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Simplified inelastic electron tunneling spectroscopy based on low-noise derivatives
Journal
Scientific Reports
Date Issued
2022-12-01
Author(s)
Kesarwani, Shankar
Misra, Shobhna
Saha, Dipankar
Della Rocca, Maria Luisa
Roy, Indrajit
Ganguly, Swaroop
Mahajan, Ashutosh
Abstract
A standard experimental setup for Inelastic Electron Tunneling Spectroscopy (IETS) performs the measurement of the second derivative of the current with respect to the voltage (d2I/ dV2) using a small AC signal and a lock-in based second harmonic detection. This avoids noise arising from direct differentiation of the current-voltage characteristics (I–V) by standard numerical methods. Here we demonstrate a noise-filtering algorithm based on Tikhonov Regularization to obtain IET spectra (i.e. d2I/ dV2 vs. V) from measured DC I–V curves. This leads to a simple and effective numerical method for IETS extraction. We apply the algorithm to I–V data from a molecular junction and a metal-insulator-semiconductor tunneling device, demonstrating that the computed first/second derivatives have a workable match with those obtained from our lock-in measurements; the computed IET spectral peaks also correlate well with reported experimental ones. Finally, we present a scheme for automated tuning of the algorithm parameters well-suited for the use of this numerical protocol in real applications.