A nondestructive type of measurement, picosecond transient thermoreflectance, is proposed to determine cluster sizes, surface coverage, or the fractal dimension of light absorbing species of submonolayer coverage on surfaces and interfaces. The idea is to use a high-repetition-rate pump-and-probe technique of high dynamic range to excite the molecules on the surface selectively and to monitor the transient change of temperature through the change of reflectivity. It is shown that the range of transient reflectivity measurements is not limited by the wavelength of the probe beam, but the relaxation time of the species, and it may be in the nanometer range. An expression for the determination of the dimension of fractal structures is derived.
ASJC Scopus subject areas
- Physics and Astronomy(all)