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We demonstrate experimentally that Tamm plasmons in the near-IR can be supported by a dielectric mirror interfaced with a metasurface, a discontinuous thin metal film periodically patterned on the sub-wavelength scale. More crucially, not only do Tamm plasmons survive the nano-patterning of the metal film, but they also become sensitive to external perturbations, as a result. In particular, by depositing a nematic liquid crystal on the outer side of the metasurface we were able to red-shift the spectral position of Tamm plasmon by 35 nm, while electrical switching of the liquid crystal enabled us to tune the wavelength of this notoriously inert excitation within a 10 nm range.A Tamm plasmon (TP) is a localized resonant optical state, a quasi-particle, which exists at the interface between a metal and a dielectric (or semiconductor) Bragg mirror. It was theoretically predicted in [1] and experimentally observed in [2]. The TP dispersion lies completely within the light cone and therefore, in contrast to an ordinary surface plasmon polariton, a Tamm plasmon can be excited with both TE and TM polarized light at any angle of incidence [1]. Another advantage of a Tamm plasmon over a surface plasmon polariton is that the former appears to be almost insensitive to dissipative losses in the metal film since its electromagnetic fields are localized predominantly in the non-absorbing Bragg mirror [3]. Because of its robust nature, a Tamm plasmon has been regarded as a viable alternative to conventional surface plasmons in a wide range of applications, including refractive index sensing, optical switches, semiconductor lasers, and temperature sensors [4,5,6,7,8,9,10]. For many practical applications it is important to realize an external dynamic control over the TP wavelength. Such a task, however, presents a formidable challenge given that the fields of a Tamm plasmon reside inside the Bragg mirror and, therefore, are very difficult to access from the outside. Correspondingly, most of the approaches proposed so far involved the integration of a control element into the very structure of the Bragg mirror [4,6,11,12,13,14], which may not always appear feasible. It has also been shown that the wavelength of a Tamm plasmon could change (although irreversibly) as a result of the lateral confinement of its fields achieved by patterning the metal film on the microscale [3,15,16].In this Letter we report on the first experimental observation of a near-IR Tamm plasmon at the interface between a Bragg mirror and a nano-patterned metal film acting as a nondiffracting optical metasurface. We found that the discrete framework of the metasurface exposed Tamm plasmon to external perturbations, such as changes of the refractive index in an adjacent medium, which enabled us to dynamically control the wavelength of this weakly coupled optical state in a simple yet efficient way.

Reactive high-power impulse magnetron sputtering was used to deposit HfO 2 films on Si substrates using a voltage pulse duration, t 1 , from 100 to 200 µs and an deposition-averaged target power density, , from 7.2 to 54 Wcm-2. The effects of these processing parameters on the microstructure and properties of the films were studied by atomic force microscopy, nanoindentation, X-ray diffraction, electron diffraction and high-resolution transmission electron microscopy. Four HfO 2 films were prepared with (1) t 1 = 100 µs, = 7.2 Wcm-2 (T100S7), (2) t 1 = 200 µs, = 7.3 Wcm-2 (T200S7), (3) t 1 = 200 µs, = 18 Wcm-2 (T200S18) and (4) t 1 = 200 µs, = 54 Wcm-2 (T200S54). All films were found to be composed of an interlayer next to the Si interface followed by a nano-columnar structure layer. The interlayer structure of the films was found to contain a population of lower density nanoscale regions. A reduction in in films T200S54, T200S18, T200S7 and T100S7 caused an increase in the interlayer thickness and a decrease in the width of the nano-columnar structures from ~46 nm to ~21 nm. This microstructural change was accompanied by a concomitant change of the grain boundary

Reactive high-power impulse magnetron sputtering discharge has been studied experimentally combining optical emission, absorption, and laser-based diagnostic techniques. The quantification of the atomic ground state densities is performed using optical emission spectroscopy. Hysteresis behavior as a function of molecular oxygen flow fraction in Ar-O2 mixture has been observed for numerous discharge parameters, such as the ground state density of O atoms, density of the sputtered atoms and ions, Ar metastables, etc. The obtained atomic number densities are found to be in full agreement with the known models of reactive sputter deposition. The relevant plasma kinetic mechanisms influencing the measured trends are analyzed.

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