Origin of Periodic Modulations in the Transient Reflectivity Signal at Cryogenic Temperatures

TL;DR

This paper investigates the origin of periodic modulations in low-temperature transient reflectivity signals, attributing them to surface gas condensation effects, and proposes methods to obtain accurate measurements.

Contribution

It identifies residual gas condensation as the cause of periodic modulations in transient reflectivity at cryogenic temperatures and offers techniques to improve data reliability.

Findings

Periodic modulations are caused by surface gas condensation.

Modulations are linked to changes in linear reflectivity during measurements.

Methods to mitigate these effects and obtain reliable data are proposed.

Abstract

Periodic modulations that appear in the low-temperature transient reflectivity signal of a GaAsP/AlGaAs single quantum well is studied. Similar anomalous oscillations are also observed in layered manganite [K. Kouyama et.al. J. Phys. Soc. Jpn. 76:123702(1-3), 2007]. We show that such periodic modulations are caused by changes in the linear reflectivity of the sample during transient reflectivity measurements. Studied carried out on reflectivity of different materials under identical conditions shows that these modulations on the true transient reflectivity signal are caused by condensation of residual gases on the surface of quantum well. Methods to obtain reliable transient reflectivity data are also described.