It is essential to control the electronic properties of a graphene field effect transistor (GFET). And the ability to accurately control the intrinsic electrical transport properties and to locally change the carrier density will be significant for graphene devices. We succeeded in achieving and controlling the Dirac point (neutrality point) simply by doping block co-polymer (BCP) covered GFET with CF4 plasma. By exposing polymer covered GFET to CF4 plasma for a short time the electronic transport was altered significantly. The hexagonal structure of BCP produces patterns with nanoscale spacing for heterogeneous patterns which provides a new approach to tune the electron and the hole conductivity simultaneously. Exploitation of fluorine doping provides a general route to control electronic property of any polymer coated GFET. The BCP protected GFET could detect 1mM NaF solution in “dry” condition in 60s. The sensing property demonstrates that BCP protected GFET could be a good candidate for stable and sensitive chemical or biological sensor. Furthermore, the distinct property of two functional groups within BCP facilitates the selective sensing property. These findings pave the way for developing more stable and sensitive sensors under ambient conditions.

We report heteroepitaxial growth of VO2 thin film on c-plane sapphire by pulsed DC magnetron sputtering. X-ray diffraction experiment indicates that the 150 nm thick film is in triple-domain (020)-epitaxial structure with six-fold rotational symmetry in the basal plane; in particular, off-axis Φ scans from (011) and (220) show twin and triple peaks in each group of the diffraction profiles due to angle β mismatch and V4+-V4+ dimerization, respectively. The epitaxial relationship between VO2 and c-plane sapphire can be concluded as be , with the in-plane lattice mismatch of 2.66% (tensile) along and the out-of-plane lattice mismatch of -2.19% (compressive). Temperature dependence of resistivity in van der Pauw method shows that the resistivity changes by ~5 orders of magnitude through the metal-insulator transition, and a narrow hysteresis window of ~3 K is obtained between cooling and heating cycles with respect to phase-transition temperatures at 347.1 and 350.1 K.

Single crystalline Indium Antimonide (InSb) nanowires were synthesized by chemical vapor deposition (CVD) technique, using gold (Au) nanoparticles as catalyst, via a vapor liquid solid mechanism. Structural properties of the as-grown InSb nanowires were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Nanowire field effect transistors (NWFETs) were fabricated in back-gate configuration, on Si/SO2 substrates, using SiO2 as gate insulator. The diameter of InSb nanowires used in the fabricated devices varied from 15-80 nm. Current-voltage measurements were conducted to determine the dependence of NWFETs parameters on the InSb nanowire diameter. Carrier mobility was shown to decrease with decrease of nanowire diameter. Temperature dependen current-voltage measurements were conducted to determine the effect of operating temperature on the InSb NWFET device performance.

This paper describes first steps in preparation of an organic spin valve based on a perylene derivative (PTCTE) sandwiched between magnetite (Fe3O4) and cobalt (Co) ferromagnetic electrodes. MgO(001)/Fe3O4/PTCTE (450 nm)/Co devices were prepared with different Co soft deposition methods: off-axis dc-sputtering or Joule evaporation. Vibrating Sample Magnetometer (VSM) studies of the Fe3O4/PTCTE/Co stacks evidence spin valve behavior with magnetically uncoupled electrodes. These results are correlated with a morphological study by atomic force microscopy (AFM) of each layer and tunneling AFM (TUNA) for the investigation of inhomogeneity of current distribution in the devices. Finally, macroscopic I-V characteristics performed on the same devices will be presented and compared with TUNA results.

