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The indium supplied on c-plane GaN templates using Metal organic vapor phase epitaxy was studied by in situ X-ray reflectivity (XRR) at 800 °C. The presence of liquid indium layers on the GaN (0001) surface was demonstrated using data-fitting of XRR measurements, ex situ atomic force microscope, auger electron spectroscopy, and cross-sectional scanning electron microscope. These measurements demonstrated that a liquid indium layer coexisted with indium droplets on top of the GaN (0001) surface at 800 °C. The liquid indium film thicknesses increased with increasing TMIn supply time and did not change during cooling from 800 °C to room temperature. [ABSTRACT FROM AUTHOR]

We irradiated the soft x-ray laser (SXRL) pulses having a wavelength of 13.9 nm, a duration time of 7 ps, and fluences of up to 27 mJ/cm2 to aluminum (Al) surface. After the irradiation process, the modified surface was observed with the visible microscope, the scanning electron microscope, and the atomic force microscope. The surface modifications caused by the SXRL pulses were clearly seen, and it was found that the conical structures having about 70-150 nm in diameters were formed under a single pulse shot. The conical structures were formed in the features with the average depth of about 40 nm, and this value was in accordance with the attenuation length of the SXRL beam for Al. However, those conical structures were deconstructed under the multiple pulse shots exposure. Thermomechanical modeling of SXRL laser interaction with Al surface, which explains nanostructure surface modification, was provided. [ABSTRACT FROM AUTHOR]

Ba0.6Sr0.4TiO3/Ni0.8Zn0.2Fe2O4 (BST/NZO) composites were synthesized via the conventional solid-state reaction method. The phase composition and surface morphology of the composites were investigated using x-ray diffractometry and scanning electron microscope, respectively. The dielectric and magnetic properties of the composites were studied. The results show that the BST/NZO composites have giant dielectric constants and very high permeabilities. For the 10%BST/90%NZO composite, the dielectric constant and permeability in low frequency range are about 150 000 and 29, respectively. The giant dielectric behavior of the BST/NZO composites is mainly attributed to the Maxwell-Wagner polarization. [ABSTRACT FROM AUTHOR]

In current work, the mechanical behavior of a Zr-based bulk metallic glass at elevated temperatures (from 423 to 683 K) under high strain rate (from 5000 to 104 s-1) is investigated by an improved split Hopkinson pressure bar apparatus. Experimental results reveal that the failure stress goes down along with elevated temperature, while the strain rate dependency is relatively small. Furthermore, three different fracture modes are observed along with elevated temperature by scanning electron microscope (SEM). SEM observation results also indicate that the fractured specimen has been crystallized at temperature near Tg and the embrittlement caused by crystallization is attributed to the fracture mode changing. [ABSTRACT FROM AUTHOR]

Polyethylene oxide (PEO) and lithium salts (LiI, LiClO4, and LiCF3SO3) based composite polymer electrolytes have been prepared for different [EO]/[Li] ratio using solution casting method and characterized by x-ray diffraction (XRD), scanning electron microscope, and differential scanning calorimetry (DSC). The electrical measurements have been carried out at different temperatures. XRD patterns, field emission scanning electron micrographs, and DSC clearly depict that amorphous region in the PEO–LiClO4 composite electrolyte with [EO]/[Li]=9 is dominant over the other electrolytes. It has been observed that the electrical conductivity of the PEO–LiClO4 electrolyte is higher than that of the PEO–LiI and PEO–LiCF3SO3 composite electrolytes. It has been also observed that the hoping rate of charge carriers for the PEO–LiClO4 electrolyte is higher than that of the other two electrolytes. The concentration of charge carriers is not thermally activated and the mobility controls the temperature dependence of electrical properties. Scaling of the conductivity spectra has been performed in order to get insight into the relaxation mechanisms. [ABSTRACT FROM AUTHOR]

