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Measurement for our planet

As COP26 approaches, discover how NPL plays a key role in enabling climate action through the delivery of accurate, reliable data that supports decision making and enables low carbon innovation.

Graphene and 2D materials

Electronics testing for advanced materials

Cutting-edge electronics testing for advanced materials in variable environmental conditions

A unique electrical characterisation service

NPL has developed an environmental chamber to deliver our newest measurement service for electrical characterisation of a variety of advanced materials, and also devices and sensors, whilst being exposed to a range of different environmental conditions such as gas pollutants, humidity and a range of temperatures. It is ideal for companies developing next generation materials or sensors which need to operate under these harsh conditions.

Environmental transport systemThis service would be useful for organisations troubleshooting manufacturing processes to understand the impact different material selection and environmental conditions have on production efficiencies and product performance. It would also be beneficial for companies wanting to explore lateral market opportunities for existing products in different environmental conditions and therefore diversify their product offering. 


The service allows measurements of electrical transport and magneto-transport properties (sheet resistance, carrier type, density and mobility) of either continuous thin films (e.g. atomically thin or of a complex multi-layered structure) or patterned devices. Measurements can be performed at temperatures ranging from room temperature to 200 °C and in variable environmental conditions from vacuum (10-5 mbar) to 0-90% relative humidity. Additionally, combination of gases, e.g., NO2, NH3 can be introduced in the chamber at variable concentrations as low as tens of parts-per-billion using mass flow controllers. The measurement system is automated to enable the impact of long-term effects of controlled environments.

Reliable identification of the electronic propertiesThe environmental transport system allows quick and reliable identification of the electronic properties of continuous films/ heterostructures without a need of expensive and time-consuming patterning. Most importantly, it allows monitoring of the electronic properties of a material dependent on short- and long-term environmental changes. This is of particular importance for sensitive materials, such systems as 2D materials, organic electronics, materials with photovoltaic properties and touch sensors.

The technique

Initial in-situ annealing of the sample allows for desorption of airborne adsorbates and thus measurements of the intrinsic properties of the material. Highly controllable change of the environmental conditions is achieved using electronic control of a calibrated humidifier (with traceable measurements) and use of gas mixtures and mass spectrometry for monitoring of gas concentration (including mixtures of different gases).

Initial in-situ annealingThe system consists of an environmentally controlled chamber, in which a van der Pauw transport measurement system is mounted. Specially designed clamps ensure a soft landing of electrodes without mechanical damage of the sample. Measurements are automatic, with the system programmed and controlled using a LabView program.

Furthermore, environmental measurements can be done on films and patterned devices (e.g. Hall channel or Hall cross types).





Benefits

  • Vacuum annealingMeasurement procedure for characterisation of electrical properties of specific materials, without a need for device patterning.
  • Efficient restoration of intrinsic properties of the material by mild vacuum annealing.
  • Response of graphene and other advanced materials to changes in environmental pollutants
  • Measurements of the intrinsic electronic properties of the material in a vacuum, so that they are not affected by environmental adsorbates and contamination.
  • Accurate monitoring of environmental effects (both those of interest and undesirable ones)
  • Automatic measurements for long time stability and reproducibility

Who might be interested in using this technique 

Any company or academic group who produces electrical advanced materials or is looking to incorporate these materials into products, such as: 

  • 2D materials, e.g., single and multi-layer graphene (not for inks and powders)  

  • Gas sensors 

  • Devices, including Hall bar and Hall sensors 

  • Organic films and electronics 

  • Photovoltaic materials, e.g., thin-film Si, Cadmium sulfide (CdS), Cadmium telluride (CdTe) 

  • Touch/pressure sensors 

  • Electrical materials sensitive to different environments 

  • Gases, humidity, vacuum, high temperature 

  • Instrumentation 

Applications

  • Graphene and related material
  • Semiconductor industries
  • Photovoltaic industries
  • Touch sensors industries

References

  1. L. J. van der Pauw, Philips Tech. Rev., 20, 220-4 (1958) 
  2. L. J. van der Pauw, Philips Res. Repts., 13, 1-9 (1958) 
  3. C. Melios et al., Carbon, 103, 273-280 (2016) 
  4. V. Panchal et al., 2D Mater., 3, 15006 (2016) 
  5. C. Melios et al., 2D Mater., 5 022001 (2018) 

Don’t see what you are looking for? Our diverse skill set enables us to provide bespoke solutions. Please contact us to discuss your requirements.

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