TY - JOUR

T1 - Femtosecond Laser Crystallization of Ultrathin a-Ge Films in Multilayer Stacks with Silicon Layers

AU - Чэн, Надя

PY - 2025/10/16

Y1 - 2025/10/16

N2 - Ultrashort pulsed laser annealing is an efficient technique for crystallizing amorphous semi-conductors with the possibility to obtain polycrystalline films at low temperatures, below the melting point, through non-thermal processes. Here, a multilayer structure consisting of alternating amorphous silicon and germanium films was annealed by mid-infrared (1500 nm) ultrashort (70 fs) laser pulses under single-shot and multi-shot irradiation conditions. We investigate selective crystallization of ultrathin (3.5 nm) a-Ge non-hydrogenated films, which are promising for the generation of highly photostable nanodots. Based on Raman spectroscopy analysis, we demonstrate that, in contrast to thicker (above 10 nm) Ge films, explosive stress-induced crystallization is suppressed in such ultrathin systems and proceeds via thermal melting. This is likely due to the islet structure of ultrathin films, which results in the formation of nanopores at the Si-Ge interface and reduces stress confinement during ultrashort laser heating.

AB - Ultrashort pulsed laser annealing is an efficient technique for crystallizing amorphous semi-conductors with the possibility to obtain polycrystalline films at low temperatures, below the melting point, through non-thermal processes. Here, a multilayer structure consisting of alternating amorphous silicon and germanium films was annealed by mid-infrared (1500 nm) ultrashort (70 fs) laser pulses under single-shot and multi-shot irradiation conditions. We investigate selective crystallization of ultrathin (3.5 nm) a-Ge non-hydrogenated films, which are promising for the generation of highly photostable nanodots. Based on Raman spectroscopy analysis, we demonstrate that, in contrast to thicker (above 10 nm) Ge films, explosive stress-induced crystallization is suppressed in such ultrathin systems and proceeds via thermal melting. This is likely due to the islet structure of ultrathin films, which results in the formation of nanopores at the Si-Ge interface and reduces stress confinement during ultrashort laser heating.

M3 - Article

VL - 15

SP - 1

EP - 12

JO - Applied Sciences

JF - Applied Sciences

SN - 2076-3417

IS - 11082

M1 - 11082

ER -