Christopher Bruot | TU Delft (original) (raw)

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Papers by Christopher Bruot

Nature Communications, 2015

Piezoresistivity is a fundamental property of materials that has found many device applications. ... more Piezoresistivity is a fundamental property of materials that has found many device applications. Here we report piezoresistivity in double helical DNA molecules. By studying the dependence of molecular conductance and piezoresistivity of single DNA molecules with different sequences and lengths, and performing molecular orbital calculations, we show that the piezoresistivity of DNA is caused by force-induced changes in the π-π electronic coupling between neighbouring bases, and in the activation energy of hole hopping. We describe the results in terms of thermal activated hopping model together with the ladder-based mechanical model for DNA proposed by de Gennes.

ACS nano, Jan 27, 2015

Studying the structural and charge transport properties in DNA is important for unraveling molecu... more Studying the structural and charge transport properties in DNA is important for unraveling molecular scale processes and developing device applications of DNA molecules. Here we study the effect of mechanical stretching-induced structural changes on charge transport in single DNA molecules. The charge transport follows the hopping mechanism for DNA molecules with lengths varying from 6 to 26 base pairs, but the conductance is highly sensitive to mechanical stretching, showing an abrupt decrease at surprisingly short stretching distances and weak dependence on DNA length. We attribute this force-induced conductance decrease to the breaking of hydrogen bonds in the base pairs at the end of the sequence and describe the data with a mechanical model.

Physical Review B, 2011

Stimulated by recent experiments for diblock molecular junctions, we investigated a possible mech... more Stimulated by recent experiments for diblock molecular junctions, we investigated a possible mechanism to explain the giant diode property by focusing on the electron correlation effect. Based on our observation that the first-principles generalized gradient approximation (GGA) fails to account for the large rectification behavior at high voltage, we have made nonequilibrium many-body calculations using the extended Hubbard model. Theoretical

Nature Nanotechnology, 2011

Research in molecular electronics often involves the demonstration of devices that are analogous ... more Research in molecular electronics often involves the demonstration of devices that are analogous to conventional semiconductor devices, such as transistors and diodes 1 , but it is also possible to perform experiments that have no parallels in conventional electronics. For example, by applying a mechanical force to a molecule bridged between two electrodes, a device known as a molecular junction, it is possible to exploit the interplay between the electrical and mechanical properties of the molecule to control charge transport through the junction 2-8 . 1,4 ′ -Benzenedithiol is the most widely studied molecule in molecular electronics 9-18 , and it was shown recently that the molecular orbitals can be gated by an applied electric field 11 . Here, we report how the electromechanical properties of a 1,4 ′ -benzenedithiol molecular junction change as the junction is stretched and compressed. Counterintuitively, the conductance increases by more than an order of magnitude during stretching, and then decreases again as the junction is compressed. Based on simultaneously recorded current-voltage and conductance-voltage characteristics, and inelastic electron tunnelling spectroscopy, we attribute this finding to a straininduced shift of the highest occupied molecular orbital towards the Fermi level of the electrodes, leading to a resonant enhancement of the conductance. These results, which are in agreement with the predictions of theoretical models , also clarify the origins of the long-standing discrepancy between the calculated and measured conductance values of 1,4 ′ -benzenedithiol, which often differ by orders of magnitude 21 .

ACS Nano, 2010

We study the charge transport properties and electron-phonon interactions in single molecule junc... more We study the charge transport properties and electron-phonon interactions in single molecule junctions, each consisting of an octanedithiol molecule covalently bound to two electrodes. Conductance measurements over a wide temperature range establish tunneling as the dominant charge transport process. Inelastic electron tunneling spectroscopy performed on individual molecular junctions provides a chemical signature of the molecule and allows electron-phonon interaction induced changes in the conductance to be explored. By fitting the conductance changes in the molecular junction using a simple model for inelastic transport, it is possible to estimate the phonon damping rates in the molecule. Finally, changes in the inelastic spectra are examined in relation to conductance switching events in the junction to demonstrate how changes in the configuration of the molecule or contact geometry can affect the conductance of the molecular junction.

Nature Chemistry, 2015

Charge transport in molecular systems, including DNA, is involved in many basic chemical and biol... more Charge transport in molecular systems, including DNA, is involved in many basic chemical and biological processes, and its understanding is critical if they are to be used in electronic devices. This important phenomenon is often described as either coherent tunnelling over a short distance or incoherent hopping over a long distance. Here, we show evidence of an intermediate regime where coherent and incoherent processes coexist in double-stranded DNA. We measure charge transport in single DNA molecules bridged to two electrodes as a function of DNA sequence and length. In general, the resistance of DNA increases linearly with length, as expected for incoherent hopping. However, for DNA sequences with stacked guaninecytosine (GC) base pairs, a periodic oscillation is superimposed on the linear length dependence, indicating partial coherent transport. This result is supported by the finding of strong delocalization of the highest occupied molecular orbitals of GC by theoretical simulation and by modelling based on the Büttiker theory of partial coherent charge transport.

