Pd versus Au as evaporated metal contacts to molecules

Applied Physics Letters

Volumn 86, Issue 4, 2005, Pages

  Haick, Hossam ^a   Ghabboun, Jamal ^a   Cahen, David ^a  

^a WEIZMANN INSTITUTE OF SCIENCE   (Israel)

Author keywords

[No Author keywords available]

Indexed keywords

CRYSTAL ORIENTATION; CURRENT VOLTAGE CHARACTERISTICS; ELECTROSTATICS; EVAPORATION; GOLD; MONOLAYERS; PALLADIUM;

BARRIER HEIGHTS; CONTACT POTENTIAL DIFFERENCE (CPD); ELECTRON BEAM EVAPORATION; FUNCTIONAL GROUPS;

MATERIALS SCIENCE;

EID: 13644276624     PISSN: 00036951     EISSN: None     Source Type: Journal    
DOI: 10.1063/1.1854742     Document Type: Article

References (22)

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5. R. M. Metzger, T. Xu, and I. R. Peterson, J. Phys. Chem. B 105, 7280 (2001); H. H. Haick, M. Ambrico, J. Ghabboun, T. Ligonzo, and D. Cahen, Phys. Chem. Chem. Phys. 6, 4538 (2004); H. Haick, M. Ambrico, T. Ligonzo, and D. Cahen, Adv. Mater. 16, 2145 (2004).
6. R. M. Metzger, T. Xu, and I. R. Peterson, J. Phys. Chem. B 105, 7280 (2001); H. H. Haick, M. Ambrico, J. Ghabboun, T. Ligonzo, and D. Cahen, Phys. Chem. Chem. Phys. 6, 4538 (2004); H. Haick, M. Ambrico, T. Ligonzo, and D. Cahen, Adv. Mater. 16, 2145 (2004).
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8. The dipole layer effect operates at both forward and reverse bias, as explained in Ref. 3 (cf. Fig. 1 in that reference).
9. The differences in shapes of the ln(I)-V curves between the Pd and Au junctions [Figs. 1(a) and 1(b)] as well as the higher series resistance with Au, than with Pd, can be ascribed to the differences in metal film growth as described in the text These lead to effective contact areas that, although still larger than the geometrical ones, are smaller with Au than with Pd, as well as to different densities of interface states [cf. D. R. Heslinga, H. H. Weitering, D. P. van der Werf, T. M. Klapwijk, and T. Hibma, Phys. Rev. Lett. 64, 1589 (1990); E. Yablonovitch, T. Sands, D. M. Hwang, I. Schnitzer, T. J. Gmitter, S. K. Shastry, D. S. Hill, and J. C. C. Fan, Appl. Phys. Lett. 59, 3159 (1991)]. This interpretation is supported by low frequency capacitance-voltage (C-V) measurements (unpublished).
10. The differences in shapes of the ln(I)-V curves between the Pd and Au junctions [Figs. 1(a) and 1(b)] as well as the higher series resistance with Au, than with Pd, can be ascribed to the differences in metal film growth as described in the text These lead to effective contact areas that, although still larger than the geometrical ones, are smaller with Au than with Pd, as well as to different densities of interface states [cf. D. R. Heslinga, H. H. Weitering, D. P. van der Werf, T. M. Klapwijk, and T. Hibma, Phys. Rev. Lett. 64, 1589 (1990); E. Yablonovitch, T. Sands, D. M. Hwang, I. Schnitzer, T. J. Gmitter, S. K. Shastry, D. S. Hill, and J. C. C. Fan, Appl. Phys. Lett. 59, 3159 (1991)]. This interpretation is supported by low frequency capacitance-voltage (C-V) measurements (unpublished).
11. 3(+2.7 D). All values (in parentheses) are in Debye units, for the free molecules.
12. The difference in BHs of the bare Pd/GaAs and Au/GaAs junctions can be ascribed to different pinning defects at their interfaces [cf. T. Drummond, Phys. Rev. B 59, 8182 (1999)] and/or hydrogenation effects [cf. H. Y. Nie and Y. Nannichi, Jpn. J. Appl. Phys., Part 1 30, 906 (1991); ibid. 32, L890 (1993)].
13. The difference in BHs of the bare Pd/GaAs and Au/GaAs junctions can be ascribed to different pinning defects at their interfaces [cf. T. Drummond, Phys. Rev. B 59, 8182 (1999)] and/or hydrogenation effects [cf. H. Y. Nie and Y. Nannichi, Jpn. J. Appl. Phys., Part 1 30, 906 (1991); ibid. 32, L890 (1993)].
14. The difference in BHs of the bare Pd/GaAs and Au/GaAs junctions can be ascribed to different pinning defects at their interfaces [cf. T. Drummond, Phys. Rev. B 59, 8182 (1999)] and/or hydrogenation effects [cf. H. Y. Nie and Y. Nannichi, Jpn. J. Appl. Phys., Part 1 30, 906 (1991); ibid. 32, L890 (1993)].
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18. J. L. Freeouf, T. N. Jackson, S. E. Laux, and J. M. Woodall, J. Vac. Sci. Technol. 21, 570 (1982).
19. L trend for junctions with LOFO-made contacts and with ICICE-made Pd ones.
20. The systematic effect of the molecules shown in Fig. 1, supported by TOF SIMS and XPS experiments, imply the absence of significant chemical interactions between the functional groups used here and the evaporated metals, even though different functional groups may lead to (minor) differences in the growth mode of the metal, on top of the dC-X films, as was shown recently for mono- and di-thiol conjugated molecules [cf. B. de Boer, M. M. Frank, Y. J. Chabal, W. Jiang, E. Garfunkel, and Z. Bao, Langmuir 20, 1539 (2004)].
21. L trends as did adsorption of only dC-X molecules.
22. L trends as did adsorption of only dC-X molecules.