High-resolution Tunneling Electron Microscopy Research Articles

Enhanced piezoelectric output voltage and Ohmic behavior in Cr-doped ZnO nanorods

Highly crystalline Cr-doped ZnO nanorods (NRs) were synthesized by solution technique. The size distribution was analyzed by high resolution tunneling electron microscope (HRTEM) and particle size analyzer. In atomic force microscope (AFM) studies, peak to peak 8mV output voltage was obtained on the application of constant normal force of 25nN. It showed high dielectric constant (980) with phase transition at 69°C. Polarization vs. electric field (P–E) loops with remnant polarization (6.18μC/cm2) and coercive field (0.96kV/cm) were obtained. In I–V studies, Cr-doping was found to reduce the rectifying behavior in the Ag/ZnO Schottky contact which is useful for field effect transistor (FET) and solar cell applications. With these excellent properties, Cr-doped ZnO NRs can be used in nanopiezoelectronics, charge storage and ferroelectric applications.

Nanoscale structure study of boron nitride nanosheets and development of a deep-UV photo-detector

In this communication, we report on the synthesis of few atomic-layer boron nitride nanosheets (BNNSs) and their application for deep ultraviolet photo-detection. Synthesis of BNNSs is carried out by using the short-pulse plasma beam deposition technique. High-resolution tunneling electron microscopy, cathodoluminescence spectroscopy and photo-stimulated measurements are conducted and linked to characterize the BNNS morphology. The obtained BNNSs are flat with a typical size of 50 × 50 μm(2) and are optically transparent down to 210 nm. Nanoscale studies by transmission electron microscopy revealed that these nanosheets are composed of a densely packed honeycomb crystal lattice structure of covalently bonded boron and nitrogen atoms. Cathodoluminescence spectroscopy of these nanosheets revealed a single sharp excitonic peak centered at 233 nm at 300 K. The synthesized BNNSs are used to demonstrate applicability of BNNSs for detecting ultraviolet photons. The initial experimental tests of the developed prototype BNNSs based deep-ultraviolet photo-detector show that it is blind to photons with an energy less than 4 eV. The calculated output power of the detector is approximately 2 μW and the ratio between the output electrical power and the input optical power is ∼1%.

Growth, optical, and electrical properties of nonpolar m-plane ZnO on p-Si substrates with Al2O3 buffer layers

Nonploar m-plane ZnO films were grown on p-Si (111) substrates by using atomic layer deposition. X-ray diffraction and high resolution tunneling electron microscopy measurements showed that the ZnO films were 〈101¯0〉 oriented, and the crystalline quality of ZnO films was improved with an Al2O3 buffer layer, which significantly enhances the photoluminescence and reduces the reverse leakage current of ZnO/Si heterojuction.

Augmented photocatalytic activity of palladium incorporated ZnO nanoparticles in the disinfection of Escherichia coli microorganism from water

Palladium incorporated ZnO nanoparticles were synthesized using incipient wetness impregnation method in different concentrations of Pd incorporated in ZnO nanoparticles and their effects as a photocatalyst under UV laser radiations in the removal of Escherichia coli microorganism from water were studied. A significant improvement in the rate constant of the bacterial decay process was observed and discussed on the basis of the blue shifted band gap energy of nano-ZnO due to the incorporation of palladium. The morphological study of Pd incorporated ZnO nanoparticles was carried out using Field Emission Scanning Electron Microscope and High Resolution Tunneling Electron Microscope and the grain size of the synthesized material was found to be in the 15–30 nm range. The photoluminescence spectra and the absorption spectra showed a blue shift in the band gap energy of Pd incorporated ZnO nanoparticles, which positively contributed to the enhanced photocatalytic activity.

Uniform formation of Au coated polystyrene core–shell structure using metallization process

There are several methods for the fabrication of core–shell particles, including chemical reduction and self-assembly. In this study, the chemical reduction method was used to fabricate 100 nm, Au-coated polystyrene nanoparticles. The formation of the gold layer was based on the increase of gold coverage by the reaction with aniline and HAuCl 4. This method allowed for efficient control of the gold coverage and led to relatively stable products. The formation of Au clusters on the surface of the 100 nm polystyrene beads was characterized by scanning electron microscope and high resolution tunneling electron microscope. As a result, the Au-coated nanoparticles can be used in various applications such as surface plasmon resonators, drug delivery systems and electronic optical devices.

In-situ synthesis of magnetic (NiFe 2O 4/CuO/FeO) nanocomposites

In-situ synthesis of magnetic nanocomposites with (NiFe 2O 4/CuO/FeO) crystal phases has been done using a sol–gel method by taking a non-stoichiometric composition of the precursors. The average particle size of the nanocomposites was calculated using X-ray diffraction (XRD) and high resolution tunneling electron microscope (HR-TEM) and it turns out to be ∼20 nm. The vibrating sample magnetometer (VSM) measurements demonstrate the ferromagnetic nature of the nanocomposites. The synthesized nanocomposite was used to prepare magnetic fluid using tetramethylammonium hydroxide as a surfactant and its stability in the solution was also discussed.

Synthesis and Characterization of LiFePO4 and LiuTi0.01Fe0.99PO4 Cathode Materials

Nanocrystalline and doped powders were synthesized via a sol-gel preparation route. High-resolution tunneling electron microscopy observation and energy dispersive spectroscopy, mapping show the homogeneous distribution of dopant Ti cations in the crystals. Fe and O -edge X-ray absorption near-edge structure (XANES) measurements show that doping induces an increased unoccupied d-state in , resulting in an enhanced p-type semiconductivity. In situ Fe -edge XANES measurements of Ti-doped and undoped electrodes have been performed to determine the change of Fe valence during the lithium intercalation and de-intercalation processes. Both and doped cathodes demonstrate good electrochemical performance.

A Convenient Route to Functionalized Carbon Nanotubes

Reductive alkylation of single-walled carbon nanotubes (SWNTs) using lithium and alkyl halides in liquid ammonia yields sidewall functionalized nanotubes that are soluble in common organic solvents. Atomic force microscopy (AFM) and high-resolution tunneling electron microscopy (HRTEM) of dodecylated SWNTs prepared from raw HiPco nanotubes show that extensive debundling has occurred. GC-MS analysis of the byproduct hydrocarbons demonstrates that alkyl radicals are intermediates in the alkylation step.

Tungsten Oxide Nanowires on Tungsten Substrates

A simple method was discovered to prepare tungsten oxide nanowires directly from tungsten metal. The structure and composition of the nanowires were characterized by high resolution tunneling electron microscopy (HRTEM) and energy dispersive X-ray scattering (EDX), respectively. The growth mechanism and potential applications of this material are discussed.