The stability of elongated single- and multi-layered graphene nanoribbons (GNRs) are investigated by molecular-dynamics simulation. In order that GNRs are to be modeled as nanobridges connecting two terminals of electronic devices, the short edges of the GNRs are constrained. The distances between the two constrained edges are gradually increased, and the GNRs are uniaxially strained. The energies and out-of-plane deformations of such uniaxially strained GNRs are examined. The energies of multi-layered GNRs will be lower than those of isolated GNRs because the surface areas of multi-layered GNRs are smaller than the total area of the isolated GNRs. Understanding the relationship between the out-of-plane deformations and strain will lead to the control of the ripple structures of GNRs.

Interface state density profiling of the thermal oxide / n-type 4H-SiC interface which underwent post-oxidation nitric-oxide (NO) annealing showed that an interface state density of approximately 1×1011 cm−2eV−1 could be achieved at around 0.2 eV below the conduction band. It decreased exponentially by two orders to 1×109 cm-2eV-1 at around 0.9 eV from the conduction band. The values are comparable or better than other published work. The low interface state density achieved near the conduction band is important towards improved channel carrier mobility in SiC MOSFETs. A positive flat-band voltage shift of the SiC based MOS capacitor was also observed. The shift reduced under UV illumination. It could be attributed to slow acceptor-like (negatively-charged) traps, which may have contributed to the instabilities observed in drain current and threshold voltage suffered by SiC MOSFETs.

Stable, catalytically active, and inexpensive halogen electrodes are essential for the success of the regenerative hydrogen-halogen fuel cell as a competitive means of large-scale electricity storage. We report the synthesis and electrochemical testing of two novel electrode materials — ruthenium-cobalt and ruthenium-manganese alloy oxides. These alloys were fabricated by wet chemical synthesis methods as a coating on a titanium metal substrate and tested for chloride and bromide oxidation and for chlorine and bromine reduction. These alloy oxides exhibit high catalytic potency and good electrical conductivity good stability, while having a significantly reduced precious metal composition compared to commercial chloride oxidation electrodes made of the oxide of a ruthenium-titanium alloy. We tested alloys with Ru content as low as 1% that maintained good electrochemical activity. Stability tests indicate immeasurably small mass loss.

High-temperature measurements of the spatial distribution of the displacement characteristics of a thickness shear mode langasite (La3Ga5SiO14) resonator are obtained using a laser Doppler interferometer. Thereby, the resonator is excited in the fundamental mode and the third overtone. Further, the resonator is coated with a gas sensitive CeO2-x film which exceeds the metal electrode. In reducing atmospheres the conductivity of the film increases and induces an increase of the effective electrode area. This effect leads to a broadening of the mechanical displacement distribution. The latter depends strongly on the size of the excited part of the resonator which is determined by the effective size of the electrodes. The direct determination of the mechanical displacement at different oxygen partial pressures confirms a model as derived from the electrical impedance of resonator devices [1]. Further, information about the mass sensitivity distribution of resonators is obtained since the property is directly proportional to the amplitude.

Silicon nanowire solar cells were simulated using the Silvaco TCAD software kit. For optimization of speed the simulations were performed in cylinder coordinates with cylindrical symmetry. Symmetric doping was assumed with a dopant density of 1018 cm-3 in the p-type core and inside the n-type shell. In the implementation a cathode contact was wrapped around the semiconductor nanorod and an anode was assumed at the bottom of the rod. Optimization of cell efficiency was performed with regard to the rod radius and the rod length. In both optimization processes clear maxima in efficiency were visible, resulting in an optimal radius of 66 nm with the pn junction at 43.5 nm and an optimal rod length of about 48 μm. The maximum of efficiency with respect to the rod radius is due to a decrease of short-circuit current density (Jsc) and an increase of open-circuit voltage (Uoc) with radius, while the maximum with respect to the rod length is explained by the combination of an increase of Jsc and a decrease of Uoc. Fill factors stay rather constant at values between 0.6 and 0.8. Further, the influence of a back surface field (BSF) layer was surveyed in simulations. Positioning the BSF next to the cathode contact considerably improved cell efficiency. In addition, simulations with a cathode contact on top of the nanowire structure were undertaken. No severe deterioration of cell performance with increasing radius was observed so far in this configuration. Hence, nanorods with much larger radii can be used for solar cells using this contact scheme. In comparison to simulations with wrapped cathode contacts, Jsc and Uoc and therefore efficiency is considerably improved.

