Nanorod Thin Films Research Articles

Spin polarized carrier injection driven magneto-optical Kerr effect in Cr-doped ZnO nanorods

Hydrothermal growth of Cr doped ZnO nanorods (NRs) thin films was grown on glass substrates. The strong ferromagnetic (FM) and antiferromagnetic (AFM) ordering was observed in 3% and 7% of Cr doped samples. The optical excitation of the Cr doped ZnO NRs is responsible for injection of the spin-polarized carriers in the 3% Cr doped ZnO NRs through longitudinal magneto-optical Kerr effect (MOKE). We determined a negative anisotropic magnetoresistance (∼23%) originated from spin orbit coupling due to sp-d exchange interaction. we calculated the process of photon induced inverse spin Hall angle (θISHE∼3.94×10−2) close to the MOKE saturated rotation angle (θk∼0.046) for 3% Cr: ZnO. These results can open a new path of optical spin detectors for next-generation spintronic device technology.

One step synthesis of vertically grown Mn-doped ZnO nanorods for photocatalytic application

Pure and Mn-doped ZnO nanorods thin films on glass substrates were successfully synthesized by a one-step hydrothermal route. It was confirmed from XRD data that pure and Mn-doped ZnO samples show hexagonal (wurtzite) structures and the particle size was found to be in the range 27–31 nm. From XRD data it was clearly found that vertical growth along (002) plane after Mn-doping into ZnO lattice. Functional groups and chemical species were detected using FT-IR spectra. Diameter and length of ZnO nanorods were determined by TEM which is in the range 350 nm, 1–4 μm respectively. UV–Vis results exhibit red shift with increasing Mn concentration in ZnO lattice. The 5% Mn-doped ZnO sample exhibits higher fluorescence intensity in visible region with surface defects. The electrical resistance of pure and Mn-doped ZnO nanorods was demonstrated by I–V characteristics. It was explicitly outlined from Raman spectra E 2 high mode was shifted towards the higher wavenumber from 439 to 440 cm−1 owing to Mn doping in ZnO lattice. The average surface area, pore volume, and pore diameter were measured by using the BET isotherm. The photocatalytic activity of pure and Mn-doped ZnO was evaluated by the degradation of methylene blue (MB) under UV–Vis light irradiation which indicates that 5% Mn-doped ZnO nanorods have better photocatalytic activity than other samples.

Preparation and Photoelectrochemical Performances of CuSCN Thin Films Influenced by Electrodeposition Potential

In this work, p-type CuSCN nanorod thin films were successfully prepared on the fluorine-doped tin oxide (FTO) conductive substrate by a simple electrochemical deposition at different deposition potentials (i.e., −0.1, −0.2, −0.3, −0.4 V), and the influence of deposition potential on the microstructural and photoelectrochemical properties of the prepared CuSCN thin films was then explored. The prepared CuSCN films were nanorod arrays with a rhombohedral β-CuSCN structure, and the better CuSCN crystal structure was achieved when deposited at −0.4 V. The p-type characteristic of the electrodeposited CuSCN thin films were verified by Mott–Schottky measurements. The CuSCN nanorods thin films deposited at −0.2, −0.3, and −0.4 V produced ten times higher photocurrent intensities than the CuSCN thin film deposited at −0.1 V, and the CuSCN thin film deposited at −0.4 V exhibited the best photoelectrochemical performance. The enhanced photoelectrochemical performance of the CuSCN thin film deposited at −0.4 V could be attributed to the better crystal structure, the more charge carrier concentration as well as the more efficient charge separation and migration. This work offers a facile approach to prepare the p-type CuSCN nanorod thin films through electrochemical deposition, and regulate their photoelectrochemical performance by controlling the deposition potential.

INFLUENCE OF GROWTH TIME ON STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF TiO2 NANOROD ARRAYS DEPOSITED BY HYDROTHERMAL METHOD

Well-oriented TiO2 nanorod (NR) arrays were fabricated directly on conductive side of F/SnO2 substrates via hydrothermal technique. The effect of growth time on the TiO2 NR thin film was examined. Field emission scanning electron microscope revealed that NRs exhibited a tetragonal structure with square top facets. Thickness measurements indicated that the thicknesses of the samples increased from 0.234[Formula: see text][Formula: see text]m to 1.544[Formula: see text][Formula: see text]m as the growth time was extended. The investigation of XRD indicates that the TiO2 films are single-crystalline type of rutile. The effect of growth time on optical and electrical properties has been studied. With optimum growth time, dye sensitized solar cell (DSSC) efficiency of 1.48% could be reached using 1.544[Formula: see text][Formula: see text]m long TiO2 NR arrays as electrode.

