Effect of Tungsten Oxide Nanostructures on Sensitivity and Selectivity of Pollution Gases

We report on the different surface structures of tungsten oxides which have been synthesized using a simple post-annealing-free hot-filament CVD technique, including 0D nanoparticles (NPs), 1D nanorods (NRs), and 2D nanosheet assemblies of 3D hierarchical nanoflowers (NFs). The surface morphologies, crystalline structures, and material compositions have been characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy, respectively. The sensor performances based on the synthesized samples of various surface morphologies have been investigated, as well as the influences of operating temperature and applied bias. The sensing property depends closely on the surface morphology, and the 3D hierarchical nanoflowers-based gas sensor offers the best sensitivity and fastest response time to NH3 and CH3 gases when operated at room temperature.

Analysis of Defect-Free Hot Filament CVD-Grown 3C-SiC

Analysis of hot-filament CVD (HF-CVD) growth of high quality 3C-SiC on micron-sized 3C-SiC mesas is presented. Two types of growth were observed: 1) a relatively slow growth at about 1μm/hour, and 2) an almost three times faster growth, correlated with the presence of domain boundaries in, or adjacent to, the mesas. Both reveal well-defined crystallographic facets and sharp corners between them. The slower growth has been identified to be surface-nucleation-limited, seemingly defect-free, while the faster growth has been identified as being caused by defect-induced step-flow growth. A growth model is presented, yielding a growth rate of 1.18 μm/h for the defect free {111} and (100) plane and 2.8 μm/h for {110} planes.

Hot-filament CVD Growth of Vertically-aligned Carbon Nanotubes on Support Materials for Field Electron Emitters

Carbon nanotubes are used in applications such as energy storages, electronic devices. For these applications, direct assembly of the well aligned and densely packed CNTs (VACNTs) on electrically conducting substrates is of interest. In this paper, we report a direct growth of the VACNTs on several substrates by using hot-filament chemical vapor deposition (hot-filament CVD) and a catalytic buffer-layer structure. The buffer layer was the Aluminum (Al) thin film used together with iron (Fe) as the catalyst. It was found that the underneath layer (Al) was critical for obtaining the VACNT forests with high purity and good contact. The as-fabricated VACNT/support-material structures are object to test field electron emission properties. Testing results of the VACNT samples demonstrated promising field emission characteristics in term of high emitting currents.

Direct growth of nitrogen-doped graphene films on glass by plasma-assisted hot filament CVD for enhanced electricity generation

N-Doped graphene glass was prepared through a novel plasma-assisted HFCVD approach, which exhibited significantly enhanced voltage generation for energy harvesting.

Hot Filament CVD Growth of 4H-SiC Epitaxial Layers

Hot filament CVD (HFCVD) growth of undoped 4H-SiC epitaxial layers on 100 mm n-type 4o-off 4H-SiC substrates is presented as an alternate growth method for the first time. High quality crystalline material with a low density of polytype inclusions has been demonstrated and characterized with optical micrographs, SEM imaging, micro-Raman measurements, and high resolution XRD. Typical growth rates are ~3 μm/hour. Double rocking omega scans revealed diffraction peaks with a FWHM of 23 arcsec.