Transparent Conductive Oxides and Their Applications in Near Infrared Plasmonics

Abstract

Transparent conductive oxides (TCOs) have been widely used as an important component of optoelectronic devices. They are required to exhibit high performance in both visible-range transparency and electronic conductivity simultaneously. In near infrared (NIR) wavelength, these highly doped semiconductor oxide materials exhibit a drop in their real part of dielectric permittivity from positive to negative. In other words, the epsilon-near-zero (ENZ) frequency of TCO is located in NIR spectral regime. On the other hand, the imaginary part of the permittivity is relatively low which implies less optical loss when compared to noble metals. This "metal-like" permittivity dispersion characteristic of TCOs means their capability to support surface plasmons (SPs) in the NIR regime. In this paper, a summary of various physical parameters of commonly used TCOs such as ITO, AZO, and FTO, etc., is given. These parameters include carrier density, carrier mobility, plasma frequency, and ENZ wavelength. The difference among these parameters determines their diverse performance in infrared range. In this paper, the important role of TCOs for applications in the NIR/IR wavelength ranges are reinforced, as they are demonstrated in the visible range.

Tunable Metasurfaces: The Path to Fully Active Nanophotonics

“…TCOs are available with a range of different properties. [ 123–126 ] In one particular example of using TCOs for the continuous electrical tuning of metasurfaces, Ge surrounded by Al‐doped ZnO (AZO) was used to produce a reflectance difference of over 40% with gate biases from +4 to −4 V while also displaying a large phase modulation up to 270°. [ 127 ] The devices were modeled using an effective medium theory to calculate the phase shifts.…”

Second-harmonic generation enhancement in monolayer transition-metal dichalcogenides by using an epsilon-near-zero substrate

“…It is important to note that FTO presented a relatively strong SHG component, which can only be observed in the parallel polarization configuration. This FTO SHG component is possibly an evidence of some substrate local remnant (and variable) crystallinity 58 , even though the film was produced by sputtering (see Methods), which tends to yield an amorphous material. This component is not uniform along the substrate and interferes with the TMDCs SHG signal, originating the distorted SHG patterns in the parallel configuration shown in Fig.…”

Optical Losses of Frontal Layers in Superstrate CdS/CdTe Solar Cells Using OPAL2

“…Absorption plots show higher absorption in the UV range related to excitations across the fundamental energy bands. Therefore, the next evaluation steps are conducted using 200 nm TCO material as the optimum choice for TCO material in flexible CdTe design [68,69].…”

“…Absorpti show higher absorption in the UV range related to excitations across the fundame ergy bands. Therefore, the next evaluation steps are conducted using 200 nm TC rial as the optimum choice for TCO material in flexible CdTe design [68,69]. In solar cell design, configuration of the ITO layer is not just a highly tran material over the visible light region; high conductivity is also required.…”