Nanocomposite thin films of Zinc Oxide and Silicon were grown by co-evaporating powdered ZnO and Si. This resulted in nanocrystallites of ZnO being embedded in Silicon. The mismatch in crystal structures of constituent materials result in the ZnO nanocrystals to exist in a state of stress. This along with oxygen vacancies in the samples result in good Photoluminescence emission at 520nm. Also, Silicon background gave a photoluminescence emission at 620nm. The structure was found quite stable over time since the homgenously dispersed ZnO nanocrystals do not agglomerate. The nanocomposites promises to be a useful candidate for future optoelectronic devices.
Nano particles of pure ZnO, pure SnO$_2$, and nanocomposites of ZnO/SnO$_2$ were synthesized using microwave hydrothermal technique starting from aqueous solutions. Nanocomposites with different molar ratios of ZnO and SnO$_2$ were prepared. Structural, morphological and optical properties of these samples were investigated using XRD, SEM and UV-visible technique, respectively. The single phases of ZnO and SnO$_2$ could be fabricated according to XRD patterns. The relative intensities of different XRD peaks in different nanocomposite samples were different by indicating that there are some pre…
As grown ZnO:Si nanocomposites of different compositional ratios were fabricated by thermal evaporation techniques. These films were subjected to post deposition annealing under high vacuum at a temperature of $\rm 250C^o$ for 90min. The photoluminescence (PL) spectra of annealed samples have shown marked improvements both in terms of intensity and broadening. For the first time in ZnO:Si nanocomposite films we see huge UV, red and orange peaks at 310, 570 and 640nm. Structural and Raman analysis show formation of a Zn-Si-O shell around ZnO nano clusters wherein on heating $\rm Zn_2SiO_4$ comp…
Nanocomposite films of Zinc Oxide and Silicon were grown by thermal evaporation technique using varying ratios of ZnO:Si in the starting material. Analysis reveal the role of ZnO and amorphous silicon interface in contributing to relatively less common blue photoluminescence emissions (at $\sim$ 400 and 470nm). These blue peaks are observed along with the emissions resulting from band edge transition (370nm) and those related to defects (522nm) of ZnO. Careful analysis shows that along with the grain size of ZnO, a suitable compositional ratio (of ZnO to silicon) is critical for the coexistenc…
Cubic zinc oxide (rs-ZnO), metastable under normal conditions, was synthesized from the wurtzite modification (w-ZnO) at 7.7 GPa and ~800 K in the form of nanoparticles isolated in the NaCl matrix. The phase transition rs-ZnO \rightarrow w-ZnO in nanocrystalline zinc oxide under ambient pressure was experimentally studied for the first time by differential scanning calorimetry and high-temperature X-ray diffraction. It was shown that the transition occurs in the 370-430 K temperature range and its enthalpy at 400 K is -10.2 \pm 0.5 kJ mol-1.
We have synthesized MoS$_{2}$ incorporated $α$-Fe$_{2}$O$_{3}$/ZnO nanocomposites by the hydrothermal process. The effect of incorporating ultrasonically exfoliated MoS$_{2}$ on the photocatalytic performance of $α$-Fe$_{2}$O$_{3}$/ZnO nanocomposites has been demonstrated. Structural, morphological and optical characteristics of the nanomaterials are investigated by performing Rietveld refinement of powder X-ray diffraction patterns, field emission scanning electron microscopy and UV-visible spectroscopy. The photoluminescence spectra of the nanocomposites show that the recombination of photog…
Earlier studies show that organic and inorganic semiconducting materials are the most promising materials for use in temperature sensors. In this brief review, attention will be focused on temperature sensors and its applications in various fields. In addition, we have investigated the temperature sensing characteristics of nanostructured ZnO and ZnO-CuO nanocomposite. For this purpose, ZnO and ZnO-CuO nanocomposite were synthesized via chemical precipitation method. Scanning electron microscopy and X-ray diffraction of sensing materials have also performed. The average crystallite size was 45…
We fabricate and compare nanocomposite thin-film ZnO chemoresistive acetone sensors with gold or palladium nanoparticles on the surface, at low operating temperatures. The sensors are fabricated by pulsed laser deposition and operate in the temperature range 159-200oC. The ZnO films are polycrystalline, crystallizing mainly at the (002) and (101) orientations of the hexagonal phase. The nanocomposite ZnO:Au and ZnO:Pd sensors have a lower detection limit and show a response enhancement factor between 2-7, compared with pure ZnO sensors. The ZnO:Pd sensor performs better than the ZnO:Au sensor.…
The composites of strontium-doped lanthanum manganite (LSMO) with zinc oxide (ZnO) are candidate materials for energy harvesting by virtue of their magnetic and piezoelectric characteristics. They could be used to harvest energy from stray sources, such as the vibrations and electromagnetic noise from transformers and compressors within electrical grid power stations to power small diagnostic sensors, among other applications. The LSMO/ZnO nanocomposites were made by: (i) milling the two bulk powders and, (ii) a wet chemical process which resulted in core-shell structures. The electrical, piez…
