Study On Polaritons By STEM-EELS Technique

With the rapid development of plasma technology,plasma technology has played an important role in the military,which has greatly promoted the development of military modernization,long-range and science and technology.Plasma technology is mainly used in plasma interference,plasma sheath,plasma wake,plasma stealth and plasma mirror radar.The absorption of electromagnetic waves by the surface plasmon resonance model is the key to the stealth technology of tanks,ships and aircraft in the future.In this paper,the surface plasmon of the submicron structure of gold thin films has been studied by means of scanning transmission electron microscopy((STEM))and focused ion beam(FIB).The length,spacing and shape of the self-machined double-slit system are changed,and the influence of these factors on the surface plasmon and the coupling mechanism of the double-slit system are studied.The higher-order mode can be measured with the change of the slit length,and the fifth-order mode can be observed when the slit length is 1000 nm.By changing the slot spacing,it is found that this does not change the propagation direction of the wave,but has an effect on the wave intensity,and the coupling effect basically disappears when the slot spacing is larger than that of 700 nm.A new mode can be observed by changing the shape,and the propagation path of the wave can be adjusted according to the shape of the sample,so that the spectral range can be effectively adjusted according to the shape of the sample.The surface phonon polaritons of four polar materials such as sapphire,gallium nitride,silicon carbide and aluminum nitride were studied based on STEM-EELS.On the one hand,the lack of suitable light sources and detectors hinders the understanding of the properties of polar materials;on the other hand,the signal strength detected by optical means is relatively weak,so it is difficult to get a good signal-to-noise ratio for a single nano-material.The surface phonon polaritons are measured by scanning STEM-EELS method,and the spatial information and energy information are obtained at the same time,and the signal-to-noise ratio is perfect.By reducing the high voltage of the scanning transmission electron microscope and improving the energy resolution,the FWHM of the zero loss peak is reduced from 10 mev to 4.3mev.The surface phonon polaritons of the above four materials are measured and analyzed.Among the above four materials,the AlN material was deeply studied.And the new angular mode 93 mev and surface mode 102 mev are found by changing the sample size,and the effects of different size and thickness on the surface phonon polariton are analyzed by simulation.The simulation results show that with the increase of aspect ratio,the interference mode gradually appears,and the higher-order mode becomes clear gradually;when the aspect ratio is 2: 4,the interference mode gradually splits,and with the increase of length,it is obvious that the interference mode propagates from the middle to both ends,the second-order mode moves to the low-energy region,and the surface mode 102 mev does not change with the length.With the increase of the thickness of AlN,there will be a new signal peak,and gradually move to the low energy region,covering the edge of the whole nanopillar.