Composites of polyvinylidene fluoride (PVDF) filled with metallic particles of nickel (Ni) were prepared via a blending and hot-molding technique. Rescaled temperature dependence of electric and dielectric behaviors of Ni/PVDF composites were studied at wide content ranges. Results show that there is significant positive temperature coefficient effect and giant dielectric constant as the concentration of Ni is near the percolation threshold. The nonuniform distribution of filler particles in PVDF host is observed from the scanning electron microscope micrograph since they are aggregated in amorphous regions of PVDF and form a network of conducting chains. Two relaxation peak regions of dielectric constant are observed from -10 to 40 °C and from 100 to 150 °C, which can be attributed to the contribution of polar effect of PVDF. The percolation theory, the thermal expansion model, and the simple concept of polarization in the capacitors are employed to explain these experimental results. [ABSTRACT FROM AUTHOR]

We have studied the effect of annealing (at temperatures 300, 400, and 500 °C) on nanoparticulate CdS film on silicon substrate deposited by hybrid Langmuir–Blodgett chemical bath deposition technique. Width, intensity, and the line shape of the longitudinal optical phonon in Raman spectra and photoluminescence (PL) spectra suggest that the annealing brings about coalescence of nanoparticles at 300 °C, increasing the size of the nanoparticles and also increases the red region PL related to surface states. Annealing at 400 °C leads to two different coexistent states, showing larger nanoparticles and bulklike film. On further annealing at 500 °C, PL shows a drastic redshift to PL of bulklike CdS. This is well brought out by resonance Raman measurements and later confirmed by scanning electron microscope data. Most interesting observation is that PL and Raman results together are indicative of phase transformation of nanoparticulate hexagonal CdS film to bulklike cubic CdS film on annealing at 500 °C, unlike cubic to hexagonal structural phase transition observed in bulk CdS films. [ABSTRACT FROM AUTHOR]

The electrical resistance of an individual multiwalled carbon nanotube (MWCNT) as a function of mechanical strain was investigated inside a scanning electron microscope. The mechanical strain was applied to the MWCNT by a tungsten tip controlled by a nanomanipulator. The contact resistance between an individual MWCNT and the tungsten tip decreased with the addition of carbon deposition during e-beam exposure. The electrical resistance was significantly changed during the elongation process of the MWCNT and corresponded with the nanotube strain. The resistance increased abruptly at the beginning of the tube fracture. The strain sensitivities of two individual MWCNT were calculated to be about 25.2 and 25.9, respectively. The unique characteristics in electrical resistance variation for different displacements of an individual MWCNT could be used in a strain gauge for strain sensing of nanomaterials or a micromechanical device for sensing force or pressure. CNTs are very strong and highly flexible and would be ideal for these applications. [ABSTRACT FROM AUTHOR]

The ferroelectric properties of sodium nitrite (NaNO2):poly(vinyl alcohol) nanocomposite films prepared by the solvent cast method have been studied. The optimization of the ferroelectric properties of the composite films as a function of the composition gave 50 wt % to be the optimum value. The enhanced remanent polarization was observed in the composite in the frequency range of 10 Hz–1 kHz. The stability of the ferroelectric polarization shows improvement over the pure NaNO2 films. The x-ray diffraction study revealed that the strain is reduced in the composite films. The images of field emission scanning electron microscope showed the nanosize and uniform distribution of particles in 50 wt % composite. The improved values of the polarization and stability have been attributed to the reduced strain in the composite. The ferroelectric phase transition peak was observed in the differential scanning calorimetry (DSC) scan. The ferroelectric phase transition temperature of the composite film obtained from the capacitance-voltage (C–V) measurements agrees well with the DSC measurements. [ABSTRACT FROM AUTHOR]

