Properties of nanocrystalline silicon probed by optomechanics

Daniel Navarro-Urrios (Corresponding Author), Martín F. Colombano, Jeremie Maire, Emigdio Chávez-Ángel, Guillermo Arregui, Néstor E. Capuj, Arnaud Devos, Amadeu Griol, Laurent Bellieres, Alejandro Martínez, Kestutis Grigoras, Teija Häkkinen, Jaakko Saarilahti, Tapani Makkonen, Clivia M. Sotomayor-Torres, Jouni Ahopelto

Research output: Contribution to journalArticleScientificpeer-review

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Nanocrystalline materials exhibit properties that can differ substantially from those of their single crystal counterparts. As such, they provide ways to enhance and optimize their functionality for devices and applications. Here, we report on the optical, mechanical and thermal properties of nanocrystalline silicon probed by means of optomechanical nanobeams to extract information of the dynamics of optical absorption, mechanical losses, heat generation and dissipation. The optomechanical nanobeams are fabricated using nanocrystalline films prepared by annealing amorphous silicon layers at different temperatures. The resulting crystallite sizes and the stress in the films can be controlled by the annealing temperature and time and, consequently, the properties of the films can be tuned relatively freely, as demonstrated here by means of electron microscopy and Raman scattering. We show that the nanocrystallite size and the volume fraction of the grain boundaries play a key role in the dissipation rates through nonlinear optical and thermal processes. Promising optical (13,000) and mechanical (1700) quality factors were found in the optomechanical cavity realized in the nanocrystalline Si resulting from annealing at 950°C. The enhanced absorption and recombination rates via the intragap states and the reduced thermal conductivity boost the potential to exploit these nonlinear effects in applications including Nanoelectromechanical systems (NEMS), phonon lasing and chaos-based devices.
Original languageEnglish
Pages (from-to)4819-4829
Issue number16
Publication statusPublished - Nov 2020
MoE publication typeA1 Journal article-refereed


Research funding : The following support is gratefully acknowledged: the European Commission project PHENOMEN (H2020-EU-FET Open GA no. 713450), the Spanish Severo Ochoa Excellence program (SEV-2017-0706), CMST and ECA: the Spanish MICINN project SIP (PGC2018-101743-B-I00), DNU and AM: the Spanish MICINN project PGC2018-094490-B-C22. DNU holds a Ramón y Cajal postdoctoral fellowship (RYC-2014-15392); MFC and GA hold a S. Ochoa and a M. S. Curie COFUND BIST postgraduate studentship, respectively.


  • annealing
  • cavity optomechanics
  • nanocrystalline silicon


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