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Thin-film transparent heaters (TFTHs) are gaining popularity in optoelectronics and a variety of domestic applications, including smart windows, car defrosters, and other devices. The deposition and characterization of TFTHs made of gallium-doped zinc oxide (GZO) are presented in this work. GZO thin films were deposited via pulsed laser deposition on glass substrates with varying oxygen partial pressures from 0 to 10 mTorr during deposition. The samples demonstrated very low sheet resistance values between 5 and 17 Ω/sq from 0 to 10 mTorr, respectively. UV/vis transmission spectra revealed that TFTHs have a high optical transparency above 80%. GZO-based TFTHs demonstrated a consistent and repeatable joule heating effect, with temperatures reaching 76 °C with a low input voltage of 10 V. This research could guide the future use of GZO as a transparent conducting oxide material for many potential cost-effective applications from low-powered electronics to lightweight and wearable devices. [ABSTRACT FROM AUTHOR]

A series of different high κ dielectrics such as HfO2, ZrO2, and Al2O3 thin films were studied as an alternative material for the possible replacement of traditional SiO2. These large areas, as well as conformal dielectrics thin films, were grown by the atomic layer deposition technique on a p-type silicon substrate at two different deposition temperatures (150 and 250 °C). Atomic force microscopic study reveals that the surface of the films is very smooth with a measured rms surface roughness value of less than 0.4 nm in some films. After the deposition of the high κ layer, a top metal electrode was deposited onto it to fabricate metal oxide semiconductor capacitor (MOSCAP) structures. The I–V curve reveals that the sample growth at high temperatures exhibits a high resistance value and lower leakage current densities. Frequency-dependent (100 kHz to 1 MHz) C–V characteristics of the MOSCAPs were studied steadily. Furthermore, we have prepared a metal oxide semiconductor field-effect transistor device with Al-doped ZnO as a channel material, and the electrical characteristic of the device was studied. The effect of growth temperature on the structure, surface morphology, crystallinity, capacitance, and dielectric properties of the high κ dielectrics was thoroughly analyzed through several measurement techniques, such as XRD, atomic force microscopy, semiconductor parameter analysis, and ultraviolet-visible spectroscopy. [ABSTRACT FROM AUTHOR]

Vanadium oxide (VO2) thin films have drawn significant research and development interest in recent years because of their intriguing physical origin and wide range of functionalities useful for many potential applications, including infrared imaging, smart windows, and energy and information technologies. However, the growth of highly epitaxial films of VO2, with a sharp and distinct controllable transition, has remained a challenge. Here, we report the structural and electronic properties of high quality and reproducible epitaxial thin films of VO2, grown on c-axis oriented sapphire substrates using pulsed laser deposition at different deposition pressures and temperatures, followed by various annealing schedules. Our results demonstrate that the annealing of epitaxial VO2 films significantly enhances the Semiconductor to Metal Transition (SMT) to that of bulk VO2 transition. The effect of oxygen partial pressure during the growth of VO2 films creates a significant modulation of the SMT from around room temperature to as high as the theoretical value of 68 °C. We obtained a bulk order transition ≥104 while reducing the transition temperature close to 60 °C, which is comparatively less than the theoretical value of 68 °C, demonstrating a clear and drastic improvement in the SMT switching characteristics. The results reported here will open the door to fundamental studies of VO2, along with tuning of the transition temperatures for potential applications for multifunctional devices. [ABSTRACT FROM AUTHOR]

The addition of suitable metallic dopants into the indium or zinc oxide matrix is essential to obtain transparent conducting oxide (TCO) thin films for high-performance optoelectronics devices. However, scarcity of indium is one of the major challenges for the common use of indium doped tin oxide (ITO) as a TCO material for future state-of-the-art devices. To overcome the challenge, doped zinc oxide is used an alternative material for traditional ITO and retains both high transparency and electrical conductivity. One such potential material is gallium-doped zinc oxide (GZO). GZO thin films were deposited onto glass as well as Kapton substrates using the pulsed laser deposition technique. Structural, optical, and electro-thermal properties of these films were studied to assess the performance of the films as thin-film transparent heaters. The samples show a good transmittance value greater than 85% in the visible range of the electromagnetic spectrum. At room temperature, the electrical resistivity of GZO films showed a value of 110.46 × 10−4 Ω cm on glass and 2.90 × 10−4 Ω cm on the Kapton substrate, followed by a Joule heating effect, with temperatures reaching more than 120 °C at an applied voltage of ∼12 V. This high transparency, cost-effectiveness, low sheet resistance, and small surface roughness make GZO a unique and potential candidate for various practical applications not only as a transparent electrode but also as an indium free thin-film transparent heater and an affordable transparent conducting oxide in displays. [ABSTRACT FROM AUTHOR]

