Effect of laser wavelength on the thermal behavior of amorphous GST films irradiated by a single frequency-tripled picosecond laser

Abstract

In this paper, the effect of laser wavelength on the thermal behavior of amorphous Ge2Sb2Te5 (a-GST) films induced by a frequency-tripled picosecond laser was carried out using 3D surface profile, SEM, TEM and Raman measurement. Melting thresholds of a-GST films with different wavelengths of 355 nm (3.5 mJ/cm2), 532 nm (28 mJ/cm2) and 1064 nm (22.3 mJ/cm2) were obtained, respectively. It showed that with the increase of wavelength from 355 to 532 and 1064 nm, pit morphologies and crystallization degree didn’t follow a monotonous relation, which were mainly affected by melting threshold, optical penetration depth as well as photon energy. TEM images demonstrated that 532 nm laser-treated samples got more complete crystallization than those 355 nm laser treated. Besides, for the remarkable discrepancy in optical penetration depth among the three laser wavelengths, the crystallization process of a-GST at 355 and 532 nm wavelengths performed with a surficial heating mode, different from that at 1064 nm wavelength with a body heating mode. The present study paves the way to achieve the big-data storage using different wavelengths.