ZnO Nanocomposite Thin Films Research Articles

Investigations on structural, optical and electrical properties of microwave-assisted rGO:ZnO nanocomposite thin films

The reduced graphene oxide:Zinc oxide (rGO:ZnO) nanocomposite films were fabricated by an optimized wet-chemical sol–gel derived spin-coating method. A simple, fast and effective microwave-assisted approach was adopted for the reduction of the graphene oxide. The influence of rGO on the microstructural and optoelectronic properties of ZnO was studied by varying the weight ratios of rGO. The results showed significant changes in the microstructural and optoelectronic properties of the rGO:ZnO composite films. X-ray diffraction analysis confirmed the polycrystallinity of the composite films with a preferential growth orientation of the crystallites along (002) plane. Good optical transparency in the visible wavelength region was observed in all the composite films. As the weight percentage of rGO increased from 0% to 20%, the red shift of the absorption edge was noticed, indicating the weak Burstein-Moss effect. The optical bandgap of ZnO reduces as the amount of rGO increases, resulting in the reduction of transmittance in the composite thin films. The sheet resistance and therefore the resistivity of the composite films decreases with the loading of rGO into ZnO matrix. The lowest values of sheet resistance and resistivity, and the highest Figure of Merit have been recorded for 10% rGO:ZnO composite film. The obtained results illustrate that the 10% rGO:ZnO composite film could be a potential candidate for electrode applications.

Flexible La0.67Sr0.33MnO3:ZnO Nanocomposite Thin Films Integrated on Mica

The integration of functional oxide thin films on flexible substrates is critical for their application in flexible electronics. Here, to achieve flexible perovskite manganite oxide film with excellent low-field magnetoresistance (LFMR) effect, textured La0.67Sr0.33MnO3 (LSMO):ZnO nanocomposite film was deposited on a flexible mica substrate with ZnO buffer using pulsed laser deposition (PLD). Compared to the polycrystalline LSMO:ZnO nanocomposite film directly deposited on mica without buffer, the LSMO:ZnO/ZnO/mica sample exhibits larger saturation magnetization (164 emu/cm3) and higher Curie temperature (∼319 K), which results from the crystallinity and strain in the LSMO phase. In addition, the LSMO:ZnO/ZnO/mica film presents a high MR value of ∼39% at 10 K under 1 T. Furthermore, the good mechanical stretchability and property stability of the nanocomposite thin films have been demonstrated with mechanical bending.

Optical properties of Nb2O5 doped ZnO nanocomposite thin film deposited by thermionic vacuum arc

In this study, Nb2O5: ZnO nanocomposite thin film has been deposited by thermionic vacuum arc and then surface and optical properties of Nb2O5: ZnO nanocomposite thin film have been investigated. The surface and optical properties were investigated by a scanning electron microscopy and atomic force microscopy. Optical properties and band gap value were determined by UV-Vis spectrophotometer. Thickness of the film was determined as 25 nm. Weight percentages of Zn and Nb elements were found as 99.85% and 0.15%, respectively. Deposited thin films were transparent. Artificial intelligence (AI) technique is a promising and an alternative technique for research and development to determine the properties of a material. For this aim, optical band gap predictions were done. The band gap energy value was calculated 3.08 eV. The band gaps of 3.39 eV and 3.62 eV were estimated by Gaussian processes regression and Gaussian processes regression with synthetic minority over-sampling technology model, respectively. Estimated band gap value is close to the estimated value from the Tauc model. It is acceptable for the determination. But, crystal diameter and atom number values were nearly the same as experimental and predicted values. As a result, AI techniques are useful techniques for the determination of the film properties.

Nitrogen doped In2O3-ZnO nanocomposite mesoporous thin film based highly sensitive and selective ethanol sensors.

Nanocomposite metal oxide thin films exhibit promising qualities in the field of gas sensors due to the opportunities provided by the heterointerface formation. In this work, we present the synthesis of nitrogen doped mesoporous In2O3-ZnO nanocomposite thin films by a simple wet chemical method using urea as the nitrogen precursor. SEM investigation suggests the formation of mesoporous nanocomposite thin films, where the uniformity of the surface pore distribution depends on the relative proportion of In2O3 and ZnO in the composites. HRTEM investigation suggests the formation of sharp interfaces between N-In2O3 and N-ZnO grains in the nanocomposite thin films. The nanocomposite thin films have been tested for their ethanol sensing performance over an extensive range of temperatures, ethanol vapor concentrations and relative humidities. Nitrogen doped nanocomposite thin films with an equal proportion of In2O3 and ZnO exhibit excellent ethanol sensing performance at a reasonable operating temperature (∼94% at 200 °C for 50 ppm of ethanol), fast response time (∼two seconds), stability over time, enhanced resilience against humidity and selectivity to ethanol over various other volatile organic compounds. All the results indicated that nitrogen doped In2O3/ZnO nanocomposite thin films portray great possibilities in designing improved performance ethanol sensors.

