ANALYSIS AND OPTIMIZATION OF FORCE SENSITIVITY IN ATOMIC-FORCE MICROSCOPY USING OPTICAL AND ELECTRICAL DETECTION

Atomic force microscopy is a versatile tool for ultrasensitive measure ment. We explore the fundamental and practical limits to force sensiti vity that are imposed by optical and electrical deflection sensing tec hniques, and present a method for designing cantilevers to optimize fo rce sensitivity. We calculate the optimized force sensitivity to be 1. 2x10(-18) N/root Hz at a temperature of 4 K, using a gallium arsenide piezoresistive cantilever with dimensions w=0.1 mu m, t = 0.1 mu m, an d L = 81 mu m, and mechanical quality factor Q = 10(4). The optimized force sensitivities obtained using silicon piezoresistive and optical detection are not far behind. (C) 1998 American Vacuum Society.