introduction sample preparation (1,4-benzenedimethanethiol (bdmt) )

NanoTransport Laboratory

Temperature Dependent Molecular Conduction measured by the Electrochemical Deposition of Platinum E

lectrode 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


I. Introduction

II. Sample preparation

(1,4-benzenedimethanethiol (BDMT) )

III. Result and discussion: Temperature dependent molecular conduction (27K<T<300K) in lateral configuration

IV. Summary


Polyacetylene single nanofiber(PANF) Polyacetylene single nanofiber(PANF)

SEM image

Synthetic Metals 119, 53 (2001)

AFM image

0.8 micron

Poster 24: Bio Kim et al.


Scanning tunneling microscope

M. Dorogi, et al., Phys. Rev. B, 52, 9071 (1995)

S. Datta, et al., Phys. Rev. Lett. 79, 2530 (1997)


Conducting atomic force microscope

X. D. Cui, et al., Science, 294, 571 (2001) D. J. Wold, et al., J. Am. Chem. Soc. 123, 5549 (2001)


Mechanically controlled break junction

M. A. Reed, et al., Science, 278, 252 (1997)

J. Reichert, et al., Phys. Rev. Lett. 88, 176804 (2002)


Electromigration break junction

H. Park, et al., Appl. Phys. Lett. 75, 301 (1999)

J. Park, et al., Nature 417, 722 (2002)


Angle evaporation

J. O. Lee, et al., Nano Lett. 3, 113 (2003)

N. B. Zhitenev, et al., Phys. Rev. Lett. 88, 226801 (2002)


Others

J. G. Kushmerick, et al., Nano Lett. 3, 897 (2003)

J. K. N. Mbindyo, et al., J. Am. Chem. Soc. 124, 4020 (2002)


Molecular conduction measured by the electromigration technique

1. Electromigration

H. Park, et al., Nature 407, 57 (2000) 200 nm

2 ㎛

2. Electrode design

20 nm height of Au electrode without adhesion layer


3. Breaking of Au line

4. AFM and SEM image of nano gap

NanoTransport LaboratoryY. V. Kervennic, et al., Appl. Phys. Lett. 80, 321 (2002)

(2) reducing the separation of electrodes using electrochemical deposition of Pt

(1) SAM on top of Au electrode/nanoparticles

Our method: Molecular conduction measured by the electrochemical deposition

David L. Klein et al., APL 68, 2574 (1996)


A

3. deposit Pt electrochemically

Pt

4. measure IV characteristics

A

this

1. grow self-assembled monolayers (SAMs)

SAMs

pin hole

2. compose circuit and drop solution

A

aqueous solution of 0.1 M of K2PtCl4 and 0.5 M of H2SO4

Our method: (1) + (2)

combination of electrochemical deposition and SAMSchematic diagram


Electrochemical deposition process of Pt

R > 10 G

time

Optical microscope image confirms the deposition of Pt on one side.

After drying electrolyte

In situIn the electrolyte In the electrolyte

In the electrolyte


100 nm

Pt

Pt

before depositionafter deposition

AFM & FESEM image

height ~ 700 nm

side view (conjecture)

Pt

SiO2


Measurement results & discussion

openR > 10 G

shortR ~ 5 k

samplenon-Ohmic

At Room Temperature


Temperature 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.

sample 1



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.

sample 1


Tunneling at low temperature (T<40K)

Fowler-Nordheim tunneling: log(I /V2) -1/V∝

sample 1


Temperature dependent I-V characteristics (100K<T<300K)sample 2



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.

sample 2


I-V characteristics – sample 2

No switching or NDR effect upon voltage sweep at T=27K

After sweeping the voltage, the current is increased ~5 times

At T=27K

At T=27K


I-V characteristics (30K<T<100K)

And the RTS-like fluctuation at 50 K < T < 60 K is disappeared

sample 2


Tunneling at low temperature (T<40K)

Fowler-Nordheim Tunneling: log(I /V2) -1/V∝

sample 2


Model for the asymmetric I-V characteristics

HOMO

LUMO

Chemisorbed Pt

Physisorbed Pt

positive bias to ‘physisorbed Pt’

negative bias to ‘physisorbed Pt’

eV

eVContact between base Pt and SAM is much better (chemisorbed) than contact between electrochemically grown Pt and SAM (physisorbed).


Summary

· Temperature dependent molecular conduction was measured by the electrochemical deposition of platinum electrode to the self-assembled monolayer of 1,4-benzenedimethanethiol (BDMT) in lateral configuration.

· I-V characteristics are non-Ohmic and asymmetric in all measured temperature range. (27 K < T < 300 K)

· For T>40K, the I-V characteristics are semiconductor-like.· For T40K, the I-V characteristics are temperature independent following the Fowler-Nordheim type Tunneling conduction. ( log (I /V2) -1/V )∝


Acknowledgement:

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.

introduction sample preparation (1,4-benzenedimethanethiol (bdmt) )

Documents