SnO2–ZnO nanocomposite thin films: The influence of structure, composition and crystallinity on optical and electrophysical properties

SnO2–ZnO thin films consisting of nanoscale crystallites were obtained on glass and silicon substrates by solid-phase low-temperature pyrolysis. The synthesized materials were studied by XRD and SEM methods, electrophysical and optical properties were evaluated, as well as the band gap was calculated. It was shown that regardless of the phase composition all films were optically transparent in the visible range (310–1000 nm). The nanocrystallites’ minimum size, the highest activation energy of the conductivity and the smallest band gap calculated for indirect transitions were shown for a thin film 50SnO2–50ZnO. It was assumed that the band gap decreasing might be attributed to the existence of surface electric fields with a strength higher than 4 × 105 V/cm.

Optical characterizations of PMMA/metal oxide nanoparticles thin films: bandgap engineering using a novel derived model

We synthesize and optically characterize pure PMMA and PMMA incorporated with metal oxides nanoparticles (MO NPs) such as ZnO, CuO, TiO2 and SiO2 NPs nanocomposite thin films with weight concentration of 10% using dip-coating technique. SEM images of MO NPs show that all NPs have nearly an average size of around 50 nm. The optical parameters such as, optical parameters (n and k), optoelectronics properties, dispersion, band-gap energy and band structure of as-prepared nanocomposite thin films were determined by analyzing the transmittance and reflectance spectra. Mainly, optical band-gap energy (Eg) and the thickness of thin films are evaluated to a high degree of accuracy by utilizing Q-functional derived using a mathematical model recently published. The Q(E) is a functional containing experimental transmission and reflection data and the incident photon energy. The Eg value of un-doped PMMA thin films is found to be 4.273 eV. This value decreases as pre-selected MO NPs are introduced into thin films. These values are in excellent agreement with those determined using Tauc method. The FTIR technique is employed to elucidate the vibrational bands of the nanocomposites and the intermolecular bonding between PMMA matrix and the MOs NPs. Thermal stability is investigated by employing thermogravimetric analysis (TGA) at temperatures up to 400 °C. The obtained TGA thermograms indicate that adding MOs NPs to PMMA yield thin films of better thermal stability. The obtained doped thin films show a great promise for fabricating high-efficient optoelectronic devices.

Charge Transport Behavior of Al-Doped ZnO Incorporated with Reduced Graphene Oxide Nanocomposite Thin Film

ZnO is utilized as a promising material for various electronic and energy areas due to its outstanding chemical stability, abundance, non-toxicity, and low cost. However, controlling electronic transport properties of ZnO by facile strategy is still necessary for wider applications. Here, we synthesized reduced graphene oxide incorporated Al-doped ZnO nanocomposite thin film prepared by the electrospray deposition method and investigated the electronic transport behavior. The electron transport in pristine Al-doped ZnO thin film is strongly affected by grain boundary scattering, but significant enhancement of carrier mobility is observed in reduced graphene oxide-incorporated Al-doped ZnO nanocomposite thin film. The results demonstrate that this hybrid strategy with graphene has an important effect on the charge transport behavior in ZnO polycrystalline materials.

Visible light photoconductivity studies of gold nanoparticle embedded ZnO thin films for photo detector application

This report demonstrates the visible photo response of gold nanoparticles (AuNPs) embedded ZnO nanocomposite (AuNPs-ZnO) thin films. The AuNPs-ZnO films were prepared by sandwiching DC sputtered AuNPs in between two RF sputtered ZnO layers deposited on p-Si. Crystal phase purity and surface morphology were characterized by the x-ray diffraction and scanning electron microscope. The formation of AuNPs was confirmed by observing the plasmonic dip in optical transmittance. Photoconductivity study was done by recording current–voltage characteristics of the films in the presence of visible light. The ratio of light to dark current was found to be enhanced by two to three orders of magnitude with the inclusion of AuNPs. The observed photocurrent enhancement was found to vary with both AuNPs concentration and sandwich thickness. The highest responsivity observed with the fabricated nanocomposite films was of 0.012 A W−1. The dominant reason for the visible photoconductivity and for the enhancement in photocurrent was ascribed to the plasmonic properties of AuNPs-ZnO composite film. This study paves a new approach to design and fabricate devices for optoelectronic applications.

