Localized thin film damage sourced and monitored via pump-probe modulated thermoreflectance

Damage in the form of dewetting and delamination of thin films is a major concern in applications requiring micro- or nano-fabrication. In non-contact nanoscale characterization, optical interrogation must be kept to energies below damage thresholds in order to conduct measurements such as pump-probe spectroscopy. In this study, we show that the thermoreflectance of thin films can indicate the degree of film damage induced by a modulated optical heating source. By adjusting the absorbed power of the pump heating event, we identify the characteristics of the change in the thermoreflectance signal when leading up to and exceeding the damage threshold of gold films of varying thicknesses on glass substrates.