Materials Science & Engineering

Facility Management, Cornell Center of Materials Research







Bio

I joined the MS&E faculty and CCMR staff in 2002. Previously (1995-2002) I had been active as a Research Associate in the MS&E department investigating glass and semiconducting surfaces with primary support from the Cornell Center for Materials Research. I was also a Lecturer in MS&E (1992-1994) and conducted my post-doctoral research at Cornell (1991-1995). My Ph.D. in Applied and Engineering Physics (Cornell 1991) addressed the atomic structure of microfabricated Si surfaces using the first scanning tunneling microscope built at Cornell. My B.A. was in physics and philosophy (Yale, 1981, summa cum laude); subsequently I spent a year on a DAAD fellowship at the Max Planck Institute in Stuttgart, Germany. I am a member of the Materials Research Society. 

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Teaching

Courses Spring 2012: none

Courses Summer 2012: Materials Chemistry (MS&E 3010)

Courses Fall 2012:  Introduction to Nanotechnology (ENGRI 1110)

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Facility Management

CCMR Bard Materials Facility

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Research

Nanoporous metals: thin-films and membranes In an industry-university collaboration, I and my students are studying nanoporous gold (NPG), which is made by dealloying a 30% Au/70% Ag alloy in acid, producing a tortuous porous network with an initial pore size of ~30 nm. We have produced NPG both from films ~500 nm thick deposited via sputtering an alloy target and from 200 micron thick rolled-sheet membranes. Controlling the pore size is important for practical applications: annealing at moderate temperatures increases the pore size to several microns in a few hours. We have focused on understanding the mechanisms that drive this increase in pore size. We have also been investigating electromagnetic enhancement effects associated with the nanoroughness of NPG and have observed surface-enhanced Raman scattering (SERS) from thin-film NPG adsorbed with dodecanethiol molecules. I am interested in developing NPM for energy and sensing applications. Catalysts can be plated onto NPG and remain catalytically active; hence thin-film NPM is promising for electrodes in microfabricated fuel cells. NPM also has potential as the electrode in photoelectrochemical devices where charge transfer to conductors must take place over nanoscale dimensions. Its demonstrated optical enhancement makes NPG suitable for biosensors based on fluorescence and Raman scattering. I am particularly interested in combining the filtration properties of NPG with SERS to develop a sensor for rapid detection of bacteria such as E. coli.

Glass surfaces: Many of the properties of glasses are determined by the heterogeneity at the nanoscale of composition and structure. Investigating heterogeneities in composition and structure at surfaces allows the application of powerful surface-sensitive imaging and spectroscopy techniques, which, when combined with surface modification, have enormous potential for developing new functionality in glass. We have applied ultra-high vacuum (UHV) non-contact atomic force microscopy (NC-AFM) to glasses fractured in-situ, ion sputtered ex-situ, and electron beam irradiated in-situ. The fracture surfaces of silica, calcium aluminosilicates, and a commercial boroaluminosilicate display glass all exhibit globular features 5 to 10 nm in width and <1 nm in height. When ion sputtered or electron beam irradiated, the display glass exhibits similar globular features. We have also developed a method to image some of these glass surfaces using scanning tunneling microscopy (STM). After either electron bombardment or laser irradiation at elevated temperature, the fracture surfaces of the display glass are sufficiently conductive to allow imaging and spectroscopy at moderate tunneling currents (picoamperes). The topographic images acquired with NC-AFM and STM are identical, implying that the induced conductivity is spatially uniform, opening up the possibility of near-atomic resolution of structural and chemical features of glasses. The directional surface roughness caused by ion-beam sputtering illustrates how nanoscale variations in glass morphology can be exploited. We have used display glass roughened by sputter-erosion to align liquid crystal (LC) molecules. Conventional LC displays use a polymer layer to align the LC’s, but display or sensor structures that use LC’s for guiding light at higher temperatures or for bistable switching of LC orientations may benefit from glass substrates with useful alignment and anchoring properties.

Current Graduate Students:
Totka Ouzounova (Ph.D student)


Patents

"Fabrication of Atomic Step-Free Surfaces" (#5,910,339) with J.M. Blakely, S. Tanaka, R.M. Tromp

Affiliations

Materials Research Society, American Ceramic Society

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Selected Publications (out of more than 30 peer-reviewed or edited)

“Enzyme-catalysed assembly of DNA hydrogel,” S.H. Um, J.B. Lee, N. Park, S.Y. Kwon, C.C. Umbach, D. Luo, Nature Materials 5, p. 797 (2006)


“Radiation-induced surface conductivity in an alkaline-earth boroaluminosilicate glass measured with elevated-temperature scanning probe microscopy,” M.J. Polking and C.C. Umbach, Journal of the American Ceramic Society 88, p. 2442 (2005)


