Abstract
We report a noise mapping strategy for the reliable identification and analysis of noise sources in molecular wire junctions. Here, different molecular wires were patterned on a gold substrate, and the current-noise map on the pattern was measured and analyzed, enabling the quantitative study of noise sources in the patterned molecular wires. The frequency spectra of the noise from the molecular wire junctions exhibited characteristic 1/f2 behavior, which was used to identify the electrical signals from molecular wires. This method was applied to analyze the molecular junctions comprising various thiol molecules on a gold substrate, revealing that the noise in the junctions mainly came from the fluctuation of the thiol bonds. Furthermore, we quantitatively compared the frequencies of such bond fluctuations in different molecular wire junctions and identified molecular wires with lower electrical noise, which can provide critical information for designing low-noise molecular electronic devices. Our method provides valuable insights regarding noise phenomena in molecular wires and can be a powerful tool for the development of molecular electronic devices.
Highlights
Molecular wires (MWs) are the basic building blocks of molecular electronic devices[1,2,3,4,5,6]
A Pt-based conducting probe installed on a contact mode atomic force microscopy (AFM) system approached the sample, forming a metal/MW/metal (Pt probe) junction
The contact force between the probe and MW layer was maintained at 1 μNusing the contact force feedback loop of the AFM system
Summary
We have developed a noise mapping strategy for the reliable identification and analysis of electrical noise in MW junctions In this strategy, we patterned different MWs on the same gold substrate and placed a conductive AFM probe on the pattern to measure the electrical currents and noise PSD spectra simultaneously. By scanning the probe above the MW patterns during the measurement, maps of the electrical currents and noise PSDs were obtained and used for the comparative analysis of the electrical resistance values and the noise characteristic parameters in different MWs, respectively. We quantitatively compared the frequency of such bond-fluctuation events and identified MWs with lower electrical noise, which could be an important guideline for designing low-noise molecular electronic devices Considering that it has been extremely difficult and time consuming to measure the noise characteristics of MWs reliably in the past, our strategy can be a powerful tool and should be a significant breakthrough for the basic research and device applications of MW-based devices
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