Single Liquid Precursor Research Articles

Evolution of elemental distribution in single liquid precursor–derived nanocomposite solid oxide cell electrodes at nanoscale and its impact on electrochemical performance stability

Evolution of elemental distribution in single liquid precursor–derived nanocomposite solid oxide cell electrodes at nanoscale and its impact on electrochemical performance stability

Fast preparation of (111)‐oriented β‐SiC films without carbon formation by laser chemical vapor deposition from hexamethyldisilane without H2

Abstract(111)‐oriented β‐SiC films were prepared by laser chemical vapor deposition using a diode laser (wavelength: 808 nm) from a single liquid precursor of hexamethyldisilane (Si(CH3)3–Si(CH3)3, HMDS) without H2. The effects of laser power (PL), total pressure (Ptot) and deposition temperature (Tdep) on the microstructure, carbon formation and deposition rate (Rdep) were investigated. β‐SiC films with carbon formation and graphite films were prepared at PL ≥ 170 W and Pto ≥ 1000 Pa, respectively. Carbon formation strongly inhibited the film growth. β‐SiC films without carbon formation were obtained at Ptot = 400‐800 Pa and PL = 130‐170 W. The maximum Rdep was about 50 μm·h−1 at PL = 170 W, Ptot = 600 Pa and Tdep = 1510 K. The investigation of growth mechanism shows that the photolytic of laser played an important role during the depositions.

Nitrogen-Doped Graphene Synthesized from a Single Liquid Precursor for a Field Effect Transistor

Opening the band gap of graphene is among the most important issues in modulating its electrical properties for electronic device applications. In this study, we report on the synthesis of nitrogen-doped graphene for field effect transistors. The graphene doped with nitrogen was synthesized by thermal chemical vapor deposition using a single liquid precursor of dimethylformamide, which contains both carbon and nitrogen sources. Material characterization by Raman spectroscopy, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy confirmed the successful synthesis of high-quality nitrogen-doped graphene with a thickness of two or three atomic layers. By simply using dimethylformamide as a liquid precursor, we could dope N into graphene with a doping level of 0.64 at.%. The synthesized graphene was used to fabricate a field effect transistor, the characteristics of which were systematically studied at different temperatures (15–105°C) in air and in a vacuum. Results showed that the synthesized graphene exhibits p-type behavior in air but n-type behavior in a vacuum with a band gap of about 0.03 eV. The field effect mobility calculated at room temperature was 359 cm2 V−1 s−1. The fabricated field effect transistor has potential applications in electronic devices.

Synthesis of nitrogen-doped graphene by the thermal chemical vapor deposition method from a single liquid precursor

In this work we report the synthesis of nitrogen-doped graphene using an ambient pressure chemical vapor deposition technique on polycrystalline Ni substrates with a single liquid precursor, as the source of both carbon and nitrogen. Nitrogen atom substitution of the so-formed graphene was confirmed by X-ray photoelectron spectroscopy. The signal from sp2 bonded carbon atoms decreased in the nitrogen-doped graphene at longer deposition times. Spatially resolved Raman mapping results and transmission electron microscopy images show that the nitrogen-doped graphene formed with varying thickness from a monolayer to >10 layers. The effects of growth temperature and deposition time on the level of nitrogen doping, number of layers, and the quality of the nitrogen-doped graphene layer were investigated.

Deposition of Bio‐Integration Ceramic Hydroxyapatite by Pulsed‐Pressure MOCVD Using a Single Liquid Precursor Solution

AbstractPulsed‐pressure (PP) metal‐organic(MO)CVD is used to deposit layers of calcium phosphate onto flat bio‐medical grade titanium (Ti6Al4V) substrates. Inexpensive calcium lactate and trimethyl phosphate (TMP), combined in a methanol solution, forms the precursor. A range of precursor mixtures is studied by thermogravimetric analysis (TGA) to assess reaction pathways. The surface topography, morphology, composition, and crystallinity are studied over a range of deposition temperatures and precursor concentrations. The resulting films are analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD), Raman spectroscopy (RS), and micro‐indentation. The films are continuous and the size of surface structures increases at higher temperatures and precursor concentration. The films consist of amorphous calcium phosphate in elemental Ca/P ratios similar to the standard bio‐ceramic, hydroxyapatite (1.66).

