Photothermal Effects and Heat Conduction in Nanogranular Silicon Films

Abstract

We present results on the photothermal (PT) and heat conductive properties of nanogranular silicon (Si) films synthesized by evaporation of colloidal droplets (drop-casting) of 100 ± 50 nm-sized crystalline Si nanoparticles (NP) deposited on glass substrates. Simulations of the absorbed light intensity and photo-induced temperature distribution across the Si NP films were carried out by using the Finite difference time domain (FDTD) and finite element mesh (FEM) modeling and the obtained data were compared with the local temperatures measured by micro-Raman spectroscopy and then was used for determining the heat conductivities k in the films of various thicknesses. The cubic-to-hexagonal phase transition in Si NP films caused by laser-induced heating was found to be heavily influenced by the film thickness and heat-conductive properties of glass substrate, on which the films were deposited. The k values in drop-casted Si nanogranular films were found to be in the range of lowest k of other types of nanostructurely voided Si films due to enhanced phonon scattering across inherently voided topology, weak NP-NP and NP-substrate interface bonding within nanogranular Si films.

Liquid-Modulated Photothermal Phenomena in Porous Silicon Nanostructures Studied by μ-Raman Spectroscopy

“…Figure 4 shows the porosity dependent evolution of the thermal conductivity of porous Si layers with empty pores (being in good agreement with the experimental data published earlier [ 18 , 24 , 33 , 34 , 35 ]), and pores filled with hexadecane.…”

“…A similar photo-induced phase transition effect was already observed on other types of Si nanostructures, as reported earlier in the literature [ 35 , 37 , 38 ]. The photo-induced formation of the hex-Si phase is known to be stimulated by strong mechanical stresses, appearing in a homogeneously heated nanostructured Si-based sample.…”

Laser‐induced heating of porous Ge layers implanted with Ag+ and Cu+ ions

“…Optical excitation of bulk materials rarely leads to their significant heating, but nanostructured materials can be locally heated up to hundreds of degrees due to the action of exciting laser radiation. [1][2][3][4][5] Raman spectroscopy was widely used as a structural method for estimating the size parameters of semiconductor nanostructures. The peak associated with nanostructures is usually shifted towards lower wavenumbers due to the quantum confinement effect, [6][7][8] and it is possible to calculate the average diameter of their nanoelements.…”

The local crystallization thresholds under laser irradiation of the Cu+‐ion implanted Ge layers with various thicknesses

“…[1] This makes such thin layer structures very interesting model objects for studying the features of thermal conductivity in similar nanostructures by optical methods. [2][3][4] Among the optical approaches for studying thin layers, the most appropriate and informative tool is Raman spectroscopy. [5,6] Of special particular interest are nanoporous Ge (PGe) layers due to their rather high absorption and scattering of visible radiation.…”