Evaluation of a Lightly Scratched Amorphous Carbon Surface by Contact Resistance of a Conductive Diamond Tip and the Carbon Surface

Abstract

An electron-cyclotron-resonance-sputtered amorphous carbon film is scratch-scanned by an AFM and a conductive diamond tip at small contact loads (≤2μN). The electrical contact resistance between the tip and the scratched carbon surface increases upon increasing the scratching load and the number of scratching scans and decreases with increasing scratching velocity. The wear depth is less than 0.6 nm in all scratching experiments and is almost independent of the scratching load, the number of scratching scans and the scratching velocity. The change in contact resistance caused by the scratching is affected by environmental humidity. The magnitude of the change in the contact resistance is almost the same at 20 and 50% RH and increases with increasing relative humidity at humidities higher than 50% RH. The contact resistance also increases upon scratching in vacuum. The change in contact resistance is thought to be caused by tribochemical oxidation of the rubbed surface by humid air and also destruction of the graphite structure of the ECR-sputtered carbon surface.