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A two-dimensional atom encoder using one lateral-dithered scanning tunneling microscope (STM) tip and a regular crystalline lattice

In this paper, we propose a new 2D displacement atom encoder using only one lateral-dithered scanning tunneling microscope (STM) tip and one mono-crystalline area of the highly oriented pyrolytic graphite (HOPG) crystal. A high-speed lateral circular dither modulation with proper amplitude is applied to a tip scanner to position the STM tip on six specific points on the HOPG crystalline surface. Multi-tunneling-current signals obtained from the six specific points are utilized to determine the lateral 2D displacement based on the two unit lattice vectors on the HOPG crystalline surface. In addition, the interpolation method can be used in the newly proposed method to measure displacement less than the lattice spacing. In the paper, instrumentation and experiments of the new 2D displacement measurement technique are discussed. The experimental results show that the proposed technique has the capability to measure 2D displacement with a resolution of 10 pm order.