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Патент USA US3100854

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Aug. 13, 1963
L, E, HOLLANDER, JR
3,100,849
ACTIVE SOLID-STATE DEVICES USING ANISOTROPIC
'
SINGLE CRYSTAL RUTILE
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Filed June 29, 1960
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INVENTOR.
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LEWIS E.HOLLANDER, JR.
BY
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Agent
Aug- 13, 1963
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L. E HOLLANDER, JR
3,100,849
ACTIVE SOLID-STATE DEVICES USING ANISOTROPIC
SINGLE CRYSTAL RUTILE
Filed June 29, 1960
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INVENTOR.
LEWIS E. HOLLANDER,JR.
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BY
Agent
Aug. 13, 1963
L. E. HOLLANDER, JR
3,100,849
ACTIVE SOLID-STATE DEVICES USING ANISOTROPIC
SINGLE CRYSTAL RUTILE
Filed June 29, 1960v
3 Sheets-Sheet 3
INVENTOR.
LEWIS E. HOLLANDER, JR.
\
BY
'
' Agent
United States Patent 0
1 ,.
C6
‘
3,109,849
Patented Aug. 13, 1963
2
dioxide, TiO2, the electrical properties of which are de
pendent ‘on the amount of oxygen de?ciency in the TiOz
crystal lattice. For example, rutile may be varied from a
3,106,849
ACTIVE S?LiD-STATE DEVICE§ USENG ANISS
TROPIC dlNGLE QRYSTAL RU’HLE
good insulator (1013 ohm-centimeter) in the stoichiomet
Lewis E. Hollander, In, Los Altos Hills, Cali?, assignor to
Lockheed Aircraft (Iorporation, Burbank, Calif.
Filed June 29, 1960, Ser. No. 39,584
15 Claims. (Cl. Bill-88.5
ric state to a conductor (0.1 ohm-centimeter) by varying
the oxygen de?ciency in the crystal lattice. The rutile
crystal structure is .tetragonal, with a=4.4923 angstroms,
c=2.8930 angstroms and the Schonflies symmetry D4,“.
This invention relates generally to solid-state electronic
The symbols “:1” and “c” ‘are orientation axes of the
devices, and more particularly to solid-state electronic 10 crystal and, similar to the symmetry symbol “D411,” will
devices employing single crystal rutile as the solid-state
readily be understood by those skilled in the art.
. material.
The decomposition or reduction of rutile and the re
The use of solid-state materials for making new types
sultant semiconductive properties thereof have already
of electronic ‘devices, such as diodes and transistors, has
been investigated in the art and are well-known. ‘Also,
received considerable attention in recent years. One of
rutile has been advantageously used in‘ electric current
the main limitations of presently known solid-state de
recti?ers, and also, as the dielectric for capacitors (see
vices, however, is that they are limited to a speci?c tem
Patents Nos. 2,692,212; 2,695,380‘ and 2,272,330). The
perature range of operation, beyond which they will not
function satisfactorily. As a result, the use of presently
known solid-state devices in military and space applica
tions, Where operating temperature range is a prime con
use of rutile as ‘a piezoresistive transducer is disclosed in
my copending patent application, Serial No. 855,042,
?led on November 24, 1959.
As a result of considerable research and investigation of
the properties of rutile, I have discovered that for a pre
determined range of oxygen vacancy densities in single
sideration, has been severely restricted.
Accordingly, one of the main objects of this invention
is to provide new types of solid-state electronic devices
crystal rutile, conduction in the “a” and “0” crystal direc
tions is highly Kanisotropic; that is, the ratio of the re
sistivity pa in the “a” crystal direction to the resistivity
pc in the “c” crystal direction is quite considerable and
which are operable over a wide temperature range, par
ticularly ‘at the very high temperatures.