Conductive atomic-force microscopy (C-AFM) writing is attracting attention as a technique for clarifying the switching mechanism of resistive random-access memory (ReRAM) by providing a wide area filled with filaments, which can be regarded as one filament with large radius. We observed a C-AFM writing area of NiO films using SEM, and revealed a correlation between the contrast in a secondary electron image (SEI) and the resistance written by C-AFM. In addition, the dependence of the SEI contrast on the beam accelerating voltage (V accel) suggests that the resistance-change effect occurs near the surface of the NiO film. As for the effect of electron irradiation on the C-AFM writing area, it was shown that the resistance change effect was caused by exchanging oxygen with the atmosphere at the surface of the NiO film. This result suggests that the low resistance and high resistance areas are, respectively, p-type Ni1+δ O (δ < 0) and insulating (stoichiometric) or n-type Ni1+δ O (δ ≥ 0).

Large, defect-free single-phase samples of the hexagonal C14 NbFe2 and Nb(Fe,Al)2, and the cubic C15 NbCo2 Laves phases have been produced by a modified levitation melting technique. The compressive strength of NbFe2 and NbCo2 has been determined in dependence on the Nb content, that of Nb(Fe,Al)2 in dependence on the Al content. The binary phases did not show either a maximum (defect softening) or minimum (defect hardening) in strength when the Nb content was varied. Instead, for both phases an increase of the compressive strength with increasing Nb content is observed.

Carbon nanotubes (CNTs) are appealing materials for biomedical applications due to their unique chemical, electrical and mechanical properties. The emphasis of the present work is on controlling the structure and symmetry of carbon nanotubes by imposing an applied stress at the CNT growth site. CNTs were grown under these conditions using standard chemical vapor deposition (CVD) techniques and were subsequently characterized with a scanning electron microscope; the methodology and implications of this approach are discussed herein.

In this work, we perform molecular dynamics (MD) simulations to study the linear thermal transport in suspended graphene and the nonlinear thermal transport phenomena in graphene nanoribbons (GNR). We use spectral energy density analysis to quantitatively address the relative importance of different types of phonon in thermal transport in suspended graphene. Negative differential thermal conductance (NDTC) and thermal rectification in graphene nanoribbons have been studied using nonequilibrium molecular dyanmics simulations. Ballistic transport regime, sufficient temperature nonlinearity and asymmetry are found to be necessary conditions for the onset of these behaviors.

In order to apply P(VDF-TeFE) piezoelectric polymer to micro-generator as a membrane, the polymer is deposited on a substrate by spin-coating method. Since a solvent affects the film properties and surface stability, we have carried out the thermal process at a temperature higher than melting point. In the annealing process of a P(VDF-TeFE) thin film, electrical properties of the film was improved by an application of an electric field. The established study was the investigation of variations in characteristics by an application of a certain electric field. We have attempted to measure about the critical intensity of an electric field and investigate what the influences of the application is caused using a XPS spectrum in this study. Moreover, in order to control the intrusion of impurities, we have used the vacuum chamber to carry out the annealing process in it.

Nanoindentation results are very sensitive to tip rounding and neglecting the value of the tip radius produces erroneous estimation of the material elastic properties. In this study we investigate the effect of tip radius on the estimation of the Elastic modulus by means of finite element analysis of Berkovich and conical tips with different tip radii. Our numerical results were already supported by an experimental study on fused silica with Berkovich tips with different tip radii. The use of classical Oliver Pharr equation overestimated the Elastic modulus. A new analytical model that modifies the Oliver Pharr equation to consider the value of the tip radius is employed to derive the Elastic modulus from load displacement curves yielding improved results compared to the classical Oliver Pharr equation.

We have investigated the stability of short channel (1.5μm) p-Type polycrystalline silicon (poly-Si) Thin Film Transistors (TFTs) on the glass substrate under AC bias stress. The variation of threshold voltage in short channel poly-Si TFT was considerably higher than that of long channel poly-Si TFT. Threshold voltage of the short channel TFT was considerably moved to the positive direction during AC bias stress, whereas the threshold voltage of a long channel was rarely moved. The variation of threshold voltage in the short channel p-type TFT under AC bias stess was more compared to that under DC bias stress. The threshold voltage of short channel (L=1.5μm) poly-Si TFT was increased about -7.44V from -0.305V to -7.745V when VGS = 5 (base value) ~ -15V (peak value), VDS = -15V was applied for 3,000 seconds. This positive shift of threshold voltage and significantly degraded s-swing value in the short channel TFT under dynamic stress (AC) may be due to the increase of the stress-induced trap state density at gate insulator / channel interface region.

