Absorption Spectra of Crystalline and Amorphous Silicon by Photothermal Deflection Spectroscopy

The nature of the optical absorption in semiconductors at and below the absorption edge is of interest, particularly in the case of amorphous materials. The sensitivity of conventional transmission techniques are limited by the requirement of measuring the difference between two nearly equal signals. Furthermore, such techniques are highly sensitive to scattering. While adequately sensitive, the disadvantages of piezoelectric photoacoustic detection(1) are that it requires a laser as the exciting source, is highly sensitive to scattering, and requires reliable coupling between the transducer and the sample.