Spherical Growth and Surface-Quasifree Vibrations of Si Nanocrystallites in Er-Doped Si Nanostructures

Abstract

Si-based Er-doped Si nanostructures were fabricated for exploring efficient light emission from Er ions and Si nanocrystallites. High-resolution transmission electron microscopy observations reveal that Si nanocrystallites are spherically embedded in the SiO 2 matrix. Energy-dispersive x-ray analysis indicates that the Er centers are distributed at the surfaces of nanocrystallites surrounded by the SiO 2 matrix. Lowfrequency Raman scattering investigation shows that Lamb's theory can be adopted to exactly calculate the surface vibration frequencies from acoustic phonons confined in spherical Si nanocrystallites and the matrix effects are negligible.

Energy transfer in Er-dopedSiO2sensitized with Si nanocrystals

“…11 and 12͒ and different locations of Er, with respect to Si NC, have been considered. 13,14 In addition to the relatively slow ͑ s range͒ NC-mediated Er 3+ excitation, a much faster ͑100 ns range͒ and usually more dominating process has also been concluded. 15 Its physical origin has been considered recently 16 and participation of special luminescence centers in erbium excitation has been postulated in particular for low-temperature annealed samples.…”

Sensitization of Er luminescence by Si nanoclusters

“…5,7 In this heterogeneous medium ͑SiO 2 : Si-nc, Er͒ the incoming photons are captured in Si-nc due to efficient bandto-band absorption, 8 and subsequently, the excitation energy is transferred to Er 3+ ions located preferably outside Si-nc. 9,10 In this way, an efficient channel for nonresonant excitation leading to temperature-stable Er 3+ emission is realized. Moreover, electrical excitation can also be achieved and efficient electroluminescent devices have recently been demonstrated.…”

Damping of surface acoustic vibration induced by electrons trapped on SnO2 nanocrystal surface

“…[1][2][3][4][5][6][7][8][9][10][11] Recently, it has been utilized to kill virus by enhancing NC surface vibration 10 or absorbing microwave under resonant conditions. 11 In most systems consisting of free and embedded NCs, Lamb's theory 12 is suitable for explaining the frequencies of surface acoustic modes 1,2,4-7 but the damping ͓full width of half maximum ͑FWHM͔͒ cannot be obtained by this theory.…”