Enhanced magneto-transport and thermoelectric properties of MnP nanorod thin films grown on Si (1 0 0)

Abstract The MnP thin films were grown on Si (1 0 0) substrates at 300 and 400 °C using molecular beam epitaxy (MBE). The films crystallize in an orthorhombic structure. FE-SEM images indicated that both films are composed of vertically aligned MnP nanorods. However, the density of the nanorods in the film grown at 400 °C is higher than that grown at 300 °C, leading to a considerable decrease of resistivity in this sample. Both films showed a ferromagnetic behavior, but the Curie temperature increased from 275 K for the film grown at 300 °C to 325 K for the film grown at 400 °C. Anomalous Hall effect (AHE) and negative magneto-resistance (MR) were observed in the films. While both films exhibited a metallic behavior, a higher thermoelectric power factor (PF) was achieved for the film grown at 400 °C.

Colloidal analogues of polymer chains, ribbons and 2D crystals employing orientations and interactions of nano-rods dispersed in a nematic liquid crystal

Robust control over the position, orientation and self-assembly of nonspherical colloids facilitate the creation of new materials with complex architecture that are important from technological and fundamental perspectives. We study orientation, elastic interaction and co-assembly of surface functionalized silica nano-rods in thin films of nematic liquid crystal. With homeotropic boundary condition, the nano-rods are predominantly oriented perpendicular to the nematic director which is different than the mostly parallel orientation of the micro-rods. The percentage of perpendicular nano-rods are significantly larger than the parallel nano-rods. The perpendicular nano-rods create very weak elastic deformation and exhibit unusual, out-of-plane, attractive interaction. On the other hand, the nano-rods oriented parallel to the director create strong elastic deformation and shows anisotropic, in-plane, dipolar interaction. In both orientations, the induced defects reside in the nano-rods. With the help of a dynamic laser tweezers and using nano-rods as building blocks we demonstrate colloidal analogues of linear polymer chains, ribbons and two-dimensional binary crystals.

Multifunctional monoclinic VO2 nanorod thin films for enhanced energy applications: Photoelectrochemical water splitting and supercapacitor

Monoclinic VO2 nanorod thin films were deposited on indium‑tin-oxide-coated glass substrates using radio-frequency reactive magnetron sputtering at a substrate temperature of 300°C and various O2 flow rates. The thin films were characterized via standard analysis techniques. The VO2 thin films exhibited a highly crystalline monoclinic phase with an indirect band gap of ~1.73eV. At optimized O2 flow rate (4sccm), the thin films was observed nanorod structures, exhibited a remarkable photocurrent of ~0.08mAcm−2 during photoelectrochemical water splitting in the visible region. Electrochemical performance tests of the nanorod films revealed a specific capacitance of ~486mFcm−2 at a scan rate of 10mVs−1. In addition, amperometric I–t curves showed that VO2 thin film electrodes were highly stable during the photo-oxidation process. The nanorod films also exhibited a good specific capacitance of ~120mFcm−2 after 5000cycles at a scan rate of 100mVs−1. The photocurrents during photoelectrochemical water splitting and the specific capacitance of VO2 thin films deposited at O2 flow rates of 2 and 6sccm were 0.06 and 0.07mAcm−2 and 398 and 37mFcm−2, respectively. The films deposited under Ar at 8sccm and O2 at 4sccm showed the highest photoelectrochemical water splitting performance and specific capacitance, owing mainly to their nanorod-like morphology.

Growth, Single-Crystalline Rutile TiO2 Nanorod Thin Film By Hydrothermal Technique

A facile, hydrothermal technique was developed to growth, single-crystalline rutile TiO2 nanorod thin films on transparent conductive fluorine-doped tin oxide (FTO) substrates. In this study, the deferent periods(6, 9, 12, 15, and 18 hour) were selective with constant temperature at 160 oC to growth this films and growth in deferent temperature (130, 150,170,190, and 210 oC) with constant period of deposition at 6h. SEM image showed all the films were nanorodand the EDX measurement was given the portion of element that contribution in rutile TiO2 nanorod thin films. The diameter, length, and density of the nanorods could be varied by changingthe growth parameters. The XRD to determine the structure properties, and optical properties were measured of these rutile TiO2 nanorod thin films and obtained the absorbance and energy gap.

