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A supplier of nano-positioning systems for atomic-force microscopy (AFM) is using sensors from Micro-Epsilon to measure the travel distance of test items down to nanometre resolution.

The non-contact capacitive displacement sensors also have to operate in extreme conditions, with ambient temperatures of -270C, and in an ultra-high vacuum.

Attocube, based in Munich, is using two custom-designed CapaNCDT 6300 CSH1FL capacitive displacement sensors to measure the travel displacement of test items that need to be moved in the nanometre range, enabling surface topography data to be obtained.

Attocube has developed special actuator motors that are used to position the head of the microscope for these precise positioning tasks.

The system uses a piezo-ceramic positioning unit, enabling movement of the X, Y and Z axis.

The two sensors measure the positioning range, which is 1.2mm x 1.2mm.

The complete head of the microscope is cooled using liquid helium to 4K above the absolute zero point of -273C.

The traversing units operate at an ambient temperature of 4K in an ultra-high vacuum and under very strong magnetic fields.

In order to measure the X- and Y-axis movements, Attocube has integrated two Micro-Epsilon CapaNCDT 6300 sensors with its actuator motors, positioned inside the head of the microscope.

With a measuring range of 1mm, the sensors have a precision of less than 5nm and operate without contact.

Chris Jones, managing director at Micro-Epsilon (UK), said: ’The extremely low ambient temperature and ultra-high vacuum were particular challenges here.

’In ultra-high vacuums, you tend to get degassing of sensor materials and components, both within the sensor itself and the cable.

’The solution had to operate without contamination in this environment and also experience no loss in signal quality when passing sensor signals through an ultra-high-vacuum bulkhead connector.’ Since the sensors are expected to perform just as well at -269C as they are at room temperature, Micro-Epsilon used special materials for the sensor and the cable, which, as a result of their very low thermal expansion properties, provide very stable sensor measurements, according to the company.

A complete sensor solution with vacuum bulkhead was delivered to the customer requiring no modifications.

The cable supplied is a tri-axial design and the temperature stability of the complete system is 11ppm/C.

Jones said: ’We also had a very tight space envelope to work in and so we had to modify the sensor geometry to suit the installation.

’We also developed our own in-house low temperature test chamber that enables us to calibrate and test our sensors for these types of extreme application down to -200C.’ The CapaNCDT 6300 CSH1FL is now part of the standard Micro-Epsilon range of capacitive displacement sensors.

Attocube specialises in the development, manufacture and distribution of nano-positioning systems.

The company’s core competence is in ultra-high-precision spatial positioning of objects – a prerequisite for most nanotechnology applications.

Attocube’s technology enables the positioning and scanning of objects with atomic resolution, but with travel distances in the centimetre range.

It has developed systems for a variety of extreme environments, including UHV applications, low temperatures and high magnetic fields.

These systems have enabled pioneering investigations in science and industry, opening up markets in semiconductors, biotechnology, material science, medicine, chemistry and aerospace.

Atomic-force microscopes are used to image, measure and manipulate matter at the nanoscale.

The information is gathered by ’feeling’ the surface with a mechanical probe.

Piezoelectric elements that facilitate small but accurate movements on command enable the precise scanning of surfaces.

Micro-Epsilon

With over 45 years experience and more than 15,000 customers worldwide, Micro-Epsilon understands the need for accurate, robust, intelligent sensors and measurement systems.

With over 45 years experience and more than 15,000 customers worldwide, Micro-Epsilon understands the need for accurate, robust, intelligent sensors and measurement systems.

If you are measuring any type of displacement / position, temperature, speed or colour parameters, Micro-Epsilon sensors and systems provide market-leading performance, together with the fastest measuring rates, highest operating temperature ranges and smart interface capabilities. From simple, low cost sensors to high volume, customer-specific OEM solutions, Micro-Epsilon will have athe correct measurement solution for your application.

Using both contact and non-contact measurement techniques, Micro-Epsilon boasts one of the largest ranges of displacement sensors including 1D, 2D & 3D laser optical, confocal chromatic, eddy current, capacitive, inductive, draw-wire and time-of-flight technologies. Measuring ranges are from nanometers to kilometers!

For temperature measurement, there is a comprehensive range of non-contact infrared temperature sensors and thermal imaging cameras capable of measuring up to that include intelligent software packages to support configuration, analysis and management during the application. LED analysers, fibre optic sensors and Colour recognition sensors measure true colour using L*A*B and CIE.

Micro-Epsilon sensors are used throughout almost all industries: from automotive to aerospace, motorsport to metal production, semiconductor to subsea. Whether it’s an R&D, test, inspection, OEM or a process control application, Micro Epsilon measurement engineers can provide the right measurement solution.

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