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In 1−x Sn x (x = 0.06−0.51) alloy films were deposited on Si substrates by electron beam evaporation and characterized by X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and spectroscopic ellipsometry. The dielectric functions of the In 1−x Sn x alloy films were obtained in the energy range from 1.55 to 4.13 eV based on the spectroscopic ellipsometry measurements, and it is believed that a solid−solid phase transitions led to changes in ε. The phase diagram of nanometer-sized particles is different from that of the bulk material, and this phenomenon can be explained by the surface stress of the particles. The effects of alloying on the electronic band structure were studied from the perspective of first-principles calculations.

Size-dependent melting properties of nanometer-sized Indium particles with size ranging from 25.5 to 68.1 nm were studied by spectroscopic ellipsometry, and a critical size is found between 42.4 and 44.9 nm. The melting points of nanometer-sized Indium particles with size larger than critical size are almost the same as that of bulk indium, while no clear melting point was found for indium particles with size smaller than the critical size. A knee point defined as the average melting point was introduced to characterize the melting of these smaller size particles, and it depresses with decreasing size. The mechanism for size dependent melting of indium particles was discussed. This work shows that spectroscopic ellipsometry is an effective optical tool for characterizing the melting of nanometer-sized metal particles.

Bismuth selenide (BiSe), with a wide bulk band gap and single massless Dirac cone at the surface, is a promising three-dimensional topological insulator. BiSe possesses gapless surface states and an insulator-like bulk band gap as a new type of quantum matter. Different BiSe nanostructures were prepared using electron beam evaporation with high production efficiency. Structural investigations by energy-dispersive X-ray analysis, scanning electron microscopy, and X-ray diffraction revealed the sample stoichiometries and the structural transition mechanism from nanocrystals to nanoflakes. The optical properties systematically probed and analyzed by spectroscopic ellipsometry showed strong dependence on the nanostructures and were also predicted to have structure-modifiable technological prospects. The optical parameters, plasma frequencies, scattering rates of the free electrons, and optical band gaps were related to the topological properties of the BiSe nanostructures via light-matter interactions, offering new opportunities and approaches for studies on topological insulators and spintronics. The high-quality BiSe nanostructures provide advantages in exploring novel physics and exploiting prospective applications.

The temperature dependent optical properties of tin film from solid to liquid were studied by spectroscopic ellipsometry and ab initio molecular dynamics simulations. The dielectric function of liquid Sn was different from solid, and an interband transition near 1.5 eV was easily observed in solid while it apparently disappeared upon melting. From the evolution of optical properties with temperature, an optical measurement to acquire the melting point by ellipsometry was presented. From first principles calculation, we show that the local structure difference in solid and liquid is responsible for this difference in the optical properties observed in experiment.