High frequency field emission device

FIELD OF THE INVENTION 
The present invention pertains to the field of electronic grid devices for 
high frequency amplification and switching systems and, more specifically, 
to electronic grid devices pertaining to integrated circuits. 
BACKGROUND OF THE INVENTION 
Field emission devices for signal switching and amplification that utilize 
structures with one or more field emitters are known in the art. These 
prior art schemes utilize field emission structures, such as Spindt tips, 
which have sharp-featured geometries and which typically require highly 
elaborate, costly fabrication processes. Field emission devices used for 
high frequency signal modulation typically include triode configurations, 
including a cone-shaped emitter circumscribed by a proximate extraction 
gate control electrode that initiates and controls current flow from the 
tip of the field emitter toward and through the extraction gate. They 
further include an anode which collects the emitted electrons and is 
disposed within 200-5000 micrometers from the gate extraction electrode. 
The extraction gate control electrode is typically disposed within 0.1-1 
micrometers from the tip of the cone-shaped emitter. 
Prior art field emitter devices have several serious disadvantages which 
limit and complicate their use for high frequency signal amplifiers or for 
high frequency switching systems. One of these disadvantages is the high 
degree of complexity and concomitant cost of fabrication of cone-shaped 
field emitters. Typically, many steps are involved, requiring many pieces 
of process equipment to perform the various photolithographic steps. 
Another disadvantage is the high capacitance that exists between the 
closely configured gate extraction electrode and the field emitter. This 
close proximity is necessary to achieve low device turn-on potential, 
typically within the range of 60 to 100 Volts (??). This high input 
capacitance limits the high frequency performance of these devices due to 
capacitive reactance. Another disadvantage of known field emitter devices 
is the high gate leakage current that occurs at moderate collector 
potentials. The gate leakage current increases proportionately as 
collector potential decreases because the number of electrons that have 
their paths redirected from the gate to the collector diminishes. Still 
another disadvantage is high dynamic output resistance. This occurs 
because the field emission initiated by the extraction gate limits the 
number of electrons that can reach the collector, so that saturation of 
collector current develops with even moderate collector potentials. The 
high resulting output resistance makes efficient high frequency output 
coupling difficult when even small amounts of capacitive reactance are 
present in the output circuit. Another disadvantage of prior art high 
frequency amplification and switching systems includes the provision of 
low current densities thereby precluding optimal compactness of the 
device. 
Thus, there exists a need for an improved high frequency field emission 
device, suitable for use in high frequency amplification and switching 
systems, which is simple to fabricate, has low input capacitance, and 
provides a greater current density. 
Referring now to FIG. 1, there is depicted a schematic representation of a 
prior art field emission device (FED) 100. FED 100 includes a cathode 
plate 110, an anode plate 120, a spacer 130 disposed between cathode plate 
110 and anode plate 120, a dielectric layer 140 disposed on an inner 
surface of cathode plate 110, a plurality of field emitters 160 formed 
within wells in dielectric layer 140, and a gate extraction electrode 150 
formed on dielectric layer 140 and circumscribing field emitters 160. 
Cathode plate 110 and anode plate 120 are electrically conductive, and 
when appropriate potentials are applied thereto and to gate extraction 
electrode 150, electrons are caused to be emitted from the tips of field 
emitters 160. Electron extraction is initiated and controlled by the 
potential applied at gate extraction electrode 150. In order to limit 
power consumption, the distance between gate extraction electrode 150 and 
the emission tips of field emitters 160 is made very small, on the order 
of 0.1-1 micrometers. Typically, the height of dielectric layer 140 is on 
the order of 1 micrometer and is governed by processing considerations. 
The capacitance between gate extraction electrode 150 and field emitters 
160/cathode plate 110 is a significant limitation of prior art FED 100 
which precludes high frequency modulation or switching by gate extraction 
electrode 150 of the electron emission from field emitters 160. The 
capacitance per unit area of FED 100 is greater than about 3500 
pF/cm.sup.2, which is known to be unacceptable for switching or modulating 
applications with control signals having frequencies in the Ghz range that 
are applied to gate extraction electrode 150. This is due to the decrease 
in reactance of the capacitance between gate extraction electrode 150 and 
field emitters 160 with respect to increasing frequency of an input signal 
at gate extraction electrode 150. This capacitance is inversely 
proportional to the thickness of dielectric layer 140. Due to this 
micron-range thickness, the capacitance renders FED 100 unacceptable for 
use for high frequency amplification or switching applications wherein a 
control signal having a frequency in the range of 10.sup.6 -10.sup.10 
Hertz is applied to gate extraction electrode 150. High frequency control 
signals are excessively loaded by the configuration of FED 100. 