Nano-rods oxide materials for biosensor application.

Iron ions selective biosensor (Fe3+) based on zinc oxide nano-rods thin film symbolic as ZnO-(NRs)TF will be developed and prepared. The potentiometric response for ZnO-(NRs)TF deposited on conducting plastic and silicon substrates as working electrode versus reference electrode (Ag/AgCl) was found to be linear against logarithmic FeCl3 with concentration range between 10-6 M and 10-2 M. The ZnO-(NRs)TF will be grown on conducting plastic and silicon substrates using two methods (Sol - Gel and aqueous chemical growth (ACG)) by seed layers and nano-rod growth will be investigated. For fabricate an advanced extracellular iron biosensor, the ZnO-(NRs) on plastic and silicon substrates were coated with a thin layer of specific ionophore membrane to be used for iron concentration measurements in extracellular solution. The prepared sample crystallinity and microstructure will be characterized by x-ray diffraction (XRD) which, imply that ZnO-(NRs)TF sample crystallite sizes are in the nano-scale. The prepared samples morphology was characterized by Field emission scanning electron microscope (FESEM).

Facile synthesis of self-assembled WO3 nanorods for high-performance electrochemical capacitor

Hexagonal WO3 nanorod thin films have been successfully synthesized by a simple hydrothermal method using ammonium sulfate ((NH3)2SO4) as a structure directing agent. The effect of structure directing agent on structural, morphological and electrochemical properties of WO3 thin films is investigated. The nanorods with diameters of 50–200 nm and length up to several micrometers are obtained. The results demonstrate that the concentration of (NH3)2SO4 plays an important role in the growth direction and formation of self-assembled WO3 nanorods. The electrochemical measurements show that WO3 thin films demonstrate excellent electrochemical performance with a maximum specific capacitance of 538 F g−1 at 5 mV s−1, high power performance and good cycling stability (85% over 2000 CV cycles). The present work may provide a facile and versatile approach to tune the morphology and capacitive performance of WO3 thin films required for high-performance energy storage devices.

Influences of Al dopant atoms to the structure and morphology of Al doped ZnO nanorod thin film

We report our work about dependency of Al dopant atoms to the growth process of Al doped ZnO (AZO) nanorod structure. ZnO is one of type metal oxide, which is classified as semiconducting material with direct wide band gap (∼ 3.4 eV). This metal oxide is widely used in optoelectronic devices, such as solar cell, gas sensing, and photocatalyst. To produce effective photoelectrode in solar cell devices and high sensitive sensor in gas sensing application, many researchers have been modifying the nanostructure, such as inserting dopant ions, variation in deposition technique and surface modifications. By inserting some dopant ions/atoms, the structure and morphology of ZnO nanorod can be controlled. Nucleation process of nanorod structure which is growth by chemical solution method, are depend on seed layer morphology. We have prepared ZnO nanorod thin film (growth by self-assembly method) with inserting aluminum as dopant atom both in seed layer and nanorod growth solution. The morphology of ZnO nanostructured significantly changes as the existence of aluminum atoms. Based on X-ray diffraction pattern, the wurtzite structures of AZO nanorod still possessed and only affect to the small shift of lattice crystal. A high surface roughness of seed layer can produce wide radius of nanorod, since the nucleation process initiated by seed layer particle size as a template of nanorod arrangement.

Method to reduce the formation of crystallites in ZnO nanorod thin-films grown via ultra-fast microwave heating

This paper discusses the nucleation and growth mechanisms of ZnO nanorod thin-films and larger sized crystallites that form within the solution and on surfaces during an ultra-fast microwave heating growth process. In particular, the work focusses on the elimination of crystallites as this is necessary to improve thin-film uniformity and to prevent electrical short circuits between electrodes in device applications. High microwave power during the early stages of ZnO deposition was found to be a key factor in the formation of unwanted crystallites on substrate surfaces. Once formed, the crystallites, grow at a much faster rate than the nanorods and quickly dominate the thin-film structure. A new two-step microwave heating method was developed that eliminates the onset of crystallite formation, allowing the deposition of large-area nanorod thin-films that are free from crystallites. A dissolution-recrystallization mechanism is proposed to explain why this procedure is successful and we demonstrate the importance of the work in the fabrication of low-cost memristor devices.

