Automated fabrication technique of gold tips for use in point-contact spectroscopy

TL;DR

This paper introduces an automated electrochemical etching method for producing high-quality gold tips for point-contact spectroscopy, improving reproducibility and control over tip shape.

Contribution

The authors developed a systematic, automated technique for fabricating gold tips with controlled shape, replacing traditional trial-and-error methods.

Findings

Reproducible gold tips with desired shape achieved

Two-step etching process optimized for quality

PCS measurements confirm tip suitability

Abstract

For a successful point-contact spectroscopy (PCS) measurement, metallic tips of proper shape and smoothness are essential to ensure the ballistic nature of a point-contact junction. Until recently, the fabrication of Au tips suitable for use in point-contact spectroscopy has remained more of an art involving a trial and error method rather than an automated scientific process. To address these issues, we have developed a technique with which one can prepare high quality Au tips reproducibly and systematically. It involves an electronic control of the driving voltages used for an electrochemical etching of a gold wire in an HCl-glycerol mixture or an HCl solution. We find that a stopping current, below which the circuit is set to shut off, is a single very important parameter to produce an Au tip of desired shape. We present detailed descriptions for a two-step etching process for Au tips and also test results from PCS measurements using them.