Additionally, leakage currents through dielectric layer 140 act to further 
load down control signals applied to gate extraction electrode 150.

Referring now to FIG. 2, there is depicted a schematic representation of a 
high frequency field emission device 200 in accordance with the present 
invention. High frequency field emission device 200 includes a cathode 
210, a field emissive film 260 formed on an inner surface of cathode 210, 
and an anode 220 spaced from field emissive film 260 to provide an 
interspace region 265 therebetween. High frequency field emission device 
200 further includes a control electrode 250, which, in this particular 
embodiment, is positioned within interspace region 265 between cathode 210 
and anode 220, and a pair of spacer frames 230, 240 which provide standoff 
between control electrode 250 and anode 220 and between control electrode 
250 and cathode 210, respectively. Hermetic seals are formed and a vacuum 
on the order of 10.sup.-6 Torr is provided within interspace region 265. 
Cathode 210 may include a plate of glass upon which is deposited a 
conductive film, or it may include a copper substrate plated with nickel. 
Upon the conductive film, field emissive film 260 is formed. Field 
emissive film 260 includes a film of field emissive material. Suitable 
field emissive materials include diamond, diamond-like carbon, 
polycrystalline diamond, and other carbon-based and non-carbon-based 
emissive compositions which can be made as films. These field emissive 
films exhibit electronic emission at low field strengths and typically 
exhibit turn on fields on the order of 10 Volts per micron to produce 
current densities on the order of 1 mA/mm.sup.2. The formation of diamond, 
diamond-like carbon, and polycrystalline diamond films is known in the art 
and includes, for example, chemical vapor deposition processes, such as 
PECVD of methane. Suitable carbon films may also be deposited on cathode 
210 via cathodic arc deposition of a graphite source. The fabrication of 
polycrystalline diamond thin film is described in the following three 
publications, which are incorporated herein by reference: "Deposition of 
Diamond Films at Low Pressures and Their Characterization by Position 
Annihilation, Raman Scanning Electron Microscopy, and X-ray Photoelectron 
Spectroscopy", Sharma et al., Applied Physics Letters, vol. 56, 30 Apr., 
1990, pp. 1781-1783; "Characterization of Crystalline Quality of Diamond 
Films by Raman Spectroscopy", Yoshi Kawa et al. Applied Physics Letters, 
vol. 55, 18 Dec., 1989, pp. 2608-2610; and "Characterization of 
Filament-Assisted Chemical Vapor Deposition Diamond Film Using Raman 
spectroscopy", Buckley et al., Journal of Applied Physics, vol. 66, 15 
Oct., 1989, pp. 3595-3599. Clearly, it is established in the art that 
polycrystalline diamond films are realizable and may be formed on a 
variety of supporting substrate, such as, for example, silicon, 
molybdenum, copper, tungsten, titanium, and various carbides. In this 
particular embodiment, field emissive film 260 substantially covers the 
entire inner surface of cathode 210. A simple, single step deposition is 
involved in the formation of field emissive film 260. No further 
patterning steps are required. Spacer frames 230, 240 may include any 
suitable hard, insulative material, such as ceramic. Anode 220 includes an 
electrically and thermally conductive material that is suitable for use as 
a collector element, such as nickel or oxygen-free copper. In this 
particular embodiment, anode 220 is a flat plate and can be easily adapted 
to standard cooling apparati, such as a heat sink, heat pipe, or water 
clamp. In other embodiments of the present invention, the anode is 
disposed within the evacuated interspace region but does not comprise the 
external packaging element, and it may not include one continuous plate. 
