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Controlling single-molecule junction conductance by molecular interactions.

Kitaguchi Y, Habuka S, Okuyama H, Hatta S, Aruga T, Frederiksen T, Paulsson M, Ueba H - Sci Rep (2015)

Bottom Line: For the rational design of single-molecular electronic devices, it is essential to understand environmental effects on the electronic properties of a working molecule.The anchoring to the other electrode is kept stable using a chalcogen atom with strong bonding to a Cu(110) substrate.Combined with density functional theory calculations, we clarify the role of the electrostatic field in the environmental effect that influences the molecular level alignment.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.

ABSTRACT
For the rational design of single-molecular electronic devices, it is essential to understand environmental effects on the electronic properties of a working molecule. Here we investigate the impact of molecular interactions on the single-molecule conductance by accurately positioning individual molecules on the electrode. To achieve reproducible and precise conductivity measurements, we utilize relatively weak π-bonding between a phenoxy molecule and a STM-tip to form and cleave one contact to the molecule. The anchoring to the other electrode is kept stable using a chalcogen atom with strong bonding to a Cu(110) substrate. These non-destructive measurements permit us to investigate the variation in single-molecule conductance under different but controlled environmental conditions. Combined with density functional theory calculations, we clarify the role of the electrostatic field in the environmental effect that influences the molecular level alignment.

No MeSH data available.


Related in: MedlinePlus

The effect of intermolecular coupling to the molecular conductance.(a) STM image of a phenoxy dimer arranged along [001] with a separation of two atomic distance (2b0). (b) The left molecule is moved in the [10] direction by one atomic distance (a0 = 2.56 Å). (c) The molecule is further displaced. The molecular configurations are represented by (m,n), indicating the position of neighboring molecule relative to the probed molecule. The image sizes are 28 × 32 Å2. (d) Typical current plateau for the probed molecule in the (2,2), (2,1), and (2,0) configurations, together with that for the isolated monomer. The curves were obtained with the same tip apex. (e) The conductance data for the (2,2), (2,1), (2,0), (−2,−2), (−2,−1), and (−2,0) configurations are shown by circles. The calculated data for the first three are shown by squares. The data are represented by the ratio to that for an isolated molecule, and the error bars are the standard deviation of the collected data for different tips and molecules. The calculated data shown are the average values for h = 13.9 Å and h = 14.4 Å (x = 1.4 Å, Supplementary Fig. 5). (f) The position dependence of the molecular conductance displayed by the color scale. The probed molecule is located at the origin with another (perturbing) molecule located at (mb0,na0). The conductance is reduced for the configurations of (2,0), (2,±1) and (1,±1) within the experimental uncertainty and converges to that of a monomer as the molecule is brought apart.
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f3: The effect of intermolecular coupling to the molecular conductance.(a) STM image of a phenoxy dimer arranged along [001] with a separation of two atomic distance (2b0). (b) The left molecule is moved in the [10] direction by one atomic distance (a0 = 2.56 Å). (c) The molecule is further displaced. The molecular configurations are represented by (m,n), indicating the position of neighboring molecule relative to the probed molecule. The image sizes are 28 × 32 Å2. (d) Typical current plateau for the probed molecule in the (2,2), (2,1), and (2,0) configurations, together with that for the isolated monomer. The curves were obtained with the same tip apex. (e) The conductance data for the (2,2), (2,1), (2,0), (−2,−2), (−2,−1), and (−2,0) configurations are shown by circles. The calculated data for the first three are shown by squares. The data are represented by the ratio to that for an isolated molecule, and the error bars are the standard deviation of the collected data for different tips and molecules. The calculated data shown are the average values for h = 13.9 Å and h = 14.4 Å (x = 1.4 Å, Supplementary Fig. 5). (f) The position dependence of the molecular conductance displayed by the color scale. The probed molecule is located at the origin with another (perturbing) molecule located at (mb0,na0). The conductance is reduced for the configurations of (2,0), (2,±1) and (1,±1) within the experimental uncertainty and converges to that of a monomer as the molecule is brought apart.

Mentions: The height of the plateau during the tip retraction (Fig. 1b) is associated with the conductance through the molecule. The ‘on’ curves are inherently mixing two electron pathways: the electron tunneling through the molecule and the one through the tip-surface gap. While it is not possible to exactly separate them, we assume that the latter is associated with the current in the ‘off’ state. Thus, we define the molecular conductance as the conductance difference between the ‘on’ and ‘off’ states, which is determined from the current change at the junction cleavage in the I-Δz curve (both-ended arrow for the lowest curve in Fig. 1b). The value of the molecular conductance depends on the tip apex, and is distributed at (1.0 ± 0.3) × 10−2 G0 (Supplementary Fig. 2) for an isolated molecule, where G0 = 2e2/h is the quantum of conductance. Because we can repeatedly make and remove the contact to a molecule with the same tip apex, the conductance through a single phenoxy molecule can also be probed as a function of the position of a neighboring phenoxy on the surface as shown in Fig. 3.