Micro-solid oxide fuel cells (Micro-SOFCs) with yttrium-doped barium zirconate (BZY) and strontium and cobalt-doped lanthanum scandate (LSScCo) electrolytes were fabricated for low-temperature operation at 300 °C. The micro-SOFC with a BZY electrolyte could operate at 300 °C with an open circuit voltage (OCV) of 1.08 V and a maximum power density of 2.8 mW/cm2. The micro-SOFC with a LSScCo electrolyte could operate at 370 °C; its OCV was about 0.8 V, and its maximum power density was 0.6 mW/cm2. Electrochemical impedance spectroscopy revealed that the electrolyte resistance in both the micro-SOFCs was lower than 0.1 Ωcm2, and almost all of the resistance was due to anode and cathode reactions. Although the obtained maximum power density was not sufficient for practical applications, improvement of electrodes will make these micro-SOFCs promising candidates for power sources of mobile electronic devices.

In this work, we present progress towards device fabrication using purified, semiconducting-enriched SWNT as the base material. Nanotubes were deposited in different densities (low, moderate, and high density) with different gate length of transistors and effect of each parameter has been studied using DC measurements. It is been shown that the nanotube network density plays a significant role in controlling the performance of such devices. By controlling the density of nanotubes in the network, we laid down a road map to predict and enhance the device performance based on their mobility and on/off ratio. From this work the DC analysis of devices characterization shows a mobility more than 90 cm2/V-s and also on/off ratios as high as, 105 have been achieved. We have demonstrated the first density-control technique over the nanotube network as a key point to modify the transistor’s mobility and on/off ratio [1]. When dense network mats of nanotubes were deposited, devices outperformed with higher mobility more than 90 cm2/V-s, enabling a faster switching speed. While relatively low-density mats yielded devices with on/off ratio of more than 105, which makes this technique feasible for low power nanoelectronics. Besides, the effect of various gate lengths have been studied which reveals an interesting trend between the channel length and the mobility.

Many reported CuIn1-xGaxSe2 (CIGS) thin films for high-efficiency solar cells have been prepared via a two-stage process that consists of a high-vacuum film deposition step followed by selenization with excess H2Se gas or Se vapor. Removing toxic gas and high-vacuum requirements from this process would greatly simplify it and make it less hazardous. We report the formation of CuIn1-xGaxSe2 (x = 0, 0.25, 0.50, 0.75, 1.0) thin films achieved by rapid thermal annealing of spray-deposited CuIn1-xGaxS2 and Se in the absence of an additional selenium source. To prepare the Se layer, commercial Se powder was dissolved by refluxing in ethylenediamine/2,2-dimethylimidizolidine. After cooling to room temperature, this mixture was combined with 2-propanol and the resulting colloidal Se suspension was sprayed by airbrush onto a heated glass substrate. The resulting film was coated with nanocrystalline CuIn1-xGaxS2 via spray deposition of a toluene-based “nanoink” suspension. The two-layer sample was annealed at 550 oC in an argon atmosphere for 60 minutes to form the final CIGS product. Scanning electron microscopy images reveal that film grains are 200-300 nm in diameter and comparable to sizes of the reactant CuIn1-xGaxS2 nanoparticles. XRD patterns are consistent with the chalcopyrite unit cell and calculated lattice parameters and A1 phonon frequencies change nearly linearly between those for CuInSe2 and CuGaSe2.

Human genomic structural variation (SV) is significant factor in genome complexity, and thus has substantial implications to the cause, development and progression of genetic diseases. These SVs, ranging in size of 1kbp-1Mbp, are challenging to assess with current technologies. As such, we have developed a commercial system (nanoAnalyzer® 1000) for the rapid linear analysis of genomes at single-molecule level.