Thermal stability of self-assembled ordered three-phase Au-BaTiO3-ZnO nanocomposite thin films via in situ heating in TEM.

Thermal stability of oxide-metal nanocomposites is important for designing practical devices for high temperature applications. Here, we study the thermal stability of the self-assembled ordered three-phase Au-BaTiO3-ZnO nanocomposite by both ex situ annealing under air and vacuum conditions, and by in situ heating in TEM in a vacuum. The study reveals that the variation of the annealing conditions greatly affects the resulting microstructure and the associated dominant diffusion mechanism. Specifically, Au nanoparticles show coarsening upon air annealing, while Au and Zn either form a solid solution, with Zn atomic percentage less than 10%, or undergo a reverse Vapor-Liquid-Solid (VLS) mechanism upon vacuum annealing. The distinct microstructures obtained also show different permittivity response in the visible and near-infrared region, while retaining their hyperbolic dispersion characteristics enabled by their highly anisotropic structures. Such in situ heating study in TEM provides critical information about microstructure evolution, growth mechanisms at the nanoscale, and thermal stability of the multi-phase nanocomposites for future electronic device applications.

Impact of Sputtering Power on Properties of CdO:ZnO Thin Films Synthesized by Composite Method for Oxygen Gas Sensing Application

The present work reports the impact of RF sputtering power on CdO:ZnO (3:1) nanocomposite thin films deposited by sputtering. The structural, morphological, optical and electrical properties of CdO:ZnO thin films deposited at 40 W, 60 W, 80 W and 100 W RF sputtering power were investigated. The structural and morphological results show that high sputtering power improves the crystallinity of thin films. The thin film deposited at 80 W has (111) and (002) phases corresponding to mixed cubic and wurtzite crystal structure, whereas surface morphology of 100 W thin film shows that particles are densely agglomerate. The energy-dispersive x-ray spectrum shows the presence of Cd and Zn atoms in the CdO:ZnO nanocomposite samples. The films show 75–85% transparency in the visible region and a large variation in optical bandgaps from 2.6 eV to 3.5 eV was observed for the samples deposited at 40–100 W with lowest value for the 80 W thin film. I–V characteristics of all the CdO:ZnO thin films show an ohmic nature and resistance varies from 104 Ω to 109 Ω, suitable for resistive based gas sensor. The optimized thin film of CdO:ZnO deposited at 80 W was used for oxygen gas sensing applications 25–200°C operating temperatures and 25.4% sensor response was observed. The response and recovery times were found 10–20 s. Overall study reflects appreciable impact of RF sputtering power on different parameters under investigation.

Investigation on Band Gap of CuO–ZnO Nanocomposite Thin Films and Stability of CuO–ZnO Nanofluids

Investigation on Band Gap of CuO–ZnO Nanocomposite Thin Films and Stability of CuO–ZnO Nanofluids

Thermal-induced structural and optical investigations of Ag[sbnd]ZnO nanocomposite thin films

In the present paper, we have successfully synthesized AgZnO nanocomposite thin films by RF-magnetron sputtering technique at room temperature. Systematic investigations of thermal-induced structural and optical modifications in AgZnO thin films have been observed and described. The AgZnO thin films were annealed at three different temperatures of 300 °C, 400 °C and 500 °C in vacuum to prevent the oxidation of Ag. The presence and formation of Ag nanoparticles were estimated by transmission electron microscopy. X-ray diffraction analysis revealed the structural information about the crystalline quality of ZnO. The crystallinity as well as the crystallite size of the films have been found to be improved with annealing temperatures. The estimated crystallite size was ∼15.8 nm for as-deposited film and 19.0 nm for the film at a higher temperature. The chemical composition and structural analysis of as-deposited film were carried out by X-ray photoelectron spectroscopy. A very sharp absorption band appeared at ∼540 nm for Ag NPs that is associated with the surface plasmon resonance band of Ag. A noticeable red shift of about ∼12 nm has been recorded for films annealed at 500 °C. Atomic force microscopy has been utilized to examine the surface morphology of the as-deposited and annealed films. The grain size was found to be increase with increasing annealing temperature, while no significant changes were observed in the roughness of AgZnO thin films. Raman spectroscopy revealed lattice defects and disordering in the films after the thermal annealing.

