Noise spectroscopy of tunable nanoconstrictions: molecule-free and molecule-modified

Abstract

Devices with metallic nanoconstrictions functionalized by organic molecules are promising candidates for the role of functional devices in molecular electronics. However, at the moment little is known about transport and noise properties of nanoconstriction devices of this kind. In this paper, transport properties of bare gold and molecule-containing tunable cross-section nanoconstrictions are studied using low-frequency noise spectroscopy. Normalized noise power spectral density (PSD) S /I dependencies are analyzed for a wide range of sample resistances R from 10 Ohm to 10 MOhm. The peculiarities and physical background of the flicker noise behavior in the low-bias regime are studied. It is shown that modification of the sample surface with benzene-1,4-dithiol molecules results in a decrease of the normalized flicker noise spectral density level in the ballistic regime of sample conductance. The characteristic power dependence of normalized noise PSD as a function of system resistance is revealed. Models describing noise behavior for bare gold and BDT modified samples are developed and compared with the experimental data for three transport regimes: diffusive, ballistic and tunneling. Parameters extracted from models by fitting are used for the characterization of nanoconstriction devices.

Nanoscale Mapping of Carrier Mobilities in the Ballistic Transports of Carbon Nanotube Networks

“…As shown in Figure c,d, the regions with low or high charge trap density correspond mostly to those of CNT bundles or individual CNTs , respectively. The scaling behavior of σ ∝ N T –1 in the CNT bundle regions can be explained by the ballistic transport as reported previously. , Briefly, the current-normalized noise PSD can be written by a Hooge’s equation like where α H , Δ N , e , v , R , and V are the Hooge’s parameter, the number of carriers in a segment Δ x Δ y , an electric charge, a characteristic carrier velocity, the resistance of a segment Δ x Δ y , and an applied bias at a segment Δ x Δ y , respectively. In the case of a ballistic transport, the carrier velocity v corresponds to the thermal velocity .…”

“…The scaling behavior of σ ∝ N T –1 in the CNT bundle regions can be explained by the ballistic transport as reported previously. , Briefly, the current-normalized noise PSD can be written by a Hooge’s equation like where α H , Δ N , e , v , R , and V are the Hooge’s parameter, the number of carriers in a segment Δ x Δ y , an electric charge, a characteristic carrier velocity, the resistance of a segment Δ x Δ y , and an applied bias at a segment Δ x Δ y , respectively. In the case of a ballistic transport, the carrier velocity v corresponds to the thermal velocity . Thus, the normalized PSD can be described as where T and m e are the temperature and the mass of an electron, respectively.…”

“…In the case of a ballistic transport, the carrier velocity v corresponds to the thermal velocity. 39 Thus, the normalized PSD can be described as…”

The Characterization of Electronic Noise in the Charge Transport through Single‐Molecule Junctions

“…Flicker noise of the molecule‐free and the molecule‐containing bare junctions were also investigated by the MCBJ technique, and this indicated that the noise level decreased in the ballistic regime of conductance after the modification of the molecule (1,4‐benzenedithiol, BDT). [ 50 ] The results of these reports are valuable for improving the basic knowledge of the development of flicker noise in molecular junctions.…”

The Evolution of the Charge Transport Mechanism in Single‐Molecule Break Junctions Revealed by Flicker Noise Analysis

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challenging to reveal the evolution of the charge transport mechanism from the conductance characterization of singlemolecule conductance. In the past decade, numerous data analysis methods were introduced to process the conductance traces, including statistical methods, [4][5][6][7] analytical modeling, [8,9] electronic noise analysis, [10][11][12][13][14][15] and machine learning and deep learning methods. [16][17][18] Among these methods, analysis of flicker noise from the single-molecule junctions has suggested to shed new light on the understanding of charge transport mechanisms of singlemolecule junctions.

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