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DIAMOND BASED SENSORS & DEVICES

 

Micro-mechanical resonators based on cantilevers are excellent tools to measure tiny forces as their resonant frequencies are modified when cantilevers are mass loaded. While micro-cantilevers are among the most sensitive acoustic sensors still they are expected to access higher quality factor values by using a combination of nanocrystalline diamond with a piezoelectric actuator material. Already diamond/AlN micro-cantilevers were fabricated and used as a very sensitive gas pressure sensor. Moving forward, currently work is carried out on their optimisation towards their application in biological and chemical sensing devices.

Another device based on acoustic waves, is the so-called thickness shear mode resonator, of which the most know example is the simple quartz crystal microbalance. This devices is historically known for its use in thickness monitoring in vacuum deposition machines. In more recent years, it has found use as a biosensor in the QCM and QCM-D techniques. Within WBGM the use of new piezoelectric materials that are stable at high temperatures is investigated. An example is langasite. The stability at high temperatures enables to deposit a thin NCD layer on top of the material, leading a device combing the advantageous properties of a thickness shear mode resonator with those of diamond as described on other places of this site.

As diamond is a radiation hard and transparent for the visible part of the spectrum, it forms an ideal candidate to be used as a so-called “solar blind” UV-sensor material. The CVD technology allows the deposition of thin layers, undoped as well as p- and n-type doped, enabling the creation of full diamond photoconductor and photodiode structures. While the former consists out of a planer metal-semiconductor-metal (MSM) structure, photodiodes are based on vertical p-i-n-diodes using boron and phosphorous doped layers in combination with several etching and metallisation schemes. Currently, the solar radiometer LYRA (http://lyra.oma.be/), onboard the ESA satellite PROBA-2 (http://www.esa.int/esaMI/Proba/SEMSD5ZVNUF_0.html), is investigating four ultraviolet bands in the solar spectrum, making use of diamond UV-detectors created at IMO-IMOMEC in collaboration with several partners, including NIMS, Japan.