SFG on functional organic interfaces

COLL 454

Hongke Ye, Hongke.Ye@jhu.edu1, Jia Huang, jhuang40@jhu.edu2, Jung-Rae Park, migoogpark@gmail.com1, Howard E. Katz, hekatz@jhu.edu3, and David H. Gracias, dgracias@jhu.edu4. (1) Department of Chemical and Biomolecular Engineering, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, (2) Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, (3) Departments of Materials Science and Engineering and Chemistry, Johns Hopkins University, 103 Maryland Hall, 3400 N. Charles Street, Baltimore, MD 21218, (4) Department of Chemical and Biomolecular Engineering and Department of Chemistry, Johns Hopkins University, 3400 N Charles Street, 125 Maryland Hall, Baltimore, MD 21218
It is very difficult to probe buried interfaces; non-linear optical spectroscopy overcomes this challenge due to symmetry considerations. Simultaneous electrical measurements and sum frequency generation (SFG) vibrational spectra were obtained on three organic field effect transistors (OFETs) fabricated with the semiconductors; 5, 5'-bis(4-hexylphenyl)-2,2'-bithiophene (6pttp6), 1,1'-bis(4-hexylphenyl)-2,2'-bithiophene (2pttp2) and pentacene. In-situ measurements during gating of the OFETs show strong correlations between vibrational spectra and electronic properties. One correlation involved the dependence of the structural changes in the molecular end chains and the dependence of saturation source-drain current on gate voltage ; the correlation was observed only at negative gate voltages (when carrier injection was possible) and the correlation was more pronounced for 6pttp6 (with the longer end chains) as compared to 2pttp2. A second correlation between the dependence of SF non-resonant background and electronic mobility on gate voltage was observed for all three OFETs at both positive and negative gate voltages.
 

Processes at Functional Plasmonic and Electronic Interfaces
2:00 PM-5:35 PM, Wednesday, August 22, 2007 BCEC -- 153A, Oral

Division of Colloid & Surface Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007