Growing atomically smooth, single-crystalline silver thin films is of utmost importance to meet the high optical performance requirements of several applications. In particular, this is required to reduce undesired losses in devices such as plasmonic circuits, plasmonic sensors, or solar cells. However, growing such high quality films is not a straightforward task because silver is a fast-diffusing species prone to forming rough surfaces rather than smooth ones. In this paper, Aleksandr S. Baburin and coworkers report a method to grow atomically smooth, oriented silver thin films using an electron-beam evaporation setup. Their method consists in two steps. First, a silver seed layer is deposited on a single-crystalline silicon substrate held at 350°C. Second, this substrate is cooled to room temperature and more silver is deposited to form a 100-nm–thick continuous film. The so-formed silver film shows reduced losses, enabling surface plasmon polariton propagation with a record characteristic length near 200 µm. This is measured by monitoring, in a far-field optical microscope, the intensity of light scattered by nanogrooves located along the plasmon propagation path. Such a length is twice that of the current state-of-the-art and is close to the theoretical limit.
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