AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP6
Theoretical and Experimental Comparison Studies of the Electronic Structure of Molecular Carborane Films

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: S. Balaz, University of Nebraska-Lincoln
Authors: S. Balaz, University of Nebraska-Lincoln
L.G. Rosa, University of Nebraska-Lincoln
A.N. Caruso, University of Nebraska-Lincoln
J.I. Brand, University of Nebraska-Lincoln
Y.B. Losovyj, Louisiana State University
P.A. Dowben, University of Nebraska-Lincoln
Correspondent: Click to Email
Semiconducting boron carbide represents a new class of semiconductoing materials with applications in neutron detection and radioactive decay calorimetry [1,2]. The key to making a good boron carbide semiconductor requires materials fabrication by chemical vapor deposition (usually with plasma, electron beam, or synchrotron radiation assisted decomposition of the molecular precursor). The properties of the semiconducting boron carbide appear to be intimately connected to the source compound used. There is no obvious reason why different isomers of the closo-carborane, dicarbadodecaborane C@sub 2@ B@sub 10@H@sub 12@, should result in such different semiconducting properties [2,3]. Utilizing the synchrotron photoemission, and exploiting photovoltaic charging as a test of the n-type and p-type semiconductor behavior [4], during the deposition process, is key to developing the necessary understanding. Theory suggests little difference in electronic structure but profound differences are observed in experiment. Theoretical calculations from semiempirical calculations of the isolated 1,2 closo-carborane (orthocarborane) and 1,7 closo-carborane (metacarborane) molecules indicate that these isoelectronic carboranes should be very similar in HOMO-LUMO gap (highest occupied - lowest unoccupied molecular orbital). These calculations predicted 10.97 eV for the orthocarborane and 10.87 eV for the metacarborane. Since the two carboranes differ only in the positions of the two included carbon atoms and theory predicted the electronic states to be so close, great similarity in chemical and physical behavior would be expected, but is not observed. @FootnoteText@ [1]Robertson et al.,JP APL 80(19): 3644-3646 (2002) [2]A. N. Caruso et al., Journal of Physics Condensed Matter 16, L139 (2004) [3]A. N. Caruso et al., APL 84, 1302 (2004) [4]J.E. Demuth et al., Phys. Rev. Lett. 56, 1408-1411 (1986)[5]A.P. Hitchcock et al. J. Phys. Chem. B 101, 3483 (1997) .