Observation of the transition from tunneling to hopping carrier transport through single oligothiophene molecules

MRS Proceedings ◽

10.1557/proc-1091-aa05-75 ◽

2008 ◽

Vol 1091 ◽

Author(s):

Ryo Yamada ◽

Hiroaki Kumazawa ◽

Shoji Tanaka ◽

Hirokazu Tada

Keyword(s):

Linear Dependence ◽

Transport Mechanism ◽

Carrier Transport ◽

Electrical Conductance ◽

Break Junction ◽

Carrier Transport Mechanism ◽

Molecular Length

AbstractElectrical conductance of single oligothiophene molecules with a length in the range from 2 to 9 nm was measured as a function of molecular length by a break junction method. The resistance of oligothiophenes increased exponentially from 5-mer to 14-mer while that of molecules longer than 17-mer showed linear dependence on their length. These results indicated that the carrier transport mechanism changed from tunneling to hopping around 14-mer of which the length is approximately 6 nm.

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MECHANISM OF ELECTRICAL CONDUCTION THROUGH SINGLE OLIGOTHIOPHENE MOLECULES

Functional Materials Letters ◽

10.1142/s1793604710001470 ◽

2010 ◽

Vol 03 (04) ◽

pp. 245-248 ◽

Cited By ~ 2

Author(s):

SEE KEI LEE ◽

RYO YAMADA ◽

HIROKAZU TADA ◽

SHOJI TANAKA

Keyword(s):

Charge Transport ◽

Scanning Tunneling Microscope ◽

Transport Mechanism ◽

Electrical Conductance ◽

Scanning Tunneling ◽

Break Junction ◽

Charge Transport Mechanism ◽

Transport Mechanisms ◽

Thermally Activated ◽

Molecular Length

The temperature dependence of electrical conductance of oligothiophene molecules with the length of 2.2 nm (5-mer), 5.6 nm (14-mer) and 6.7 nm (17-mer) was measured by break junction method with a scanning tunneling microscope to clarify the charge transport mechanisms. The conductance of 17-mer molecule increased exponentially with temperature whereas the conductance of 5-mer and 14-mer molecules did not change. These results indicate that the dominant charge transport mechanism changed from tunneling to thermally activated hopping at molecular length around 6.7 nm (17-mer).

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Electrical Conductance of Single Oligothiophene Molecular Wires: Temperature Effect

MRS Proceedings ◽

10.1557/opl.2011.12 ◽

2011 ◽

Vol 1286 ◽

Author(s):

See Kei Lee ◽

Ryo Yamada ◽

Shoji Tanaka ◽

Hirokazu Tada

Keyword(s):

Transport Mechanism ◽

Carrier Transport ◽

Electrical Conductance ◽

Molecular Wires ◽

Scanning Tunneling ◽

Molecular Junction ◽

Break Junction ◽

Charge Carrier Transport ◽

Tunneling Microscopy ◽

Hopping Transport

ABSTRACTWe investigated temperature dependence of the electrical conductance of single oligothiophene molecular wires with the length of 2.2 nm (5-mer), 5.6 nm (14-mer) and 6.7 nm (17-mer) by using the scanning tunneling microscopy break junction method. Results show that the dominant charge carrier transport for 5-mer molecule is tunneling while for 17-mer molecule is hopping. The carrier transport mechanism of 14-mer are tunneling transport (T ≤ 350 K) and hopping transport (T > 350 K) indicating that hopping and tunnelling transport are competitive process in the molecular junction.

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