Crossref journal-article
Wiley
Advanced Materials (311)
Abstract

AbstractWe compile, compare, and discuss experimental results on low‐bias, room‐temperature currents through organic molecules obtained in different electrode–molecule–electrode test‐beds. Currents are normalized to single‐molecule values for comparison and are quoted at 0.2 and 0.5 V junction bias. Emphasis is on currents through saturated alkane chains where many comparable measurements have been reported, but comparison to conjugated molecules is also made. We discuss factors that affect the magnitude of the measured current, such as tunneling attenuation factor, molecular energy gap and conformation, molecule/electrode contacts, and electrode material.

Bibliography

Salomon, A., Cahen, D., Lindsay, S., Tomfohr, J., Engelkes, V. B., & Frisbie, C. D. (2003). Comparison of Electronic Transport Measurements on Organic Molecules. Advanced Materials, 15(22), 1881–1890. Portico.

Authors 6
  1. A. Salomon (first)
  2. D. Cahen (additional)
  3. S. Lindsay (additional)
  4. J. Tomfohr (additional)
  5. V.B. Engelkes (additional)
  6. C.D. Frisbie (additional)
References 81 Referenced 788
  1. 10.1126/science.1064354
  2. 10.1063/1.882658
  3. 10.1063/1.473523
  4. 10.1021/ja0268332
  5. 10.1021/ja982157l
  6. 10.1021/ja004055c
  7. 10.1016/S0009-2614(97)00014-6
  8. 10.1103/PhysRevLett.89.086802
  9. 10.1088/2058-7058/13/6/26
  10. 10.1063/1.124354
  11. 10.1103/PhysRevLett.88.176804
  12. 10.1021/jp026324m
  13. 10.1021/ja971921l
  14. 10.1021/ja991613i
  15. 10.1038/35004539
  16. 10.1103/PhysRevB.68.035416
  17. We use current at low bias voltage because the lower the bias the smaller the possibilities for measurement artifacts for extraneous effects on the results (from e.g. series resistance effects) and for resonant tunneling.
  18. We used the number of molecules in the contact area as estimated in the original papers. For alkylthiol chains the footprint is taken as approximately 0.2 nm2.
  19. Y. Selzer M. A. Cabassi D. L. Allara personal communication 2003.
  20. S. Datta Electronic Transport in Mesoscopic Systems Cambridge University Press Cambridge2001.
  21. 10.1016/S0301-0104(02)00372-5
  22. This value was calculated for conjugated molecules. It is likely that for saturated moleculesm* will be closer to 1.
  23. 10.1063/1.1702682
  24. 10.1103/PhysRevLett.89.138301
  25. 10.1126/science.1081572
  26. 10.1021/ja015661q
  27. 10.1103/PhysRevB.65.245105
  28. 10.1021/ja0177511
  29. 10.1002/1439-7641(20020916)3:9<799::AID-CPHC799>3.0.CO;2-V
  30. 10.1021/ja994468h
  31. 10.1126/science.271.5256.1705
  32. 10.1063/1.1702682
  33. 10.1088/0957-4484/13/1/302
  34. 10.1021/jp0206065
  35. C. D. Frisbie unpublished.
  36. 10.1126/science.1087481
  37. 10.1021/ja027090n
  38. 10.1021/ja0101532
  39. A. P. Labonte Ph.D. Thesis Purdue University2002.
  40. 10.1021/jp9838184
  41. Using Equation 4 and assuming an effective mass of 1 we find within this simple model a tunneling barrier of 0.6–2.4 eV for β values of 0.5–1 Å–1.
  42. S. Tsury A. Salomon D. Cahen unpublished.
  43. 10.1021/j100111a006
  44. 10.1021/j100115a023
  45. Hole tunneling through organic molecules is the term commonly used to describe non‐resonant tunneling via the HOMO of the molecule whereas the term electron tunneling is used for tunneling via the LUMO.
  46. If this is correct then the reason that for systems with two chemicontacts to the electrodes β indeed slowly decreases with applied voltage [33 34] would need to be ascribed to a stiffer structure and the recent results of Wang et al. [16] to the presence of a very small number of molecules in a geometrically restricted space.
  47. 10.1021/ja9601191
  48. This finding that β does not appear to depend on the contact metal although the barrier height could be expected to change with contact metal suggests that charge transfer on contact positions the Fermi level approximately in the gap as expected in the absence of strong chemical interactions [27].
