Laser heating effect on Raman spectra of Si nanocrystals embedded into SiOx matrix

Abstract

Abstract. Influence of combined size confinement effect and effect of local laser heating on the first-order Raman spectrum of silicon nanocrystals embedded into SiO x matrix has been studied. Increase of the local temperature of Si nanocrystals caused by laser illumination with the power density up to 10 mW/m 2 was estimated from the ratio of the Stokes/anti-Stokes peak intensities. Almost linear dependence of nanocrystals local temperature on the power density of exciting radiation with a rate of 63.6 Km 2 /mW has been found. The phonon line shape at power densities, when no laser heating effect is registered, was shown to be described well within the correlation length model of phonon confinement of Si nanocrystals with the size L = 9.2 nm. Observed phonon softening and broadening with increase of the exciting power density is considered as temperatureinduced vibration anharmonicity with the decay of optical phonons through three-and four-phonon processes and corresponding anharmonic constants have been determined.

3D Core–Shell TiO2@MnO2 Nanorod Arrays on Microcantilevers for Enhancing the Detection Sensitivity of Chemical Warfare Agents

“…They correspond, respectively, to the (Mn–O) stretching vibration in the basal plane of the MnO 6 sheet and to the symmetric stretching vibration (Mn–O) of the MnO 6 groups . The broad peak between 900 and 1000 cm –1 corresponds to the superposition of three transverse optical phonons ∼2TO­(X), 2TO­(W), and 2TO­(L) of silicon. , We observed that the intensity of the bands associated to Si and TiO 2 decreases after the synthesis of MnO 2 nanoflakes, confirming the covering of TiO 2 NRs by this nanomaterial. XRD and Raman results show that the low temperature of the synthesis leads to amorphous MnO 2 nanoflakes.…”

Review of Existing Standards, Guides, and Practices for Raman Spectroscopy

“…88 The effect of local laser heating in the Raman spectrum of Si nanocrystals was also confirmed by Nikolenko. 89 Confocal micro-Raman spectroscopy is used because of its increased optical and depth resolution. Sampling depth, especially in transparent materials, has a direct effect in lateral resolution.…”

“…88 The effect of local laser heating in the Raman spectrum of Si nanocrystals was also confirmed by Nikolenko. 89…”

Raman Measurements of Optical Phonon Scattering in Sub-Micron Si_(1-x)Ge_x Films

“…However, the exact physical mechanism for this asymmetry is not explained in the literature beyond the phenomenological PCM model. Several studies have questioned the phonon confinement model, suggesting that the asymmetry could instead originate from laser heating [159][160][161][162][163][164], or Fano resonance [165][166][167][168].…”

“…Other studies challenged the assertion that the asymmetry is due to Fano resonance and contend that it is instead caused by inhomogeneous laser heating [159][160][161][162][163][164]. These studies hypothesize that due to the finite spot size of the laser and finite penetration depth, the probe laser creates large temperature gradients.…”