Black Si Photocathode with a Conformal and Amorphous MoS Catalytic Layer Grown Using Atomic Layer Deposition for Photoelectrochemical Hydrogen Evolution.

We demonstrated how the photoelectrochemical (PEC) performance was enhanced by conformal deposition of an amorphous molybdenum sulfide (a-MoS) thin film on a nanostructured surface of black Si using atomic layer deposition (ALD). The a-MoS is found to predominantly consist of an octahedral structure (S-deficient metallic phase) that exhibits high electrocatalytic activity for the hydrogen evolution reaction with a Tafel slope of 41 mV/dec in an acid electrolyte. The a-MoS has a smaller work function (4.

Co-catalytic Effects of CoS on the Activity of the MoS Catalyst for Electrochemical Hydrogen Evolution.

MoS is a promising material to replace the Pt catalyst in the electrochemical hydrogen evolution reaction (HER). It is well known that the activity of the MoS catalyst in the HER is significantly promoted by doping cobalt atoms. Recently, the Co-Mo-S phase, in which cobalt atoms decorate the edge positions of the MoS slabs, has been identified as a co-catalytic phase in the Co-doped MoS (Co-MoS) with low Co content.

A comprehensive study on atomic layer deposition of molybdenum sulfide for electrochemical hydrogen evolution.

Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs).

Nanostructures of Indium Gallium Nitride Crystals Grown on Carbon Nanotubes.

Nanostructure (NS) InGaN crystals were grown on carbon nanotubes (CNTs) using metalorganic chemical vapor deposition. The NS-InGaN crystals, grown on a ~5-μm-long CNT/Si template, were estimated to be ~100-270 nm in size. Transmission electron microscope examinations revealed that single-crystalline InGaN NSs were formed with different crystal facets.

Importance of hydrophilic pretreatment in the hydrothermal growth of amorphous molybdenum sulfide for hydrogen evolution catalysis.

Amorphous molybdenum sulfide (MoSx) has been identified as an excellent catalyst for the hydrogen evolution reaction (HER). It is still a challenge to prepare amorphous MoSx as a more active and stable catalyst for the HER. Here the amorphous MoSx catalysts are prepared on carbon fiber paper (CFP) substrates at 200 °C by a simple hydrothermal method using molybdic acid and thioacetamide.

Highly uniform and vertically aligned SnO2 nanochannel arrays for photovoltaic applications.

Nanostructured electrodes with vertical alignment have been considered ideal structures for electron transport and interfacial contact with redox electrolytes in photovoltaic devices. Here, we report large-scale vertically aligned SnO2 nanochannel arrays with uniform structures, without lateral cracks fabricated by a modified anodic oxidation process. In the modified process, ultrasonication is utilized to avoid formation of partial compact layers and lateral cracks in the SnO2 nanochannel arrays.

High turnover frequency of hydrogen evolution reaction on amorphous MoS2 thin film directly grown by atomic layer deposition.

Recently amorphous MoS2 thin film has attracted great attention as an emerging material for electrochemical hydrogen evolution reaction (HER) catalyst. Here we prepare the amorphous MoS2 catalyst on Au by atomic layer deposition (ALD) using molybdenum hexacarbonyl (Mo(CO)6) and dimethyl disulfide (CH3S2CH3) as Mo and S precursors, respectively. Each active site of the amorphous MoS2 film effectively catalyzes the HER with an excellent turnover frequency of 3 H2/s at 0.

Novel chemical route for atomic layer deposition of MoS₂ thin film on SiO₂/Si substrate.

Recently MoS₂ with a two-dimensional layered structure has attracted great attention as an emerging material for electronics and catalysis applications. Although atomic layer deposition (ALD) is well-known as a special modification of chemical vapor deposition in order to grow a thin film in a manner of layer-by-layer, there is little literature on ALD of MoS₂ due to a lack of suitable chemistry. Here we report MoS₂ growth by ALD using molybdenum hexacarbonyl and dimethyldisulfide as Mo and S precursors, respectively.

