Girijavallabhan, C P; Radhakrishnan, P; Nampoori, V P N; Sajan, D George(Physical Review, American Physical Society, October 16, 2003)
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Abstract:
In this paper, we report the in-plane and cross-plane measurements of the thermal diffusivity of double
epitaxial layers of n-type GaAs doped with various concentrations of Si and a p-type Be-doped GaAs layer
grown on a GaAs substrate by the molecular beam epitaxial method, using the laser-induced nondestructive
photothermal deflection technique. The thermal diffusivity value is evaluated from the slope of the graph of the
phase of the photothermal deflection signal as a function of pump-probe offset. Analysis of the data shows that
the cross-plane thermal diffusivity is less than that of the in-plane thermal diffusivity. It is also seen that the
doping concentration has a great influence on the thermal diffusivity value. Measurement of p-type Be-doped
samples shows that the nature of the dopant also influences the effective thermal diffusivity value. The results
are interpreted in terms of a phonon-assisted heat transfer mechanism and the various scattering process
involved in the propagation of phonons.
Nampoori, V P N; Vallabhan, C P G; George, A K; Radhakrishnan, P; Rajasree, K; Vidyalal, V(Elsevier, July , 1998)
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Abstract:
he phenomenon of single beam mirage effect, otherwise known as photothermal deflection (PTD) effect using a He–Ne laser beam has been employed to detect phase transitions in some liquid crystals. It has been observed that anomalous changes in amplitude occur in the PTD signal level near the transition temperature. The experimental details and the results of measurements made in liquid crystals E8, M21 and M24 are given in this paper.