Influence of intraband transitions on the electron thermoreflectance response of metals

Ultrashort pulsed lasers have repeatedly been demonstrated as effective too ls for the observation of transport properties on atomistic time and length scales. Transient thermoreflectance scans of a Au thin film taken using a 200 fs pulsed laser are compared to the parabolic two step model using both the assumption of a linear relationship between reflectance and temperatur e and using an intraband reflectance model. In this study, the incident pho ton energy was less than the interband transition energy, therefore the the rmoreflectance response is primarily due to intraband transitions. The intr aband transitions are influenced by the electron and lattice temperatures t hrough the electron collisional frequency. (C) 2001 American Institute of P hysics.