Electric lamp and discharge devices – Discharge devices having a thermionic or emissive cathode
Reexamination Certificate
2000-08-11
2002-11-12
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Discharge devices having a thermionic or emissive cathode
C313S495000, C313S311000, C313S309000, C313S351000
Reexamination Certificate
active
06479924
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ferroelectric emitter. More specifically, the present invention relates to a side electrode emitter in which electrodes are attached to the top surface or at side edges of a ferroelectric layer.
2. Description of the Related Art
Ferroelectric emission by switching allows for a simple process in electron emission lithography. In the past, electron emission suitable for lithography has been obtained by applying an external magnetic field or heat. However, a conventional ferroelectric emitter cannot guarantee electron emission where the distance between two electrodes for applying a power is too wide or too narrow for switching.
For example, in the conventional ferroelectric emitter, if the distance between the two electrodes is too wide, then an electric field cannot reach the center portion of the ferroelectric emitter. Thus, a switching effect does not occur in a ferroelectric region. If, on the other hand, the distance between the two electrodes, or a gap of a mask pattern, is too narrow, then the mask pattern formed on a ferroelectric layer in a ferroelectric emitter absorbs electrons during electron emission, so that electrons flow through the patterned mask. Moreover, an isolated pattern, such as a doughnut shape, cannot be switched because the two electrodes are not connected to each other.
In contrast to ferroelectric switching, pyroelectric emission can provide a uniform emission of electrons regardless of the characteristics of a gap of a mask pattern. Pyroelectricity refers to the production of polarization changes by temperature variations. Due to such properties, when a material is subjected to a temperature change, the magnitude of a spontaneous polarization changes to affect bound charges, so that a current flows through electrodes.
If an emitter is heated and this process occurs in a vacuum, then bound charges, which are electrons screening on the surface of the emitter, are released in a vacuum, which is called pyroelectric emission. In this case, uniform emission is allowed whether a gap of the mask pattern is wide or narrow. Furthermore, pyroelectric emission enables electron emission in an isolated pattern such as a doughnut pattern. Although it facilitates electron emission, pyroelectric emission has several disadvantages. One of these disadvantages is the requirement of re-poling or heating the emitter above the Curie temperature for re-emission.
SUMMARY OF THE INVENTION
A feature of the present invention is to provide a ferroelectric emitter that allows electron emission in both wide and narrow gaps of a mask layer and in an isolated pattern such as a doughnut shape for ferroelectric switching emission lithography, while facilitating re-poling in pyroelectric emission.
The present invention provides a ferroelectric emitter including: a ferroelectric layer having a first side and an opposing second side and a top surface, a first electrode formed adjacent the first side and the top surface of the ferroelectric layer, a second electrode formed adjacent the opposing second side and the top surface of the ferroelectric layer; and a mask layer having a predetermined pattern and formed along the top surface of the ferroelectric layer between the first and second electrodes.
In a preferred embodiment of the present invention, the mask layer is formed by exposing a predetermined region of the top surface of the ferroelectric layer, and the orientation of the crystal lattice of a ferroelectric material of the ferroelectric layer is developed so as to form an acute angle with the direction of an electric field induced when a voltage is applied to the electrodes.
The present invention also provides a ferroelectric emitter including: a ferroelectric layer having a first side and an opposing second side and a top surface, a first electrode formed along the first side edge of the ferroelectric layer, a second electrode formed along the opposing second side edge of the ferroelectric layer, and a mask layer having a predetermined region and formed along the top surface of the ferroelectric layer.
In another preferred embodiment of the present invention, the mask layer is formed so as to expose a predetermined region of the top surface of the ferroelectric layer, and the orientation of the crystal lattice of a ferroelectric material of the ferroelectric layer is developed so as to form a predetermined angle with the direction of an electric field induced when a voltage is applied to the electrodes.
REFERENCES:
patent: 6028322 (2000-02-01), Moradi
patent: 6359383 (2002-03-01), Chuang et al.
Lee & Sterba, P.C.
Patel Ashok
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