Nanoimprint lithography is a low cost method which produces trillions of nanostructures on a substrate. One application of this technology is patterned magnetic media where a single imprint on a disk can create a masking layer with more than a trillion nanostructures. Several challenges exist to imprinting bit patterned media (BPM) at a density greater than 1Tbit/in2. This technology would allow an extension of hard drive magnetic recording at densities greater than 1Tbit/in2. One such challenge is imprint resist mechanical properties where the imprinted masking layer should be free of thickness variations and resist flop-over. Herein we describe the nanoindentation mechanical properties of several imprint resist systems along with analysis of imprinted features of BPM at densities between 200-482 Gdots/in2.

We report electrochemical characteristics of hydrogen terminated charge-transfer doped intrinsic microcrystalline diamond films. Microcrystalline diamond was synthesized by Direct- Current Plasma Enhanced Chemical Vapor Deposition (DC-PECVD) in methane diluted by hydrogen. The diamond films were subjected to further treatment by microwave plasma in pure hydrogen to increase the hydrogen termination of the diamond surfaces and their negative electron affinity. When the diamond is exposed to the ambient moisture, valance electrons tend to tunnel from the first few atomic layers of the diamond surface to the adsorbed water adlayer. This charge transfer process results in the surface of hydrogen-terminated diamond behaving like a p-type semiconductor.

Electrochemical characteristics of hydrogen-terminated diamond films were exposed to an air plasma for depleting the surface hydrogen atoms and then re-hydrogenated the same diamond films with atomic hydrogen. Cyclic voltammetry in 0.1M H2S04 aqueous solution and 0.01M Fe(CN)6 -4/-3+0.1M KCl aqueous solution was applied to reveal high current density and wide potential window for hydrogen-terminated diamond grown on silicon substrates. The faceted surface morphology has been observed by SEM. The crystalline characteristics and carbon phases in the diamond film were examined by Raman spectroscopy.

The industrial dyeing apparatus excavated in Pompeii have been preserved and remain in situ. To understand Pompeii’s economy, and its place in the Roman world, it is necessary to first understand the capabilities of a single industry. Before this study, the size of the dyeing industry was calculated by applying theory to a superficial measurement of the remains. This study was the first to realise that to understand an industry it was necessary to reconstruct and use the relevant parts.

The most comprehensive survey of the apparatus was undertaken. A full-scale physical replica was constructed from materials that physically and thermally matched the originals. This study was the first to define the dyeing cycle time, temperatures reached and fuel type and quantity required. Finite Element Analysis (FEA) was used to model a virtual replica to show the effect of external influences on the materials during use. The lead metal data did not exist before this study. This was the first use of FEA to model an archaeological apparatus or artefact of more than one material. The dyeing industry had been far smaller than originally thought.

Archaeological virtual replications tend to be aesthetic. This study produced a rare physical replication. When this is combined with data from the original survey and physical replicas each apparatus is now ‘preserved by record’ and may be recreated. Some of the apparatus in Pompeii have been amended in an attempt to reconstruct and preserve them. This study has shown that the amendments are incorrect and potentially misleading.

Prior to this study the size of the industry was a controversial ‘unanswerable’ question. This study provided a solid foundation that answered the question and illustrated a new approach, through a method that provided a means of preserving the apparatus for the future.

