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 cleave d mica surface is unstable, it is urged to systematically investigate the t ribological properties of mica to design the experimental rules of the refe rence sample mica for friction measurements. Experimental results show that the friction of mica varies with the cleaving time, humidity and surface s tate of tip. The friction measured with different tips on mica varies in th e range of +/-15%. For a new tip, the friction increases with the tip's wea r and then becomes stable. For new cleaved mica, the friction increases wit hin the first two hours and then keeps unchanged. The friction of mica also decreases with the relative humidity because of its hydrophilicity.