-
Another object of this invention is to provide new types
of solid-state electronic devices employing single crystal
may be at least of the order of 2,000 to 1 over a very wide
temperature range. It was found that the anisotropy in
A further object of this invention is to provide solid 30 conduction isrelati-vely small where the oxygen vacancy
state modulation, ampli?cation ‘and computation devices
density is high corresponding to a “c” axis resistivity p6
employing single crystal rutile as the solid~state material.
of 10*1 ohm-centimeter, but increases markedly as the
The speci?c nature of the invention, as well ‘as other
density of vacancy sites is decreased, until an oxygen
objects, uses and advantages thereof, will clearly appear
vacancy ‘density corresponding to a resistivity pc of the
35
from the following description and the accompanying
order of 103 ohm-centimeters is reached where the aniso
drawing in which:
tropic eiiect appears to be a maximum. Beyond this
rutile as the solid-state material.
‘
FIG. 1 is a graph showing the anisotropic conduction
ratio pa/pc which has been discovered in single crystal
maximum, the "anisotropy decreases until it becomes rela
tively small at an oxygen vacancy density corresponding
to a resistivity pc of 108 ohm-centimeter. These results
are illustrated in the graph of FIG. 1 which is a plot of
rutile ‘for the “a” and “0” crystal directions at tempera
tures of —20° Centigrade, 23‘? centigrade and 50° centi
grade.
the anisotropic ratio pa/pc versus the “c” axis resistivity
FIGS. 2-4 are schematic diagrams ‘of ‘a microscopic
element of single crystal rutile which will be used in ex
pliaining the theoretical operation of the invention. FIG.
pc at temperatures of v—2(l" centigrade, 23° centigrade
and 50° centigrade. Since the resistivity of rutile is de
pendent upon its oxygen vacancy density, the resistivity pc
‘single crystal rutile having relatively few oxygen vacancies
density present.
2 is a schematic diagram of a microscopic element of 45 in the graph of FIG. 1 is ‘a measure of the oxygen vacancy
therein; FIG. 3 is a schematic diagram of a microscopic
'
The anisotropic e?fect shown in the graph of FIG. 1
element of single crystal rutile having su?icient oxygen
is believed to be a result of the differences in the points
vacancies so that the electron orbits just over-lap in the
of transition in the “a” and “c” crystal directions between
50
“0” crystal ‘direction; ‘and FIG. 4 is a schematic diagram
the two types of conduction-eimpurity band conduction
showing how the electron orbits of the single crystal rutile
and band gap conduction-—which appear ‘to be possible
element of FIG. 2 are affected by the application of an
in non-stoichiometric rutile. At low ‘oxygen vacancy
electric ?eld E in the “a” crystal direction.
densities corresponding to :a high resistivity p0 of greater
FIG. 5 is via schematic diagram of an embodiment of
than 108 ohm-centimeters, band gap conduction is the
a solid-state ampli?er and modulator employing single
principal means of conduction in both the “a” and “c”
crystal rutile as the solid-state material in accordance with
crystal directions.
’
the invention.
As the oxygen vacancy density increases, however,
FIG. 6 is a perspective schematic diagram of an em
conduction in the ‘.‘c” direction becomes predominant-1y
bodiment of a solid-state double modulation device em
impurity brand conduction at a very much smaller vacancy
ploying ‘single crystal rutile as the solid-state material in 60 density than in the “a” direction. For example, impurity
accordance with the invention.
‘
’ band conduction predominates in the "c” direction where
‘FIG. 7 is a perspective schematic diagram of an em!
the resistivity pc is of the order of 103 ohm-centimeters,
bodiment of a solid-state computer device employing sin
‘out in the “a” direction signi?cant impurity band conduc
gle crystal rutile \as the solid-state material in accordance
65 tion appears only for values of the resistivity pc of less
with the invention.
than 1 ohm-centimeter. Since in rutile the conductivity
FIG. 8 is a schematic diagram of ‘an embodiment of
for impurity band conduction is very much higher than
a dielectric ampli?er employing single crystal rutile as the
for band gap conduction, the large anisotropic charac
dielectric material in accordance with the invention.
teristic shown in the graph of FIG. 1 results.
The differences in transition ‘between band gap conduc
tion and impurity conduction in the “a” and “0” directions
may be understood from consideration of the crystal lat
Like numerals designate like elements throughout the
?gures of the drawing.
