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MOSCOW, May 11. /TASS/. Russian physicists from the Technological Institute for Superhard and Novel Carbon Materials, the Moscow Institute of Physics and Technology (MIPT) and the Siberian Federal University have mathematically modelled diamond-based microstructures for producing compact high sensitivity sensors, the MIPT press service said.
Russian scientists proposed a mathematical model and experimentally studied acoustic waves in the piezoelectric layered structure (aluminum nitride AlN thin film on the diamond substrate) and found a number of ways of decreasing the effects of spurious peaks. "In the future, diamond crystal based structures may be able to be used as high sensitivity sensors to detect pressure, acceleration, temperature, the thickness of ultrathin films, etc." MIPT said.
A piezoelectric layered structure is a "sandwich" of various different 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 will have seen the piezoelectric effect in lighters (pressing the button compresses the piezoelectric, which provides enough voltage for a spark). However, aside from lighters, the effect is used in microphones, precise micromanipulators, and many kinds of sensors for pressure, humidity, temperature etc.
The effect of an electric field on a piezoelectric, in this case a thin film of aluminum nitride AlN, leads to deformation and causes elastic waves, which 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 an echo that can be heard when you shout in a tunnel or into a wide tube.
Frequencies and other characteristics of these oscillations depend on the properties of the materials, as well as the geometry of the structure. This means that detectors can be made that are able to detect even individual bacteria that have become attached to their surface - the bacteria slightly increase the mass of the entire system and shift the resonant frequency.
Using mathematical modelling, scientists studied in detail the spectrum of various acoustic modes occurring within the diamond structure. Researchers succeeded in selecting and identifying different types of waves and forming dispersion laws for them. The results obtained will be useful in the development of microwave acoustoelectronic devices.
The paper has been published in Applied Physics Letters.
Typical scheme of PLS with a possible acoustic wave propagation. Image: MIPT press-serviceMIPT