Single zinc oxide (ZnO) nanopillars grown by the vapor-liquid-solid process on a-plane sapphire are investigated by spatially resolved cathodoluminescence on the nanometer scale in a scanning electron microscope. Spectra were recorded by exciting luminescence along single pillars and across the underlying wetting layer. Luminescence from the excited pillar spots exhibited sharp bound exciton lines and intrinsic free-exciton recombination, whereas the wetting layer showed only very weak luminescence. Along the pillars, virtually no shift of the lines was observed. This is interpreted as evidence for strain-free growth of the pillars. In the bottom region of the pillars aluminum incorporation from the substrate material was found. There are indications for an incorporation of gallium along the pillars due to unintentional doping introduced by the source material. The spot-resolved results are compared to integral photoluminescence measurements with large-area excitation carried out on the same sample region. [ABSTRACT FROM AUTHOR]

X-ray studies performed during the growth of CdCO3 and MnCO3 crystals from supersaturated aqueous solutions, at fatty acid monolayer templates, reveal that the nucleates are nearly three-dimensional powders below a threshold supersaturation. However, at higher supersaturations, the crystals are preferentially oriented with the {0 1 2} direction vertical. Scanning electron microscope images of samples transferred to substrates show discrete crystals at low concentrations, while at higher concentrations the crystals self-aggregate to form linear chains and sheets. The authors speculate that preferential alignment at the organic-inorganic interface is enhanced as a consequence of oriented aggregation of crystals. The role of monolayer-ion interactions in governing the morphologies and the resulting orientation of the inorganic nucleate is discussed. [ABSTRACT FROM AUTHOR]

The ferroelectric properties and leakage current mechanisms of preferred oriented Bi3.25La0.75Ti3O12 (BLT) thin films deposited on La0.5Sr0.5CoO3 by the polymeric precursor method were investigated. These films showed excellent ferroelectric properties in terms of large remnant polarization (2Pr) of 47.6 μC/cm2 and (2Ec) of 55 kV/cm, fatigue-free characteristics up to 1010 switching cycles, and a current density of 0.7 μA/cm2 at 10 kV/cm. X-ray diffraction and scanning electron microscope investigations indicate that the deposited films exhibit a dense, well-crystallized microstructure having random orientations and with a rather smooth surface morphology. The improved ferroelectric and leakage current characteristics can be ascribed to the platelike grains of the BLT films, which make the domain walls easier to be switched under external field. [ABSTRACT FROM AUTHOR]

Copper-induced lateral growth of polycrystalline germanium (poly-Ge) at temperatures as low as 150 °C was enabled by the application of an external mechanical stress during the annealing step of sample processing. An equivalent compressive strain of 0.05% was externally applied at 150 °C for 10 h to a deposited amorphous Ge layer and crystalline growth rates of 2.5 and 1.8 μm/h were observed in directions parallel and perpendicular to the stress axis, respectively. These results were confirmed by scanning electron microscope and transmission electron microscopy (TEM) analyses. In addition, TEM and x-ray diffraction analyses indicate that a fraction of poly-Ge annealed in the presence of applied compressive stress possessed a tetragonal structure with space-group P43212. The presence of the tetragonal phase is hypothesized to be the primary mechanism responsible for the lateral growth of poly-Ge. [ABSTRACT FROM AUTHOR]

Porous silicon carbide fabricated from p-type 4H and 6H SiC wafers by electrochemical etching in hydrofluoric electrolyte is studied. An investigation of the dependence on wafer polarity reveals that pore formation is favored on the C face while complete dissolution occurs on the Si face. When the etching is done on the C face, the pore wall thickness decreases with increasing current density. The morphology of the front surface of the sample depends on the prior treatment of the workpiece surface. The porosity is estimated based on the analysis of scanning electron microscope images, charge-transfer calculations, and gravimetric analysis. [ABSTRACT FROM AUTHOR]