Other collector/anode materials and configurations suitable for use in a 
high frequency field emission device in accordance with the present 
invention will be apparent to one skilled in the art. In this particular 
embodiment, control electrode 250 includes a gridded mesh which is gold 
plated. Control electrode 250 overlies field emissive film 260 and has 
contacts for applying a high frequency input signal thereto. The distance 
between control electrode 250 and field emissive film 260 is greater than 
50 micrometers, preferably greater than 250 micrometers. The distance 
between field emissive film 260 and anode 220 is within of 1-4 
millimeters. In the operation of high frequency field emission device 200, 
a potential source 270 is operably coupled to field emissive film 260 for 
applying an appropriate potential thereto. A high frequency input signal 
is applied to control electrode 250 by an ac signal source 280. A DC 
voltage source 275 is operably coupled to anode 220, which is maintained 
at a potential, within a range of about 1000-5000 volts, positive with 
respect to that provided at cathode 210 for extracting and collecting 
electrons from field emissive film 260. Control electrode 250 
modulates/deflects the trajectories of electrons emitted from field 
emissive film 260, thereby modulating the electron flow in response to the 
high frequency input signal from ac signal source 280. The modulated 
electron flow is received by anode 220 and an output signal 290 is thereby 
generated. Diamond and diamond-like carbon films provide surface current 
densities which are much greater than the tip field emitters of the prior 
art. Thus, the dimensions of high frequency field emission device 200 can 
be made very compact. Additionally, the capacitance between control 
electrode 250 and field emissive film 260 is substantially less than that 
of prior art field emission triodes, such as FED 100 (FIG. 1), due to the 
greater inter-electrode distances. The reduction in capacitance is 
sufficient to render high frequency field emission device 200 useful for 
modulating the emission current according to a high frequency input 
signal. Additionally, the absence of a dielectric layer between the 
electrodes precludes leakage currents which would otherwise load down 
control signals that are applied to control electrode 250. The packaging 
of high frequency field emission device 200 may be made comparable to 
modern integrated circuit packages so that it is easily integrated into, 
for example, stripline and microstripline circuits. 
Referring now to FIG. 3, there is depicted a sectional view of high 
frequency field emission device 200 taken along the section lines 3--3 of 
FIG. 2. FIG. 3 further illustrates the grid-like configuration of control 
electrode 250, which includes a plurality of apertures 255. Electrons 
emitted from field emissive film 260 travel through apertures 255 as 
regulated by the input voltage applied to control electrode 250. Electrons 
which are not deflected to a suitable extent by the high frequency input 
signal, are received by anode 220, thereby contributing to output signal 
290. In other embodiments of the present invention, more than one control 
electrode is included, each control electrode including a coated mesh 
configuration and being spaced vertically, within the interspace region, 
from the other control electrode(s). In this manner, tetrodes and pentodes 
may be made. 
Referring now to FIGS. 4 and 5, there are depicted cross-sectional (FIG. 4) 
and sectional (taken along the section line 5--5 in FIG. 4) views of a 
high frequency field emission device 400 in accordance with the present 
invention. High frequency field emission device 400 includes a cathode 
410, a patterned field emissive film 460 formed on an inner surface 415 of 
cathode 410, and an anode 420 spaced from patterned field emissive film 
460 to provide an interspace region 465 therebetween. High frequency field 
emission device 400 further includes a patterned control electrode 450, 
which includes a layer of patterned, highly conductive material formed on 
inner surface 415 between portions of patterned field emissive film 460, 
and a spacer frame 440 which provides standoff between cathode 410 and 
anode 420. The highly conductive material comprising patterned control 
electrode 450 may include a metal such as tungsten, molybdenum, or copper, 
which is formed by standard deposition and patterning techniques, known to 
one skilled in the art. Cathode 410 may include a plate of glass upon 
which is deposited a patterned conductive film which underlies patterned 
field emissive film 460, or it may include a copper substrate plated with 
a similary patterned layer of nickel. Upon this patterned conductive film, 
patterned field emissive film 460 is formed. Patterned field emissive film 
460 includes a film of field emissive material, such as diamond, 
diamond-like carbon, as described with reference to FIG. 2. In this 
particular embodiment, patterned field emissive film 460 covers a portion 
of inner surface 415 of cathode 410. The sections of patterned field 
emissive film 460 are spaced from, and are alternately disposed with 
respect to, the sections of patterned control electrode 450. The distance 
between the adjacent sections is predetermined and is sufficient to 
preclude generation of excessive inter-electrode capacitance. Spacer frame 
440 includes any suitable hard, insulative material, such as ceramic. 