The core of our system is a nanofluidic chip consisting of an array of channels with a diameter less than 100 nm, nanofabricated on the surface of a silicon substrate. Thousands of unamplified genomic DNA molecules of 100’s kbps to several Mbps can be isolated and linearly streamed into the array for analysis in a parallel fashion. Fluorescently labeled sequence-specific signatures can then be identified and aligned to reference patterns at high resolution with custom software. This automated, multi-color imaging platform will enable a wide range of applications, such as accurate sequencing assembly, discovering genome structural variations, and uncovering epigenomic content. Nanochannel arrays promise to substantially lower the barriers of entry for single-molecule DNA analysis for scientists and clinicians, greatly impacting the advancement of molecular diagnostics, personalized medicine, and biomedical research.

As a part of a systematic study on cation-exchanged MOF-74-M, we report a partial snapshot of our recent work achieved via a fully periodic first principle approach. Structures are reported for bulk MOF-74-Mg, Mn, Ni, and Zn as computed at DFT-B3LYP level of theory; enthalpies of adsorption for CO and CO2 in interaction with MOF-74-Ni, and Zn are also investigated as obtained at B3LYP+D* level, which is able to take into account the long-range dispersion interaction between adsorbate and adsorbant, through an a-posteriori scheme. Results are discussed and compared with available experimental data. To the authors’ knowledge this represents the first description of MOF-74-Mn structure and of the interaction of the mentioned molecules with MOF-74-Zn.

The surface potential (SP) undulation on the surfaces of tris(8-hydroxyquinolinato) aluminum (III) (Alq3) films has been investigated with Kelvin probe force microscopy (KFM) and scanning near-field optical microscope (SNOM)-KFM. The SP undulation observed on the amorphous Alq3 films with thicknesses of up to 300 nm showed a cloud-like morphology of 200–300 nm in lateral size. The temporal change of SP undulation was traced through cyclic measurement with KFM observation with intermittent photoexposure, as well as in situ localized photoexcitation with SNOM-KFM. We concluded that the origin of the SP undulation is the nonuniform distribution of charged traps and drift mobility in the Alq3 films.

Ge nanocrystals embedded in silica matrix have been synthesized on Si substrate by co-sputtering of SiO2 and Ge using RF magnetron sputtering technique. The as-deposited films were subjected to microwave annealing at 800 and 9000C. Rutherford backscattering spectrometry (RBS) has been used to measure the Ge composition and film thickness. The structural characterization was performed by using X-ray diffraction (XRD) and Raman spectrometry. XRD measurements confirmed the formation of Ge nanocrystals. Raman scattering spectra showed a peak of Ge-Ge vibrational mode around 299 cm−1, which was caused by quantum confinement of phonons in the Ge nanocrystals. Surface morphology of the samples was studied by atomic force microscopy (AFM). Variation of nanocrystal size with annealing temperature has been discussed. Advantages of microwave annealing are explained in detail.

Resistive switching properties of silver nanoparticles hosted in an insulating polymer matrix (poly(N-vinyl-2-pyrrolidone) are reported. Planar devices structures using interdigitated gold electrodes were fabricated. These devices have on/off resistance ratio as high as 103 , retention times reaching to months and good endurance cycles. Temperature-dependent measurements show that the charge transport is weakly thermal activated (73 meV) for both states suggesting that nanoparticles will not aggregate into a metallic filament.

Lithographically prepared gold nanodots and nanowires were placed onto a thermal sensor film to measure heat absorption. These identical wires are also subjected to dark field scattering measurements allowing for a comparison between absorption and scattering at the excitation wavelength. An increasing liner trend is found to exist between nanowires of increasing aspect ratio. The nanostructures also exhibit a decreasing temperature change with increasing wire length with a constant laser flux of 1.3 x 1010 W/m2.