Optical and structural properties of silicon‐rich silicon oxide films: Comparison of ion implantation and molecular beam deposition methods

Nikitin, Timur; Aitola, Kerttu; Новиков, С. В.; Räsänen, Markku; Velagapudi, Rama; Sainio, Jani; Lahtinen, Jouko; Mizohata, Kenichiro; Ahlgren, T.; Khriachtchev, Leonid

doi:10.1002/pssa.201127028

Cited by 12 publications

(21 citation statements)

References 35 publications

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“…It should be mentioned that not all the Si excess forms Si-nc seen in the Raman spectra, producing absorption and measured as elemental Si by XPS. A substantial part of Si excess forms Si suboxides and very small Si particles; moreover, a part of the Si particles is amorphous, that is, the Si crystallization is not complete after furnace annealing3536. The values obtained for absorption coefficient and refractive index are similar to those measured previously for SiO x films with x from ~1.3 to 1.6 (volumetric proportion of elemental Si from ~10 to 4%)35.…”

Section: Resultssupporting

confidence: 84%

“…The absorption coefficient and Raman intensity proportionally correlate with each other, increasing with the Si excess. These parameters are known to be proportional to the amount of elemental (‘metallic’) Si measured by X-ray photoelectron spectroscopy (XPS)3536. The refractive index also increases with the amount of elemental Si.…”

Section: Resultsmentioning

confidence: 99%

“…According to the deposition parameters, the O/Si concentration ratio x was estimated in the present sample from 1.5 (coordinate 0) to 1.8 (coordinate 7 cm). The deposition procedure was previously tested for similar samples using XPS and time-of-flight elastic recoil detection analysis, and these methods systematically showed larger Si concentrations ( x smaller by 10–20%), which is possibly connected with the complex processes of deposition chemistry3536.…”

Section: Methodsmentioning

confidence: 99%

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Giant Raman gain in silicon nanocrystals

et al. 2012

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Nanostructured silicon has generated a lot of interest in the past decades as a key material for silicon-based photonics. The low absorption coefficient makes silicon nanocrystals attractive as an active medium in waveguide structures, and their third-order nonlinear optical properties are crucial for the development of next generation nonlinear photonic devices. Here we report the first observation of stimulated Raman scattering in silicon nanocrystals embedded in a silica matrix under non-resonant excitation at infrared wavelengths (~1.5 μm). Raman gain is directly measured as a function of the silicon content. A giant Raman gain from the silicon nanocrystals is obtained that is up to four orders of magnitude greater than in crystalline silicon. These results demonstrate the first Raman amplifier based on silicon nanocrystals in a silica matrix, thus opening new perspectives for the realization of more efficient Raman lasers with ultra-small sizes, which would increase the synergy between electronic and photonic devices.

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Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Giant Raman gain in silicon nanocrystals

et al. 2012

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“…In this section, we describe the properties of SiO x ( x < 2) films on silica substrates for different annealing temperatures (400–1200 °C) and Si contents ( x from ~1.3 to ~1.98) [ 115 , 116 , 117 , 118 ]. The SiO x films (thickness from ~1.5 to ~2.5 μm) are deposited on silica substrates by MBD.…”

Section: Resultsmentioning

confidence: 99%

Optical and Structural Properties of Si Nanocrystals in SiO2 Films

Nikitin

Khriachtchev

2015

Nanomaterials

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Optical and structural properties of Si nanocrystals (Si-nc) in silica films are described. For the SiOx (x < 2) films annealed above 1000 °C, the Raman signal of Si-nc and the absorption coefficient are proportional to the amount of elemental Si detected by X-ray photoelectron spectroscopy. A good agreement is found between the measured refractive index and the value estimated by using the effective-medium approximation. The extinction coefficient of elemental Si is found to be between the values of crystalline and amorphous Si. Thermal annealing increases the degree of Si crystallization; however, the crystallization and the Si–SiO2 phase separation are not complete after annealing at 1200 °C. The 1.5-eV PL quantum yield increases as the amount of elemental Si decreases; thus, this PL is probably not directly from Si-nc responsible for absorption and detected by Raman spectroscopy. Continuous-wave laser light can produce very high temperatures in the free-standing films, which changes their structural and optical properties. For relatively large laser spots, the center of the laser-annealed area is very transparent and consists of amorphous SiO2. Large Si-nc (up to ~300 nm in diameter) are observed in the ring around the central region. These Si-nc lead to high absorption and they are typically under compressive stress, which is connected with their formation from the liquid phase. By using strongly focused laser beams, the structural changes in the free-standing films can be made in submicron areas.

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“…This belief is based on the exceptionally pronounced nonlinear optical phenomena due to the third-order electron and phonon nonlinearities in silicon nanocrystals [6]. According to recent experiments with silicon nanocrystals embedded in fused silica [6][7][8][9][10][11][12][13], the Raman gain and nonlinear Kerr coefficients of individual nanocrystals may exceed those of bulk silicon by about 6 and 4 orders of magnitude, respectively [2,7,8]. These unique physical properties are enhanced further by the capability of relatively tight (compared to silica) optical confinement by silicon-nanocrystal composites, whose refractive index may be conveniently altered in a sufficiently broad range by varying the excess of silicon in the composite [14,15].…”

Section: Introductionmentioning

confidence: 99%

Engineering optical nonlinearities in silicon–nanocrystal waveguides

et al. 2013

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The strength of the nonlinear optical effects in silicon-nanocrystal waveguides can be varied as required for applications by altering the geometry of the waveguide and the composition of its nonlinear core. By studying theoretically the geometric and composition dependencies of the mode overlap factors responsible for the nonlinear interaction between the pump and Stokes optical fields, which are separated by the Raman shift in silicon, we demonstrate that this strength can be varied in a wide range, thus offering broad opportunities for engineering optical nonlinearities in silicon-nanocrystal waveguides. The numerically calculated mode overlap factors are useful in modeling light propagation through nonlinear silicon-nanocrystal waveguides governed by the recently derived generalized nonlinear Schrödinger equations.

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Optical and structural properties of silicon‐rich silicon oxide films: Comparison of ion implantation and molecular beam deposition methods

Cited by 12 publications

References 35 publications

Giant Raman gain in silicon nanocrystals

Giant Raman gain in silicon nanocrystals

Optical and Structural Properties of Si Nanocrystals in SiO2 Films

Engineering optical nonlinearities in silicon–nanocrystal waveguides

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