A Simple Laboratory Method to Pattern Sub‐Millimeter Features of Conductive Films of Gold and Indium Tin Oxide

A simple laboratory photolithography method for patterning 100 nm thick gold and indium tin oxide (ITO) films on glass slides with 100 µm resolution without the need of special equipment is described. During the procedure, the conductive films are coated with a commercial screen printing emulsion using a modified drill as spin‐coater, then placed in contact with a negative photomask, and exposed to a 20 W light source for 30–60 min. The excess photoresist is washed off with water, and the glass slides are baked at 210°C to produce a mechanically and chemically resistant coating. The substrates are then etched in dilute aqueous HNO3/HCl (gold) or 6 n HCl (ITO) to remove exposed gold and ITO films. After etching, the photoresist is removed by etching with peroxosulfuric acid (gold) or scraped off with a razor blade (ITO) leaving a conductive pattern. The procedure requires between 3 and 5 h of time, depending on experience.