Research Theme: Applications and Fundamentals of Diamondoids
Initially discovered in petroleum, diamondoids are cage-like organic molecules whose structure can be superimposed upon bulk diamond. These diamond-crystal cages are fused together and terminated by hydrogen. The smallest diamonoid is adamantane, consisting of a single diamond cage; tetramantane, a higher diamondoid, is constructed by four cages. By modifying these molecules with synthetic techniques, they can be selectively functionalized on surfaces. The electronic, optical, mechanical and thermal properties of these diamondoid surfaces may exhibit properties of both single-crystal diamond as well as nanomaterials, with applications as high-efficiency field emitters in molecular electronics, seed crystals for diamond growth, or as robust mechanical coatings.
In collaboration with Z.X. Shen's group at Stanford, we have observed monochromatic electron photoemission from large-area self-assembled monolayers of functionalized tetramantane-6-thiol. The photoelectron spectra of the diamondoid monolayers exhibited a peak at the low–kinetic energy threshold; up to 68% of all emitted electrons were emitted within this single energy peak. The intensity of the emission peak is indicative of diamondoids being negative electron affinity materials. With an energy distribution width of less than 0.5 electron volts, this source of monochromatic electrons may find application in technologies such as electron microscopy, electron beam lithography, and field-emission flat-panel displays.
(A) Photoelectron spectra of [121]tetramantane-6-thiol SAMs grown on Ag substrates, collected with 55-eV photon energy. The strong peak at 1-eV kinetic energy contains 68% of the total photoelectrons. The dotted line is a 50-times enlargement of valence band features. The inset shows the same spectra in a double logarithm plot. (B) Photoelectron spectrum collected on [121]tetramantane-6-thiol SAM covered by C60 sublimed in situ. The strong electron-emission peak disappears after C60 coverage. (C) Photoelectron spectrum collected on an annealed [121]tetramantane-6-thiol SAM.
Related Publications
Origin of the Monochromatic Photoemission Peak in Diamondoid
Monolayers.
William A. Clay, Zhi Liu, Wanli Yang, Jason D. Fabbri, Jeremy E. Dahl, Robert M. K. Carlson, Yun
Sun, Piero A. Pianetta, Nicholas Melosh, and Zhi-Xun Shen. Nano Letters. 9(1), 57 (2009)
Diamondoids as low-K dielectric materials.
W. A.
Clay, T. Sasagawa, M. Kelly, J. E. Dahl, R. M. K. Carlson, N. Melosh, and Z.-X. Shen. Applied Physics Letters.
93, 172901 (2008)
Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol
Monolayers on Gold.
Trevor M. Willey, Jason D. Fabbri, Jonathan R. I. Lee, Peter R. Schreiner, Andrey A. Fokin,
Boryslav A. Tkachenko, Nataliya A. Fokina, Jeremy E. P. Dahl, Robert M. K. Carlson, Andrew L. Vance, Wanli Yang, Louis J.
Terminello, Tony van Buuren, and Nicholas A. Melosh. Journal of the American Chemical Society. 130(32),
10536 (2008)
Suspension of nanoparticles in SU-8: Processing and
characterization of nanocomposite polymers.
H.C. Chiamori, J.W. Brown, E.V. Adhiprakasha, E.T. Hantsoo, J.B.
Straalsund, N.A. Melosh and B.L. Pruitt. Microelectronics Journal. 39(2), 228 (2008)
Monochromatic Electron Photoemission from Diamondoid
Monolayers
W. L. Yang, J. D. Fabbri, T. M. Willey, J. R. I. Lee, J. E. Dahl, R. M. K. Carlson, P. R. Schreiner, A. A.
Fokin, B. A. Tkachenko, N. A. Fokina, W. Meevasana, N. Mannella, K. Tanaka, X. J. Zhou, T. van Buuren, M. A. Kelly, Z.
Hussain, N. A. Melosh, and Z.-X. Shen. Science. 316, 1460 (2007)
Isolation and
Structure of Higher Diamondoids, Nanometer-Sized Diamond Molecules.
J. E. Dahl, S. G. Liu and R. M. K. Carlson. Science 299, 96 (2003).