Subnanometer Positioning and Drift Compensation With Tunneling Current

Blanvillain, Sylvain; Voda, Alina; Besançon, Gildas; Buche, Gabriel

doi:10.1109/tcst.2013.2248364

Cited by 10 publications

(1 citation statement)

References 24 publications

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“…LBH is assumed to be constant in the design of STM control systems. 8,10,11,22,23 However, this assumption is inconsistent with the variable nature of the LBH and may lead to closed-loop instabilities in STMs. 18,24 We propose to continuously update the PI controller gains in order to preserve the closed-loop stability despite variations in the LBH.…”

Section: Introductionmentioning

confidence: 99%

On the effect of local barrier height in scanning tunneling microscopy: Measurement methods and control implications

Tajaddodianfar

Moheimani

Owen

et al. 2018

Review of Scientific Instruments

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A common cause of tip-sample crashes in a Scanning Tunneling Microscope (STM) operating in constant current mode is the poor performance of its feedback control system. We show that there is a direct link between the Local Barrier Height (LBH) and robustness of the feedback control loop. A method known as the "gap modulation method" was proposed in the early STM studies for estimating the LBH. We show that the obtained measurements are affected by controller parameters and propose an alternative method which we prove to produce LBH measurements independent of the controller dynamics. We use the obtained LBH estimation to continuously update the gains of a STM proportional-integral (PI) controller and show that while tuning the PI gains, the closed-loop system tolerates larger variations of LBH without experiencing instability. We report experimental results, conducted on two STM scanners, to establish the efficiency of the proposed PI tuning approach. Improved feedback stability is believed to help in avoiding the tip/sample crash in STMs.

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