Rutile is one of three crystal modi?cations of titanium
3,100,849
4
tice ‘of rutile. The lattice spacing in the “c” direction is
0.6441 of the spacing in the “a” direction. Thus, for an
electron trapped on a titanium ion resulting from an oxy
gen vacancy in a rutile crystal lattice, the electron orbit
will be elliptical with a Bohr radius in the “c” direction of
about 90 angstroms and only about 40 angstroms in the
“a” direction. Since for impurity band conduction the
electrons are never ‘free, the electron orbits must overlap
in order to have conduction. If a suf?cient oxygen
vlacancy density exists so that the electron orbits just over
ductivity discussed above. It the oxygen vacancy density
is chosen so that the resistivity is sufficiently high in both
the “a” and “0” directions to make the dielectric con
stants meaningful, it will be found that the dielectric con
stant in the “a” direction is about 80 and in the “c’tdirec
tion about 180.
It has also been found that the application of an applied
?eld E in various directions is able to exert a signi?cant
eliect on the dielectric constants obtained in the “a” and
“c” crystal directions. In particular, an applied ?eld E
in the “a” crystal direction produces a marked effect on
the dielectric constant in the “c” direction.
tively large distance in the “a” direction, thereby giving
Because of the new properties of rutile I have discovered
rise to a very large anisotropy in conductivity.
and which are discussed ‘above, it now becomes possible
FIGS. 2-4 will now be used to present a physical pic
ture of the anisotropic conduction phenomenon in single 15 to devise new and improved types of electronic devices
employing single crystal rutile as the solid-state material.
crystal rutile and indicate how it may be controlled by the
Examples of such devices are illustrated in FIGS. 5~7.
application of an electric ?eld E.
Because rutile is such a high temperature material (rutile
In FIG. 2 a portion of a microscopic element 25 of
melts at about 1800*” centignade), rutile solid-state de
‘ single crystal rutile having relatively vfew oxygen vacan
cies (such as would occur for a resistivity p0 of greater 20 vices are inherently operable up to very high temperatures.
In FIG. 5 a rectangular parallelepiped element 125 of
than 108) is indicated with its “c” and “or” taxes oriented
single crystal rutile has “0” and “a” crystal axes oriented
as shown. Typical electron orbits ‘are indicated by the
as shown, the longitudinal axis of the element 125 being
elliptical dashed lines 10. The elliptical orbits 10‘ are
lap in the “c” direction, they will still be spaced by a rela
elongated in the “c” direction as explained previously.
parallel to the “c”, direction and perpendicular to the “a”
The oxygen vacancy density of the rutile ele
It can be seen that the orbits 10v are very far apart in 25 direction.
both the “a” and “0” directions. Conduction is therefore
of the band gap type and the anisotropic ratio pa/pc is rela
tively small.
.
'
FIG. 3 shows the microscopic element of single crystal
merit 125 is chosen so that a large anisotropic conduction
exists between the “a” and “c” axes. Ideally, an oxygen
vacancy density corresponding to a “c” axis resistivity p0
of the order of 1013 ohm-centimeters is preferable, since
rutile with its oxygen vacancy sites increased to a suffi
the maximum anisotropic effect occurs in this region.
cient density so that the elliptical orbits Iti- just overlap in
However, as shown in the graph of FIG. 1 an appreciable
the “c” direction {as shown. It will be noted that for this
condition the orbits are still far from touching in the “a”
direction. Since the electrons must overlap to permit
any signi?cant amount of conduction, the resistivity in the
“a” direction where an appreciable spacing exists is very
large as compared to the “c” direction where the orbits
are just touching. For an oxygen vacancy density corre
sponding to a resistivity pc in the “c” direction of about
10-3 ‘ohm-centimeters, the ratio pa/pc of the resistivities in
the “a” and “0” directions is of the order of 2,000. A
typical single-crystal rutile sample, therefore, might have
anisotropy is present over quite a large range so that the
selection or the particular oxygen vacancy density is not
critical.
In FIG. 5, two mutually perpendicular pairs of elec
trodes are‘now provided in contact with the single crystal
rutile element 125. The electrodes 26 and 28 are on
opposite faces of the element 125 so that current ?ow
therebetween is substantially parallel to the “0” crystal
direction, while the electrodes23 and 27 are on opposite
faces of the element 125‘ so that current flow therebetween
is substantially parallel to an “a” crystal direction.
