Semi insulating N-gallium nitride (GaN) on sapphire surface reflection dataset obtained at millimeter wave frequencies 107.35-165 GHz.

A systematic collection of voltage reflection data for semi-insulating N-GaN wafer surface along with the reference reflection voltages are accomplished using a very stable continuous wave (CW) frequency stable probe source. The 2″ diameter direct-bandgap 5 µm silicon doped 105 Ω-cm GaN on 434 µm sapphire is a commercial sample and was mounted in the path of collimated BWO generated millimeter wave beam with spot size ∼3 mm and rotated 64.5° to millimeter wave reflected energy into an antenna fed zero-bias Schottky barrier diode (ZBD), a negative polarity detector with responsivity 3.6 V/mW. Data obtained pertain to photon energies between 400 and 700 µeV (107.35-165 GHz). Data contains the 30-sample average and respective standard deviations for reference (mirror) and N-GaN reflected voltages. Anomalies in d.c. reflection coefficients (based on the raw data) are identified for users.

Millimeter wave direct-current transmission and reflection spectral data of some organic photo-responsive materials.

Voltage data acquired after probe signal transmitted through the organic film and reflected off the film surface as a function of 0.36 mW millimeter wave signal frequency in the range 110-160 GHz. Five different organic photovoltaic (OPV) materials and one 95:5 blend produced at 2 spin rates are used. These materials are a) fluorinated 2-alkyl-benzol[d] [1-3]triazole (FTAZ), a high hole-mobility polymer used for transistors and photovoltaics, b) diketopyrrolopyrrole (DPP3T), an acceptor polymer used in field-effect transistors (FET), c) Y5(PffBT4T-2OD) film that possesses remarkable temperature controllable morphology, d) a neat conjugated polymer P3HT, Poly(3-(hexylthiophene-2,5diyl) film that is used in optoelectronic devices and as a conductive binder for Li-ion batteries, e) phenyl-C61-butyric acid methyl ester (PCBM) films and its soluble derivatives used as n-type organic semiconductors, and f) excitonic photovoltaic material 95%:5% donor-acceptor blend P3HT:PCBM produced by 2 different spin rates. Measurement of direct-current (dc) transmitted and reflected power (RF voltage signal) are measured using a newly developed continuous wave (CW) D-waveguide band probe (110-160 GHz) apparatus named time-resolved millimeter wave conductivity (TR-mmWC) [1]. Transmission and first surface reflection voltages are captured by a zero-bias Schottky barrier diode (ZBD) and converted to relevant dc voltages. Original voltage signal datasets attached with this can be utilized for photovoltaic, dielectric property estimation, and other semiconductor physics applications. A manually collected dataset of transmission and reflection coefficient at incident probe power level ∼0.9 mW for 95:5 P3HT:PCBM films produced at 2 different spin rates, and one separately only for the neat P3HT film are also presented here in tabular form.

A time-resolved millimeter wave conductivity (TR-mmWC) apparatus for charge dynamical properties of semiconductors.

This article demonstrates a contactless, time-resolved, millimeter wave conductivity apparatus capable of measuring photoconductivity of a diverse range of materials. This cavity-less system determines the time-dependent magnitude of a sample's charge carrier density-mobility product by monitoring the response of a continuous, millimeter-wave probe beam following excitation of the sample by an ultrafast laser pulse. The probe beam is tunable from 110 GHz to 170 GHz and the sample response data can be obtained over the sub-nanosecond to millisecond time interval. This system has been tested on silicon wafers, S-I GaAs, perovskite thin films, SiO2-Ge(nc), and CdSxSe1-x nanowire samples. We demonstrate a minimum detectable photoconductance change of ∼1 µS, an estimated time resolution for conductance decay of ∼100 ps, and a dynamic range greater than 57 dB. The calibration constant of the system, needed for quantitative calculation of photoconductivity from experimental data, has been determined using silicon wafers. This system has several advantages over currently used microwave and terahertz techniques, such as facile tunability of probe frequency and substantially wider time range for study of decay kinetics, while maintaining an open sample environment that enables characterization of a wide range of sample sizes under controlled environmental conditions.

