Microstructure of the MgH2 Synthesized by Hydriding Chemical Vapor Deposition

2006 ◽  
Vol 971 ◽  
Author(s):  
Itoko Saita ◽  
Tomohiro Akiyama
Keyword(s):  
Chemical Vapor Deposition ◽  
Hydrogen Storage ◽  
Vapor Deposition ◽  
Hydrogen Diffusion ◽  
Chemical Vapor ◽  
Hydrogen Desorption ◽  
Plateau Pressure ◽  
Equilibrium Pressure ◽  
Significant Difference ◽  
Before And After

ABSTRACTIt is hardly achieved to prepare highly pure MgH2 by the conventional method of solid-gas reaction between solid magnesium and hydrogen; therefore, we proposed and succeeded to synthesize MgH2 by Hydriding Chemical Vapor Deposition (HCVD). Very interestingly, the HCVDed MgH2 was made of single crystals with fibrous figures; however, further detail of the HCVDed product had not been studied. Therefore the aim of this study was to examine the HCVDed MgH2 in hydrogen storage and to observe the microstructure of the HCVDed MgH2 after the hydrogen desorption and absorption.As the results of Pressure-Composition-Isotherm (PCT) measurement, the HCVDed MgH2 reversibly absorbed and desorbed 7.6 mass% hydrogen, as much as the theoretical maximum hydrogen capacity of magnesium, without any activation treatment. The equilibrium pressure was slightly lower than the reported value. Before and after the PCT measurement, the HCVDed MgH2 did not showed noticeable difference in figure; however, MgHx, which was prepared dehydriding the HCVDed MgH2 in the PCT, showed significant difference in figure: It had zebra stripes in the SEM observation. This observation showed that the hydrogen storage and release went in the radious direction and the hydrogen diffusion was no more rate-limiting. The phase boundaries of Mg and MgH2 involving strain should affected on the plateau pressure in PCT.

Comparisons of Gallium Nitride and Indium Nitride Properties after CF4 / Argon Reactive Ion Etching

2002 ◽  
Vol 743 ◽  
Author(s):  
Marie Wintrebert-Fouquet ◽  
K. Scott ◽  
A. Butcher ◽  
Simon K H Lam
Keyword(s):  
Chemical Vapor Deposition ◽  
Low Temperature ◽  
Vapor Deposition ◽  
Indium Nitride ◽  
Reactive Ion Etching ◽  
Film Surface ◽  
Chemical Vapor ◽  
Electrical Characteristics ◽  
Ion Etching ◽  
Before And After

ABSTRACTWe present a comparative study of the effects of low power reactive ion etching (RIE) on GaN and InN. This new, highly chemical, dry etching, using CF4 and Ar, has been developed for thin nitride films grown at low temperature in our laboratories. GaN films were grown by remote plasma enhanced-laser induced chemical vapor deposition and InN films were grown by radio-frequency RF reactive sputtering. Commercial GaN samples were also examined. Optical and electrical characteristics of the films are reported before and after removing 100 to 200 nm of the film surface by RIE. We have previously shown that the GaN films, although polycrystalline after growth, may be re-crystallized below the growth temperature. Removal of the surface oxide has been found to be imperative since a polycrystalline residue remains on the surface after re-crystallization.

Growth, microstructure, charge transport, and transparency of random polycrystalline and heteroepitaxial metalorganic chemical vapor deposition-derived gallium–indium–oxide thin films

2002 ◽  
Vol 17 (12) ◽  
pp. 3155-3162 ◽  
Author(s):  
Anchuan Wang ◽  
Nikki L. Edleman ◽  
Jason R. Babcock ◽  
Tobin J. Marks ◽  
Melissa A. Lane ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Indium Oxide ◽  
Vapor Deposition ◽  
Carrier Density ◽  
Metalorganic Chemical Vapor Deposition ◽  
Chemical Vapor ◽  
Root Mean Square Roughness ◽  
Minor Role ◽  
Significant Difference ◽  
Metalorganic Chemical

Gallium–indium–oxide films (GaxIn2⊟xO3), where x = 0.0–1.1, were grown by low-pressure metalorganic chemical vapor deposition using the volatile metalorganic precursors In(dpm)3 and Ga(dpm)3 (dpm = 2,2,6,6-tetramethyl-3,5-heptanedionato). The films were smooth (root mean square roughness = 50–65 Å) with a homogeneously Ga-substituted, cubic In2O3 microstructure, randomly oriented on quartz or heteroepitaxial on (100) yttria-stabilized zirconia single-crystal substrates. The highest conductivity of the as-grown films was found at x = 0.12, with σ = 700 S/cm [n-type; carrier density = 8.1 × 1019 cm⊟3; mobility = 55.2 cm2/(V s); dσ/dT<0]. The optical transmission window of such films is considerably broader than that of Sn-doped In2O3, and the absolute transparency rival or exceeds that of the most transparent conductive oxides known. Reductive annealing, carried out at 400–425 C° in a flowing gas mixture of H2 (4%) and N2, resulted in increased conductivity (σ 1400 S/cm; n-type), carrier density (1.4 × 1020 cm⊟3), and mobility as high as 64.6 cm2/(V s), with little loss in optical transparency. No significant difference in carrier mobility or conductivity is observed between randomly oriented and heteroepitaxial films, arguing in combination with other data that carrier scattering effects at high-angle grain/domain boundaries play a minor role in the conductivity mechanism.