An input signal em indicated by the generator 50 is _
a resistance of 1,000 ohms in the “c” direction and 2. meg
connected between the “a” taxis electrodes 23 and 27 by
ohms in the "a” direction.
FIG. 4 shows how the application of an electric ?eld E 45 means of thelead wires 23’ and 2,7’, and a D.-C. voltage
to the microscopic ‘single crystal rutile element 25 of
FIG. 3 in the “a” direction affects theelectron orbits 10.
It is seen that the application of the electric ?eld E causes
the electron orbits 10 to be “bowed out” so that they are
no longer overlapping in the “c” direction. Conduction
will thus be drastically reduced in the “c”. direction, but in
the “a”- direction only arnegligible e?ect will occur be
cause even'when “bowed out” the orbits will still be rela
source 60' in series with a resistor 55 are connected be
tween the “c” axis electrodes. 26 and 28 by means of the
lead wires 26' and 28’.
From the previous discussion regarding the electron
orbits of single crystal rutile and the effect of an ap
plied electric ?eld thereon in the “a” direction, 'it will
be understood that variationsin the input signal em will
cause corresponding variationsin the resistance appear
ing between‘the "~‘c” axis electrodes 26 and 28. The:
tively far apart. The application ‘of the electric ?eld E in
the “a” direction is thus able to exert signi?cant control 55 voltage em appearing across these electrodes 26 and 2-8
in‘ the circuit of FIG. 5, therefore, will be a representa
pver the conductivity in the ‘>‘c” direction.
tion of the input signal em; and, because the input resist
" The particular condition shown in FIG. 3 where the
ance appearing between the “a” axis electrodes 23 and 27 ‘
oxygen vacancy density is such that the electron orbits
is very large as compared to the resistance across the “c”
are just touching in the “c” direction is the optimum situ
ation which produces thegreatest anisotropy and the max 60. ‘axis electrodes 26 and 28, it has been found that an ap
preciable power gain may be achieved. Preferably, the
imum sensitivity of control. However, useable anisot
load resistor ‘55'- should be large ‘compared to the resistance
ropies and sensitivities are also obtained for other oxygen
appearing across the “c” axis electrodes 26 and 28.
vacancy densities. Also, instead of using an applied
If an A.-C. source were substituted ‘for the D.-C.
?eld E, other means could be employed to perturb the
orbits 10 in order to control the conductivity in the “c” 65 source 60 in FIG. 5, it will be realized that the output
signal em would then be the A.-C. source amplitude
- direction, such as by the use of magnetic ?elds, acoustic
vibrations or photon stimulation. The direction of appli
modulated by the input signal em.
cation, of the applied ?eld E or the other perturbing means
illustrated in FIG. 5 may also be advantageously em
employed is not critical, the important requirement for
control being the perturbing of the electron orbits 10 to
ployed for modulation purposes.
FIG. 6 is a perspective schematic diagram showing how
an A.-C. signal ec indicated at 94)’ may be amplitude modu
lated by two signals em and em indicated at 70‘ and .80,
respectively, in accordance with the invention. The single
crystal rutile element 125 shown in FIG. 61 may be the
‘an extent which ‘W111 affect conductivity in the “c” direc
tion.
'
_
' Another effect which has been observed in single crys
tal rutile is that a signi?cant anisotropy in dielectric con- .
Thus, the, device
stant is also‘present as well as the large anisotropy in con 75 same as that of FIG. 5 with the addition of the electrodes
rd
J
3,100,849
d
21 and 29 on the remaining two opposite faces at sub-v
stantially the same longitudinal location. It will be
noted that two “a” directions are shown which exist be
vided on one of the unused faces and one or more
longitudinally spaced smaller electrodes could be pro
cause there are two “a” directions in the rutile crystal.
1The A.-C. signal so to be modulated is connected in CR
series with the load resistor 5'5 across the “c” direction
electrodes ‘26 and 28 by means of the lead wires 26’ and
vided on the opposite ‘face.
