Thermal measuring and testing – Determination of inherent thermal property
Patent
1994-06-22
1997-09-16
Cuchlinski, Jr., William A.
Thermal measuring and testing
Determination of inherent thermal property
374121, 374128, G01N 2520
Patent
active
056673000
ABSTRACT:
There is provided a method of measuring thermal diffusivity of solids and electronic lifetimes and defect properties of semiconductors useful for in-situ, non-destructive monitoring of engineered materials and electronic substrates. The method, termed photothermal rate window method, involves irradiating a sample with a repetitive square laser pulse of duration .tau..sub.p and period T.sub.0 and monitoring the temperature profile by measuring the photothermal signal emitted from the sample. The period T.sub.0 of the repetitive heating pulse is maintained constant and the pulse duration .tau..sub.p is varied in the range between 0 and T.sub.0 with the temperature measured at each value of .tau..sub.p. The method of measuring semiconductor recombination lifetimes involves irradiating a sample and scanning one of either the period T.sub.0 and the pulse duration .tau..sub.p of the repetitive laser pulse with the other held constant. The photothermal signal emitted from the surface is measured. Defect energy states in semiconductors are measured by irradiating the sample with a repetitive laser pulse of duration .tau..sub.p and period T.sub.0 (both fixed) and monitoring the photothermal signal as the sample temperature is scanned. Defect levels are correlated with extremum in the profile. The photothermal signal in all the foregoing methods is input into a lock-in amplifier which measures the fundamental Fourier component of the signal. The output of the lock-in amplifier is fitted to a theoretical model of the photothermal response of a repetitively irradiated sample to obtain the thermal diffusivity, or the recombination lifetime.
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Mandelis Andreas
Munidasa Mahendra
Cuchlinski Jr. William A.
Hirshfeld Andrew
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