Ultrasonic Emission from Nanocrystalline Porous Silicon

Abstract

A simple layer structure composed of a metal thin film and a porous silicon layer on a silicon substrate generates intense and wide-band airborne ultrasounds. The large-bandwidth and the fidelity of the sound reproduction are leveraged in applications varying from sound-based measurement to a scientific study of animal ecology. This chapter describes the basic principle of the ultrasound generation. The macroscopic properties of the low thermal conductivity and the small heat capacity of nanocrystalline porous silicon thermally induce ultrasonic emission. The state-of-the-art of the achievable sound pressure and sound signal properties is introduced, with the technological and scientific applications of the devices.

Nanostructured copper/porous silicon hybrid systems as efficient sound-emitting devices

“…In the particular case of sound-emitting devices, nanoPS has been demonstrated as a versatile material to fabricate efficient devices [ 5 ]. Since its optical and thermal properties can be easily tuned by changing its porosity, nanoPS offers great versatility aiming at adjusting its photo-acoustic response [ 6 ]. In addition, devices based on this material have been proposed as sound transmitters [ 7 ] or even to obtain three-dimensional images [ 8 ].…”