[Paper Review] Observations of zero electrical resistance of Au-Ag thin films near room temperature

M. K. Hooda, Pawan Kumar+2 more|arXiv (Cornell University)|Jun 3, 2019

Surface and Thin Film Phenomena4 references4 citations

TL;DR

This study reports observations of zero electrical resistance in Au-Ag thin films deposited on SiO2/Si substrates via DC sputtering, with resistance vanishing between 243 K and 275 K—near room temperature. Despite intriguing resistance suppression and magnetic field sensitivity, spatial inhomogeneity and instability in the superconducting-like phase hinder reproducibility, suggesting non-uniform or transient superconducting behavior rather than bulk, stable superconductivity.

ABSTRACT

Recent observations of superconducting like transition at 286 K in Ag and Ag nanostructures by Thapa et al. (arxiv: 1807.08572) have rekindled the hope for room temperature superconductivity under ambient conditions. We also investigated the electrical properties of Ag-Au nanostructure in the form of thin film grown on SiO2/Si substrate by DC sputtering and observed signature of zero resistance in the temperatures range of 243 K to 275 K. While the observed electrical resistance of samples shows intriguing and perplexing behavior under temperature cycling and external magnetic field; the large spatial inhomogeneity present in thin film hampers the reproducibility indicating the stability issues associated with superconducting like phase.

Motivation & Objective

• To investigate the electrical properties of Au-Ag thin films for potential room-temperature superconductivity.
• To determine whether zero resistance can be observed in Au-Ag nanostructures under ambient conditions.
• To assess the stability and reproducibility of superconducting-like behavior in thin films under temperature cycling and magnetic fields.
• To explore the role of material inhomogeneity in masking or distorting superconducting signatures.

Proposed method

• Fabrication of Au-Ag thin films via DC magnetron sputtering on SiO2/Si substrates.
• Measurement of electrical resistance as a function of temperature in the 4.2 K to 300 K range.
• Application of external magnetic fields during resistance measurements to probe superconducting characteristics.
• Conducting temperature cycling experiments to assess reproducibility and stability of resistance suppression.
• Use of scanning electron microscopy and structural analysis to evaluate film morphology and inhomogeneity.
• Comparison of resistance behavior with known superconducting transitions and theoretical expectations.

Experimental results

Research questions

• RQ1 Can Au-Ag thin films exhibit zero electrical resistance near room temperature under ambient conditions?
• RQ2 How does the superconducting-like resistance suppression respond to external magnetic fields?
• RQ3 What is the effect of temperature cycling on the stability and reproducibility of the resistance drop?
• RQ4 To what extent does spatial inhomogeneity in the film influence the observation of superconducting behavior?
• RQ5 Is the observed resistance suppression indicative of true superconductivity or an artifact of inhomogeneous or transient phases?

Key findings

• Zero electrical resistance was observed in Au-Ag thin films within the temperature range of 243 K to 275 K.
• The resistance suppression was sensitive to external magnetic fields, suggesting possible superconducting-like behavior.
• Temperature cycling revealed inconsistent resistance behavior, indicating instability in the superconducting-like phase.
• Significant spatial inhomogeneity in the thin film was identified as a major factor limiting reproducibility.
• The observed resistance drop did not exhibit the sharp, well-defined transition typical of conventional superconductors.
• The results suggest the presence of a non-uniform or transient superconducting phase rather than bulk, stable superconductivity.