Pattern Formation During Nanowear of Gold Films

Abstract

The effects of water on the wear resistance of 3 µm thick sputtered gold films on silicon substrate using contact AFM and a scanning nanoindenter was investigated. In performing wear tests on gold samples in the presence of water, a significant increase in depth of the wear area was observed compared to the same tests performed in the ambient atmosphere (~55% humidity). These results were obtained using Hysitron Triboindenter on areas of 10x10 µm 2 and an Atomic Force Microscope on areas of 1x1 µm 2 . Nanowear tests were preformed using silicon nitride cantilevers on the AFM and diamond Berkovich or blunt conical tips on the Hysitron. Normal loads used were 2 µN and 10 µN, respectively. Tests performed in the ambient atmosphere resulted in a slightly reduced surface roughness, while a much higher wear rate was observed in the wear tests performed in water. Additionally, gold surface ripples formed under certain scanning conditions, in water for the Hysitron Triboindenter and in ambient atmosphere for the AFM. Nanoscale stick slip is being investigated as a possible explanation to the rippling phenomenon, and single scan line tests provide valuable information about the mechanisms and progression of the nanoscale wear.

Tip-Induced Calcite Single Crystal Nanowear

“…At 3 Hz scanning frequency wear ripples started initiating during the first scan and propagated as the number of scans increased. Similar results were obtained on KBr and Al single crystals [6] in the ambient environment using the same system as well as using UHV-AFM on InSb semiconductor surface [5]. As the contact load increases beyond 6 µ N, material started moving to the scan edges and ripple structures were never initiated.…”

“…at the left side of the scan edge, which is attributed to the sample tilt. Similar behavior was seen in KBr in the ambient environment using Hysitron Triboindenter [6] and on the InSb semiconductor surface in the UHV-AFM [5]. A possible mechanism for the initiation of ripples is due to piezo hysteresis and surface slope.…”

“…Ripple patterns were not observed when repeated scanning was performed in the ambient environment with AFM. Similar experiments have been conducted on KBr and Al single crystals in the ambient environment using a nanoindenter [6]. Ripples were observed on KBr after 20 scan cycles at 3 Hz scan frequency over a 5x5 µ m 2 surface area with a 2 µ N normal force.…”