Frequency modulation atomic force microscopy (FM-AFM) is a technique that can be used for imaging surface atoms by detecting the interaction forces between the outermost atom of a probing tip and the surface atoms. In recent studies, at room temperature (RT), we have been able to create artificial two-dimensional surface structures using the FM-AFM [1,2].
Neighboring atoms embedded in the plane of the surface were interchanged by scanning a tip with fine control. The results of the interchange atom manipulation have paved the way for creating future atomic-scale devices such as the solid state quantum computer [3]. One of the technically difficult issues for realizing atomic devices using the FM-AFM technique at RT is long-time precise tip-sample positioning. In this contribution, we would like to describe a novel method for the tip-sample positioning with atomic precision at RT. In our experimental scheme, three-dimensional position feedback with atom tracking [4] detects the thermal drift velocity that is constant for a period of time at RT. The detected thermal velocity is used as the model for implementing the feedforward in order to compensate for the thermal drift. The combination of the atom tracking and feedforward techniques provides a virtually low temperature environment and enables distortion-compensated imaging at even RT. We also performed two-dimensional force mapping and qualitative atom manipulation experiment on a Si(111)-(7x7) surface, using this technique at RT.
[1] N. Oyabu et al., Nanotechnology vol.16, p.S112 (2005).
[2] Y. Sugimoto et al., Nature Materials vol.4, p.156 (2005).
[3] B. E. Kane, Nature vol.393, p.133 (1998).
[4] M. Abe et al., Appl. Phys. Lett. vol.87, p.173503 (2005).
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