Modeling of Pyrolytic Laser-Assisted Chemical Vapor Deposition: Effects of Kinetics and Choice Of Substrate

1987 ◽  
Vol 101 ◽  
Author(s):  
D.C. Skouby ◽  
K.F. Jensen
Keyword(s):  
Gas Phase ◽  
Vapor Deposition ◽  
Laser Intensity ◽  
Chemical Vapor ◽  
Reaction Rates ◽  
Desorption Kinetics ◽  
Temperature Dependent ◽  
Finite Element Approach ◽  
Element Approach ◽  
Adsorption Desorption

ABSTRACTThe pyrolytlc laser-assisted deposition of metals Is modeled. A finite element approach is used to solve for temperatures and gas-phase concentrations In a transient calculation. The model accommodates the use of temperature-dependent physical properties as well as the occurrence of irregularly shaped deposits. Volcano-like deposits’ are predicted under certain conditions of gas pressure and laser intensity. The effect of using substrates with different thermal conductivities is investigated. Using adsorption-desorption kinetics such that the reaction rates have sharp maxima with respect to temperature, volcanoes of varying depths are modeled.

H2S Gas Sensor Based on WO3 Nanostructures Synthesized via Aerosol Assisted Chemical Vapor Deposition Technique

2019 ◽  
Vol 11 (9) ◽  
pp. 1247-1256 ◽  
Author(s):  
T. Shujah ◽  
M. Ikram ◽  
A. R. Butt ◽  
M. K. Shahzad ◽  
K. Rashid ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Gas Sensors ◽  
Vapor Deposition ◽  
Gas Sensing ◽  
Chemical Vapor ◽  
Desorption Kinetics ◽  
Nanostructured Surfaces ◽  
Vapor Deposition Technique ◽  
H2s Gas Sensor ◽  
Adsorption Desorption

Herein we demonstrate tungsten oxide (WO3 nanostructures based resistive type sensors for hydrogen sulfide (H2S) gas sensing utility. The WO3 dynamic layers have been deposited upon alumina substrates pre-patterned with gold (Au) interdigitated electrodes. For comparative study, two distinct WO3 nanostructures (S-425 and S-450) have been synthesized using Aerosol Assisted Chemical Vapor Deposition (AACVD) technique at varied deposition temperatures i.e., 425 and 450 °C, respectively. The gas detecting properties of both sensors were investigated against varied concentration (0-60 ppm) of H2S gas levels. The electrical resistance of fabricated gas detectors has been observed at DC bias of 5 V and low operating temperature 250 °C. Specifically, when concentration of H2S gas increases from 0-10 ppm, average resistance of the S-425 and S-450 gas sensors was observed to decrease by 96.5% and 97.6%, respectively. In general, the sensing mechanism of gas sensors proposed in this work can be associated with ionosorption of oxygen species over WO3 nanostructured surfaces. However, the significantly enhanced sensing performance of S-450 sensor may be attributed to improved crystallinity in its structure and improved ions adsorption/desorption kinetics at nanorods surface morphology.

scholarly journals Gas Phase Chemistry of Trimethylboron in Thermal Chemical Vapor Deposition

2017 ◽  
Vol 121 (47) ◽  
pp. 26465-26471 ◽  
Author(s):  
Mewlude Imam ◽  
Laurent Souqui ◽  
Jan Herritsch ◽  
Andreas Stegmüller ◽  
Carina Höglund ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Gas Phase ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Thermal Chemical Vapor Deposition ◽  
Gas Phase Chemistry ◽  
Phase Chemistry

scholarly journals Gas-phase aluminium acetylacetonate decomposition: Revision of the current mechanism by VUV synchrotron radiation

2021 ◽  
Author(s):  
Sebastian Grimm ◽  
Seung-Jin Baik ◽  
Patrick Hemberger ◽  
Andras Bodi ◽  
Andreas Kempf ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Synchrotron Radiation ◽  
Gas Phase ◽  
Vapor Deposition ◽  
Aluminium Oxide ◽  
Chemical Vapor ◽  
Phase Decomposition ◽  
Common Precursor ◽  
Current Mechanism

Although aluminium acetylacetonate, Al(C5H7O2)3, is a common precursor for chemical vapor deposition (CVD) of aluminium oxide, its gas phase decomposition is not very well investigated. Here, we studied its thermal...

Quantitative Modelling of Nucleation Kinetics in Experiments for Poly-Si Growth on Sio2 by Hot-Wire Chemical Vapor Deposition

2001 ◽  
Vol 664 ◽  
Author(s):  
Maribeth Swiatek ◽  
Jason K. Holt ◽  
Harry A. Atwater
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Nucleation Density ◽  
Hot Wire ◽  
Nucleation Kinetics ◽  
Temperature Dependent ◽  
Cluster Density

ABSTRACTWe apply a rate-equation pair binding model of nucleation kinetics [1] to the nucleation of Si islands grown by hot-wire chemical vapor deposition on SiO2 substrates. Previously, we had demonstrated an increase in grain size of polycrystalline Si films with H2 dilution from 40 nm using 100 mTorr of 1% SiH4 in He to 85 nm with the addition of 20 mTorr H2. [2] This increase in grain size is attributed to atomic H etching of Si monomers rather than stable Si clusters during the early stages of nucleation, decreasing the nucleation density. Atomic force microscopy (AFM) measurements show that the nucleation density increases sublinearly with time at low coverage, implying a fast nucleation rate until a critical density is reached, after which grain growth begins. The nucleation density decreases with increasing H2 dilution (H2:SiH4), which is an effect of the etching mechanism, and with increasing temperature, due to enhanced Si monomer diffusivity on SiO2. From temperature-dependent measurements, we estimate the activation energy for surface diffusion of Si monomers on SiO2 to be 0.47 ± 0.09 eV. Simulations of the temperature-dependent supercritical cluster density lead to an estimated activation energy of 0.42 eV ± 0.01 eV and a surface diffusion coefficient prefactor of 0.1 ± 0.03 cm2/s. H2-dilution-dependent simulations of the supercritical cluster density show an approximately linear relationship between the H2 dilution and the etch rate of clusters.

Electron Paramagnetic Resonance Studies of Intrinsic Bonding Defects and Impurities in SiO2 Thin Solid Films

1985 ◽  
Vol 61 ◽  
Author(s):  
Robert N. Schwartz ◽  
Marion D. Clark ◽  
Walee Chamulitrat ◽  
Larry Kevan
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Rf Sputtering ◽  
Chemical Vapor ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Pressure Chemical ◽  
Defects And Impurities ◽  
Electron Paramagnetic

ABSTRACTElectron paramagnetic resonance (EPR) spectroscopy has been used to identify paramagnetic intrinsic bonding defects and impurities in as-deposited thin solid SiO2 films. Thin films grown by E-beam vacuum deposition, RF sputtering, thermal oxidation of polysilicon, plasma enhanced chemical vapor deposition (PECVD), and low pressure chemical vapor deposition (LPCVD) techniques have been examined. Some of the growth techniques yield films that have paramagnetic centers similar to those found in bulk radiation-damaged vitreous SiO2. A new temperature dependent EPR center was observed in PECVD SiO2 films and has been assigned to trapped NO2. Slow-motional EPR lineshape theory was used to analyze the temperature dependent spectra.

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