Ultrasonic guided wave sensitivity of piezopolymer films subjected to thermal exposure

This paper presents the loss in piezoelectric performance of piezopolymer film sensors like PVDF and P(VDF-TrFE) and P(VDF-TrFE)/ZnO nanocomposite thin films due to thermal exposure. Changes in the material structure through XRD diffraction analysis reveal the high stability of P(VDF-TrFE) and P(VDF-TrFE)/ZnO nanocomposites films after subjecting to thermal exposure above 120 °C. Loss in the crystalline β-phase of PVDF film was observed after thermal exposure above 80 °C accompanied by shrinkage. Loss of crystalline β-phase is lesser in constrained films as compared to free films. Next, the piezoelectric coefficient d33 measured using dynamic force method suggests highest stability of PVDF film at higher temperature as compared to P(VDF-TrFE) and P(VDF-TrFE)/ZnO nanocomposite thin film. In addition, the constrained PVDF film shows better stability of piezoelectric coefficient d33 than the unconstrained PVDF films. Using the guided wave the piezoelectric coefficient d31 of these films was measured. Among these films, PVDF films show excellent stability in the piezoelectric coefficient d31 when subjected to thermal exposure. P(VDF-TrFE) and P(VDF-TrFE)/ZnO thin films retain piezoelectricity up to 90 °C, whereas PVDF films retain piezoelectricity up to 120 °C.

CdO:ZnO nanocomposite thin films for oxygen gas sensing at low temperature

CdO:ZnO nanocomposite were synthesized via sol-gel technique and optimized for oxygen sensing. The transport properties of the CdO:ZnO thin films were analyzed for enhancing the gas sensing properties at low operating temperatures. CdO:ZnO (1:3) nanostructure was obtained that has a 25 nm grain size with a 4.870 Å lattice constant. A highly transparent thin film of CdO:ZnO (3:1) with hollow sphere morphology and band gap of 2.4 eV was found to be less resistive. The sensing parameters such as sensor response, response time, recovery time, selectivity and stability of sensor were analyzed for different operating temperatures based on resistivity measurements. CdO:ZnO thin films of volume ratio 3:1 has the best sensitivity of 98.96 at an operating temperature of 150 °C. The present studies are encouraging for the realization of CdO:ZnO nanocomposite based sensor for efficient oxygen sensing properties at low temperatures fabricated with a low cost simple spin coating technique.

Nanostructural, optical and heterojunction characteristics of PEDOT™/ZnO nanocomposite thin films

Poly(3,4-ethylenedioxythiophene), Tetra Methacrylate (PEDOT™)/ZnO nanocomposite thin films were fabricated by the conventional spin coating method and characterized by X-ray diffraction technique. The results indicated that ZnO nanopowder has a polycrystalline nature with a hexagonal system and mean crystallite size of 53.1 nm. The main important optical parameters were extracted by using the spectrophotometer methodology covering the range of 200–2500 nm. A direct allowed transition with the onset and fundamental energy gaps were found to be 1.9 and 3.9 eV. The current density-voltage characteristics of PEDOT™/ZnO nanocomposite film/n-Si heterojunction showed diode-like behavior. Temperature dependence of series and shunt resistances was investigated. The high value of ideality factor (η) can be referred to the influence of an interfacial layer. Temperature dependence of barrier height indicated the presence of inhomogeneous barrier at an interface which is considered to be the reason for the observed behavior of the barrier height with temperature.

Preparation and Characterization of Polyaniline/ZnO Composite Sensor

Polyaniline ZnO nanocomposite thin films were prepared via an electrochemical synthesis route on ITO coated glass substrates ZnO nanoparticles were uniformly dispersed in to the polyaniline matrix Interaction between ZnO nanoparticle and polyaniline has been studied using X ray diffraction XRD UV Vis absorption spectroscopy PL spectroscopy AFM and I V characteristics The ammonia gas sensing behaviors of the polyaniline ZnO composites were examined at room temperature It was observed that the composite films showed good sensitivity improved doping state and enhanced photoluminescence behaviour

Photoluminescence and electrochemical properties of transparent CeO2–ZnO nanocomposite thin films prepared by Pechini method

