Solid-state excimer devices and processes for producing same

Details Solid-state excimer devices and processes for producing same Solid-state excimer devices and processes for producing same

2000-10-20

2003-09-02

Patel, Ashok (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Solid-state type

C313S503000, C313S506000

Reexamination Certificate

active

06614178

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the design and structure of electronic devices in which transition of rare-gas and halogen atoms are electrostatically induced in solid thin films. The electric double layer and large polarization consequently formed in the films are utilized as the operation principle of the devices. The invention also relates to devices with electrodes and the processes for producing the devices.
BACKGROUND OF THE INVENTION
Dielectricity and polarization of conventional dielectric materials used for electronic devices are not large enough for the future development of ultrahigh density memories, ultrahigh sensitivity sensors and a new generation of piezoelectric and actuator devices. Therefore, new materials that possess superb dielectric characteristics are required and have been investigated to replace conventional dielectric materials. Studies on the design and preparation of devices are also needed for the application of the new materials.
For example, BaTiO
3
is widely known as a high-dielectric material and is used in many devices such as condensers and positive thermal coefficient (PTC) devices. However, the origin and mechanism of dielectric field formation in BaTiO
3
crystals are due to the small dislocation, approximately 0.1 angstrom (0.1×10
−10
m), of central Ti ions relative to the Ba ions in a unit cell.
Similarly, the relative dislocations of central ions in unit cells of conventional ferroelectric materials, such as PbTiO
3
, PbZrTiO
3
and Bi-containing layer-by-layer compounds (so-called Y
1
materials), are very small. Since these conventional crystalline materials have the essential restriction that the central ions must move within the sharply bound potential of crystalline unit cells, a long-range charge dislocation, such as a charge-separation on the order of three to four angstroms, cannot principally be expected. Therefore, these materials will not become superdielectric materials that exceed dielectric constants of conventional materials.
Some organic compounds such as liquid crystals also show spontaneous polarization. However, a dislocation of plus and minus charges originating from the presence of functional groups in these materials is limited inside the molecules. Therefore a long-range, i.e., three to four angstroms, charge-separation cannot be expected.
As is mentioned above, the advent of new materials that have charge-separation or dielectric constants one or two orders of magnitude larger than conventional materials have been eagerly awaited. If such materials were invented, they would be called superdielectric materials. The materials will show giant dielectricity and polarization.
On the other hand, excimer-formation is well known as a reaction resulting in a long-distance charge-separation. Excimer lasers and lamps have been commercialized using this reaction. Excimers are metastable species that are formed via high-energy input such as pulse-discharge or ultraviolet (UV) light irradiation on rare-gas/rare-gas or rare-gas/halogen mixtures. The possibility of applying the reaction to laser oscillation and UV light sources has already been realized and discussed in the 1960s.
UV lasers were then commercialized in the 1970s. At present, they are commonly used as light sources in stepper systems for semiconductor processes. Furthermore, successful development of excimer lamps that provide deep UV light has widened the application of excimer-formation reactions in the industry.
Both the physical and chemical understanding of the properties and characteristics of excimers have rapidly progressed. Energy potentials, formation and emission mechanisms, non-radiative relaxation processes and application of the excimer reactions to optical devices are well summarized and published in literature such as “Excimer Lasers, Second Enlargement Edition, ed. by Ch. K. Rhodes, Springer-Verlag (Berlin, Heidelberg, New York, Tokyo, 1984).”
However, application of excimer reactions to industrial fields other than optical devices has not been pursued to date; neither any research nor idea relating to the application of excimer reactions to electronic devices has been reported.
The inventor has long been engaged in researches on “Formation and relaxation mechanisms of excimers in condensed media” and “Preparation and evaluation of electronic thin films.” By combining knowledge and experience obtained through these researches, the inventor has formulated the following idea: If excimers could be formed in solid thin films under electrically static conditions, we will have devices that show huge polarization and an electric double layer.
First of all, the inventor's views on characteristics of excimers as potential electronic devices are summarized below:
1) Huge Polarization
As is described before, the relative charge-separation or charge dislocation of conventional dielectric materials is on the order of 0.1 angstrom. On the other hand, excimers are formed when rare-gases and halogens are excited into full-charge-transfer states: plus and minus charges are separated in the excimer molecule by three to four angstroms. Hence excimers have huge polarization compared with conventional dielectric materials. If excimers could be formed in solid thin films, we would have superdielectric materials that have dielectricity two orders of magnitudes higher than conventional materials. Then these films can be applied to ultrahigh-density memories, ultrahigh-sensitivity sensors and a new generation of piezoelectric devices and actuators.
2) Stability in Solid
Excimers easily relax to their ground states by colliding with other molecules in the vapor phase and show low quantum efficiency. In contrast, all of the excimers formed in the solid phase can be used as the driving force of devices because of the lack of collisional deactivation processes.
3) Delocalization of Holes
Holes of excimers trapped in low-temperature solid Xe can be delocalized in the Xe matrix in a manner similar to electrons transiting into their Rydberg states. Delocalized holes are trapped in the matrix without recombining with electrons. Only when the temperature of the matrix is raised, does the recombination of holes and electrons proceed, and recombination luminescence, i.e., thermo-luminescence, is observed. This mechanism was first reported by N. Schwentner, M. E Fajardo and V. A. Apkarian in “Rydberg series of charge-transfer excitations in halogen-doped rare gas crystals,” Chem. Phys. Lett., Vol 154, pp.237, (1989). If such delocalization process could be attained in a solod thin film following charge-separation reactions in excimer molecules, it would be possible to form and stabilize the electric double layer. This kind of device could give rise to ultrahigh capacitors, new types of limiters and memories.
4) Varieties of Combinations
There are many excimer species. Molecular sizes, energy levels in excitation and relaxation processes, and transition probabilities of excimers can be controlled by changing the combination of parent atoms, i.e., rare-gases (Ar, Kr, Xe) and halogens (F, Cl, Br, I). Therefore, we can choose the rare-gas and halogen dopants in accordance with the structure and band gap of the host matrix. The flexibility in combining rare-gases and halogens widens the freedom in designing devices. In particular, Xe is very useful for device design, since it can react and make charge-transfer complexes with many kinds of atoms and radicals other than halogens, such as sulfur (S), oxygen (O) and hydroxide (OH) radicals.
Note that all of the characteristics and properties of excimers mentioned above have been investigated and observed in cryogenic rare-gas crystals and liquids by optically exciting the systems with UV light or by electric discharge. In order to apply these characteristics and properties to electronic devices in the real world, development of the following new technologies has been indispensable: doping of parent atoms of excimers into electronic materials such as ceramics; and excimer-formation under ambient tem

Affiliated with

Also associated with

Rating

Solid-state excimer devices and processes for producing same does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Solid-state excimer devices and processes for producing same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid-state excimer devices and processes for producing same will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3058326