High-performance digital control system for scanning tunnelling microscopy

Abstract

This paper describes a flexible, completely digital, scanning tunnelling microscope developed around a fixed-point (TMS320C542) digital signal processor. During the development special attention has been paid to the cost of the instrument, without limiting its performance, and in some regards enhancing it. The instrument has been developed and tested in the air, at room temperature, and atomic resolution has been achieved. Its software provides a maximum of support to the user. The tip approach is completely automated. The control parameters can be adjusted based on an on-line identification and off-line (in simulation) optimization. This technique is completely integrated to the control software. It greatly simplifies the parameter optimization, and completely eliminates the risk of collision between the tip and the sample during the optimization. The scanning of the image and control of the tunnelling current are implemented in software by the DSP. This allows the precise identification and real-time compensation of the capacitive coupling between the scan tube electrodes and the current detector. The image analysis and processing software allows slope compensation, as well as the presentation of differential image, two-dimensional FFT and three-dimensional image.

Open source scanning probe microscopy control software package GXSM

“…Previous publications on various special and universal SPM control hardware cover computer controlled analog or digital feedback loops [5][6][7][8][9] and are demonstrative, but less available ͑mostly home made hardware͒ to the scientist as they are not maintained nor supported like GXSM is. This article presents the major updates and new developments of the GXSM software project and will focus on the new data acquisition and control design and new features since the first publication.…”

Micromanipulation platform for micro- and nanoscale applications

“…A computer is used only to control an offset parameter and to read measurement data. However, modern microcontroller technology enables fully digital control at a >1 kHz frequency, as has been shown with the Scanning Tunneling Microscope (STM) [8]. Thus, the digital control scheme could be realized in emerging instruments even more efficiently, enabling new functions.…”

Soft Control of Scanning Probe Microscope with High Flexibility

“…Obviously the original analog control circuits (Binnig et al , 1982;Munoz et al , 1998) fail to meet this requirement. The digital control methods popular nowadays are usually composed of a computer and digital circuits such as a digital signal processor (DSP) (Wong and Welland 1993;Baselt et al , 1993;Heuel et al , 1994;Barchesi et al , 1997;Scheuring et al , 1998;Boudreau et al , 2002). The digital circuits perform the core control routine which is to a large extent fixed by the original designer, and the modifications require professional knowledge and abundant experience.…”