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With the development of electronic devices towards miniaturization, light weight and integration, dielectric thin film-capacitors for recoverable energy storage applications have attracted ever-growing interests owing to their fast charging and discharging rate. In continuation to our investigations for achieving high energy density, we have grown lead free BaZr0.2Ti0.8O3 (BZT)/Ba0.7Ca0.3TiO3 (BCT) heterostructures and studied the structural, dielectric, ferroelectric and energy density characteristics. The BZT/BCT bilayer epitaxial heterostructures were grown on La0.67Sr0.33MnO3 (LSMO) buffered LaAlO3 (LAO) single crystal substrate by optimized pulsed laser deposition technique. The ferroelectric phase transition has been probed above room temperature with relaxor behavior. These nanostructures show high discharge and charge energy densities of 9.74 and 26.55 J/cm3, respectively. These heterostructures show high dielectric permittivity, large polarization and high energy density characteristics well above room temperature which may be useful for both high power and energy density device applications. [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]

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]

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]

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]

The large mismatch of the coefficients of thermal expansion (CTE) between the metal contact and CdZnTe exerts thermal stress at the metal/CZT interface, which causes mechanical degradation of the contact in addition to the poor adhesion of the metallic thin film to CZT. To form a reliable and stable interface, the contact material should have better adhesion and a close match of the coefficients of thermal expansion with CZT/CdTe. Here, we report on our investigations of a novel non-metallic contact layer for use in radiation detector applications. The proposed ZnO:Al contact layer offers better adhesion due to the oxide interface, higher hardness and better matching of the CTE with CZT. It has high prospects for a reliable and stable device structure that can serve as a replacement to the common metallic electrodes used today. We evaluated AZO contacts to CZT and extracted the electronic characteristics, such as resistivity and mobility-lifetime product of electrons, and compared the results of the same characterization measurements for CZT with gold contacts. The present observations showed that the characteristics of CZT detectors with AZO contacts are nearly identical to the same detectors with gold contacts. [ABSTRACT FROM AUTHOR]

Hyperbolic metamaterials create artificial anisotropy using metallic wires suspended in dielectric media or alternating layers of a metal and dielectric (Type I or Type II). In this study we fabricated ZnO/Al:ZnO (AZO) multilayers by the RF magnetron sputtering deposition technique. Our fabricated multilayers satisfy the requirements for a type II hyperbolic metamaterial. The optical response of individual AZO and ZnO films, as well as the multilayered film were investigated via UV-vis-IR transmittance and spectroscopic ellipsometry. The optical response of the multilayered system is calculated using the nonlocal-corrected Effective Medium Approximation (EMA). The spectroscopic ellipsometry data of the multilayered system was modeled using a uniaxial material model and EMA model. Both theoretical and experimental studies validate the fabricated multilayers undergo a hyperbolic transition at a wavelength of 2.2 μm. To our knowledge this is the first AZO/ZnO type II hyperbolic metamaterial system fabricated by magnetron sputtering deposition method. [ABSTRACT FROM AUTHOR]