In this paper, we report the high temperature mediated structural phase transformation from B1 to B2 phase in solgel derived Cd0.2Zn0.8O nanocomposite thin film for the temperature range of 700 to 900 degree centigrade. Xray diffraction pattern provides a direct and unambiguous indication of phase evolution with increase in annealing Temperature from 700 to 900 degree centigrade along with coexistence of wurtzite phase throughout the whole transformation regime. In fact, significant reduction in lattice parameters in case of transformed B2 phase, extracted by Rietveld refinement provides a dir…
Nanocomposite metal oxide thin films exhibit assuring qualities in the field of gas sensors because of the collective opportunities provided by the heterointerface formation. In this work, we present the synthesis of nitrogen doped mesoporous In$_2$O$_3$-ZnO nano-composite thin films by simple wet chemical method using urea as the nitrogen precursor. SEM investigation suggests formation of mesoporous nano-composite thin films, where the uniformity of surface pore distribution depends on the relative proportion of In$_2$O$_3$ and ZnO in the composites. HRTEM investigation suggest formation of s…
This work reports the successful solid state synthesis of ZnO/NiFe2O4 nanocomposite by calcinations of both green synthesized ZnO nanorods and NiFe2O4 prismatic nanorods at high temperature (850 °C) for ten hours. These nanomaterials were characterized for structural, functional groups and morphological studies using XRD, FTIR and SEM respectively. The photocatalytic activity of the catalysts was assessed through photodegradation of methylene blue (MB) dye. The photocatalytic studies reveal that the ZnO/NiFe2O4 nanocomposite exhibits high degradation efficiency under UV light. The study shows …
As grown ZnO:Si nanocomposite films fabricated by thermal evaporation showed broad photoluiminescence (PL) spectra due to merging of four prominent peaks viz 370, 410, 470 and 520 nm. Investigations revealed the role of interface in contributing to the two blue peaks at 410 and 470 nm. While the 470 nm is found to vary with ZnO grain size and their density, the 410 nm peak is attributed to the volume of shell surrounding ZnO nanoparticles. This study shows the contribution of ZnO cluster size and their density, as influenced by film thickness, in the PL spectra of the samples.
Nanocomposite films were fabricated by supersonic cluster beam deposition (SCBD) of palladium clusters on Poly(methyl methacrylate) (PMMA) surfaces. The evolution of the electrical conductance with cluster coverage and microscopy analysis show that Pd cluster are implanted in the polymer and form a continuous layer extending for several tens of nanometers beneath the polymer surface. This allows the deposition, using stencil masks, of cluster-assembled Pd microstructures on PMMA showing a remarkably high adhesion compared to metallic films obtained by thermal evaporation. These results suggest…
Vanadium (IV) oxide is one of the most promising materials for thermochromic films due to its unique, reversible crystal phase transition from monoclinic (M1) to rutile (R) at its critical temperature (T$_c$) which corresponds to a change in optical properties: above T$_c$, VO$_2$ films exhibit a decreased transmittance for wavelengths of light in the near-infrared region. However, a high transmittance modulation often sacrifices luminous transmittance which is necessary for commercial and residential applications of this technology. In this study, we explore the potential for synthesis of VO$…
The ZnO films, 25 nm thick were deposited by e-beam evaporation of ZnO (99.9%) pellets onto native oxide covered silicon (100) substrates. Details of the interface chemical composition and the chemical depth profile have been deduced as follows: Adsorbed OH surface/OH: ZnO Interface/Pure ZnO thin film/ZnO:H: Si Interface/H:SiO2/SiO2/Si(100). The physical profile of the crater formed by the SIMS depth profiling was measured with a Tencor P-2 profilometer as depth profiling showed uniform ion milling and good consistency with film thickness (25 nm) measured by SIMS depth profile (25.4 nm).
Large scale molecular dynamics simulations are used to study the dispersion of nanoparticles (NPs) in a polymer film during solvent evaporation. As the solvent evaporates, a dense polymer-rich skin layer forms at the liquid/vapor interface, which is either NP rich or poor depending on the strength of the NP/polymer interaction. When the NPs are strongly wet by the polymer, the NPs accumulate at the interface and form layers. However when the NPs are only partially wet by the polymer, most NPs are uniformly distributed in the bulk of the polymer film with the dense skin layer serving as a barri…
Plasmonic Cu nanoparticles were in-situ grown into a Cu$_2$O semiconductor matrix by using reactive magnetron sputtering and adjusting the amount of oxygen available during the synthesis in order to prevent the oxidation of part of copper atoms landed on the film surface. Varying only the oxygen flowrate (OFR) and using a single Cu target it was possible to observe the evolution in the simultaneous formation of metallic Cu and Cu$_2$O phases for oxygen-poor conditions. Suchformation is accompanied by the development of the surface plasmon band (SPB) corresponding to Cu, as evidenced by UV-Vis …