Monoclonal antibodies are increasingly used in the treatment of cancer due to their enhanced targeting and immune system stimulation properties. Dosage guidelines typically do not account for personal cancer load or metabolism, thereby possibly affecting treatment outcome or causing unwanted side effects. The requirement for an assay that can quickly and precisely measure the concentration of the monoclonal antibody in a serum sample of a patient during therapy is unmet. A bead-based assay with peptide antigen mimetics has been developed to rapidly determine the concentration of antibody drug present in serum specimens with high sensitivity. Alemtuzumab (anti-CD52) and rituximab (anti-CD20) antigen mimetic peptides, as discovered by phage display, were synthesized on 10 um TentaGel resin beads using conventional solid phase peptide synthesis techniques. The beads were modified to allow for multiplexing and microfluidic handling via fluorescent labeling and magnetic functionalization. The antigen-displaying fluoromagnetic particles were incubated with spiked serum samples which allowed free antibody to be captured. Primary antibody detection was performed on alemtuzumab while rituximab detection was used to compensate for non-specific serum binding to the beads. After washing, the beads were incubated with a fluorescently tagged secondary label for detection by flow cytometry. (Results) A fast, low cost, specific assay has been developed with several key techniques which allows detection at low concentration (0.1ug/ml) of spiked samples. Primary to achieving this detection limit was the implementation of a compensation scheme where two antigen mimetic peptides behave linearly (R2=0.996) which enables the calculation of the zero response of the antigen mimetic peptide of interest (alemtuzumab antigen mimetic) while measuring the zero response of the compensatory antigen mimetic peptide (rituximab antigen mimetic) during primary assay measurement. This reduces fluorescence response variation due to variations present due to sample preparation, storage and different patients because of the equivalent interactions these effects have on the compensatory beads. The developed assay is therefore robust against serum variation and enables a lower limit of detection.

We describe a facile and direct method for the functionalization of single-walled carbon nanotubes with 4’-substituted phenyls and biphenyls. By means of Raman spectroscopy and thermogravimetric analysis we demonstrate that a simple protocol of a direct chemical grafting in acetonitrile solution of the corresponding diazonium salts at room temperature results in a formation of stable aryl monolayers on carbon nanotubes.

We develop Si-based nano-photonic devices for the control of light at the nano-scales. We design high quality (Q) factor photonic crystal nanobeam cavities for a variety of Si compatible materials with low index, such as silicon rich oxide and silicon nitride, all with Q > 9,000 and small mode volumes. We apply these cavity designs to active materials such as Sinanocrystal doped silicon oxide and Er doped silicon nitride. By placing emitters in these cavities, we demonstrate that the cavity enhances emission processes. We show that the free carrier absorption process is greatly enhanced in the nanobeam cavities at both room and cryogenic temperatures. In addition, we demonstrate that nanobeam cavities made of Er-doped amorphous silicon nitride have enhanced absorption and gain characteristics compared to earlier designs that included silicon in the cavity. Because of the reduced losses, we observe linewidth narrowing and material transparency at both room temperature and cryogenic temperatures.

Epitaxial ZnO layers heavily doped with Ga (GZO) were grown at 400 °C under metaland oxygen-rich conditions in terms of metal-to-reactive oxygen ratio by plasma-assisted molecular beam epitaxy (MBE). Several atomic force microscopy (AFM) techniques were used to characterize the surface morphology and electrical properties of these GZO films in ambient conditions. Local I-V spectra indicate that layers grown under both O-rich and metal-rich conditions are highly resistive until a relatively high voltage sweep (±12 V) is used. After removal of an insulating surface layer, conduction is possible at lower voltages, but eventually the film resistivity increases and it again becomes insulating. In addition to local I-V spectra, local charge injection and subsequent surface potential measurements were used to probe surface charging characteristics. For charge injection experiments, a reverse-bias voltage is applied to the sample while scanning in contact mode with a metallized tip. The resultant change in surface potential due to trapped charge is subsequently observed using scanning Kelvin probe microscopy (SKPM). The layers deposited in a metal-rich environment demonstrate the expected behavior, but the O-rich layers show anomalous negative and positive charging. Finally, surface photovoltage (SPV) measurements using above-bandgap UV illumination were performed. The GZO layers produce SPV values of 0.4 to 0.5 eV, where the films deposited in an O-rich environment have slightly higher SPV values and faster restoration.

