This work probes radiative polaritons in thin oxide layers as a mean to capture and absorb broadband infrared radiation and transform it into heat. A heat recovery mechanism, based on the Seebeck effect, is used as the tool of the investigation. Heat production challenges the current understanding which views the excitation of radiative polaritons as only accompanied by the emission of electromagnetic radiation. The heat recovery mechanism presented here can inspire the design of infrared energy harvesting devices, similar to photovoltaic cells, and other devices to convert energy from a wide range of the electromagnetic radiation spectrum using thermoelectric power generators. V

The mechanism that activates a bi-junction power generator under the effects of heat is the Seebeck effect, that is, the production of voltage difference DV(t) is directly proportional to the temperature difference DT(t) between the ''hot'' and ''cold'' junctions of the device. This phenomenon is well established and is known as thermoelectric power generation. Here, it is shown that, instead, the causal and linear relationship between DV(t) and DT(t) is lost when continuous broadband infrared (CB-IR) radiation illuminates a bi-junction power generator in an insulated compartment. The observed phenomenon is IR power generation. Heat transfer calculations fail in explaining the experimental trends. The interaction between CB-IR radiation and the charge carriers in the bi-junction power generator might play a role in the DV(t) production, depending upon the geometry of the experimental setup. The longitudinal propagation of collective oscillations, for example, polaritons, in the plates protecting the ''hot'' and ''cold'' junctions of the bi-junction power generator could explain the DV(t) production and the characteristic time constants. The findings should be considered in the design, fabrication, and improvement of thermopiles, power meters, and IR energy-harvesting devices.

Upon excitation in thin oxide films by infrared radiation, radiative polaritons are formed with complex angular frequency ω, according to the theory of Kliewer and Fuchs (1966 Phys. Rev. 150 573). We show that radiative polaritons leak radiation with frequency ω(i) to the space surrounding the oxide film. The frequency ω(i) is the imaginary part of ω. The effects of the presence of the radiation leaked out at frequency ω(i) are observed experimentally and numerically in the infrared spectra of La(2)O(3) films on silicon upon excitation by infrared radiation of the 0TH type radiative polariton. The frequency ω(i) is found in the microwave to far infrared region, and depends on the oxide film chemistry and thickness. The presented results might aid in the interpretation of fine structures in infrared and, possibly, optical spectra, and suggest the study of other similar potential sources of electromagnetic radiation in different physical scenarios.

Due to their unique properties, nano-composite polyhedral oligomeric silsequioxane (POSS) copolymer films are attractive for various applications. Here we show that their natural hydrophobic character can become hydrophilic when the films are modified by a thin oxide layer, up to 8 nm thick, prepared using atomic layer deposition. A proper choice of the deposition temperature and thickness of the oxide layer are required to achieve this goal. Unlike other polymeric systems, a marked transition to a hydrophilic state is observed with oxide layers deposited at increasing temperatures up to the glass transition temperature ($110 C) of the POSS copolymer film. The hydrophilic state is monitored through the water contact angle of the POSS film. Infrared absorbance spectra indicate that, in hydrophilic samples, the integral of peaks corresponding to surface Al-O (hydrophilic) is significantly larger than that of peaks linked to hydrophobic species.

Through simulations, this work explores the effects of conducting, semiconducting, and insulating substrates on the absorption of infrared radiation by radiative polaritons in oxide layers with thicknesses that range from 30 nm to 9 μm. Using atomic layer deposition, oxide layers can be formed in the nanometer scale. Our results suggest that the chemistry and conductivity of the substrate determine the amount of absorption by radiative polaritons in oxide layers thinner than the skin depth. The effects of the chemistry and conductivity of the substrate are especially effective for oxide films thinner than about 250 nm, which we label as the substrate sensitive thickness of the oxide film.