  49. Although different tunneling barriers result when Ag or Au contacts are used the measured β values are the same for alkanethiol junctions independent of the type of metal contacts. This occurs presumably because the Fermi level is well within the gap of the insulating molecule. The differences in the barrier height for tunneling are reflected in the contact resistances rather than in the β value.
  50. 10.1021/jp962954a
  51. 10.1021/jp001528t
  52. D. R. Stewart D. A. A. Ohlberg P. A. Beck C. N. Lau R. S. Williams unpublished.
  53. 10.1021/cr9502357
  54. 10.1126/science.1065708
  55. 10.1002/1521-4095(20020605)14:11<789::AID-ADMA789>3.0.CO;2-H
  56. This results in an additional potential drop due to the difference in dielectric constant (actually polarizability) of the molecule and that of vacuum.
  57. n = 1 3 5 7 9.
  58. We note that molecule–electrode interactions at the contact can be significant also in the absence of a formal chemical bond as illustrated in the papers by Vilan et al. [59 60]. There the interaction was ascribed to polarization of the spillover electron density outside the metal electrode (cf. also Ishii et al. [61]).
  59. 10.1021/jp026779b
  60. 10.1002/adfm.200290009
  61. 10.1002/(SICI)1521-4095(199906)11:8<605::AID-ADMA605>3.0.CO;2-Q
  62. E. A. Rhoderick R. H. Williams Metal‐Semiconductor Contacts 2nd ed. Clarendon Oxford1988.
  63. We note that in the junctions used by Selzer et al. there is an additional S–C bond which is not present in Liu's junction. This means we actually compare between Hg–S–(CH2)9CH3|Si and Si–(CH2)9CH3|Hg. Furthermore there will probably be some difference in angles between the molecules and the electrodes.
  64. 10.1126/science.278.5336.252
  65. {'key': 'e_1_2_1_66_2', 'first-page': '2847', 'volume': '109', 'author': 'Tian W.', 'year': '1998', 'journal-title': 'J. Chem. Phys.'} / J. Chem. Phys. by Tian W. (1998)
  66. A. V. Tivanski Y. He H. Liu G. C. Walker D. H. Waldeck unpublished.
  67. 10.1063/1.120195
  68. 10.1021/jp013476t
  69. 10.1063/1.1512815
  70. 9 10‐Bis(20‐para‐mercaptophenyl)ethynyl anthracene.
  71. 10.1103/PhysRevB.56.4722
  72. 10.1021/ja992936h
  73. 10.1063/1.124354
  74. 10.1021/jp0343786
  75. 10.1021/jp9831278
  76. 10.1002/1521-3951(200209)233:1<59::AID-PSSB59>3.0.CO;2-6
  77. Single molecule currents measured by break junction [78] and by CP‐AFM under solvent [69] on the same molecule are between 1.5 and 3 orders of magnitude lower.
  78. 10.1063/1.1289650
  79. 10.1016/S0301-0104(02)00616-X
  80. A surprising result of this study of carotenoids is the close agreement between first‐principles theory and the data. The only input to the theory lay in checking Hartree–Fock calculations to assure that the measured bond alternation was reproduced. This simple approach yields anI–Vcurve quite close to what is measured (cf. Fig. 5a in Ramachandran et al. [74]). When Coulomb blockading is taken into account using parameter values obtained by fitting alkane data for the same gold spheres and using the calculatedI–Vcurve to obtain the needed molecular resistance agreement between theory and experiment is remarkable (cf. Fig. 5b in Ramachandran et al. [74]).
  81. In one direction of the bias.
Dates
Type When
Created 21 years, 9 months ago (Nov. 21, 2003, 5:12 p.m.)
Deposited 1 year, 9 months ago (Nov. 20, 2023, 9:18 p.m.)
Indexed 1 month, 3 weeks ago (June 27, 2025, 10:03 a.m.)
Issued 21 years, 9 months ago (Nov. 17, 2003)
Published 21 years, 9 months ago (Nov. 17, 2003)
Published Online 21 years, 9 months ago (Nov. 20, 2003)
Published Print 21 years, 9 months ago (Nov. 17, 2003)
Funders 0

None

@article{Salomon_2003, title={Comparison of Electronic Transport Measurements on Organic Molecules}, volume={15}, ISSN={1521-4095}, url={http://dx.doi.org/10.1002/adma.200306091}, DOI={10.1002/adma.200306091}, number={22}, journal={Advanced Materials}, publisher={Wiley}, author={Salomon, A. and Cahen, D. and Lindsay, S. and Tomfohr, J. and Engelkes, V.B. and Frisbie, C.D.}, year={2003}, month=nov, pages={1881–1890} }