Ultra-low-loss metal films with high-quality single crystals are in demand as the perfect surface for nanophotonics and quantum information processing applications. Silver is by far the most preferred material due to low-loss at optical and near infrared (near-IR) frequencies. In a recent study now published on Scientific Reports, Ilya A. Rodionov and an interdisciplinary research team in Germany and Russia reported a two-step approach for electronic beam evaporation of atomically smooth single crystalline metal films. They proposed a method to establish thermodynamic control of the film growth kinetics at the atomic level in order to deposit state-of-the-art metal films.
The researchers deposited 35 to 100 nm thick, single-crystalline silver films with sub-100 picometer (pm) surface roughness with theoretically limited optical losses to form ultrahigh-Q nanophotonic devices. They experimentally estimated the contribution of material purity, material grain boundaries, surface roughness and crystallinity to the optical properties of metal films. The team demonstrated a fundamental two-step approach for single-crystalline growth of silver, gold and aluminum films to open new possibilities in nanophotonics, biotechnology and superconductive quantum technologies. The research team intends to adopt the method to synthesize other extremely low-loss single-crystalline metal films.
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