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In the present work, ZnO nanorods and Ag nanoparticles (NPs) decorated ZnO nanorods (NRs) were synthesized on a Si/SiO2 substrate by a simple chemical hydrothermal route. Various characterization techniques studied phase formation, surface morphology, and elemental composition of prepared samples. Gas sensing measurements for pristine ZnO and Ag/ZnO NRs have been carried out under a low detection limit (2–10 ppm). The highly crystalline nature of NRs aided in achieving a great sensing response. The ZnO NRs exhibit a sensing response of 934% towards 10 ppm NO2 at a working temperature of 180 °C. However, Ag/ZnO sensor gives the highest sensing response of 1075% for 10 ppm NO2 at a working temperature of 180 °C. The cause behind the increment of Ag/ZnO sensor response is explained via chemical and electronic models. These observations make an energy-efficient sensor for the detection of NO2 in the environment. [ABSTRACT FROM AUTHOR]

Vertically well aligned ZnO nanorods (NRs) were grown on Si(100) substrate using RF magnetron sputtering technique. Scanning electron microscopy images confirms uniform distribution of NRs on 2 in. wafer with average diameter, height and density being ~75 nm, ~850 nm, and ~1.5 × 1010 cm-2, respectively. X-ray diffraction reveals that the ZnO NRs are grown along c-axis direction with wurtzite crystal structure. Cathodoluminescence spectroscopy, which shows a single strong peak around 3.24 eV with full width half maxima 130 meV, indicates the high crystalline and optical quality of ZnO and very low defect density. Vertically aligned nanosensors were fabricated by depositing gold circular Schottky contacts on ZnO NRs. Resistance responses of nanosensors were observed in the range from 50 to 150 °C in 1% and 5% hydrogen in argon environment, which is below and above the explosive limit (4%) of hydrogen in air. The nanosensor's sensitivity increases from 11% to 67% with temperature from 50 to 150 °C and also shows fast response time (9-16 s) and moderate recovery time (100-200 s). A sensing mechanism is proposed based on Schottky barrier changes at heterojunctions and change in depletion region of NRs. [ABSTRACT FROM AUTHOR]

Self-aligned ZnO nanorods (NRs) were grown on n-Si(100) substrate by RF sputtering techniques. The NRs are uniformly grown on 2-inch wafer along [0001] direction. Single-crystalline wurtzite structure of ZnO NRs was confirmed by X-ray diffraction. The average diameter, height, and density of NRs are found 48 nm, 750 nm, and 1.26×1010 cm–2, respectively. The current-voltages (I-V) characteristics of ZnO NRs/Si heterojunction (HJ) were studied in the temperature range of 120–300K and it shows a rectifying behavior. Barrier height (ϕB) and ideality factor (η) were estimated from thermionic emission model and found to be highly temperature dependent in nature. Richardson constant (A*) was evaluated using Richardson plot of ln(Io/T2) versus q/kT plot by linear fitting in two temperature range 120–180K and 210–300 K. Large deviation in Richardson constant from its theoretical value of n-Si indicates the presence of barrier inhomogeneities at HJ. Double Gaussian distribution of barrier height with thermionic equation gives mean barrier heights of 0.55±0.01 eV and 0.86±0.02 eV for two different temperature regions 120–180K and 210–300 K, respectively. Modified Richardson plot provided two values of Richardson constant for two temperature regions. However, for higher temperature range (210–300 K), the calculated value of Richardson constant ~123 A cm–2 K–2 was close to the ideal Richardson constant for n-Si. [ABSTRACT FROM AUTHOR]

Ba0.5Sr0.5TiO_3 (BST) thin films were deposited on sapphire substrate by RF magnetron sputtering techniques and interdigital capacitor (IDC) structures were fabricated using photolithography. Gamma irradiation induced changes of the BST based tunable capacitor have been investigated under various doses from 0 kGy to 600 kGy. Structural and surface morphological studies have been carried out for un-irradiated and irradiated film and revealed that the grain sizes and crystallinity are strongly depended on gamma irradiation doses. The leakage current is increased with increasing gamma irradiation doses due to creation of charge carriers and large numbers of defect in close proximity, provided path for charge carriers. The capacitance of the IDC devices decreased with increasing gamma dose up to 50 kGy and thereafter capacitance gradually increased with radiation doses and reached higher than the un-irradiated device at 600 kGy for 1 MHz frequency. The observed tunability (\sim 25\% ) of the un-irradiated device was found nearly constant with gamma irradiation doses. This study shows that gamma ray induced defects play important role to the electrical properties of the devices and the BST based devices are highly resistant to gamma radiation, which reflects possible use in space and nuclear applications. [ABSTRACT FROM AUTHOR]

ZnO thick Stress relaxed films were deposited by reactive magnetron sputtering on 2"-wafer of SiO2/Si at room temperature. The residual stress of ZnO films was measured by measuring the curvature of wafer using laser scanning method and found in the range of 0.18 x 109 × 11.28 x 109 dyne/cm2 with compressive in nature. Sputter pressure changes the deposition rates, which strongly affects the residual stress and surface morphologies of ZnO films. The crystalline wurtzite structure of ZnO films were confirmed by X-ray diffraction and a shift in (0002) diffraction peak of ZnO towards lower 2θ angle was observed with increasing the compressive stress in the films. The band gap of ZnO films shows a red shift from ~3.275 eV to ~3.23 eV as compressive stress is increased, unlike the stress for III-nitride materials. A relationship between stress and band gap of ZnO was derived and proposed. The stress-free growth of piezoelectric films is very important for functional devices applications. [ABSTRACT FROM AUTHOR]

To provide a more sustainable future, development and implementation of green electronics incorporating natural materials has become an essential requirement. In this study, we demonstrated a low-temperature and low-cost fabrication route to develop chitosan/PVP (CHP) substrate for flexible electronics device applications. A combination of natural polymer (chitosan) and synthetic polymer (poly(vinylpyrrolidone), PVP) has been used to fabricate biodegradable, low-cost, and flexible substrate. The CHP substrate has been prepared by the solution casting method. The CHP flexible substrate demonstrates a high optical transmittance (∼90% in the visible region), high-temperature stability (up to 250 °C), smooth surface, and good mechanical stability along with a high biodegradation rate (within 6 days) into the soil. Radio frequency (RF) sputtering and thermal evaporation techniques have been used to deposit high-quality ZnO thin films and Au/Ti electrodes over the CHP substrate. This fabricated metal-semiconductor-metal (MSM) device gives a clear indication about the accountability of the CHP polymer substrate as a potential option for flexible electronics. The current-voltage characteristic with flat and bending cycles (three flat-bending-flat cycles) shows almost same current conduction. These flexible CHP substrates can find a new way toward environmentally friendly, flexible electronics.