One-Step Chemical Vapor Deposition Synthesis of 3D N-doped Carbon Nanotube/N-doped Graphene Hybrid Material on Nickel Foam.

3D hybrid nanostructures connecting 1D carbon nanotubes (CNTs) with 2D graphene have attracted more and more attentions due to their excellent chemical, physical and electrical properties. In this study, we firstly report a novel and facile one-step process using template-directed chemical vapor deposition (CVD) to fabricate highly nitrogen doped three-dimensional (3D) N-doped carbon nanotubes/N-doped graphene architecture (N-CNTs/N-graphene). We used nickel foam as substrate, melamine as a single source for both carbon and nitrogen, respectively. The morphology and microstructure were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, isothermal analyses, X-ray photoelectron microscopy and Raman spectra. The obtained 3D N-CNTs/N-graphene exhibits high graphitization, a regular 3D structure and excellent nitrogen doping and good mesoporosity.

Large Area Synthesis of Vertical Aligned Metal Oxide Nanosheets by Thermal Oxidation of Stainless Steel Mesh and Foil.

We report here the synthesis of metal oxide nanosheets (MONs) directly grown on stainless steel substrates by thermal oxidation in the presence of trace amounts of water. The morphology and microstructure of MONs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and atomic force microscopy (AFM). The composition of MONs was determined by the energy dispersive system and X-ray diffraction patterns. The results showed that the as-synthesized MONs were ultrathin, vertically aligned, and mostly transparent. They were polycrystalline and were composed primarily of Cr2O3 and (Fe, Mn)3O4. The optimal condition to synthesize the MONs with an optimal ultra-high surface atom ratio were determined by varying the temperature and time required for the growth of the MONs. It was found that the lateral size of MONs gradually increases as the temperature rises from 1000 to 1100 °C. An optimal temperature of 1100 °C is obtained in terms of the growth density, size and transparency degree growth morphology, and quality. The structure of MONs changes from two-dimensional to three-dimensional networks when the synthesis time is prolonged to more than 1 h.

Enhanced Performance of E-Bike Motive Power Lead-Acid Batteries with Graphene as an Additive to the Active Mass.

The effects of both graphene nanoplatelets and reduced graphene oxide as additives to the negative active material in valve-regulated lead-acid batteries for electric bikes were investigated. Low-temperature performance, charge acceptance, cycle performance, and water loss were investigated. The test results show that the low-temperature performance, charge acceptance, and large-current discharge performance of the batteries with graphene additives were significantly improved compared to the control battery, and the cycle life under 100% depth of discharge condition was extended by more than 52% from 250 to 380 cycles. Meanwhile, the amount of water loss from the batteries with graphene changed only slightly compared with the control cells. The excellent performance of the batteries can be ascribed to the graphene promoting the negative-plate charge and discharge processes and suppressing the growth of lead sulfate crystals.

Melamine as a single source for fabrication of mesoscopic 3D composites of N-doped carbon nanotubes on graphene.

Integration of two-dimensional graphene and one-dimensional carbon nanotubes (CNTs) to create potentially useful 3D mesoscopic carbon structures with enhanced properties relative to the original materials is very desirable. Here, we report a novel and simple route using chemical vapor deposition (CVD) methods to fabricate bead-like nitrogen-doped CNT/graphene composites (NCNT/G) via a simple pyrolysis of the N-rich melamine in the presence of graphene oxide (GO) as a substrate using a Mn-Ni-Co ternary catalyst. We have characterized these structures by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, isothermal analyses, and X-ray photoelectron spectroscopy. The three dimensional NCNT/G hybrids have unique network structures, moderate graphitization, high specific surface area, good mesoporosity, and N doping, which makes them promising materials for applications in energy storage and conversion.