Bc. Li et Sy. Zhang, THEORETICAL MODELING OF OBLIQUELY CROSSED PHOTOTHERMAL DEFLECTION FORTHERMAL-CONDUCTIVITY MEASUREMENTS OF THIN-FILMS, International journal of thermophysics, 19(2), 1998, pp. 615-624
A three-dimensional theoretical model has been developed to calculate
the normal probe beam deflection of the obliquely crossed photothermal
deflection configuration in samples which consist of thin films depos
ited on substrates. Utilizing the dependence of the normal component o
f probe beam deflection on the cross-point position of the excitation
and probe beams, the thermal conductivity of the thin film can be extr
acted from the ratio of the two maxims of the normal deflection amplit
ude, which occurs when the cross-point is located near both surfaces o
f the sample. The effects of other parameters, including the intersect
angle between the excitation and the probe beams in the sample, the m
odulation frequency of the excitation beam, the optical absorption and
thickness of the thin films, and the thermal properties of substrates
on the thermal conductivity measurement of the thin film, are discuss
ed. The obliquely crossed photothermal deflection technique seems to b
e well suited for thermal conductivity measurements of thin films with
a high thermal conductivity but a low optical absorption, such as dia
mond and diamond-like carbon, deposited on substrates with a relativel
y low thermal conductivity.