Generation and patterning of Si nanoparticles by femtosecond laser pulses
The unique optical properties of nanoparticles are highly sensitive in respect to particle shapes, sizes, and localization on a sample. This demands for a fully controlled fabrication process. The use of femtosecond laser pulses to generate and transfer nanoparticles from a bulk target towards a collector substrate is a promising approach. This process allows a controlled fabrication of spherical nanoparticles with a very smooth surface. Several process parameters can be varied to achieve the desired nanoparticle characteristics. In this paper, the influence of two of these parameters, i.e. the applied pulse energy and the laser beam shape, on the generation of Si nanoparticles from a bulk Si target are studied in detail. By changing the laser intensity distribution on the target surface one can influence the dynamics of molten material inducing its flow to the edges or to the center of the focal spot. Due to this dynamics of molten material, a single femtosecond laser pulse with a Gaussian beam shape generates multiple spherical nanoparticles from a bulk Si target. The statistical properties of this process, with respect to number of generated nanoparticles and laser pulse energy are investigated. We demonstrate for the first time that a ring-shaped intensity distribution on the target surface results in the generation of a single silicon nanoparticle with a controllable size. Furthermore, the generated silicon nanoparticles presented in this paper show strong electric and magnetic dipole resonances in the visible and near-infrared spectral range. Theoretical simulations as well as optical scattering measurements of single silicon nanoparticles are discussed and compared.
KeywordsFemtosecond Laser Pulse Laser Pulse Energy Silicon Nanoparticles Liquid Silicon Molten Silicon
The authors acknowledge financial support of this work by the priority program SPP1391 “Ultrafast Nanooptics” and SPP1327 “Optical generation of Sub-100 nm structures for biomedical and technical applications,” the project CH 179/20-1, and the Collaborative Research Center/Transregio 123 Planar Optronic Systems of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG), as well as the Laboratory of Nano and Quantum Engineering (LNQE), Hannover. A.B.E. acknowledges support by the Russian Foundation for Basic Research, Grant No. 12-02-00528. The authors further acknowledge support by the Center for Quantum Engineering and Space-Time Research (QUEST).
- 1.M. Faraday, Philos. Trans. R. Soc. Lond. A 147, 145 (1857) Google Scholar
- 3.S. Davey, Nat. Chem. (2010) Google Scholar
- 14.A.I. Kuznetsov, A.E. Miroshnichenko, Y.H. Fu, J. Zhang, B. Luk’yanchuk, Sci. Rep. 2 (2012) Google Scholar
- 20.J. Eggers, arXiv preprint physics/0111003 (2001)
- 21.H.C. Hulst, H. Van De Hulst, Light Scattering by Small Particles (Courier Dover Publications, New York, 1957) Google Scholar
- 22.C.F. Bohren, D.R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley-Vch, New York, 2008) Google Scholar