HRTEM characterization of YBa 2Cu 3O 7− δ thick films on LaAlO 3 substrates

High-quality superconducting YBa 2Cu 3O 7− δ (YBCO) thick films with thickness over 2 μm were grown on LaAlO 3 (LAO) substrates by photo-assisted metalorganic chemical vapor deposition (PhA-MOCVD) with a single liquid precursor delivery system. The YBCO thick films fabricated are single-crystal like with no visible grain boundaries or voids. Surface and interface microstructures of YBCO thick films have been systematically investigated by scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. Large precipitates were observed on the surface of these films. These precipitates are mostly composed of crystalline BaCu 3O 4, along with some polycrystalline and amorphous YBCO phases, and were found to exist only on top of the YBCO films, with no penetration into the films. The high quality of the prepared YBCO thick films was confirmed further by the results of X-ray diffraction and T c/ J c measurements. Thus, these thick YBCO films prepared by PhA-MOCVD have promising application potential in fields such as coated conductors.

Microstructures of epitaxial YBa/sub 2/Cu/sub 3/O/sub 7-δ/ thick films grown by photoassisted metal-organic chemical vapor deposition

Epitaxial, high-quality YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thick films were grown by a photoassisted metal-organic chemical vapor deposition technique with a single liquid precursor delivery system, and characterized by X-ray diffraction (XRD), scanning electron microscopy, and low-high-resolution transmission electron microscopy techniques. Very dense and single-crystal-like film structure was observed in all of these YBCO thick films. Large precipitates on these thick films were identified as BaCu/sub 3/O/sub 4/, sprinkled only at surface of these YBCO thick films. YBCO thick films with high crystalline and superconductive quality were confirmed by data of XRD analyses and superconductivity measurements. At the same time, the reason why epitaxial YBCO thick films with high-quality single-crystal-like structure can be grown up to about 4.5 /spl mu/m thick is illustrated from the point of view of photoactivation. It is also found that these thick films were optimally oxygenated with their superconductive properties in concern.

Single liquid precursor delivery photo-assisted metalorganic chemical vapor deposition of high quality YBa 2Cu 3O 7− x thin/thick films

High quality superconducting YBa 2Cu 3O 7− x (YBCO) films were deposited on LaAlO 3 ( 1 0 0 ) substrates at a high growth rates of 0.2–1 μm /min with high reproducibility by a novel photo-assisted metalorganic chemical vapor deposition process with single liquid precursor delivery technique. The photo irradiation technique can dramatically increase the growth rate and the single liquid precursor delivery technique can significantly improve the process reproducibility. X-ray diffraction analysis indicated that single phase, c-axis oriented and well ab-aligned YBCO films were high reproducibly prepared. The as-grown YBCO films showed critical temperatures ( T c) of 91 K with the transition width ( ΔT c) less than 1 K, and self-field critical current densities ( J c) of 4.6×10 6 A/cm 2 at 77 K.

Chemical vapor deposition of Pb1−xLaxTiO3

Abstract We report chemical vapor deposition (CVD) of PbLaTiO3 films for integrated pyroelectric devices. Pb(thd)2, La(thd)3 and Ti(O-Pr)2(thd)2 were introduced to the reactor via a single liquid precursor solution that is vaporized. Substrate temperatures were approximately 535°C and post deposition annealing was not used. Films were deposited on fused silica and Pt metallized Si substrates. The liquid delivery technique permitted excellent composition control and films on fused silica were predominantly [100] oriented with trace amounts of [110] and [111] present. Pyroelectricity for 0.7μm thick films deposited on Pt metallized Si was measured using a modified Byer-Roundi technique and pyroelectric coefficients as high as 90 nC/cm2·K were observed. The high crystalline quality and pyroelectric properties are attributed to the excellent composition control afforded by the liquid delivery CVD technique.