Nanocomposite thin films of CeO2–ZnO with different molar ratios of Zn/Ce (=0, 0.25, 0.5, 0.75 and 1) were prepared by the Pechini sol–gel route. Various spectroscopic and electrochemical techniques were applied to investigate the films. XRD patterns of all the samples exhibited the peaks corresponding to cubic fluorite structure of ceria and the (101) and (103) peaks of ZnO with hexagonal structure was just observed in the sample with molar ratio of 1. EDS confirmed the presence of constituent of element in the samples. FESEM images of the films showed a surface composed of nanograins. AFM analysis revealed that root mean square roughness was enhanced as molar ratio of Zn/Ce increased. Moreover, fractal dimension of surfaces were calculated by cube counting approach. Optical measurements indicated that the film with molar ratio of 1 has the highest transmission and lowest reflectivity. The optical band gap values varied between 2.95 and 3.42 eV. The compositional dependence of refractive index and extinction coefficient were reported. The UV and blue emission appeared in PL spectra. The highest photoluminescence emission intensity was observed in the 1:1 molar ratio sample. The cyclic voltammetry measurements indicated the highest charge density (9.75 mC cm−2) and diffusion coefficient (3.507 × 10−17 cm2 s−1) belonged to the Ce/Zn (1:1) thin film.

MWCNT Doped ZnO Nanocomposite Thin Film as LPG Sensing

A compound material of multi-walled carbon nanotubes (MWCNTs) coated with ZnO was synthesized at ambient conditions. The X-ray diffraction, UV–visible spectroscopy, scanning electron microscope (SEM) and transmission electron microscopy results confirmed that the existence of ZnO nanoparticles inside the MWCNTs. The gas sensing properties of the material were studied. ZnO-based composites on MWCNTs treated at room temperature shows enhanced performance as sensors, making them suitable for practical applications. Sensor structure showed a better sensing response (S ~61.57) at operating room temperature towards 1500 ppm LPG with an average sensitivity 41.95. Furthermore, the gas sensor responses increased linearly with the increment of the gas concentrations of LPG.

Ion beam induced evolution of surface morphology and optical properties of SnO2–ZnO nanocomposite thin films

SnO2–ZnO nanocomposite thin films, prepared by a simple carbothermal reduction based vapor deposition method, were irradiated with 8MeV Si3+ ions for engineering the morphological and optical properties. The surface morphology of the nanocomposites was studied by atomic force microscopy (AFM), while the optical properties were investigated by photoluminescence spectroscopy (PL) and Raman spectroscopy. AFM studies on the irradiated samples revealed growth of nanoparticles at lower fluence and a significant change in surface morphology leading to the formation of nanosheets and their aggregates at higher fluences. A tentative mechanism underlying the observed ion induced evolution of surface morphology of SnO2–ZnO nanocomposite is proposed. PL studies revealed strong enhancement in the UV emissions from the nanocomposite thin film at lower fluence, while a drastic decrease in the UV emissions along with a significant enhancement in the defect emissions has been observed at higher fluences.

Integration of CdTe–ZnO nanocomposite thin films into photovoltaic devices

Quantum-scale semiconductor nanoparticles offer unique, size-dependent optical and electronic properties of import to enhanced photovoltaic conversion efficiency. The present study addresses the integration of CdTe nanocrystal assemblies, used as spectral sensitizers, into thin film photovoltaic heterojunction devices. CdTe nanocrystals, embedded in an electrically active ZnO matrix, form a nanocomposite offering control of both spectral absorption and photocarrier transport behavior through the manipulation of nanophase assembly (ensemble effects). A sequential RF-magnetron sputter deposition technique affords the control of semiconductor nanophase spatial distribution relative to the heterojunction plane in a hybrid, ZnO–P3HT test structure. Energy conversion performance, (J–V and quantum efficiency (QE) response) was examined as a function of the location of the CdTe nanophase absorber region using both 1-D device modeling (SCAPS) and the experimental examination of analogous P3HT–ZnO based hybrid thin film devices. Enhancement in simulated QE over a spectral range consistent with the absorption region of the CdTe nanophase (i.e. 400–475nm) is confirmed in the experimentally determined external quantum efficiency (EQE). Moreover, a trend of decreasing efficiency in this spectral range with increasing separation between the CdTe nanophase region and the heterojunction plane is observed. The results are interpreted in terms of carrier scattering/recombination length mitigating the successful transport of photocarriers across the junction.