Experimental and theoretical study of ultraviolet-induced structural/optical instability in non silicon-based luminescence

James Malloy, Kevin Mantey, Yulia Maximenko, Ersin Bahceci, Huw Morgan, Zain Yamani, Jack Boparai, Krithik Puthalath, Munir H. Nayfeh

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Nano silicon is emerging as an active element for UV applications due to quantum confinement-induced widening of the Si bandgap, amenability to integration on Si, and less sensitivity to temperature. NanoSi-based UV applications include deep space exploration, high temperature propulsion, solar photovoltaics, and particle detection in high energy accelerators. However, the viability of the technology is limited by a complex nanoSi optical quenching instability. Here, we examined the time dynamics of UV-induced luminescence of sub 3-nm nanoSi. The results show that luminescence initially quenches, but it develops a stability at ∼50% level with a time characteristic of minutes. Upon isolation, partial luminescence recovery/reversibility occurs with a time characteristics of hours. To discern the origin of the instability, we perform first principles atomistic calculations of the molecular/electronic structure in 1-nm Si particles as a function of Si structural bond expansion, using time dependent density functional theory, with structural relaxation applied in both ground and excited states. For certain bond expansion/relaxation, the results show that the low-lying triplet state dips below the singlet ground state, providing a plausible long-lasting optical trap that may account for luminescence quenching as well as bond cleavage and irreversibility. Time dynamics of device-operation that accommodates the quenching/recovery time dynamics is suggested as a means to alleviate the instability and allow control of recovery, which promises to make it an effective alternative to UV-enhanced Si or metal-based wide-bandgap sensing technology
Original languageEnglish
Article number044501
JournalJournal of Applied Physics
Issue number4
Early online date24 Jul 2018
Publication statusE-pub ahead of print - 24 Jul 2018


  • silicon
  • nanoparticle
  • UV-photosensor
  • triplet
  • luminescence
  • structural
  • instability
  • reversible
  • TD-DFT
  • simulation


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