Epitaxial lateral overgrown (ELOG) gallium nitride (GaN) on SiC is being studied as a possible substrate for blue laser diodes. A defect density below 2.2 × 107 cm-2 in the wings, compared to 2 × 109 cm-2 in the windows, was achieved. Interaction of the overgrown GaN with the SiO2 mask causes a few degree wing tilt and a transition region of high defect density between windows and wings. Diminished PL, strong tensile stress, and a defect correlated line at around 3.4 eV emerge in this up to two-micron-wide transition region. By changing the mask material from SiO2 to SiN we were able to reduce the wing tilt drastically to below 0.7°. This eliminates the defective transition region and extends the low strain and the low defect density area of the ELOG wings. The methods used to study strain, wing tilt, and threading dislocations in the ELOG samples are microphotolmninescence (μPL), transmission electron microscopy, x-ray diffraction, and scanning electron microscope. We also demonstrate the use of the faust momentum of the μPL spectra as an effective means to measure strain distribution. [ABSTRACT FROM AUTHOR]

Eight percent of Mn was successfully diluted into nonpolar ZnO films deposited by pulsed laser deposition on single crystal (100) SrTiO3 substrates. X-ray diffraction patterns and energy-dispersive X-ray spectroscopy confirmed high crystallinity of the films and excluded unintentional magnetic doping. A unique surface domain structure was observed by scanning electron microscope and atomic force microscope, which might play a vital role to strain release induced by lattice mismatch between nonpolar (11-20) ZnO film and (100) SrTiO3 substrate. In addition, the films showed strong ferromagnetism with a large coercivity HC~180Oe at room temperature. The large magnetic moment is ascribed to carrier-mediated exchange interaction between the Mn ions, where the majority of the carriers are oxygen vacancies. [ABSTRACT FROM AUTHOR]

The C-V electrical characterization of microstructures on a standard probe station is limited by the magnification of the imaging system and the precision of the probe manipulators. To overcome these limitations, we examine the combination of in situ electrical probing and a dual column scanning electron microscope/focused ion beam system. The imaging parameters and probing procedures are carefully chosen to reduce e-beam damage to the metal oxide semiconductor capacitor device under test. Estimation of shunt capacitance is critical when making femtofarad level measurements. C-V measurements of micron size metal-oxide-silicon capacitors are demonstrated. [ABSTRACT FROM AUTHOR]

We have developed a high brightness picosecond electron gun. We have used it to replace the thermionic electron gun of a commercial scanning electron microscope (SEM) in order to perform time-resolved cathodoluminescence experiments. Picosecond electron pulses are produced, at a repetition rate of 80.7 MHz, by femtosecond mode-locked laser pulses focused on a metal photocathode. This system has a normalized axial brightness of 93 A/cm2 sr kV, allowing for a spatial resolution of 50 nm in the secondary electron imaging mode of the SEM. The temporal width of the electron pulse is 12 ps. [ABSTRACT FROM AUTHOR]

A surface analysis system has been newly developed with combination of ultrahigh vacuum scanning electron microscope (SEM) and wide-movable scanning tunneling microscope (STM). The basic performance is experimentally demonstrated. These SEM and STM images are clear enough to obtain details of surface structures. The STM unit moves horizontally over several millimeters by sliding motion of PZT actuators. The motion resolution is proved to be submicrometers. The STM tip mounted on another PZT scanner can be guided to a specific object on the sample surface during SEM observation. In the observation of a Si(111) surface rapidly cooled from high temperature, the STM tip was accurately guided to an isolated atomic step and slightly moved along it during SEM observation. The STM observation shows an asymmetry of the (7×7)-transformed region along the step between the upper and lower terraces. (7×7) bands continuously formed along the edge of terraces, while (7×7) domains distributed on the terraces slightly far from the step. These experiments show the wide-movable STM unit resolves a gap of observation area between SEM and STM and the system enables a specific object found in the SEM image to be observed easily by STM. [ABSTRACT FROM AUTHOR]

We study frost formation and its impact on icephobic properties of superhydrophobic surfaces. Using an environmental scanning electron microscope, we show that frost nucleation occurs indiscriminately on superhydrophobic textures without any particular spatial preference. Ice adhesion measurements on superhydrophobic surfaces susceptible to frost formation show increased adhesion over smooth surfaces with a strong linear trend with the total surface area. These studies indicate that frost formation significantly compromises the icephobic properties of superhydrophobic surfaces and poses serious limitations to the use of superhydrophobic surfaces as icephobic surface treatments for both on-ground and in-flight applications. [ABSTRACT FROM AUTHOR]

