結晶格子と走査型トンネル顕微鏡を用いた原子トラッキング制御の高安定化 : 原子エンコーダの検証

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In this article, we propose a technique for highly stabilized atom-tracking control of a scanning tunneling microscope (STM) tip by referring to an atomic point (or atomic array) on a regular crystalline surface. Graphite crystal, whose lattice spacing is approximately 0.25nm, was utilized as the reference. To enhance stability of the atom-tracking control against external disturbances, a new atom-tracking controller, which consists of integrator, tracer and limiter units, was developed. The integrator unit is designed to eliminate the steady-state error due to thermal drift. A phase-lag low-pass filter is utilized as the tracer unit to compensate the disturbance due to vibration/acoustic noise. To improve the phase margin of the controller, the limiter unit consists of a phase-lead high-pass filter and a saturator whose output is less than one-half of the lattice spacing. The performance of the stabilized technique, which is to combine the new tracking controller with enhanced STM stiffness, was evaluated using internal/external artificial disturbance generators. The experimental results show that the proposed method has a high capability for maintaining atom-tracking control without any jumping of the STM tip to neighboring atoms, even in a noisy environment. The method was also applied to atom-stepping control of the STM tip by referring to some crystalline axis. The atom-stepping control atom by atom along the crystalline axis over a range of 200 atoms, at a rate of 10 atoms/sec, was performed without missing the atomic array.
社団法人精密工学会の論文
2004-11-05

結晶格子と走査型トンネル顕微鏡を用いた原子トラッキング制御の高安定化 : 原子エンコーダの検証

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