A scanning thermal microscope (SThM) in the dc regime was used to study the thermal conductivity of homogeneous in-depth meso-porous silicon in the form of thin films on a monocrystalline silicon substrate. Measurements for different film porosities (30–80%) and thicknesses (100 nm–8 µm) were performed in order to estimate the influence of both layer porosity and thickness on the thermal conductivity values of porous silicon (PS). An analytical model predicting the SThM measurement in the case of ultra-thin monolayered samples was used to calibrate the technique, to analyse experimental data and to determine the thermal conductivity of meso-porous layers. Effective thermal conductivity of meso-PS films was found to decrease when the porosity increases. The effective thermal conductivities measured for thick porous layers (several µm) are in good accordance with those measured by micro-Raman-spectroscopy on bulk meso-PS samples. For submicrometric thicknesses (<1 µm), the effective thermal conductivity of layers decreases significantly with decreasing layer thickness due to the increased sensitivity of measurements to the thermal resistance of the film/substrate interface. An intrinsic thermal conductivity of PS was calculated independently of the film thickness and the values of interfacial thermal resistances were thus estimated. From the apparatus point of view, the results obtained show that the depth being sensed is of the order of a few micrometres for insulating materials and depends on the thermal conductivity of the films.

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Localization of quantum dots (QDs) in the vicinity of metal nanoparticles (NPs) is known as one of the most efficient ways to increase their photoluminescence (PL). Despite the important recent advances achieved in II-VI QDs, only a seven-fold plasmon-induced PL enhancement is reported for Si QDs. In our paper we show that the plasmon-induced strong local PL enhancement of Si QDs in an SiN matrix can reach a 60-fold gain level. This important result was achieved on original tunable "nano-Ag/SiN(X)" plasmonic structures. In particular, we show that (i) localization of Si QDs in hot spot regions created by several randomly arranged Ag NPs and (ii) careful tuning of the multi-polar plasmon bands of Ag NPs to match resonant absorption and emission wavelengths of Si QDs, lead to the important enhancement of their PL intensity.