Professor Umran S. Inan

Winter 1999-00

Date: Wednesday, January 26, 2000
Time: 4:15-5:30 PM; Refreshments at 4:00 PM
Location: 380-380X

Fundamentals and Experimental Studies of a He-Xe Microdischarge for Plasma Display Panels

Dr. Olivier Postel
Space Systems Development Laboratory, Stanford University


During the past five years, we have seen a rapid emergence of flat panel displays using thin film transistor and liquid crystal technologies. Plasma displays Panels (PDP) offer improved viewing angle, faster update speeds (refresh rates), and a crisper picture quality, since they use gas discharge excitation of color phosphors. This technology is positioned to exploit the standards defined for high definition television (HDTV), and is likely to become commonplace in large-area commercial display applications and home entertainment systems. At present, plasma displays are used only in limited applications, because of the high power requirements and relatively high cost of manufacture, compared to other display alternatives.

In modern PDP discharges, each pixel is composed of three separate addressable microdischarges, one for each of the primary colors (red, green, and blue). The plasma, usually of mixture of He and Xe or Ne and Xe, is initiated by applying a high voltage between the address electrode and the opposite co-planar sustain electrodes, while an AC voltage is applied between the sustain electrodes. A red, green, or blue phosphor is excited by the vacuum ultraviolet (VUV) emitted by each microdischarge. The plasma display is expected to dominate the large-area flat panel display market, the properties of which are challenged only by field emission displays, which are still in their early stages of development. However, there is still a need for improvement in display performance, in order for this technology to meet its full market potential. The plasma displays suffer from a relatively low efficiency (only some 1 2 % of the power invested is emitted as visible light from the phosphor, or approximately 1 lm/W) and potentially compromised performance with time due to sputtering of the dielectric materials on the cell wall.

In the Thermosciences Division at Stanford, we are working on a simplified DC co-planar He/Xe discharge to gain a more detailed understanding of the discharge physics and chemistry. The electrical characteristics and VUV emission have been determined for a wide range of operating conditions (discharge pressure and power, gas composition, ) and revealed the presence of a hetero-molecular ion that has not been reported in any previous study. Future advanced diagnostics (laser absorption, laser induced fluorescence and mass spectrometry) will be presented that will enables us to measure the physical and chemical plasma properties in greater details.