Problems of Using a Solvent-cleansed Silicon Oxide Substrate as the Friction Reference Sample at the Nanoscale

For comparative friction studies, a reference sample, which holds stable and reproducible frictional characteristics, is required. Here, we have studied the frictional properties of native silicon oxide and silicon oxide formed through wet thermal oxidation by using lateral force microscopy. Once cleansed using solvents such as acetone, the friction measured on these frequently-used reference materials undergoes gradual change by a series of scanning. The friction is observed to increase with the number of scans and reaches about 1.5 times the initial value. We find that soft baking at 150 ◦ C - 200 ◦ C for 30 minutes can eliminate this problem.