Exploring the dielectric function of platinum

Despite many years studies, there is still a significant discrepancy between the first-principles calculations and experimental measurements of platinum's optical properties in the existing literature. In this work, we explain the reason for this discrepancy by combining spectroscopic ellipsometry (SE) measurements and density functional theory (DFT) calculations. Pt films were fabricated by electron beam physical vapor deposition, and their properties were measured with SE. The dielectric function and consequently plasma frequency, relaxation constant, and interband spectra were then retrieved using the Drude-Lorentz model. DFT calculations of plasma frequency and interband contribution (Lorentz part) in random-phase approximation show a good match between the experimental and theoretical parameters, providing valuable insights into the electronic and optical properties of platinum. The effect of possible defects is studied with DFT as well. The data for the dielectric function of platinum is tabulated in the spectral range of 200--3500 nm and offers important implications for its potential applications in optoelectronic devices and plasmonic systems. The long-standing discrepancy between theory and experiment is explained by insufficient and inaccurate data in the infrared region of the spectrum, which is important for reliable separation of inter and intraband transition contributions to the spectrum and determination of the plasma frequency.