Laser-induced thermal desorption of moisture from a surface in atmospheric conditions

Abstract

Moisture adsorbed on a gold, copper, or silicon surface in atmospheric conditions can be detected by using a pulsed laser-induced heating of the surface (transient temperature rise ≲100°C), and a continuous probe laser beam parallel to the surface to detect the transient refractive-index changes. The probe deflection signal can be interpreted as due to a compression pulse (produced by the heating and moisture desorption at the sample surface), followed by a rarefraction (produced by cooling and diffusional moisture readsorption). Using this interpretation of the transient probe deflection signal, the amount of moisture adsorbed at the samples for various surface temperatures and absolute moisture content in an ambient gas (e.g., nitrogen) can be monitored.