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arXiv · 1606.08836

High spatial frequency laser induced periodic surface structure formation in germanium by mid-IR femtosecond pulses

Drake. R. Austin·Kyle R. P. Kafka·Yu Hang Lai·Zhou Wang·Kaikai Zhang·Hui Li·Cosmin I. Blaga·Allen Y. Yi·Louis F. DiMauro·Enam A. Chowdhury
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Abstract

Formation of high spatial frequency laser induced periodic surface structures (HSFL) in germanium by femtosecond mid-IR pulses with wavelengths between $λ=2.0$ and $3.6 \; \mathrm{μm}$ was studied with varying angle of incidence and polarization. The period of these structures varied from $λ/3$ to $λ/8$. A modified surface-scattering model including Drude excitation and the optical Kerr effect explains spatial period scaling of HSFL across the mid-IR wavelengths. Transmission electron microscopy (TEM) shows the presence of a $30 \; \mathrm{n m}$ amorphous layer above the structure of crystalline germanium. Various mechanisms including two photon absorption and defect-induced amorphization are discussed as probable causes for the formation of this layer.

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Drake. R. Austin, Kyle R. P. Kafka, Yu Hang Lai, Zhou Wang, Kaikai Zhang, Hui Li, Cosmin I. Blaga, Allen Y. Yi, Louis F. DiMauro, Enam A. Chowdhury. 2016-06-28. High spatial frequency laser induced periodic surface structure formation in germanium by mid-IR femtosecond pulses. https://doi.org/10.1063/1.4964737

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