Ricerc@Sapienza

This paper shows a detailed analysis of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO2) film deposited on silicon wafer. The vanadium dioxide phase transition is studied in the wide mid-infrared range 2-12 μm, by analyzing the transmittance and the reflectance measurements, and the calculated emissivity from the sample. The temperature behavior of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in vanadium dioxide which has been explained by applying the Maxwell Garnett effective medium approximation theory.

This paper studies the IR properties of a VO2-based multilayer structure with an emittance that increase with the temperature. A good tunability of the emissivity in long-wave infrared spectral region (8–12 µm) has been detected, with a positive emissivity differential of about 0.2. The transition of the long wave emissivity ε with the temperature is fully reversible according to a hysteresis cycle, with a transition temperature of 67 °C and a thermal bandwidth of only 8 °C. The multilayer structure also shows two emission peaks both in the heating cycle and in the cooling cycle.

Phase-transition materials provide exciting opportunities for controlling optical properties of photonic devices dynamically. Here, we systematically investigate the infrared emission from a thin film of vanadium dioxide (VO2). We experimentally demonstrate that such thin films are promising candidates to tune and control the thermal radiation of an underlying hot body with different emissivity features. In particular, we studied two different heat sources with completely different emissivity features, i.e. a black body-like and a mirror-like heated body.