Nature Communications, 2015

Piezoresistivity is a fundamental property of materials that has found many device applications. ... more Piezoresistivity is a fundamental property of materials that has found many device applications. Here we report piezoresistivity in double helical DNA molecules. By studying the dependence of molecular conductance and piezoresistivity of single DNA molecules with different sequences and lengths, and performing molecular orbital calculations, we show that the piezoresistivity of DNA is caused by force-induced changes in the π-π electronic coupling between neighbouring bases, and in the activation energy of hole hopping. We describe the results in terms of thermal activated hopping model together with the ladder-based mechanical model for DNA proposed by de Gennes.

ACS nano, Jan 27, 2015

Studying the structural and charge transport properties in DNA is important for unraveling molecu... more Studying the structural and charge transport properties in DNA is important for unraveling molecular scale processes and developing device applications of DNA molecules. Here we study the effect of mechanical stretching-induced structural changes on charge transport in single DNA molecules. The charge transport follows the hopping mechanism for DNA molecules with lengths varying from 6 to 26 base pairs, but the conductance is highly sensitive to mechanical stretching, showing an abrupt decrease at surprisingly short stretching distances and weak dependence on DNA length. We attribute this force-induced conductance decrease to the breaking of hydrogen bonds in the base pairs at the end of the sequence and describe the data with a mechanical model.

Physical Review B, 2011

Stimulated by recent experiments for diblock molecular junctions, we investigated a possible mech... more Stimulated by recent experiments for diblock molecular junctions, we investigated a possible mechanism to explain the giant diode property by focusing on the electron correlation effect. Based on our observation that the first-principles generalized gradient approximation (GGA) fails to account for the large rectification behavior at high voltage, we have made nonequilibrium many-body calculations using the extended Hubbard model. Theoretical

Nature Nanotechnology, 2011

Research in molecular electronics often involves the demonstration of devices that are analogous ... more Research in molecular electronics often involves the demonstration of devices that are analogous to conventional semiconductor devices, such as transistors and diodes 1 , but it is also possible to perform experiments that have no parallels in conventional electronics. For example, by applying a mechanical force to a molecule bridged between two electrodes, a device known as a molecular junction, it is possible to exploit the interplay between the electrical and mechanical properties of the molecule to control charge transport through the junction 2-8 . 1,4 ′ -Benzenedithiol is the most widely studied molecule in molecular electronics 9-18 , and it was shown recently that the molecular orbitals can be gated by an applied electric field 11 . Here, we report how the electromechanical properties of a 1,4 ′ -benzenedithiol molecular junction change as the junction is stretched and compressed. Counterintuitively, the conductance increases by more than an order of magnitude during stretching, and then decreases again as the junction is compressed. Based on simultaneously recorded current-voltage and conductance-voltage characteristics, and inelastic electron tunnelling spectroscopy, we attribute this finding to a straininduced shift of the highest occupied molecular orbital towards the Fermi level of the electrodes, leading to a resonant enhancement of the conductance. These results, which are in agreement with the predictions of theoretical models , also clarify the origins of the long-standing discrepancy between the calculated and measured conductance values of 1,4 ′ -benzenedithiol, which often differ by orders of magnitude 21 .

ACS Nano, 2010

We study the charge transport properties and electron-phonon interactions in single molecule junc... more We study the charge transport properties and electron-phonon interactions in single molecule junctions, each consisting of an octanedithiol molecule covalently bound to two electrodes. Conductance measurements over a wide temperature range establish tunneling as the dominant charge transport process. Inelastic electron tunneling spectroscopy performed on individual molecular junctions provides a chemical signature of the molecule and allows electron-phonon interaction induced changes in the conductance to be explored. By fitting the conductance changes in the molecular junction using a simple model for inelastic transport, it is possible to estimate the phonon damping rates in the molecule. Finally, changes in the inelastic spectra are examined in relation to conductance switching events in the junction to demonstrate how changes in the configuration of the molecule or contact geometry can affect the conductance of the molecular junction.

Nature Chemistry, 2015

Charge transport in molecular systems, including DNA, is involved in many basic chemical and biol... more Charge transport in molecular systems, including DNA, is involved in many basic chemical and biological processes, and its understanding is critical if they are to be used in electronic devices. This important phenomenon is often described as either coherent tunnelling over a short distance or incoherent hopping over a long distance. Here, we show evidence of an intermediate regime where coherent and incoherent processes coexist in double-stranded DNA. We measure charge transport in single DNA molecules bridged to two electrodes as a function of DNA sequence and length. In general, the resistance of DNA increases linearly with length, as expected for incoherent hopping. However, for DNA sequences with stacked guaninecytosine (GC) base pairs, a periodic oscillation is superimposed on the linear length dependence, indicating partial coherent transport. This result is supported by the finding of strong delocalization of the highest occupied molecular orbitals of GC by theoretical simulation and by modelling based on the Büttiker theory of partial coherent charge transport.