Observation of localized strains on vertically grown single-walled carbon nanotube forests via polarized Raman spectroscopy.

Vertically grown single-walled carbon nanotube (V-SWCNT) forests, synthesized by water-assisted plasma-enhanced chemical vapor deposition, were studied using polarized micro-Raman spectroscopy. Among three different sections (root, center and end) along the vertical growth direction, the degree of V-SWCNT alignment was highest in the center section. Raman frequency red-shifts up to 7 and 13 cm(-1), for RBM and G-band, respectively, were observed in the center section, with respect to the Raman frequencies measured in the root and the end sections.

Large-scale assembly of 'type-switchable' field effect transistors based on carbon nanotubes and nanoparticles.

We report the large-scale assembly of type-switchable field effect transistors (FETs) based on carbon nanotubes (CNTs) and nanoparticles (NPs). In this device, the charges stored in NPs adjacent to ambipolar CNT channels were adjusted to control the carrier type and density in the channels. We demonstrated the real-time reconfiguration of individual FET types and logic circuit functionality.

Doping of carbon nanotubes using low energy ion implantation.

Carbon nanotubes (CNTs) were implanted with thermally decomposed oxygen (O2+) and nitrogen (N2+) ions at an acceleration voltage of 20 V. With a low dose of oxygen ions, the CNT-FET exhibited p-type behaviors with substantial changes in threshold voltage and in the slope of the source-drain current (l(sd)). However, at high dosages, the device exhibited metallic behaviors.

Thin film transistors using preferentially grown semiconducting single-walled carbon nanotube networks by water-assisted plasma-enhanced chemical vapor deposition.

Nearly perfect semiconducting single-walled carbon nanotube random network thin film transistors were fabricated and their reproducible transport properties were investigated. The networked single-walled carbon nanotubes were directly grown by water-assisted plasma-enhanced chemical vapor deposition. Optical analysis confirmed that the nanotubes were mostly semiconductors without clear metallic resonances in both the Raman and the UV-vis-IR spectroscopy.

Noise characteristics of single-walled carbon nanotube network transistors.

The noise characteristics of randomly networked single-walled carbon nanotubes grown directly by plasma enhanced chemical vapor deposition (PECVD) are studied with field effect transistors (FETs). Due to the geometrical complexity of nanotube networks in the channel area and the large number of tube-tube/tube-metal junctions, the inverse frequency, 1/f, dependence of the noise shows a similar level to that of a single single-walled carbon nanotube transistor. Detailed analysis is performed with the parameters of number of mobile carriers and mobility in the different environment.

Thin film transistors of single-walled carbon nanotubes grown directly on glass substrates.

We report a transistor of randomly networked single-walled carbon nanotubes on a glass substrate. The carbon nanotube networks acting as the active components of the thin film transistor were selectively formed on the transistor channel areas that were previously patterned with catalysts to avoid the etching process for isolating nanotubes. The nanotube density was more than 50 microm(-2), which is much larger than the percolation threshold.

Low-temperature growth of single-walled carbon nanotubes by water plasma chemical vapor deposition.

Preferential growth of pure single-walled carbon nanotubes (SWNTs) over multi-walled carbon nanotubes (MWNTs) was demonstrated at low temperature by water plasma chemical vapor deposition. Water plasma lowered the growth temperature down to 450 degrees C, and the grown nanotubes were single-walled without carbonaceous impurities and MWNTs. The preferential growth of pure SWNTs over MWNTs was proven with micro-Raman spectroscopy, high-resolution transmission electron microscopy, and electrical characterization of the grown nanotube networks.

Sulfidative purification of carbon nanotubes integrated in transistors.

We demonstrate a simple purification method of carbon nanotubes via sulfidation reaction of carbon, C + 2S --> CS2, to selectively remove carbonaceous impurities from nanotubes. The sulfidative purification of carbon nanotubes integrated in field-effect transistors results in a dramatic improvement of switching characteristics due to removal of carbonaceous impurities.