TY - JOUR

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

AU - Cheng, Yuzhu

AU - Bulgakov, Alexander v.

AU - Bulgakova, Nadezhda m.

AU - Beránek, Jiří

AU - Kacyuba, Aleksey v.

AU - Volodin, Vladimir a.

N1 - A.V.B., N.M.B. and J.B. acknowledge support from the European Regional Development Fund and the State Budget of the Czech Republic (project SENDISO, no. CZ.02.01.01/00/22_008/0004596). The study of A.V.K. was supported by the Ministry of Science and Higher Education of the Russian Federation (theme no. FWGW-2025-0023). The study of V.A.V. and Y.C. was supported by the Ministry of Science and Higher Education of the Russian Federation (theme No. FSUS-2024-0020). The study of Y.C. was also supported by Program of China Scholarship Council, grant no. 202310100100. Femtosecond Laser Crystallization of Ultrathin a-Ge Films in Multilayer Stacks with Silicon Layers / Y. Cheng, A. V. Bulgakov, N. M. Bulgakova, J. Beránek, A. V. Kacyuba, V. A. Volodin // Applied Sciences (Switzerland). – 2025. – Vol. 15, No. 20. – P. 11082. – DOI 10.3390/app152011082

PY - 2025/10/16

Y1 - 2025/10/16

N2 - Ultrashort pulsed laser annealing is an efficient technique for crystallizing amorphous semiconductors 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 semiconductors 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.

KW - silicon–germanium multilayer structures

KW - ultrathin films

KW - femtosecond laser annealing

KW - selective crystallization

KW - stress confinement

KW - Raman spectroscopy

UR - https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105020242522&origin=inward

U2 - 10.3390/app152011082

DO - 10.3390/app152011082

M3 - Article

VL - 15

SP - 11082

JO - Applied Sciences

JF - Applied Sciences

SN - 2076-3417

IS - 20

ER -