AVS 51st International Symposium
    Nanometer-scale Science and Technology Thursday Sessions
       Session NS1-ThA

Paper NS1-ThA7
Atomic Level Analysis of Polythiophene by the Scanning Atom Probe

Thursday, November 18, 2004, 4:00 pm, Room 213C

Session: Nanoscale Imaging
Presenter: O. Nishikawa, Kanazawa Institute of Technology, Japan
Authors: O. Nishikawa, Kanazawa Institute of Technology, Japan
M. Taniguchi, Kanazawa Institute of Technology, Japan
M. Ihara, Kanazawa Institute of Technology, Japan
H. Kato, Kanto Gakuin University, Japan
S. Takemura, Kanto Gakuin University, Japan
Correspondent: Click to Email
Thin films of conductive polythiophene grown by the electrochemical process on silicon and ITO substrates are investigated by utilizing unique capability of the scanning atom probe (SAP). The thickness of the films is 10 to 30 μm and the dopant is BF4-. Since the variation of the field emission current I with the applied voltage V to the polythiophene is related with the work function of the specimen surface, the I-V curves, the F-N plot, were obtained. The slope and intercept of the F-N plots (S-I chart) indicates that the work function does not vary with the synthesizing process and the substrate. The comparison of the S-I chart of CNT, W and Si shows that the work function of the polythiophene is close to that of Si. The variation of the S-I chart with temperature also suggests that the polythiophene films are semi-conductive because the emission current varies with temperature as Si. The SAP analysis was conducted by applying voltage pulses or laser pulses. The mass spectra of the detected ions are closely related with the structure of the polythiophene. The Most abundant ions have the masses 80 to 83 which indicates that these ions are SC4Hn, the basic unit of the polythiophene. The ratio of the number of sulphur atoms to that of carbon atoms is 1 to 4 as expected. The detection of various ions such as C+, C2+ and SC3Hn+ suggests that some areas not polymerized and stay in the graphite like state. All sulphur atoms were found as a clustering atom with carbon and hydrogen such as SC4Hn2+ and SC3Hn+. Since the evaporation field of doubly charged ions is usually higher than that of singly charged ions, the detection of doubly charged cluster ions indicates that the SC4Hn2+ clusters are very stable and the atoms forming the clusters are fairly strongly bound. No oxidation of the polythiophene was noticed.