Presentation on theme: "(Applied Physics Letters, 2004 (in press))"— Presentation transcript:
1(Applied Physics Letters, 2004 (in press)) Temperature Dependent Molecular Conduction measured by the Electrochemical Deposition of Platinum Electrode in Lateral Configuration(Applied Physics Letters, 2004 (in press))B. Kim*, S. J. Ahn*, J. G. Park*, S. H. Lee*, E. E. B. Campbell**, Y. W. Park** School of Physics, Seoul National University, Korea** Department of Experimental Physics, Gothenburg University and Chalmers University of Technology, Sweden
2IntroductionSample preparation(1,4-benzenedimethanethiol (BDMT) )III. Result and discussion: Temperature dependent molecular conduction (27K<T<300K) in lateral configurationIV. Summary
3Polyacetylene single nanofiber(PANF) Poster 24: Bio Kim et al.0.8 micronAFM imageSEM imageSynthetic Metals 119, 53 (2001)
4Scanning tunneling microscope S. Datta, et al., Phys. Rev. Lett. 79, 2530 (1997)M. Dorogi, et al., Phys. Rev. B, 52, 9071 (1995)
5Conducting atomic force microscope X. D. Cui, et al., Science, 294, 571 (2001)D. J. Wold, et al., J. Am. Chem. Soc. 123, 5549 (2001)
6Mechanically controlled break junction J. Reichert, et al., Phys. Rev. Lett. 88, (2002)M. A. Reed, et al., Science, 278, 252 (1997)
7Electromigration break junction J. Park, et al., Nature 417, 722 (2002)H. Park, et al., Appl. Phys. Lett. 75, 301 (1999)
8Angle evaporationN. B. Zhitenev, et al., Phys. Rev. Lett. 88, (2002)J. O. Lee, et al., Nano Lett. 3, 113 (2003)
9Others J. G. Kushmerick, et al., Nano Lett. 3, 897 (2003) J. K. N. Mbindyo, et al., J. Am. Chem. Soc. 124, 4020 (2002)
10Molecular conduction measured by the electromigration technique 2. Electrode design1. Electromigration200 nm2 ㎛20 nm height of Au electrode without adhesion layerH. Park, et al., Nature 407, 57 (2000)
113. Breaking of Au line4. AFM and SEM image of nano gap
12Molecular conduction measured by the electrochemical deposition Our method:Molecular conduction measured by the electrochemical deposition(1) SAM on top of Auelectrode/nanoparticlesDavid L. Klein et al., APL 68, 2574 (1996)(2) reducing the separation ofelectrodes using electrochemicaldeposition of PtY. V. Kervennic, et al., Appl. Phys. Lett. 80, 321 (2002)
13Our method: (1) + (2)combination of electrochemical deposition and SAMSchematic diagram1. grow self-assembled monolayers (SAMs)SAMspin hole2. compose circuit and drop solutionAaqueous solution of 0.1 M of K2PtCl4 and 0.5 M of H2SO4A3. deposit Pt electrochemicallyPt4. measure IV characteristicsAthis
14Electrochemical deposition process of Pt In the electrolyteIn situIn the electrolyteIn the electrolytetimeR > 10 GOptical microscope image confirms the deposition of Pt on one side.After drying electrolyte
15AFM & FESEM image before deposition after deposition height ~ 700 nm PtPt100 nmheight ~ 700 nmPtSiO2side view (conjecture)
17Temperature dependent I-V characteristics (160K<T<300K) sample 1Temperature dependent I-V characteristics (160K<T<300K)The I-V characteristics are non-Ohmic and asymmetric in all temperature range, and current decreases upon cooling (semiconductor- like temperature dependence) .The asymmetriccharacteristics are originated by the difference of the two contacts: one Pt electrode is chemisorbed and the other Pt electrode is physisorbed.to the molecule.
18Temperature dependent I-V characteristics (29K<T<120K) sample 1Temperature dependent I-V characteristics (29K<T<120K)There is no significant temperature dependence in the I- V characteristics below 40 K. This means that the tunneling conduction is dominant at T< 40K.
19Tunneling at low temperature (T<40K) sample 1Tunneling at low temperature (T<40K)Fowler-Nordheim tunneling:log(I /V2) ∝ -1/V
21Temperature dependent I-V characteristics (27K<T<100K) sample 2Temperature dependent I-V characteristics (27K<T<100K)I-V curves show very stable behavior below 0.85 V, but the current fluctuates for V> 0.85 V at 50 K < T < 60 K.
22I-V characteristics – sample 2 No switching or NDR effect upon voltage sweep at T=27KAt T=27KAt T=27KAfter sweeping the voltage,the current is increased ~5 times
23I-V characteristics (30K<T<100K) sample 2I-V characteristics (30K<T<100K)And the RTS-like fluctuation at50 K < T < 60 Kis disappeared
24Tunneling at low temperature (T<40K) sample 2Tunneling at low temperature (T<40K)Fowler-Nordheim Tunneling:log(I /V2) ∝ -1/V
25Model for the asymmetric I-V characteristics positive bias to ‘physisorbed Pt’LUMOeVChemisorbedPtPhysisorbedPtnegative bias to ‘physisorbed Pt’HOMOeVContact between base Pt and SAM is much better (chemisorbed) than contact between electrochemically grown Pt and SAM (physisorbed).
26Summary · Temperature dependent molecular conduction was measured by the electrochemical deposition of platinumelectrode to the self-assembled monolayer of1,4-benzenedimethanethiol (BDMT) in lateral configuration.· I-V characteristics are non-Ohmic and asymmetric in allmeasured temperature range. (27 K < T < 300 K)· For T>40K, the I-V characteristics are semiconductor-like.· For T40K, the I-V characteristics are temperatureindependent following the Fowler-Nordheim typeTunneling conduction. ( log (I /V2) ∝ -1/V )
27Acknowledgement:This work was supported by the National Research Laboratory (NRL) program of the Ministry of Science and Technology (MOST), Korea.Work done in Sweden was supported by the Sweden Strategic Research Fund (CARAMEL consortium) and STINT.Partial support for Yung Woo Park was provided by the Royal Swedish Academy of Science.