We have recently presented a novel method for a complete thermoelectric characterization [J. de Boor, V. Schmidt. Adv. Mater. 22:4303, (2010)]. This method is based on the well-known electrical van der Pauw method and allows measurement of the electrical and thermal conductivity, the Seebeck coefficient and the thermoelectric figure of merit. After a short review of this method we will discuss the systematic measurement errors of the method. It turns out that radiative heat loss can affect the thermal conductivity measurement significantly. We will give a simple estimation for the relative error due to radiation losses and discuss error minimizing strategies.

ZnO/Au/ZnO (ZAZ) electrodes grown on flexible PEN substrates were evaluated as transparent electrodes for organic light-emitting devices (OLEDs). OLEDs fabricated with the ZAZ electrodes showed reduced leakage in contrast to control OLEDs on ITO and reduced ohmic losses at high current densities. At a luminance of 25000 cd/m2, the lum/W efficiency of the ZAZ electrode based device was 5% greater than for the device on ITO. The ZAZ electrodes also allow for a broader spectral output in the green wavelength region of peak photopic sensitivity compared to ITO. The results have implications for electrode choice in display technology.

Organic thin-film transistors (OTFTs) using cross-linked olefin polymer as a gate insulator were fabricated on a plastic film. An olefin polymer layer was formed by spin-coating and baking at temperatures below 150°C. Pentacene was used as an organic semiconductor layer. The fabricated OTFTs with a short 5-μm-long channel showed a mobility of 0.1-0.2 cm2/Vs and a current ON/OFF ratio of 107. These OTFTs also exhibited good stable performance in the atmosphere. On the basis of the results, we fabricated a 5 inches OTFT-driven flexible active-matrix organic light emitting diode (AMOLED) display. The gate insulator, some metal wirings and electrodes on the OTFT backplane were formed on the plastic film by photolithography. After fabrication of the OTFT backplane, OLED layers were formed by vacuum deposition through a shadow-mask. Clear color moving images were observed on the flexible display even when it was bent.

The results obtained by direct nano-patterning demonstrate the potential of the SPM-based techniques that include surface scratching to create 3D nanostructures. Such techniques became known as tribo-nanolithography and have prospects of being successfully implemented in the future nanofabrication industry. An important obstacle to this, however, is the effect of wear at the nanometer scale which is critical to the stability of tribo-nanolithoraphic processes. Such stability is achievable via in-depth theoretical and experimental studies of friction at the nanoscale along with the development of pioneering equipment. Our work presents the results of experimental fabrication of nanostructures formed by nanoscratching with the use of the multifunctional scanning tunneling microscopy previously developed by the authors. The authors attempted scratching the silicon surface by using a boron-doped diamond tip. This operation was undertaken in the same direction sequentially with the tip sliding a side of the groove by one of the tip’s facets and the consequent surface scanning. Although not being applicable to non-conductive surfaces, the proposed technique has significant advantages. One advantage is related to the high stiffness of the tunneling probe as compared to the stiffness of the AFM cantilever. High stiffness and perpendicularity of the tip to the surface during surface processing eliminates bending beam effects on the typical AFM and ensures machining effectiveness. Purposely synthesized boron-doped single-crystal diamonds were used as a tip material. The results of experimental fabrication of nanostructures formed by nanoscratching with the use of the multifunctional scanning probe are demonstrated and discussed.

Although Helium Ion Microscopy (HIM) was introduced only a few years ago, many new application fields are budding. The connecting factor between these novel applications is the unique interaction of the primary helium ion beam with the sample material at and just below its surface. In particular, the HIM secondary electron (SE) signal stems from an area that is very well localized around the point of incidence of the primary beam. This makes the HIM well-suited for both high-resolution imaging as well as high resolution nanofabrication. Another advantage in nanofabrication is the low ion backscattering fraction, leading to a weak proximity effect. The lack of a quantitative materials analysis mode (like EDX in Scanning Electron Microscopy, SEM) and a relatively low beam current as compared to the SEM and the Gallium Focused Ion Beam are the present drawbacks of the HIM.