Acousto-Electric Effect

Acousto-Electric Effect


the appearance of a direct current or emf in metals (or semiconductors) as a result of the action of an intensive elastic high frequency wave, ultrasonic or hypersonic, in the direction of its propagation. The appearance of the current is related to the transmission of the momentum (and the corresponding part of the energy) from the sonic wave to the current carriers—conduction electrons and electron holes. This transmission leads to a directed motion of the carriers—that is, to an electrical current. The acousto-electric effect is analogous to other effects of “dragging” (piggybacking) elements of a medium by an intensive acoustic wave propagating in the medium—for example, acoustic winds. In the acousto-electric effect the hypersonic wave causes such a deformation of the conductor that local electric fields appear in it, propagating along the conductor together with the wave; these fields also lead to “dragging” of the current carriers. The acousto-electric effect is a nonlinear phenomenon.

The acousto-electric effect was first experimentally encountered by Weinrich, Sanders, and Whiet (USA) in single crystals of germanium (Ge). However, in the common semiconductors and metals the acousto-electric effect is insignificant. In semiconductor crystals, which have piezoelectric properties, such as CdS, the acousto-electric emf reaches 800 to 1,000 mV/cm at a sound intensity of approximately 0.01 W/cm2.

The acousto-electric effect is utilized for the measurement of the power of ultrasonic signals. Its most effective use is for the investigation of the interaction of elastic oscillations in the crystallic lattice (phonons) with current carriers.


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