Abstract:

Epitaxial growth of thin films of materials has played a crucial role in a wide range of applications in electronics, optoelectronics, and magneto-optics. Among the various growth techniques, liquid-phase epitaxy (LPE) is the simplest and the cheapest route in producing device-quality layers. The other most utilized techniques for the production of electronic and optoelectronic devices is centered on metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). These techniques can readily be used to produce multilayer structures with atomic-layer control, which is fundamental to the nanoscale engineering.  More recently, a low temperature atomic layer epitaxy (ALEp) has been developed to produce crystalline semiconductor films with properties comparable to those from conventional growth processes, but at roughly half the growth temperature.  A comparison of the various epitaxy techniques suggests that no single technique can best satisfy the needs of all materials/devices. Therefore suitable combinations are needed in microelectronics, optoelectronics, solar cells, thermophotovoltaics, thermo-electric, semiconductor electrochemical devices, magnetic/magneto-optical devices, and microelectromechanical systems.  In this presentation, high resolution x-ray diffraction of epitaxial films grown by all these techniques will be presented and discuss their crystal quality and in some cases the formation of metastable phases.   Examples of II-VI, III-V semiconductor films and their superlattices will be shown and their crystalline quality discussed.  In addition, data on metallic films such as Fe, Co, and Nb grown on GaAs and sapphire substrates will be presented.

In addition to epitaxial films, examples of bulk and nano-materials where metastable phases are formed will be discussed.   Methane gas hydrates samples collected from Gulf of Mexico will be analyzed in terms of different crystallographic structures and discussed in terms of their stability in thermodynamic parameters

Biography:

Dr. Syed B. Qadri received his MS in mathematics and PhD in physics from Ohio State University in 1979.  He worked as a post doc at Stanford Synchrotron Radiation from 1980-1983 using synchrotron radiation EDXRD to investigate high pressure/temperature phase transitions using diamond anvil cell.   He worked as senior scientist at Naval Reseach Laboratory from 1983 till 2021.  He retired in 2021.  He has published over 600 archival journal papers and holds 40 patents.  He has rerceived numerous awards including Washington Academy of Science for excellence in research, US Navy civilian meritorious award, and Marquis life time achuevement.  He has received numerous best paper awards from NRL and Japanese Society of Applied Physics.

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All faculty, researchers and students are invited to attend.