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Simultaneous in situ Optical Monitoring Techniques during Crystal Growth of ZnSe by Physical Vapor TransportZnSe crystals grown in sealed ampoules by the physical vapor transport method were monitored in situ using three techniques, simultaneously. A Michelson interferometer was set-up to observe the growth rate and surface morphological evolution. An interference pattern (interferogram) is formed by the interaction between the reflection of a HeNe laser (632.8 nm wavelength) off the crystal-vapor interface and a reference beam from the same laser. Preliminary results indicate that the rate of growth/thermal-etching can be calculated using analog data acquisition and simple fringe counting techniques. Gross surface features may also be observed using a digital frame grabber and fringe analysis software. The second in situ technique uses optical absorption to determine the partial pressures of the vapor species. The Se2 and Zn vapor species present in the sealed ampoule absorb light at characteristic wavelengths. The optical absorption is determined by monitoring the light intensity difference between the sample and reference beams. The Se2 Partial pressure profile along the length of the ampoule was estimated from the vibronic absorption peaks at 340.5, 350.8, 361.3 and 379.2 nm using the Beer's law constants established in the calibration runs of pure Se. Finally, because the high temperature crystal growth furnace contains windows, in situ visual observation of the growing crystal is also possible. The use of these techniques not only permits in situ investigation of high temperature vapor growth of semiconductors, but also offers the potential for real time feed back on the growing crystal and allows the possibility of actively controlling the growth process.
Document ID
19990019571
Acquisition Source
Marshall Space Flight Center
Document Type
Other
Authors
Su, C.- H.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Feth, S.
(Hughes STX, Inc. Greenbelt, MD United States)
Lehoczky, S. L.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1998
Subject Category
Solid-State Physics
Meeting Information
Meeting: Vapor Growth and Epitaxy (ICVGE 10)
Location: Jerusalem
Country: Israel
Start Date: July 26, 1998
End Date: July 31, 1998
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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