Anode 420 includes an electrically and thermally conductive material that 
is suitable for use as a collector element, such as nickel or oxygen-free 
copper. Anode 420 is flat and can be easily adapted to standard cooling 
apparati, such as a heat sink, heat pipe, or water clamp. In the operation 
of high frequency field emission device 400, a DC voltage source 470 is 
operably coupled to patterned field emissive film 460 for applying an 
appropriate potential thereto. Additionally, patterned control electrode 
450 is operably coupled to a high-frequency input signal source 480, as 
schematically depicted in FIG. 5. The distance between adjacent sections 
of control electrode 450 and field emissive film 460 is greater than 50 
micrometers, preferably greater than 250 micrometers. The distance between 
field emissive film 460 and anode 420 is within of 1-4 millimeters. In the 
operation of high frequency field emission device 400, a low voltage is 
applied field emissive film 460 by DC voltage source 470; a high frequency 
input signal is applied to control electrode 450 by high-frequency input 
signal source 480; and anode 420 is maintained at a potential, within a 
range of about 1000-5000 volts, (positive with respect to that provided at 
cathode 410) by a DC voltage source 475, thereby extracting and collecting 
electrons from field emissive film 460. Control electrode 450 
modulates/deflects the electrons emitted from field emissive film 460, 
thereby modulating the electron flow in response to the high frequency 
input signal from ac signal source 480. The modulated electron flow is 
received by anode 420 and an output signal 490 is thereby generated. The 
distance between patterned field emissive film 460 and anode 420 is 
suitable for realizing, at patterned field emissive film 460, an electric 
field having suitable strength to provide electron emission therefrom, as 
indicated by arrows in FIG. 4. This distance is great enough to realize a 
suitably low inter-electrode capacitance. The appropriate field strength 
is dependent upon the identity of the emissive material comprising 
patterned field emissive film 460. Very short response times and electron 
transit times may be realized by making the distance between anode 420 and 
cathode 410 very small, and, simultaneously, making the thickness of each 
portion of patterned control electrode 450 very thin. Diamond and 
diamond-like carbon films provide current densities which are much greater 
than those of tip field emitters of the prior art. Thus, the dimensions of 
high frequency field emission device 400 can be made very compact. 
Additionally, the capacitance between patterned control electrode 450 and 
patterned field emissive film 460 is substantially less than that of prior 
art field emission triodes, such as FED 100 (FIG. 1), due to the greater 
inter-electrode distances. This inter-electrode capacitance may be 
designed to be less than about 50 pF/cm.sup.2, which is substantially less 
than that of prior art FED 100 (FIG. 1). The reduction in capacitance is 
sufficient to render high frequency field emission device 400 useful for 
high frequency amplification and switching systems. Additionally, the 
absence of a dielectric layer between the electrodes precludes leakage 
currents which would otherwise load down control signals that are applied 
to patterned control electrode 450. In other embodiments of the present 
invention, the patterning of patterned control electrode 450 and/or 
patterned field emissive film 460 may include patterns other than parallel 
strips. 
Referring now to FIG. 6, there is depicted a cross-sectional view of a high 
frequency field emission device 500 in accordance with the present 
invention. High frequency field emission device 500 includes a substrate 
510 having an inner surface 515, a plurality of dielectric members 562 
attached to inner surface 515, a cathode 563 formed on the upper surfaces 
of dielectric members 562, a patterned field emissive film 560 formed on 
cathode 563, and a patterned control electrode 550. Patterned control 
electrode 550 is formed on inner surface 515, between dielectric members 
562, and includes a layer of patterned highly conductive material, which 
may include a metal such as tungsten, molybdenum, or copper, and is formed 
by standard deposition and patterning techniques, known to one skilled in 
the art. High frequency field emission device 500 further includes an 
anode 520 spaced from patterned field emissive film 560 to extract and 
collect electrons therefrom, as indicated by arrows in FIG. 6, and a 
spacer frame 540 which provides standoff between substrate 510 and anode 
520. Substrate 510 may include a glass plate, or it may include a copper 
substrate, if heat dissipation is required. Patterned field emissive film 
560 includes a film of field emissive material, such as diamond, 
diamond-like carbon, or others, as described with reference to FIG. 2. A 
suitable method for making high frequency field emission device 500 
includes first forming patterned control electrode 550 on inner surface 
515 and, thereafter, depositing a layer of a dielectric material, such as 
silicon dioxide, over the entire patterned surface of substrate 510. Then, 
a layer of metal suitable for cathode 563 is deposited upon the dielectric 
layer. Upon the metal layer is formed a layer of the diamond or 
diamond-like carbon or other predetermined field emissive material. 