“Nanoscale morphologies resulting from surface treatments of display glass in vacuum,” C. C. Umbach and Jack M. Blakely, Journal of Non-Crystalline Solids 349, p. 267 (2004)


"Nanoscale pattern transfer using sputter-induced corrugations formed at the Si/SiO2 interface," C. G. Allen, M. Daniels, C. C. Umbach, J. M. Blakely in “Nanopatterning--From Ultralarge-Scale Integration to Biotechnology” ed. by L. Merhari et al., MRS Sym. Proc. Ser. 705 p. 119 (2002)


"Spontaneous nanoscale corrugation of ion-eroded SiO2 : the role of ion irradiation-enhanced viscous flow," C. C. Umbach, R. L. Headrick, and K.-C. Chang, Phy. Rev. Lett. 87, p. 246104 (2001)


"A sub-picoampere scanning tunneling microscope for oxide surfaces,” C.C. Umbach and J.M.Blakely, Applied Surface Science 175-176, p. 746 (2001)


“Topography and lattice strain development on patterned Si surfaces”, J.M. Blakely and C.C. Umbach, Micron 30, p. 3, (1999)


"Atomic steps in the decay of 1- and 2-dimensional gratings”, J.M. Blakely, C.C. Umbach, and S. Tanaka, in Dynamics of Crystal Surfaces and Interfaces, ed. by P.M. Duxbury and T.J. Pence (Plenum, New York 1997)


"Specular and diffuse scattering of x-rays from a fusion-drawn glass surface," C.C. Umbach and J.M. Blakely, Nuclear Instruments and Methods in Physics Research 133, p. 50 (1997)


"Chemical treatment of LCD glass substrates," J.G. Couillard, D.G. Ast, C.C. Umbach, J.M. Blakley, C.B. Moore, F.P. Fehlner, Journal of Non-Crystalline Solids 222, p. 429 (1997)


"Step permeability and the relaxation of biperiodic gratings on Si(001)" So Tanaka, N.C. Bartelt, C.C. Umbach, R.M. Tromp and J.M. Blakely, Phys. Rev. Lett. 78, p. 3342 (1997)


"Annealing instabilities in small fabricated structures," S. Tanaka, C.C. Umbach, and J.M. Blakely, Surf. Sci. 372, p. L298-L300 (1997)


"Fabrication of arrays of large step-free regions on Si(001)," S. Tanaka, C.C. Umbach, J.M. Blakely, M. Mankos, and R.M. Tromp, Applied Physics Letters 69 p. 1235 (1996)


"Characterization of large-area arrays of nanoscale Si tips fabricated using thermal oxidation and wet etching of Si pillars," C.C. Umbach, Q. Shen, B. Weselak,J.M. Blakely, J. Vac. Sci. Tech. B 14, (1996)


"Fabrication of bi-periodic sinusoidal structures on Si," S. Tanaka, C.C. Umbach, and J.M. Blakely, Applied Physics Letters 68, p. 1966 (1996)


"Atomic diffusion and strain measurements on Si grating structures by x-ray diffraction," S. Tanaka, C.C. Umbach, Q. Shen, and J.M. Blakely, MRS Symp. Proc. Ser. 380 p. 61 (1995)


"Epitaxy of germanium on Si(001) grating templates,” C.C. Umbach and J.M. Blakely, MRS Sym. Proc. Ser. 317, p. 3 (1993)


"Pairing of curved atomic steps at the extrema of periodic gratings on Si(001)," C.C. Umbach, M.E. Keeffe, and J.M. Blakely, J. Vac. Sci. Tech. A 10, p. 1000 (1993)


"Scanning tunneling microscope studies of one-dimensional periodic corrugated silicon surfaces," C.C. Umbach, M.E. Keeffe, and J.M. Blakely, J. Vac. Sci. Tech. A 9, p. 1014 (1991)


"Scanning tunneling microscope studies of phase separation on Si(001) surfaces with periodic step density," C.C. Umbach, M.E. Keeffe, and J.M. Blakely, J. Vac. Sci. Tech. B 9, p. 721 (1991)


"Surface self-diffusion, capillarity and surface steps," J.M. Blakely and C. Umbach, in Diffusion at Interfaces: Microscopic Concepts, ed. M. Grunze, H.J. Kreuzer, J.J. Weimer (Springer, Berlin 1988)


"Ellipsometric studies of electronic interband transitions in CdxHg1-xTe," L. Vina, C. Umbach, M. Cardona,L. Vodopyanov, Phys. Rev. B, vol. 29, no. 12, p.6752-60 (1984)


"The absorption edge of ultraheavily doped Si," L. Vina, C. Umbach, M. Cardona, A. Compaan, A. Axmann, Solid State Commun., vol. 48, no. 5, p. 457-9 (1983)

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Copyright 2002
Last revised: March 18, 2012 .
ccu1@cornell.edu (Kit Umbach)