Gallium nitride (GaN) is exceedingly apposite for liquid-based sensor applications because of their high internal piezoelectric polarization, chemical and high temperature stability. In this work, the interaction between GaN and H2O has been investigated using a novel methodology. We report the fabrication of single crystal GaN lamella with thickness of few hundreds of nanometer using focused ion-beam milling technique, for sensing applications. Results signify that the device resistivity increases with time at room temperature during the GaN-H2O interaction. Such a change in electrical resistivity is explained based on the electron transfer and electrochemical reactions at the surface of GaN. Study of the surface chemistry transformation of the tested GaN lamella is conducted using high-angle annular dark-field scanning transmission electron microscopy coupled with electron energy loss spectroscopy (EELS) and energy dispersive x-ray spectroscopy (EDS) techniques. EDS and EELS results signify the presence of a region containing Ga and O at the interface of the H2O/GaN which is a result due to the adsorption of molecular H2O and its dissociation products implying the occurrence of GaN-water reaction.
The interaction between gallium nitride (GaN) and H 2 O has been thoroughly investigated using a novel methodology involving the fabrication of a well-defined nanometer scale GaN lamella by means of a focused ion beam milling technique. Electrical characterization results show that the exposure of the GaN surface to water at room temperature causes the device resistivity to continuously increase, which makes the GaN lamella a stable polar liquid sensor. To explain the relationship between the reduced conductivity of GaN and water dissociation on the GaN surface, we utilize surface sensitive x-ray photoelectron spectroscopy and density-functional theory calculations to investigate surface oxidation of the dry and wet GaN surface. Our studies show that the water molecules are stably adsorbed on the GaN surface and are favorable to being dissociated into hydrogen atoms and hydroxyl groups on the GaN surface even if the surface is oxidized.
Anti-organic fouling performance of titanium dioxide (TiO2) can be enhanced by extending its light absorption and photocatalytic capability from ultra-violet to the visible range through hydrogenation. In this work, we aim at studying the impact of hydrogenation on the performance of both electron beam-deposited TiO2 thin films and hydrothermally grown TiO2 nanostructures on titanium substrates. Hydrogenation of these TiO2-deposited titanium substrates (TiO2/Ti) are achieved in relatively low-temperature low-pressure chemical vapor deposition chamber without any noble diatomic hydrogen dissociation catalyst, such as platinum. Our study shows that these hydrogenated TiO2/Ti have better light absorption ability and the titanium substrate itself serves as the active catalyst for hydrogen dissociation and diffusion. By applying hydrogenation to the TiO2 nanostructures, we can enhance photocatalytic performance by 50% through methylene blue degradation experiments. We have also evaluated the effect of hydrogenation on carrier density and mobility in TiO2/Ti. We recommend the hydrogenation of hydrothermally grown TiO2 nanostructure on titanium substrates for scalable photocatalytic applications.
This paper presents a study of the effects of electron beam (e-beam) exposure on the chemical and physical properties of FLARE™ 1.0X, a non-fluorinated member of the FLARE™ family of poly(arylene ether) dielectric coatings. Spin-coated films of this poly(arylene ether) were cured by large-area e-beam exposure, as well as by conventional thermal processing. Neither swelling nor dissolution was observed for the e-beam cured films after immersion in N-methylpyrrolidone (NMP) at 90 °C for 1 hour. The glass transition temperature (Tg) for films cured with a low e-beam dose is slightly higher than, or nearly the same as, the (Tg) for thermally-cured films (∼ 270 °C). However, the Tg for films cured with a high e-beam dose exceeds 400 °C. Dielectric constants of e-beam cured films and thermally cured films are nearly the same. FTIR spectra of FLARE™ films obtained before and after e-beam exposure suggest that e-beam curing does not induce any significant change in the chemical structure. Increased solvent resistance, higher Tg, and low dielectric constant are properties that make this e-beam cured poly(arylene ether) film an excellent candidate for interlevel dielectric integration processes.
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