My research focuses on topics involving nanoscale science, engineering, and technology: viz. growth and design of heterostructures for multi-junction solar cells, quantum and optoelectronic devices, properties and performance of semiconductor devices and materials using molecular-beam epitaxy, electrical, optical, and materials characterization techniques, processing of semiconductors, metals, and insulators for device fabrication. Earlier topics included co-integration of CMOS with III-V materials for single-chip, digital-system applications such as high-speed A/D conversion, communications, radar, and optoelectronics. Other studies involved high-k dielectric gate insulators, silicon-on-lattice-matched insulators for three-dimensional stacking of thin-film transistors, transport and Hall measurements in graphene, tip-based nanomanufacturing in Si-based systems, and radiation tolerance in nanoelectronic and quantum devices.
Past physics investigations include studies of semiconductors in low-dimensional configurations, experimental condensed-matter physics, transport and magnetoconduction in mesoscopic systems, quantum Hall effect, macroscopic quantum effects, magnetic (bulk and surface) phenomena, many-body effects in quantum solids/liquids, and high temperature superconductivity. Related topics include weak localization and Coulomb interactions in 2-D systems.
I founded one of the nation's first university centers focused on nanoscale science and technology at Texas A&M University in 1989. It was called the Center for Nanostructure Materials and Quantum Device Fabrication (NanoFAB Center) and was established under the auspices of the Texas Engineering Experiment Station (TEES) in the TAMU System. Ten years later I moved the center, now known as the Nanotechnology Research and Education Center, to the University of Texas at Arlington where a clean room was built in a dedicated 30,000 sq. ft. building for nanotechnology activities.
My earliest research involved studies of the thermodynamic properties of helium isotopes, especially nuclear magnetism in solid 3He, fluid transport, and nuclear magnetic resonance (NMR) studies of the normal and superfluid phases of 3He. This work required in-house fabrication of highly specialized apparatus for very low-temperature (0.0003 K) and high-magnetic-field (15 T) studies. Some of this work utilized fast Fourier-transform pulsed-NMR spectroscopy, millikelvin cryogenic techniques, adiabatic demagnetization (CMN), high-field superconducting magnets, pulsed and continuous wave NMR in 3He, Cu, Pt to 1 mK and lower, compressional cooling of 3He (Pomeranchuk effect), 3He-4He dilution refrigerators, SQUID devices, and nuclear-hyperfine magnetic cooling of PrNi5 to 0.0003K.