AFM

Our Activities

  • Nanostructuring with Electrolytical STM and AFM
  • Readout for Massively Parallel AFM
  • Compact AFMs
  • Study of SACE with AFM

Nanostructuring with Electrolytical STM

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Scanning probe microscopes (SPM), originally used for imaging, have been successfully used to modify surfaces at the nanometer scale. It has been shown that an STM tip or a metal tool operating inside an electrolyte can be used to modify surfaces locally. As the deposition / etching are controlled by electrode potentials, it is a relatively simple process. This method is applicable to a large number of systems and another advantage, true for all SPM systems, is that it is possible to view the modified surface in-situ. Our goal is to study the localized deposition of noble metals like Pt on ideal surfaces like HOPG and gold and also on non-ideal surfaces like BDD (boron doped diamond). Nanoparticles of noble metals are of interest to electrochemists for their catalytical properties.

A home built STM, based on the Besocke principle, is used for experiments in electrolyte. The image shows platinum deposited by using nanosecond pulses on gold (Au (111)).

Readout for Massively Parallel AFM

Compact AFMs

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Scanning probe microscopes have found many applications, but they are still quite bulky. Compact AFMs hold promise for new applications such as micro-nano robotics and sensors. Our group has developed different kinds of compact piezo xy, xyz stages and integrated them with piezoelectric cantilevers to form very compact AFMs – Credit Card AFMs. The goal is to develop AFMs with the following features : (1) compact and easy to integrate, (2) minimum components and assembly and (3) inexpensive.

Monolithic or quasi monolithic XY, XYZ piezo stages have been designed and fabricated. Stages have range of 10 to 20 µm in x,y and 30 to 50 µm in z. Novel techniques like lever mechanism, geometry and bimorph effects have been used to amplify the piezo motion and flexure hinges have been incorporated in the stages. Analytical and Finite Element Analysis is used to study and optimise the stages. The stages are cut out of piezo plates by laser cutting.

Piezoelectric cantilevers (provided by Nikon, Japan) are used which eliminates bulky optics. Apart from self sensing, these cantilevers can also be used for feedback actuation with high bandwidth.

Credit Card AFMs have been used to demonstrate position sensing in conjunction with nanometer gratings. A promising application in the field of micro robotics is to use AFMs mounted on micro robots for tracking / positioning with nanometer precision. We have successfully demonstrated Tracking Nanostructures with Microrobots using AFM.

Study of SACE with AFM

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Spark Assisted Chemical Engraving (SACE) is a novel micro-machining technology which makes use of electrode effects to machine glass and other non-conducting materials. While SACE process itself is being thoroughly investigated, the goal of this research is to explore the limits of SACE with respect to machining dimensions. Dependance on tool size has been studied by using sharp tips produced by electrochemical etching of tungsten wires. These tips are bent into cantilevers and used in a long range AFM setup to achieve sensitive contact detection (to avoid damaging the tip). Experiments have shown that sharp tips can reduce machining sizes and a gas film thickness of ~ 25 µm is the limiting factor for smaller machining. Tips that are almost completely insulated (e.g. with Apiezon wax) bring down the currents by more than three orders of magnitude and can considerably reduce tool wear which is quite high for non insulated tips.