(Invited) Hydrothermal Growth of Zinc Oxide (ZnO) Nanorods and Structural and Optical Studies for Soil pH Measurement Applications

Zinc Oxide (ZnO) nanorods (NRs) are developed by a hydrothermal growing method using zinc acetate as the precursor material. The synthesized ZnO particle solution deposited on the Aluminum and Glass substrate by using a spin coating and thermal evaporation method. ZnO nanoparticle layer is treated for hydrothermal growing procedure and further annealing at high temperature to obtain uniform ZnO NRs. The structural and optical properties of the ZnO NRs are examined with field emission scanning electron microscopy with Energy Dispersive Spectrometer, X-ray diffraction meter and UV visible spectrometer. The crystal qualities, grain size, diameter, and optical bandgap of the ZnO NRs were affected by the type of solvent and substrates used. The developed ZnO NRs thin film structure has high potential application in soil pH measurement. Keywords: ZnO NRs; Spin Coating; Thermal Evaporation; FESEM/EDS; XRD; UV Visible spectrometer Figure 1

Ethanol-sensitive nearly aligned ZnO nanorod thin films covered by graphene quantum dots

Graphene quantum dots (GQDs) were simply synthesized by pyrolysis of citric acid, and zinc oxide nanorods (ZnO NRs) were grown on pre-seeded glass substrates by a solvothermal method. Finally, the GQDs were dropped on the ZnO NR thin film. It was found that the incorporation of GQDs eliminated the photoluminescence (PL) intensity of the ZnO NR thin film, suggesting that electrons of ZnO can be readily transferred to GQDs, contributing to the passing current. Finally, the ethanol sensing analysis was performed, showing that the incorporation of GQDs enhanced the sensitivity of ZnO NR thin film to ethanol gas, and the mechanism behind the enhancement was discussed.

Bipolar resistive switching and memristive properties of hydrothermally synthesized TiO2 nanorod array: Effect of growth temperature

In the present work, the hydrothermal approach is employed to develop 1D-TiO2 nanorod array memristive devices and the effect of hydrothermal growth temperature on TiO2 memristive devices is studied. X-ray diffraction (XRD) analysis suggested that the rutile phase is dominant in the developed TiO2 nanorod array. Field emission scanning electron microscopy (FESEM) images show well adherent and pinhole free one dimensional (1D) TiO2 nanorods. The presence of titanium and oxygen in all the samples was confirmed by energy dispersive X-ray spectroscopy (EDS). Furthermore, growth of the 1D TiO2 nanorods depends on the growth temperature and uniform growth is observed at the higher growth temperatures. The well-known memristive hysteresis loop is observed in the TiO2 nanorod thin films. Furthermore, resistive switching voltages, the shape of I-V loops and (non)rectifying behavior changed as the growth temperature varied from 140 °C to 170 °C. The biological synapse properties such as paired-pulse facilitation and short-term depression are observed in some devices. The detailed electrical characterizations suggested that the developed devices show doubled valued charge-magnetic flux characteristic and charge transportation is due to the Ohmic and space charge limited current.

Graphene quantum dots enhance UV photoresponsivity and surface-related sensing speed of zinc oxide nanorod thin films

Thin films of almost vertically-grown zinc oxide nanorods (ZnO NR) were prepared via a solvothermal method, and graphene quantum dots (GQDs) were synthesized by pyrolyzing citric acid. Various amounts of GQDs were loaded onto ZnO NR thin films by applying a dip-coating process for different times. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffractometry (XRD) were employed to characterize the structures. UV–visible spectra of the thin films showed no significant change in the bandgap (~3.3eV) after incorporating GQDs, which is appropriate for visible-blind UV sensing applications. Photoluminescence (PL) spectra showed a significant decrease in the PL intensity of the ZnO NR thin film after incorporating GQDs, suggesting that the generated electrons can be better separated from their hole counterparts and hence contribute to the generated photocurrent. Finally, UV sensing analysis was performed, indicating that GQDs can enhance both the UV-induced photocurrent and the sensing speed of ZnO NR thin films; however, the improvement in the surface-related UV sensing was higher than in the bulk-related one, which could be attributed to the numerous active sites and edge effects of GQDs. The enhanced photocurrent was discussed based on the band diagram.