One of the ways to mitigate the world energy crisis is to harvest clean and green energy from waste-heat, which is abundant, ubiquitous, and free. Energy harvesting of this waste-heat is one of the most encouraging methods to capture freely accessible electrical energy. Ferroelectric materials can be used to harvest energy for low power electronic devices, as they exhibit switchable polarization, excellent piezoelectric and pyroelectric properties. The most important characteristic of ferroelectric materials, in the context of energy harvesting, is their ability to generate electric power from a time-dependent temperature change. In this work, we grew highly c-axis oriented heterostructures of BaZr0.2Ti0.8O3 (barium zirconium titanate, BZT)/Ba0.7Ca0.3TiO3 (barium calcium titanate, BCT) on SrRuO3 (strontium ruthenate, SRO) and deposited on SrTiO3 (strontium titanate, STO) single crystalline substrate using pulsed laser deposition (PLD) technique. We investigated the structural, electrical, dielectric, and pyroelectric properties of the above-mentioned fabricated heterostructures. The wide range of θ–2θ X-ray diffraction (XRD) patterns only shows (00l) reflection peaks of heterostructures and the substrate which confirmed that the films are highly c-axis oriented. We are also capable to convert the low-grade waste-heat into electrical energy by measuring various temperature-dependent ferroelectric hysteresis loops of our nanostructure films via pyroelectric Ericsson cycles and the structures show an energy conversion density ~ 10,970 kJ/m3 per cycle. These devices exhibit a large pyroelectric current density of ~ 25 mA/m2 with 11.8 °C of temperature fluctuation and the corresponding pyroelectric coefficient of 3425 μC/m2K. Our research findings suggest that these lead-free relaxor-ferroelectric heterostructures might be the potential candidates to harvest electrical energy from waste low-grade thermal energy. [ABSTRACT FROM AUTHOR]

With a metal to insulator transition (MIT) temperature of ∼68 °C to 70 °C, which is close to room temperature (RT), vanadium oxide (VO2) has piqued interest in research communities for several applications, such as Mott-transistors and smart windows. This unique characteristic and multi-faceted application of VO2 makes it ideal for several fields, from consumer electronics to defense applications. However, despite this advantage over several other materials, VO2 has some serious shortcomings. In this paper, we attempt to address these issues, such as higher than RT transition temperature, metastability of the material, and its need for a separate heater layer to trigger the MIT, by using a stoichiometrically downgraded multi-layered structure that can both demonstrate the MIT property and serve as an embedded heater layer. This eliminates the need to use a system with a different material such as aluminum-doped zinc oxide. By using the multi-layered structure, we were able to achieve a transition temperature of ∼48 °C, which is ∼22 °C lower than the transition temperature of bulk VO2 films. We also noted a reduction of over 50% in transmission in the infra-red region by application of less than 15 V, as well as an enhancement of ∼10% in the visible region transmission beyond the MIT temperature, which demonstrates the potential of this structure to be used as an energy-efficient smart window device. [ABSTRACT FROM AUTHOR]

The metal-to-insulator transition (MIT) closest to room temperature of 68–70 °C as shown by vanadium oxide (VO2), compared with other transition metal oxides, makes it a potential candidate for smart window coating. We have successfully fabricated a potential smart window device after the optimum design of a multilayered thin film structure made out of transparent conducting oxide (aluminum doped zinc oxide) and pure VO2 using pulsed laser deposition technique. This comprehensive study is based on two different configurations for multi-layered structure approach, with the intention to reduce the transition temperature, as well as to maintain the MIT properties that would strengthen the potential of the structure to be used for a smart window device. By creating a multi-layered structure, we were able to create a low powered device that can operate less than 15 V that leads to significant decline in the infrared transmission by a magnitude of over 40% and provided sufficient heat to trigger the MIT at a temperature around 60 °C, which is almost 10 °C lower than its bulk counterpart. This finding would positively impact the research on VO2 thin films, not only as smart windows but also for numerous other applications like bolometers, infrared detectors, Mott transistors and many more. [ABSTRACT FROM AUTHOR]

Highly sensitive large-scale tin oxide (SnO2) nanostructures were grown on a glass substrate by thermal evaporation of a mixture of anhydrous tin (II) chloride (SnCl2) and zinc chloride (ZnCl2) powders at 550°C in air. We demonstrate a single cell vapor deposition system to precisely control nanostructural morphology of SnO2 by changing the weight ratio of SnCl2 and ZnCl2 and growth temperature. The morphology and structural property of as-grown nanostructures were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The SEM images revealed that the SnO2 nanostructures with different densities, sizes, and shapes can be achieved by adjusting the weight ratio of SnCl2 and ZnCl2. A thin film gas sensor based on SnO2 nanostructures with diameter ∼20 nm and length ∼100 nm showed ∼85% sensitivity and 53 seconds of response time, whereas the nanorods with diameter ∼100 nm and length ∼ 1μm showed ∼50% sensitivity with 198 seconds response time. The nanostructured material with small size and shape showed better sensitivity on sensing at room temperature compared to previously reported SnO2 based sensors. [ABSTRACT FROM AUTHOR]