Sensors

Diamond-based microstructures could produce microsensors

 

A collaborative of Russian researchers has mathematically modelled diamond-based microstructures for producing compact, high-sensitivity sensors. The study investigates the problem of selecting a useful acoustic signal taking into account the excitation of Lamb waves in promising microwave microresonators with substrates of synthetic diamonds.

The scientists proposed a mathematical model and experimentally studied acoustic waves in the piezoelectric layered structure, described their dispersion and proposed a number of ways to decrease the effects of spurious peaks.

In the future, diamond crystal-based structures may be used as high sensitivity sensors to detect pressure, acceleration, temperature and the thickness of ultrathin films. The paper has been published in Applied Physics Letters.

"I think that the results we have obtained from a piezoelectric layered structure based on synthetic diamonds are ahead of world-class research in this field. Our microresonators were used to obtain resonances at record high microwave frequencies in a range of up to 20 GHz, with the quality factor remaining at several thousand.

The behaviour of diamond as a substrate for the acoustic microresonator was very significant and I hope that using diamonds in acoustics and electronics will lead to more exciting discoveries," said the corresponding author of the study, Boris Sorokin, in an interview with MIPT's Communications Office.

The quality factor is a feature of an oscillating system. It describes how quickly oscillations die down in a system; the higher the quality factor, the smaller the energy loss.

A piezoelectric layered structure is a "sandwich" of various materials with a piezoelectric effect. This term means that under compression or tension, an electric field occurs around the material—and when an electrical voltage is applied, the material itself changes shape.

Non-scientists have seen the piezoelectric effect in lighters, which have piezoelectrics that provide enough voltage for a spark. The effect is also used in microphones, precise micromanipulators, and many kinds of sensors for pressure, humidity and temperature.

Another important application of piezoelectrics is in highly stable piezoelectric resonators, which enable quartz clocks to display time accurately and computers to run programs smoothly.

The effect of an electric field on a piezoelectric, in this case a thin film of aluminium nitride AlN, leads to deformation and causes elastic waves that pass to the substrate in the same way that an elastic wave falling on the piezoelectric film causes an electric field.

When it reaches the edge of the substrate, the wave is reflected and within the layers of several materials, a number of oscillations occur at the same time—this effect resembles a sonic echo that can be heard when shouting in a tunnel or into a wide tube.

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