Field-Theoretic Simulations of the Distribution of Nanorods in Diblock Copolymer Thin Films.

Using block copolymer microphases to guide the self-assembly of nanorods in thin films can give rise to polymeric materials with unique optical, thermal, and mechanical properties beyond those found in neat block copolymers. Often the design and manufacture of these materials require exquisite control of the nanorod distribution, which is experimentally challenging due to the large parameter space spanned by this class of materials. Simulation approaches, on the other hand, can access the thermodynamics that contribute to the nanorod distribution and hence offer valuable guidance toward the design and manufacture of the materials. In this work, we employ complex Langevin field-theoretic simulations to examine the thermodynamic forces that govern the assembly of nanorods in thin films of block copolymers with a particular focus on vertically oriented cylindrical and lamellar domains. Our simulations show that the nanorod geometry, the substrate selectivity for the distinct blocks of the copolymer, and the film thickness all play important roles in engineering both the nanorod orientation and spatial distribution in diblock copolymer thin films. In addition, we employ thermodynamic integration to examine how the nanorods alter the stability of vertical and horizontal domains in thin films, where we find that the tendency of the nanorods to stabilize a vertical orientation depends on both the film thickness and the nanorod concentration.

Single step chemical growth of ZnMgS nanorod thin film and its DFT study

Herein, ZnMgS nanorod (NR) thin film has been grown by facile single step chemical bath deposition technique. Initially, vertically aligned ZnMgS NR having ∼3 µm length and diameter of ∼200 nm were deposited on commercial glass substrate. The morphology characterizations of this nanorod thin film were observed by FE-SEM and TEM. The randomly oriented hexagonal type nanorods were grown on the glass surface. The strong and highly intense (0 0 2) peak in the XRD pattern along with the calculated low compressive strain indicates vertical growth of high-quality crystalline ZnMgS nanorods. The films showed a direct band transition at ∼3.62 eV. The photosensing properties of NR thin film of ZnMgS showed an excellent photoresponsivity of 34.6 μA/Watt and photosensitivity 99% respectively under illumination of 100 W/cm2 at a bias voltage 5 V. The obtained experimental results were found to be consistent with theoretical results obtained using DFT.

Preparation and spectroscopic analysis of zinc oxide nanorod thin films of different thicknesses

AbstractZinc oxide thin films with different thicknesses were prepared on microscopic glass slides by sol-gel spin coating method, then hydrothermal process was applied to produce zinc oxide nanorod arrays. The nanorod thin films were characterized by various spectroscopic methods of analysis. From the images of field emission scanning electron microscope (FESEM), it was observed that for the film thickness up to 200 nm the formed nanorods with wurtzite hexagonal structure were uniformly distributed over the entire surface substrate. From X-ray diffraction analysis it was revealed that the thin films had good polycrystalline nature with highly preferred c-axis orientation along (0 0 2) plane. The optical characterization done by UV-Vis spectrometer showed that all the films had high transparency of 83 % to 96 % in the visible region and sharp cut off at ultraviolet region of electromagnetic spectrum. The band gap of the films decreased as their thickness increased. Energy dispersive X-ray spectroscopy (EDS) showed the presence of zinc and oxygen elements in the films and Fourier transform infrared spectroscopy (FT-IR) revealed the chemical composition of ZnO in the film.

In situ decoration of CuSCN nanorod arrays with carbon quantum dots for highly efficient photoelectrochemical performance

In this work, the in situ decoration of CuSCN nanorod thin films with carbon quantum dots (CQDs) was achieved through a one-pot electrochemical deposition process. The hybridization of CQDs would not change the nanorod structure and p-type characteristic of CuSCN thin film. Compared with the pristine CuSCN thin film, the CQDs/CuSCN composite thin film exhibited significantly improved photoelectrochemical (PEC) activities. The photocurrent intensity of the composite thin film electrode was approximately 6.5 times that of the CuSCN thin film electrode. The improved PEC activities could be ascribed to the highly efficient generation, separation and migration of excited charge carriers derived from the decoration of CQDs on the surface of CuSCN nanorods, as verified by the electrochemical impedance spectra (EIS), photoluminescence, charge extraction, intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) measurements. The superior PEC properties of the CQDs/CuSCN composite thin film make it a promising hole transporting material or photocathode material for practical PEC applications including solar cells and PEC water splitting.