It will be remembered from the previous discussion
that the dielectric constant of single crystal rutile is also
?eld dependent, particularly in regard to the dielectric
constant in the “c” direction in response to a ?eld applied
28’. The ?rst modulating signal cm is connected across
in the “a” direction. It is possible, therefore, to devise
the “a” direction electrodes 27 and 23 by means of the
single crystal rutile electronic devices whose operation
lead wires 27' and 23’, respectively, and the other modu 10 is dependent upon capacitance Variation eifects as well
lating signal am is connected across the “a” direction elec
as conductance variation effects as just described. Such
trodes 21 and 29 'by means of the lead wires 21’ and 29’,
a device is, illustrated in FIG. 8 in which a single crystal
respectively.
7
rutile element 225 is oriented with “a” and “0” crystal axes
It will be understood that the resistance appearing be
as shown. The oxygen vacancy density in the element
tween the “c” axis electrodes 26 ‘and ‘28 Will vary as a
225 is chosen to be relatively small (resistivity high) so
result of the cumulative effect of the applied electric
that the element 225 has the characteristics of a, low loss
?elds in both “a” directions, the e?'ects in the two “a” di
dielectric.
rections being additive because both pairs of “a.” direc
Electrodes 226 and ‘223 are provided on opposite faces
tion electrodes have substantially the same longitudinal
of the element so as to be space ‘opposed in a direc
location. The output voltage eout appearing across the 20 tion substantially parallel to the “c” crystal direction,
“c” electrodes 26 and 28, therefore, will be the A.-C.
while electrodes 223 and 227 are provided on opposite
signal ec amplitude modulated by the sum of the modu
faces of the element 225 so as to be space opposed in a
lation signals eml and em.
direction substantially parallel to an “a” crystal direc
If the A.-C. voltage source :20 indicated at 9% in FIG. 6
tion.
were replaced by a D.-C. source, the modulation signals 25
An input signal em indicated by the generator 50} is
em and em; would then both appear in the output signal
connected between the “a” axis electrodes 223 and .227 by
eout, and because of the large ratio of input resistance to
means of the lead wires 223’ and 227’, and an A.-C.
output resistance, each will experience a signi?cant power
source 90 in series with a load resistor 55 are connected
gain.
between the “c” axis electrodes 226 and 2.28 by means
It will now be appreciated that by applying one input
of the lead Wires 2426' and 228’.
signal in each “a” direction as shown in FIG. 6, the eilects
The input signal em applies an electric ?eld-parallel to
of each are essentially added in the output without the
the “a” axis of the element 255 which causes correspond
need for causing signi?cant interaction therebctween, be
ing variations in the capacitance appearing across the
cause of the relatively high input resistances which are .
“c” axis electrodes 226 and 228. An output voltage eout
present in the “a” direction. Of course, as in lany solid
will therefore be obtained which is representative of the
state device, capacitive coupling between electrodes is a
input signal em. Such a device ‘as shown in FIG. 8 could
possibility at higher frequencies, but the techniques ap
be employed for modulation or ampli?cation in a variety
plied to known solid-state devices for reducing capacita
of ways which will occur to those skilled in the art. Also,
tive coupling effects can also be applied to single crystal
additional electrodes could be employed on the unused
rutile devices for the present invention.
faces ‘of the element 225 to achieve greater versatility. '
‘FIG. 7 is a perspective schematic diagram illustrating
In providing single-crystal rutile elements for use in
how a solid-state computer device may be devised using
constructing electronic devices in accordance with the
single ‘crystal rutile as the solid~state material. The rutile
present invention, a variety of well known techniques.
