A Three-Dimensional Analysis of the Flow and Heat Transfer for the Modified Chemical Vapor Deposition Process Including Buoyancy, Variable Properties, and Tube Rotation

1991 ◽  
Vol 113 (2) ◽  
pp. 400-406 ◽  
Author(s):  
Y. T. Lin ◽  
M. Choi ◽  
R. Greif
Keyword(s):  
Heat Transfer ◽  
Chemical Vapor Deposition ◽  
Secondary Flow ◽  
Vapor Deposition ◽  
Axial Velocity ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Variable Properties

A study has been made of the heat transfer, flow, and particle deposition relative to the modified chemical vapor deposition (MCVD) process. The effects of variable properties, buoyancy, and tube rotation have been included in the study. The resulting three-dimensional temperature and velocity fields have been obtained for a range of conditions. The effects of buoyancy result in asymmetric temperature and axial velocity profiles with respect to the tube axis. Variable properties cause significant variations in the axial velocity along the tube and in the secondary flow in the region near the torch. Particle trajectories are shown to be strongly dependent on the tube rotation and are helices for large rotational speeds. The component of secondary flow in the radial direction is compared to the thermophoretic velocity, which is the primary cause of particle deposition in the MCVD process. Over the central portion of the tube the radial component of the secondary flow is most important in determining the motion of the particles.

Analysis of Buoyancy and Tube Rotation Relative to the Modified Chemical Vapor Deposition Process

1990 ◽  
Vol 112 (4) ◽  
pp. 1063-1069 ◽  
Author(s):  
M. Choi ◽  
Y. T. Lin ◽  
R. Greif
Keyword(s):  
Secondary Flow ◽  
Vapor Deposition ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Horizontal Tube ◽  
Deposition Process ◽  
Secondary Flows ◽  
Secondary Motion

The secondary flows resulting from buoyancy effects in respect to the MCVD process have been studied in a rotating horizontal tube using a perturbation analysis. The three-dimensional secondary flow fields have been determined at several axial locations in a tube whose temperature varies in both the axial and circumferential directions for different rotational speeds. For small rotational speeds, buoyancy and axial convection are dominant and the secondary flow patterns are different in the regions near and far from the torch. For moderate rotational speeds, the effects of buoyancy, axial and angular convection are all important in the region far from the torch where there is a spiraling secondary flow. For large rotational speeds, only buoyancy and angular convection effects are important and no spiraling secondary motion occurs far downstream. Compared with thermophoresis, the important role of buoyancy in determining particle trajectories in MCVD is presented. As the rotational speed increases, the importance of the secondary flow decreases and the thermophoretic contribution becomes more important. It is noted that thermophoresis is considered to be the main cause of particle deposition in the MCVD process.

The Heat Transfer Problem for the Modified Chemical Vapor Deposition Process

1987 ◽  
Vol 109 (3) ◽  
pp. 642-646 ◽  
Author(s):  
M. Choi ◽  
H. R. Baum ◽  
R. Greif
Keyword(s):  
Heat Transfer ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Transfer Problem ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Heat Transfer Problem ◽  
Chemical Vapor Deposition Process ◽  
Variable Properties ◽  
Vapor Deposition Process

The heat transfer problem related to the modified chemical vapor deposition process has been analyzed in the high Peclet number limit. Variations in the axial, angular, and radial directions are presented. Of particular interest are the effects of tube rotation and variable properties on the temperature profiles.

A Three-Dimensional Analysis of Particle Deposition for the Modified Chemical Vapor Deposition (MCVD) Process

1992 ◽  
Vol 114 (3) ◽  
pp. 735-742 ◽  
Author(s):  
Y. T. Lin ◽  
M. Choi ◽  
R. Greif
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Secondary Flows ◽  
Circumferential Direction ◽  
Forced Flow ◽  
Flow Rates ◽  
Entry Length

A study has been made of the deposition of particles that occurs during the modified chemical vapor deposition (MCVD) process. The three-dimensional conservation equations of mass, momentum, and energy have been solved numerically for forced flow, including the effects of buoyancy and variable properties in a heated, rotating tube. The motion of the particles that are formed is determined from the combined effects resulting from thermophoresis and the forced and secondary flows. The effects of torch speed, rotational speed, inlet flow rate, tube radius, and maximum surface temperature on deposition are studied. In a horizontal tube, buoyancy results in circumferentially nonuniform temperature and velocity fields and particle deposition. The effect of tube rotation greatly reduces the nonuniformity of particle deposition in the circumferential direction. The process is chemical-reaction limited at larger flow rates and particle-transport limited at smaller flow rates. The vertical tube geometry has also been studied because its symmetric configuration results in uniform particle deposition in the circumferential direction. The “upward” flow condition results in a large overall deposition efficiency, but this is also accompanied by a large “tapered entry length.”

Coherent island formation of Cu2O films grown by chemical vapor deposition on MgO(110)

2001 ◽  
Vol 16 (8) ◽  
pp. 2408-2414 ◽  
Author(s):  
P. R. Markworth ◽  
X. Liu ◽  
J. Y. Dai ◽  
W. Fan ◽  
T. J. Marks ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Strain Relaxation ◽  
Three Dimensional ◽  
High Mobility ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Growth Conditions ◽  
Island Formation ◽  
Transmission Electron

Cuprous oxide (Cu2O) films have been grown on single-crystal MgO(110) substrates by a chemical vapor deposition process in the temperature range 690–790 °C. X-ray diffraction measurements show that phase-pure, highly oriented Cu2O films form at these temperatures. The Cu2O films are observed to grow by an island-formation mechanism on this substrate. Films grown at 690 °C uniformly coat the substrate except for micropores between grains. However, at a growth temperature of 790 °C, an isolated, three-dimensional island morphology develops. Using a transmission electron microscopy and atomic force microscope, both dome- and hut-shaped islands are observed and are shown to be coherent and epitaxial. The isolated, coherent islands form under high mobility growth conditions where geometric strain relaxation occurs before misfit dislocation can be introduced. This rare observation for oxides is attributed to the relatively weak bonding of Cu2O, which also has a relatively low melting temperature.

Electron Beam Assisted Chemical Vapor Deposition of Gold in an Environmental Tem

1995 ◽  
Vol 388 ◽  
Author(s):  
John Kouvetakis ◽  
Renu SharmA ◽  
B. L. Ramakrisna ◽  
Jeff Drucker ◽  
Paul Seidler
Keyword(s):  
Electron Beam ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Deposition Process ◽  
In Situ Observation ◽  
Beam Irradiation ◽  
Environmental Tem ◽  
Diffraction Patterns

AbstractWe demonstrate a novel technique for in situ observation of the chemical vapor deposition of high purity gold using ethyl(trimethylphosphine)gold(I). an environmental transmission electron microscope with 3.8 eV resolution was used to observe and compare the growth of the material with or without electron beam irradiation (120 keV) with Si (100) substrate temperatures ranging from 125-200 °C. Typical precursor pressures of 10-4 Torr and E-beam irradiation resulted in rapid growth of virtually continuous gold films. thermal deposition without the beam resulted in low nucleation densities, low deposition rates, and island-like growth. Images and diffraction patterns acquired during the deposition process indicated polycrystalline gold and elemental analysis at the nanometer scale showed that the films had excellent chemical purity. atomic force microscopy was also used to investigate the three dimensional morphology of the materials. the most notable result of the deposition process is the dramatic enhancement of the growth rate due to the beam irradiation.

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.

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