Controlling single-molecule junction conductance by molecular interactions.

Kitaguchi Y, Habuka S, Okuyama H, Hatta S, Aruga T, Frederiksen T, Paulsson M, Ueba H - Sci Rep (2015)

The effect of intermolecular coupling to the molecular conductance.(a) STM image of a phenoxy dimer arranged along [001] with a separation of two atomic distance (2b0). (b) The left molecule is moved in the [10] direction by one atomic distance (a0 = 2.56 Å). (c) The molecule is further displaced. The molecular configurations are represented by (m,n), indicating the position of neighboring molecule relative to the probed molecule. The image sizes are 28 × 32 Å2. (d) Typical current plateau for the probed molecule in the (2,2), (2,1), and (2,0) configurations, together with that for the isolated monomer. The curves were obtained with the same tip apex. (e) The conductance data for the (2,2), (2,1), (2,0), (−2,−2), (−2,−1), and (−2,0) configurations are shown by circles. The calculated data for the first three are shown by squares. The data are represented by the ratio to that for an isolated molecule, and the error bars are the standard deviation of the collected data for different tips and molecules. The calculated data shown are the average values for h = 13.9 Å and h = 14.4 Å (x = 1.4 Å, Supplementary Fig. 5). (f) The position dependence of the molecular conductance displayed by the color scale. The probed molecule is located at the origin with another (perturbing) molecule located at (mb0,na0). The conductance is reduced for the configurations of (2,0), (2,±1) and (1,±1) within the experimental uncertainty and converges to that of a monomer as the molecule is brought apart.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488765&req=5

f3: The effect of intermolecular coupling to the molecular conductance.(a) STM image of a phenoxy dimer arranged along [001] with a separation of two atomic distance (2b0). (b) The left molecule is moved in the [10] direction by one atomic distance (a0 = 2.56 Å). (c) The molecule is further displaced. The molecular configurations are represented by (m,n), indicating the position of neighboring molecule relative to the probed molecule. The image sizes are 28 × 32 Å2. (d) Typical current plateau for the probed molecule in the (2,2), (2,1), and (2,0) configurations, together with that for the isolated monomer. The curves were obtained with the same tip apex. (e) The conductance data for the (2,2), (2,1), (2,0), (−2,−2), (−2,−1), and (−2,0) configurations are shown by circles. The calculated data for the first three are shown by squares. The data are represented by the ratio to that for an isolated molecule, and the error bars are the standard deviation of the collected data for different tips and molecules. The calculated data shown are the average values for h = 13.9 Å and h = 14.4 Å (x = 1.4 Å, Supplementary Fig. 5). (f) The position dependence of the molecular conductance displayed by the color scale. The probed molecule is located at the origin with another (perturbing) molecule located at (mb0,na0). The conductance is reduced for the configurations of (2,0), (2,±1) and (1,±1) within the experimental uncertainty and converges to that of a monomer as the molecule is brought apart.
Mentions: The height of the plateau during the tip retraction (Fig. 1b) is associated with the conductance through the molecule. The ‘on’ curves are inherently mixing two electron pathways: the electron tunneling through the molecule and the one through the tip-surface gap. While it is not possible to exactly separate them, we assume that the latter is associated with the current in the ‘off’ state. Thus, we define the molecular conductance as the conductance difference between the ‘on’ and ‘off’ states, which is determined from the current change at the junction cleavage in the I-Δz curve (both-ended arrow for the lowest curve in Fig. 1b). The value of the molecular conductance depends on the tip apex, and is distributed at (1.0 ± 0.3) × 10−2 G0 (Supplementary Fig. 2) for an isolated molecule, where G0 = 2e2/h is the quantum of conductance. Because we can repeatedly make and remove the contact to a molecule with the same tip apex, the conductance through a single phenoxy molecule can also be probed as a function of the position of a neighboring phenoxy on the surface as shown in Fig. 3.

Bottom Line: For the rational design of single-molecular electronic devices, it is essential to understand environmental effects on the electronic properties of a working molecule.The anchoring to the other electrode is kept stable using a chalcogen atom with strong bonding to a Cu(110) substrate.Combined with density functional theory calculations, we clarify the role of the electrostatic field in the environmental effect that influences the molecular level alignment.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.

ABSTRACT
For the rational design of single-molecular electronic devices, it is essential to understand environmental effects on the electronic properties of a working molecule. Here we investigate the impact of molecular interactions on the single-molecule conductance by accurately positioning individual molecules on the electrode. To achieve reproducible and precise conductivity measurements, we utilize relatively weak π-bonding between a phenoxy molecule and a STM-tip to form and cleave one contact to the molecule. The anchoring to the other electrode is kept stable using a chalcogen atom with strong bonding to a Cu(110) substrate. These non-destructive measurements permit us to investigate the variation in single-molecule conductance under different but controlled environmental conditions. Combined with density functional theory calculations, we clarify the role of the electrostatic field in the environmental effect that influences the molecular level alignment.

No MeSH data available.


Related in: MedlinePlus