Direct measurements on electrical characteristics have been carried out in situ inside a scanning electron microscope using a multiple nanoprobe system on individual SnO2 capped ZnO nanowires (NWs) within a NW film on a Zn substrate. It is shown that while good Ohmic contacts can be made at Zn–ZnO NW and ZnO NW–SnO2 cap (when heavily doped with Zn) junctions, the overall I-V characteristics of the Zn–ZnO–SnO2 junction system differ significantly among different NWs, suggesting doping inhomogeneity in the NW film. [ABSTRACT FROM AUTHOR]

We developed a method of fast probe-to-probe approach for an independently controlled dual-probe scanning tunneling microscope (STM), which is essential to measure the transport property of nanostructures, without scanning electron microscopy (SEM). In the approach method, inchworm motors are used as the coarse positioning devices, which are controlled with a personal computer. The method enables an automatic approach of the probe to the other probe within a short time (typically 30 min). After the approach, a real distance between contact points of each probe tip to a sample can be measured from the overlapped part of the STM images obtained with individual probe. The approach method without SEM is also useful to measure the charge transport in the atmosphere, which will be essential for measurement of the bio molecules. [ABSTRACT FROM AUTHOR]

Direct imaging of atomic step morphologies and individual threading dislocations in on-axis epitaxial 4H-SiC surfaces is presented. Topographically sensitive electron images of the crystalline surfaces were obtained through forescattered electron detection inside a conventional scanning electron microscope. This technique, termed electron channeling contrast imaging (ECCI), has been utilized to reveal the configuration of highly stepped, homoepitaxial 4H-SiC films grown on 4H-SiC mesa structures. Individual threading dislocations have been consistently imaged at the core of spiral atomic step morphologies located on the 4H-SiC surfaces. The ability of ECCI to image atomic steps was verified by atomic force microscopy. [ABSTRACT FROM AUTHOR]

The authors demonstrated an investigation of the real-time growth of ZnO nanosheets via in situ observation in an environmental scanning electron microscope. It was found that ZnO nanosheets were grown in a two-stage process: [formula]-oriented nanowires were grown first, and then ZnO nanosheets grew perpendicularly on the parent nanowires along the [0001] axis. The authors’ results revealed that the change of the ZnO growth direction from [formula] (a axis) to [0001] (c axis) can be achieved by control of the growth temperature. [ABSTRACT FROM AUTHOR]

Zinc oxide tetrapods were synthesized on a large scale through thermal evaporation of zinc powder with a vapor transportation deposition method. Scanning electron microscope images gave clear evidences of twin planes at the junction of the tetrapods. Photoluminescence and waveguide behaviors of a single tetrapod were demonstrated with a near-field scanning optical microscope. [ABSTRACT FROM AUTHOR]

In situ electromigration studies on polycrystalline gold nanowires are performed using a high resolution scanning electron microscope. Simultaneously, the resistance of the gold nanowires is recorded during current stressing. The nanowires are prepared by electron beam lithography (EBL) and subsequent thermal evaporation of gold onto the resist mask. In a further EBL-process contact leads are attached to the gold nanowires to determine resistance changes of better than 5×10-4. The authors observe small resistance oscillations which occur during the scanning process. They show that these oscillations are due to the scanning process of the electron beam rather than founded on periodic changes of the void morphology. [ABSTRACT FROM AUTHOR]

The study deals with the charging effect of polyurethanes-based composites reinforced with cellulose fibers, under electronic beam irradiation in a scanning electron microscope. The results indicate that the leakage current and the trapped charge as well as the kinetics of charging process significantly change beyond a critical concentration of 10% cellulose fibers. These features are correlated with the cellulose concentration-dependence of the electrical properties, specifically resistivity and capacitance, of the composite. [ABSTRACT FROM AUTHOR]