Re-examining Electron-Fermi Relaxation in Gold Films With a Nonlinear Thermoreflectance Model

Abstract

In this work, we examine Fermi relaxation in 20 nm Au films with pump-probe themoreflectance using a thin film, intraband thermoreflectance model. Our results indicate that the Fermi relaxation of a perturbed electron system occurs approximately 1.10±0.05 ps after absorption of a 785 nm, 185 fs laser pulse. This is in agreement with reported values from electron emission experiments but is higher than the Fermi relaxation time determined from previous thermoreflectance measurements. This discrepancy arises due to thermoreflectance modeling and elucidates the importance of the use of a proper thermoreflectance model for thermophysical property determination in pump-probe experiments.