Polarization and Incidence Angle Independent Low-Profile Wideband Metamaterial Electromagnetic Absorber Using Indium Tin Oxide (ITO) Film

We use indium tin oxide (ITO), one of the representative resistive materials, for the implementation of a metamaterial electromagnetic (EM) absorber with a high absorbance in a wide frequency range. Highly symmetrical split ring resonators made of ITO film are deposited on the polyethylene terephthalate with transparent and flexible features, and such a configuration causes the proposed absorber to be insensitive to polarization and incidence angles. The proposed absorber, with a profile of only 0.171, exhibits a wideband absorbance of 7.2 GHz to 27 GHz, with a 90% absorption criterion. A prototype is built, and all the computed expectations from the full-wave EM simulations in this work are verified experimentally.

Silicon on-chip Electro-optic Modulation With Ito Film Stacks

Indium tin oxide (ITO) platform is one of the promising solutions towards state-of-the-art integrated optical modulators for silicon photonics applications. We demonstrate the way to obtain both high extinction ratio and low insertion loss electro-optic modulation with ITO-based film stack. By investigating e-beam evaporated 20 nm-thick ITO films with amorphous, heterogeneously crystalline, homogeneously crystalline with hidden coarse grains and pronounced coarsely crystalline structure, a low carrier concentration (from 1·1020 to 2·1020 cm-3) is achieved. The mechanism of oxygen migration in ITO film crystallization is proposed based on morphological features observed under low-energy growth conditions. We compare three electro-optic modulator active elements (current-voltage and optical characteristics) and reach strong ITO dielectric permittivity variation induced by charge accumulation/depletion (Δn = 0.199, Δk = 0.240 at λ = 1550nm under ±16V). Our simulations and experimental results demonstrate the unique potential to create integrated GHz-range electro-optical modulators with sub-db losses.

Preparation of High-Performance Metal-Free UV/Near Infrared-Shielding Films for Human Skin Protection

A series of metal-free UV/near infrared (NIR)-shielding coatings are successfully fabricated by shielded cathodic arc plasma evaporation (CAPE) and substrate-biased RF magnetron sputtering processes. The UV/NIR-shielding coatings comprising quarter-wave stacks of TiO2/SiO2 multilayers and high-conductivity sputter-deposited ITO films with a thickness in the range of 200–600 nm could block IRA and IRB radiations, respectively. The total thicknesses of UV/near infrared-shielding films are in the range from 375 nm to 1513.8 nm. The anatase-phase TiO2 films with absorption edge located at ∼375 nm were deposited by shielded CAPE at ∼100 °C. Further, the well-crystallized ITO films were found to have high free-electron concentrations (1.12 × 1021 cm−3), resulting in strong absorption of IRB due to the plasmon resonance absorption. The optimal optical design and ITO film thickness were investigated, and the TiO2(SiO2/TiO2)3 multilayer combined with an ITO film thickness of 400 nm was found to provide a high NIR-shielding rate of 94.8%, UVB to UVA-shielding rate of 92.7%, and average visible light transmittance of 68.1%. Further, human skin cells protected by a UV/NIR-shielding coating showed significantly decreased reactive oxygen species generation and inflammatory cytokine expression as compared to those of unprotected cells. The results demonstrate that the development of multifunction coatings have potential for transparent heat insulation windows and human skin protection against UV/IR radiations.

A Nonreciprocal Angular Selective Absorber with the Special Multilayer Structure

Due to the orderly design of the special anti-reflection structure and the absorption structure, the one-dimensional layered periodic structure has a good impedance matching in a certain frequency band and a large-angle range, providing for the realization of an angular selective absorber (ASA) with a high rectangle coefficient. For the sake of obtaining excellent absorptivity, the indium tin oxide (ITO) film is used, and it also acts as a function of tuning the absorption angle range (AAR) of the ASA by adjusting the plasma frequency. The proportional relationship between the thickness of the dielectric layers is also discussed to satisfy a good absorption function. At the same time, the ASA also possesses productive nonreciprocal performance (NP) and can also be controlled by the plasma frequency. The transfer matrix method is used for numerical simulation. Our special tunable ASA with the NP is relatively rare in previous studies, which can be applied to optical communications and military fields. Furthermore, we hope that the design we proposed can provide new possibilities for the development of the ASAs.

IMPROVEMENT IN STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF ITO FILM THROUGH AlN AND HfO2 BUFFER LAYERS

Indium Tin Oxide (ITO) films were deposited on glass substrate using radiofrequency (RF) magnetron sputtering technique. To improve the physical characteristics of the ITO film, AlN and HfO2 buffer layers were deposited on glass prior to the film deposition. The ITO/glass, ITO/AlN/glass and ITO/HfO2/glass films were annealed using CO2 laser and electrical oven heating methods. The crystallinity of the ITO film was improved due to the incorporation of AlN and HfO2 buffer layers and also by the post-deposition annealing process. The optical transmittance of the ITO was also increased due to the presence of the buffer layers. Similarly, the annealed ITO films grown on buffer layers exhibited lower values of the sheet resistance as compared to the film deposited without buffer layers. The laser annealing technique was more found to be more effective in reducing the ITO sheet resistance.