Thereafter, using appropriate etchants, a plurality of wells 566 are 
formed by selectively etching through the layer of field emissive 
material, the metal layer, and the dielectric layer, to expose patterned 
control electrode 550. The area of patterned control electrode 550 is 
preferably minimized to reduce inter-electrode capacitances. In this 
particular embodiment, the inter-electrode capacitance is reduced by the 
separation provided by the height of dielectric members 562. The 
inter-electrode capacitance is also reduced by the lateral separation of 
patterned control electrode 550 and patterned field emissive film 560, in 
the manner described with reference to FIGS. 4 and 5. The height of 
dielectric members 562 is sufficient to provide the appropriate capacitive 
characteristics and may be made substantially greater than the 
inter-electrode separations found in prior art field emission devices. The 
resulting inter-electrode capacitance may be designed to be less than 
about 50 pF/cm.sup.2, which is substantially less than that of prior art 
FED 100 (FIG. 1). Additionally, because field emissive films, such as made 
from diamond-like carbon, generate current fluxes that are several orders 
of magnitude greater than those of prior art tip emitters, devices in 
accordance with the present invention can accommodate and afford greater 
distances between adjacent portions of the field emissive film and the 
control electrode, thereby realizing improved capacitance characteristics 
over the prior art without compromising compactness of the device and 
simultaneously provide greater output currents for a device of comparable 
dimensions. In the operation of high frequency field emission device 500, 
a low voltage is applied cathode 563 by DC voltage source (not shown); a 
high frequency input signal is applied to patterned control electrode 550 
by high-frequency input signal source (not shown); and anode 520 is 
maintained at a potential, within a range of about 1000-5000 volts, 
(positive with respect to that provided at cathode 563) by a DC voltage 
source (not shown), thereby extracting and collecting electrons from 
patterned field emissive film 560. Patterned control electrode 550 
modulates/deflects the electrons emitted from patterned field emissive 
film 560, thereby modulating the electron flow in response to the high 
frequency input signal. The modulated electron flow is received by anode 
520 and an output signal 590 is thereby generated. 
Referring now to FIG. 7, there is depicted a cross-sectional view of a high 
frequency field emission device 600 in accordance with the present 
invention. High frequency field emission device 600 comprises a tetrode 
device and includes a vacuum tube configuration, wherein elements are 
generally cylindrically shaped and share a common cylindrical axis. A 
cathode 610 is centrally disposed therein and comprises a nickel-plated 
copper cylinder. A field emissive film 660 is formed on the outer surface 
of cathode 610. Field emissive film 660 is made from a carbon-based field 
emissive material known to yield field emissive films, such as 
diamond-like carbon, diamond, or amorphous carbon, as described with 
reference to FIG. 2. Non-carbon-based field emissive films may also be 
used to form field emissive film 660. A first control electrode 650 is 
generally cylindrically shaped and is centered along the axis of cathode 
610. First control electrode 650 includes a gold-plated mesh and is 
operably coupled to a voltage source (not shown). In this particular 
configuration, first control electrode 650 is spaced about 0.23 
millimeters from field emissive film 660. A second control electrode 655 
is also generally cylindrically shaped and is centered along the axis of 
cathode 610 as well. Second control electrode 655 includes a gold-plated 
mesh which is operably coupled to another voltage source (not shown). 
Second control electrode 655 is spaced about 0.9 millimeters from field 
emissive film 660. An anode 620 is similarly configured and is the 
outermost element. Anode 620 is made from an electrically and thermally 
conductive material that is suitable for use as a collector element, such 
as nickel or oxygen-free copper. Anode 620 is spaced about 3.6 millimeters 
from field emissive film 660. In one voltage configuration, field emissive 
film 660 is held at ground potential; first control electrode 650 is held 
at about -50 Volts; second control electrode 655 has a high frequency 
input applied thereto in the range of 300-500 Volts; and anode 620 is 
connected to a voltage source providing a voltage on the order of 1500 
Volts, to effect extraction of electrons from field emissive film 660. For 
this voltage configuration, a maximum current on the order of 800 amperes 
per square centimeter is supplied by high frequency field emission device 
600. This current value is about 2000 times greater than a similarly 
configured conventional thermionic vacuum tube tetrode which includes an 
oxide coating electron source. An additional improvement over prior art 
thermionic devices includes the omission of a heated filament. The 
breakage of the heated filament is the primary failure mechanism of these 
prior art devices. Due to the simple fabrication methods of the field 
emissive film included therein, high frequency field emission devices in 
accordance with the present invention may include many types of 
configurations, as exemplified by, but not limited to, the embodiments 
described herein. Additionally, due to the high current densities and low 
required field strengths of the field emissive films of the present 
device, inter-electrode distances can be made greater than those typical 
of conical/tip emitters of the prior art. These greater inter-electrode 
distances provide the distinct advantage of lower inter-electrode 
capacitances, thereby providing improved performance for high frequency 
applications. 