Remote Plasma Enhanced-Metal Organic Chemical Vapor Deposition of Zirconium Oxide/Silicon Oxide Alloy, (ZrO2)1-(SiO2)1−x (x:≤0.5), Thin Films for Advanced High-K Gate Dielectrics

1999 ◽  
Vol 567 ◽  
Author(s):  
D. Wolfe ◽  
K. Flock ◽  
R. Therrien ◽  
R. Johnson ◽  
B. Rayner ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Silicon Oxide ◽  
Chemical Vapor ◽  
Organic Chemical ◽  
Remote Plasma ◽  
Before And After ◽  
Oxidized Zirconium ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

ABSTRACTA remote plasma enhanced-metal organic chemical vapor deposition (RPE-MOCVD) process was developed for the preparation of non-crystalline (ZrO2)x-(SiO2)1−x (x ≤ 0.5) alloys, targeting the compound composition ZrSiO4with k ∼ 12.5. Shifts in Si LVV and Zr LMM AES energies with respect to elemental values showed that the deposited film was a fully-oxidized zirconium/silicon alloy. FTIR results were consistent with AES, and a Zr-O-Si bonding mode was identified in the spectra. The films were amorphous before and after RTA at 900°C for 30 sec, as monitored via RHEED. Optical absorption measurements indicated the onset of band-to-band transitions at an energy of approximately 6 eV. Finally, C-V testing showed that the films were insulating.

Optical Probe in Gadolinium Doped GaN by Metalorganic Chemical Vapor Deposition

2013 ◽  
Vol 329 ◽  
pp. 109-113
Author(s):  
Xiang Ping Shu ◽  
Andrew Melton ◽  
Zhi Ren Qiu ◽  
Lan T. Ferguson ◽  
Zhe Chuan Feng
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Chemical Vapor ◽  
Optical Probe ◽  
Temperature Dependent ◽  
Two Samples ◽  
Significant Difference ◽  
P Type ◽  
Metalorganic Chemical

Gd doping related excitons are observed in four samples with different gadolinium (Gd) adoption ratios, grown by metalorganic Chemical Vapor Deposition (MOCVD). The intensity and quenching phenomena with temperature in Gd related excitons are varied from the conduction type of samples. By temperature-dependent photoluminescence measurements the vanish effects in Gd-doping induced excitons show a significant difference from intrinsic and n-type samples to p-type samples. In the former two samples the Gd excitons disappeared beyond 200K, while in p-type samples it is still exist even in 533K.

Analysis of Unsteady Heat and Mass Transfer During the Modified Chemical Vapor Deposition Process

1998 ◽  
Vol 120 (4) ◽  
pp. 858-864 ◽  
Author(s):  
K. S. Park ◽  
M. Choi
Keyword(s):  
Mass Transfer ◽  
Chemical Vapor Deposition ◽  
Heat And Mass Transfer ◽  
Vapor Deposition ◽  
Particle Deposition ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Inlet Region ◽  
Significant Difference ◽  
Good Agreement

An analysis of unsteady heat and mass transfer in the modified chemical vapor deposition has been carried out. It is found that the commonly used quasi-steady-state assumption could be used to predict the overall efficiency of particle deposition; however, the assumption would not be valid near the inlet region where tapered deposition occurs. The present unsteady calculations have been found to be capable of predicting the detailed deposition profile correctly even from the inlet region where further optimization is needed at a practical situation. The present results have also been compared with existing experimental data and were in good agreement. It is noted that previous quasi-steady calculation resulted in a significant difference in the deposition profile near the inlet region. The effects of time-varying torch speeds were also studied. The case of a linearly varying torch speed resulted in a much shorter tapered entry than the case of a constant torch speed.

Effects of Long-Time Current Annealing to the Hysteresis in CVD Graphene on SiO2

MRS Advances ◽  
2019 ◽  
Vol 4 (61-62) ◽  
pp. 3319-3326 ◽  
Author(s):  
U. Kushan Wijewardena ◽  
Tharanga Nanayakkara ◽  
Rasanga Samaraweera ◽  
Sajith Withanage ◽  
Annika Kriisa ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Hole Transport ◽  
Ambient Conditions ◽  
Back Gate ◽  
Graphene Sample ◽  
Before And After ◽  
Long Time ◽  
Current Annealing

ABSTRACTGraphene specimens produced by chemical vapor deposition usually show p-type characteristics and significant hysteresis in ambient conditions. Among many methods, current annealing appears to be a better way of cleaning the sample due to the possibility of in-situ annealing in the measurement setup. However, long-time current annealing could increase defects in the underlying substrate. Studying the hysteresis with different anneal currents in a graphene device is, therefore, a topic of interest. In this experimental work, we investigate electron/hole transport in a graphene sample in the form of a Hall bar device with a back gate, where the graphene was prepared using chemical vapor deposition on copper foils. We study the hysteresis before and after current annealing the sample by cooling down to a temperature of 35 Kfrom room temperature with a back-gate bias in a closed cycle refrigerator.

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