The experimental rules of mica as a reference sample of AFM/FFM measurement

For the friction measurements with AFM/FFM, usually the relative values of friction signal can be obtained. In order to compare the micro-tribological properties of different samples, mica is often used as an reference sample for friction measurement. However, due to the friction force of new cleaved mica surface is unstable, it is urged to systematically investigate the tribological properties of mica to design the experimental rules of the reference sample mica for friction measurements. Experimental results show that the friction of mica varies with the cleaving time, humidity and surface state of tip. The friction measured with different tips on mica varies in the range of ±15%. For a new tip, the friction increases with the tip’s wear and then becomes stable. For new cleaved mica, the friction increases within thefirst two hours and then keeps unchanged. The friction of mica also decreases with the relative humidity because of its hydrophilicity.