Cheng-Chung Jaing

In this study, indium–tin oxide (ITO)/Nb-doping TiO₂ (TNO) double-layer transparent conductive oxide (TCO) films deposited using DC magnetron sputtering were used as a surface anti-reflection layer with an overall thickness of 100 nm for double-layer films. The simulated results showed that ITO and TNO thickness combinations of 90 nm/10 nm, 80 nm/20 nm, and 70 nm/30 nm had a higher transmittance and lower reflectance than others in the visible wavelength range. Compared to the single-layer ITO films, for ITO/TNO films deposited on the glass and silicon substrates with an optimum thickness of 80/20 nm, the reflectance was reduced by 5.06% and 4.63%, respectively, at the central wavelength of 550 nm and crystalline silicon photo response wavelength of 900 nm. Moreover, the near-infrared reflectance of the double-layer ITO/TNO with thickness combinations of 90 nm/10 nm, 80 nm/20 nm, and 70 nm/30 nm, when deposited on silicon substrates, was obviously improved by the graded refractive index lamination effect of air (1)/ITO (1.98)/TNO (2.41)/Si (3.9).

In this study, WO₃–Nb₂O₅ electrochromic films and an ITO/WO₃–Nb₂O₅/Nb₂O₅/NiVO_x/ITO all-solid-state electrochromic device were deposited using fast-alternating bipolar-pulsed magnetron sputtering using tungsten and niobium targets. The influence of different sputtering powers from the niobium target on the refractive index, extinction coefficient, optical modulation, coloration efficiency, reversibility, and durability of the WO₃–Nb₂O₅ films is discussed. The aim of this work is to find the suitable Nb proportion to increase durability and less negative effect in the electrochromic performance of Nb₂O₅-doped WO₃ films. The lifetime of the WO₃–Nb₂O₅ films is 4 times longer than pure WO₃ films when the sputtering power of the Nb target is higher than 250 W. The results show that WO₃–Nb₂O₅ composite films used for an all-solid-state electrochromic device can sustain over 3 × 10⁴ repeated coloring and bleaching cycles while the transmission modulations can be kept above 20%. The coloring and bleaching response times are 7.0 and 0.7 s, respectively.

Alumina-doped zinc oxide (AZO) films have wide range of applications in optical and optoelectronic devices. AZO films have advantage in high transparency, high stability to hydrogen plasma and low cost to alternative ITO film. AZO film was prepared by direct-current (DC) magnetron sputtering from ceramic ZnO:Al₂O₃ target. The AZO films were compared in two different conditions. The first is substrate heating process, in which AZO film was deposited by different substrate temperature, room temperature, 150 °C and 250 °C. The second is vacuum annealing process, in which AZO film with deposited at room temperature have been annealed at 250 °C and 450 °C in vacuum. The optical properties, electrical properties, grain size and surface structure properties of the films were studied by UV-VIS-NIR spectrophotometer, Hall effect measurement equipment, x-ray diffraction, and scanning electron microscopy. The resistivity, carrier mobility, carrier concentration, and grain size of AZO films were 1.92×10^-3 Ω-cm, 6.38 cm²/Vs, 5.08×10²⁰ #/cm³, and 31.48 nm respectively, in vacuum annealing of 450 °C. The resistivity, carrier mobility, carrier concentration, and grain size of AZO films were 8.72×10^-4 Ω-cm, 6.32 cm²/Vs, 1.13×10²¹ #/cm³, and 31.56 nm, respectively, when substrate temperature was at 250 °C. Substrate heating process is better than vacuum annealed process for AZO film deposited by DC Magnetron Sputtering.

A synthesis method based on a recurrent circling search algorithm is proposed for obtaining a very low loss normal-incidence broadband visible (vis) or near-infrared (NIR) antireflection (AR) coating design. Its design algorithm is quite simple and straight, and a fairly high resultant AR performance can also be achieved. It is shown that the mean residual reflectance of a broadband vis AR coating design in the range of 400–750 nm and a broadband NIR AR coating design in the range of 800–1600 nm, obtained by the recurrent circling search method using a two-material system, can be reduced to below 0.035 and 0.063%, respectively.

Normally metallic films are required for solar energy and display related coatings. To increase the absorbing efficiency or contrast, it is necessary to apply an antireflection coating (ARC) on the metal substrate. However, the design of a metal substrate is very different from the design of a dielectric substrate, since the optical constant of metallic thin film is very dependent on its thickness and microstructure. In this study, we design and fabricate ARCs on Al substrates using SiO₂ and Nb₂O₅ as the dielectric materials and Nb for the metal films. The ARC successfully deposited on the Al substrate had the following structure: air/SiO₂/Nb₂O₅/Metal/Nb₂O₅/Al. The measured average reflectance of the ARC is less than 1% in the visible region. We found that it is better to use a highly refractive material than a low refractive material. The thickness of the metallic film can be thicker with the result that it is easier to control and has a lesser total thickness. The total thickness of the ARC is less than 200 nm. We successfully fabricated a solar absorber and OLED device with the ARC structure were successfully fabricated.