A high frequency field emission device in accordance with the present 
invention may be used for radio frequency applications, such as broadcast, 
land mobile, aeronautical, and space transmitters. Other applications 
include AF power amplifiers, video drivers, and other high voltage 
applications. It may be used in both stripline and microstripline circuits 
using many existing RF semiconductor design techniques. 
Referring now to FIG. 8, there is depicted a schematic representation of a 
high frequency circuit application 700 of a high frequency field emission 
device 701 in accordance with the present invention. Within high frequency 
circuit application 700, high frequency field emission device 701 is used 
as an efficient power amplifier. High frequency circuit application 700 
includes a simple impedance transformation network 705 to provide high 
potential gain with little attenuation due to capacitive reactance. As 
depicted in FIG. 8, a high-frequency input signal source 780 is coupled to 
a control electrode 750 of high frequency field emission device 701. A 
field emissive film 760 of high frequency field emission device 701 is 
maintained at ground potential. The input capacitance, or emitter-control 
electrode capacitance, is represented by a capacitor 702, which is shown 
in dashed lines between control electrode 750 and ground. The 
anode-control electrode capacitance is represented by a capacitor 704, 
which is shown in dashed lines between an anode 720 of high frequency 
field emission device 701 and control electrode 750. The output 
capacitance is represented by a capacitor 706 between anode 720 and 
ground. Impedance transformation network 705 includes an inductor 708 and 
an inductor 710 having a mutual coupling factor M and a common connection 
to anode 720. The other side of inductor 708 is connected to a high 
potential anode source 712 that provides sufficient positive potential 
relative to field emissive film 760 to produce electron emission. The 
other side of inductor 710 is connected to a high impedance output 
terminal 714. As is well known in the art, for any frequency output signal 
wherein inductors 708, 710 have a suitable degree of mutual conductance, 
not considering losses, the signal output potential developed at high 
impedance output terminal 714 is equal to the product of the signal output 
potential developed at anode 720 and the turns ratio of inductor 710 to 
inductor 708. The turns ratio may be made very high to develop a high 
output signal potential at high impedance output terminal 714. 
Referring now to FIG. 9, there is depicted a schematic representation of a 
high frequency circuit application 800 of a high frequency field emission 
device 801 in accordance with the present invention. High frequency 
circuit application 800 includes an emitter-follower amplifier 
configuration wherein the input signal from a high-frequency input signal 
source 880 and an output signal, from an output terminal 814, are in 
phase, so that no neutralization is required for high frequency signal 
power amplification. This configuration is a simple rearrangement of the 
components shown in FIG. 8. A high potential anode source 812 is connected 
directly to an anode 820 of high frequency field emission device 801 to 
hold anode 820 at a potential supplied by high potential anode source 812. 
This configuration provides the benefit that destabilizing positive 
feedback cannot be fed from anode 820 back to a control electrode 850 of 
high frequency field emission device 801 through the capacitive reactance 
of a capacitor 804. A simple impedance transformation network 805 includes 
an inductor 808 and an inductor 810 having a mutual coupling factor M and 
a common connection to a field emissive film 860 of high frequency field 
emission device 801. The other side of inductor 808 is connected to 
ground, and the other side of inductor 810 is connected to output terminal 
814. Due to the low output impedance of this configuration, a high value 
of turns ratio may be used, thereby providing a high power output gain 
while avoiding significant losses due to stray capacitances in inductors 
808, 810. 
A high frequency field emission device in accordance with the present 
invention may be used as a high frequency modulated electron source for 
pumped solid state lasers. It may also be used as a deflection amplifier 
wherein potential is alternatively applied to selected portions of the 
control electrode to deflect electrons toward predetermined portions of 
the anode, the switching action within the control electrode being at high 
frequency. It may also be used in a magnetron wherein the modulated 
electron ribbon is further acted upon by a magnetic field provided between 
the control electrode and the anode, the magnetic field being at right 
angles to the electric field applied between the cathode and the anode. 
While we have shown and described specific embodiments of the present 
invention, further modifications and improvements will occur to those 
skilled in the art. We desire it to be understood, therefore, that this 
invention is not limited to the particular forms shown, and we intend in 
the appended claims to cover all modifications that do not depart from the 
spirit and scope of this invention.