Coupling of deep-ultraviolet photons and electrons

Abstract

Recent advances in deep-ultraviolet (DUV) spectroscopy and related technologies have targeted the observation of photon–electron coupling in widebandgap materials. The energy of a single photon of DUV light is high enough to excite an electron to the first or higher electronic levels of a material. This is the main drawback of DUV spectroscopy for soft materials since higher-order excitations are often followed by photodamage. At the same time, high photon energy can be an advantage from the viewpoint of energy conversion between photons and electrons in a wide-bandgap material. DUV spans a marginal range of wavelengths that can occur under atmospheric pressure in sunlight on Earth. Its high photon energy and availability are expected to lead to great applications in DUV photonics. As mentioned in the previous chapter, photons couple with free electrons in metals at the nanometer scale, exhibiting a localization and enhancement effect known as localized surface plasmon resonance (LSPR). LSPR has been exploited in many scientific and industrial fields, such as sensors, optical waveguides, high-sensitivity optical detection, and high-resolution microscopy (Willets and Van Duyne, Rev Phys Chem 58:267–97, 2007). In this chapter, I review some important aspects of DUV photons, mainly focusing on DUV-LSPR applications in, for example, photocatalysis, photovoltaic devices, and light-emitting diodes (LEDs), including enhancement mechanisms such as carrier generation, photoexcited lifetime modifications, emission pattern controls, and coulombic forces.