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Research Interests and Capability

J. T. Wang, Ph.D, Associate Professor,
Department of Physics, Southern University and A&M College

 

My research experience and interests are in the following areas: Ferroelectric and Piezoelectric materials and devices including thin film and related technologies and superconducting materials and electronics including experiment and theory. My present research projects are: 1. Studies of Piezoelectric Materials and Devices funded by Office of Naval Research (ONR); and 2. Superconductivity and Superconducting Electronics. With the support of ONR research grant, a state-of the-art research laboratory has been established in the Department of Physics, Southern University. If your university gives me the chance, I will acquire the research grant to establish research projects in these areas to meet the need of your department. The missions of these projects are:

Developing Ferroelectric/Piezoelectric Materials with high dielectric and piezoelectric constant for electromechanical sensor and actuator. We have fabricated PMN-PT high strain piezoelectric powder and thick film by solid state reaction process and spin-coating technique respectively. The materials have been characterized by the measurements of dielectric and piezoelectric constant versus the other electromechanical variables, such as temperature, frequencies, electric field, and stress. We grow single crystals of the piezoelectric materials mentioned above in our research laboratory. The laboratory has been equipped by furnaces for ceramic preparation, LRC meter, signal analyzer, lock-in amplifier for dielectric measurement, Gradient polar-hysteresis loop measurement, LVDT and interferometer for displacement measurement, and X-ray diffractometer for crystal structure determination.

Developing Ferroelectrics and high Tc superconductors multilayer thin film for polarization controlled superconducting devices, which could lead to the application of infrared and acoustic detectors.
The crystal structures of both Ferroelectrics and YBCO are perovskite. The multilayer thin film of ferroelectrics and YBCO can grow together nicely by film techniques. It can than be patterned by lithography or ion milling as a three terminal gate. The gate of the device is Ferroelectrics, such as PZT. The polarization of Ferroelectric gate is controlled by applied voltage pulse or temperature change or stress. When the gate changes its polarization, the superconductor layer changes its charge density. The drain-source output is, therefore affected by the polarization. If the polarization is controlled by temperature change, it could be utilized in infrared detector. If it is controlled by stress, it could be fabricated as acoustic sensor. Multilayer superconducting thin films possess other application potentials such as microwave filter and cryogenic inter-chip interconnects. In collaboration with The Center for Advanced Microstructure and Devices in Baton Rouge, we develop the thin films and micro-devices and characterize in our research laboratory.

Developing Micro-Sensor, Micro-Actuator-electromechanical transducers integrated on a microelectronic single chip. I plan to fabricate the multilayer thin film of PZT on silicon wafer or PZT/HTSC on silicon wafer by CVD or PVD and then pattern it into an array with electronic circuit in it. The two-dimensional array could serve as an infrared vidicon or acoustic vidicon for night vision or ultrasonic image detector. Using the relaxor Ferroelectric PMN-PT that exhibits the strain ten times greater than the PZT under the same applied electric field, we plan to develop micromotor, positioner by the PMN-PT thin film. PSU, MIT and Lincoln Labs has demonstrated a piezoelectric flexure wave micro-motor, The concept of this machine is that silicon wafer is coated with a thick silicon oxynitride film. After etched from the backside, Pt electrode is deposited on the surface and sequentially PZT is coated on the upper surface. Patterned electrode is plated onto upper surface of the PZT. With a field of 2 volts applied the motor rotate at a speed ~120 RPM (L. Eric Cross). Replacing PZT by PMN-PT, one can expect to achieve high rotating speed and generate larger torque.

Thomas Bifano at Boston University has developed a continuous-membrane deformable mirror. I plan to explore the research in this area with the implementation of new ideas. To replace the PZT by PMN-PT and incorporate with the photoconductor layer, we may be able to moving mirror array with certain vibration mode and to modulate the light frequency and possible to use deformable mirror to perform larger and higher display of an optical image or acoustic image. Based on this concept, It is possible to correct the time-varying optical aberrations in real time.

Developing High Permittivity Dynamic Random-Access Memory (HPDRAM) and Nonvolatile Ferroelectric Random-access Memory (NVFRAM) for computer memory technology and studying related physics

Available Equipment

In Electronic Materials Research Laboratory At Southern University:

For processing ceramic and single crystal materials:
1. 1700 ˚C Model No.IBF 51524C With Controller CC59256 PCCOM, CM. Furnaces Inc.
2. Ultra Temp Oven 6680, THT Electronics Co.
3. Oven 9039
4. CM Furnace Model 1725VT, CM Furnaces Inc.
5. One Rapid Temperature model 1730-36-3Z, CM Furances Inc.
6. 75 ton 4 Post Hydroulic Press, Rockland Research Corp.
7. Heidolph Overhead Mixer Model 2051, Brinkmann

For resistivity, dielectric constant, and piezoelectricity measurement:
8. Power Supply BOP 1000M, KEPCO
9. High Voltage Power Amplifier 609 D6, Trek Inc.
10. Digital lock-In Amplifier Model SR 830 DSP, Stanford Research System
11. High Voltage Power Supply Model 248,Stanford Research System
12. LCR meter Model 4284A, Hewlett Packard
13. Multimeter 8840, Hewlett Packard.
14. HP. Dynamic Signal Analyzer Model 35665A, Stanford Research System for FF, Signal Analyzer Model SR 780
15. Dynamic Signal Analyzer 8590L, Hewlett Packard
16. LVDT displacement Meter
17. Zygo Interfrometer

Computer control:
16. HP Model 745i/50/100, Hewlett Packard
17. HP Printer Laser Jet 4MV, Hewlett Packard

For thick film fabrication
18. Spinning Coating system
Zygo Interferometer.
LakeShore Temperature Monitor Model 218.

For crystallography
1. Rigaku D/MAX-2100V diffractometer.


Selected Publications: Click Here


 
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