element 125 and the “c” direction electrodes may be the
could be used. For example, single-crystal rutile boules
same as in FIGS. 5 and 6. However, the other electrodes
of stoiohiometirc rutile could be X-ray oriented by the
are located differently. As shown in FIG. 7,
longi
Laue backa'e?ection technique and then cut. to form ele
tudinally spaced electrodes 121, 122, 123 and 124 are
ments of a desired shape and size. After cleaning, these
provided on one longitudinal face of the element 125
elements are placed in a quartz tube furnace and reduced
and on the opposite face is provided a grounded elec
(the term reduced refers to the introduction of oxygen
trode 12-9. To each of the electrodes 121, 122, 123 50 vacancies in the crystal lattice) at 600‘0 to 700° centigrade
and 124 is connected an input signal designated W, X,
in a mixture of hydrogen and argon until the desired
Y and Z, respectively. Connected between the “c” axis
oxygen vacancy density is‘ obtained, which can be deter
electrodes 26 and 23 are a D.-C. source 6% and a load
mined from resistivity measurements. The particular
, resistor 55 in series which may be the same as in FIG. 5.
oxygen vacancy density obtained may be controlled by
The single crystal rutile element 125 may now be con 55 controlling the reaction temperature, the hydrogen-argon
sidered as made up of four series connected segments, each
mixture and the time of reduction.
segment corresponding to one of the electrodes 1211, 122,
The electrodes may be ‘provided on the reduced single
crystal rutile by any suitable means, such ‘as by the use
123 and 124. Considered in this manner it will be real
ized that the “c” direction resistance of each segment‘
of metal evaporation ‘or deposition techniques. The elec
will vary in accordance with the particular input signal 60 trode lead wires-are then suitably connected and the
W, X, Y or Z applied to its electrode 121, 122, 123 or
entire unit encapsulated if so desired.
124, respectively. Thus the output voltage‘ em obtained
will be proportional to the product WXYZ of the input
signals. For example, if all the input signals are the
same—that is, equal to X—-the output signal eout will
It is to be understood in connection with this invention
that the embodiments described and illustrated herein
are only exemplary’ and many variations and modi?ca
tions in the construction and arrangement are possible.
be proportional to X4.
For example, although a rectangular parallelepiped sin
gle~crystal rutile element is shown, it will be appreciated
that many other shapes are possible. Also, the location
Those skilled in the art will appreciate, therefore, that the ‘
newly discovered propeuties of single crystal rutile now i
make possible new, simple and compact computer devices ‘
which are capable of providing a wide variety of computer 70
operations, such as multiplication, squaring, cubing, etc.
In this connection, it will be evident that electrodes could
also be provided on the unused ‘faces of the element 125
in FIG. 7 so as to provide greater versatility.
For ex-
ample, a grounded electrode similar to 129 could ‘be pro
'
of the electrodes on the element with respect to the crys
tal axes may have other possible arrangements. Further
more, other means could be employed for making use
of the newly discovered properties, such as the use of
applied magnetic ?elds or other means for perturbing
,
the electron orbits. The present invention, therefore, is
75 to be considered as including all possible variations and
a, recess
8
modi?cations coming within the scope of the invention
as de?ned in the appended claims.
I claim as my invention: ,
l. A solid-state'electronic device having an element
of single crystal rutile as the solid-state material, said
element having an oxygen vacancy densitytchosen so
that an anisotropy in conduction exists in at least two
put signal corresponding to the variation in resistance
therebetween.
9. A solid-state electronic device comprising an ele
ment of single crystal rutile having an oxygen vacancy
density chosen so that an anisotropy in conduction exists
between “a” and “c” crystal directions in said element,
a ?rst pair of oppositely disposed electrodes provided
different mutually perpendicular directions in said ele
on said element in a direction substantially parallel to
ment, and a plurality of electrodes disposed on said ele
the “0” crystal direction thereof, a second pair of op
ment in a predetermined arrangement.
'
10 positely disposed electrodes provided on said element in
2. An element of single crystal rutile having an oxy
a direction substantially parallel to one “a” crystal di
gen vacancy chosen so that an anisotropy in conduction
rection thereof, a third pair of oppositely disposed elec
trodes provided on said element in a direction substan
exists between “a” and “0” crystal directions in said ele
tially parallel to the other “a” crystal direction thereof,
ment, a ?rst pair of oppositely disposed electrodes pro
vided on said element in a direction substantially parallel, 15 means applying a ?rst input signal between said second
pair of electrodes, means applying a second input signal
to the “0” crystal direction thereof, and a second pair of
between said third pair of electrodes, and circuit means
oppositely disposed electrodes provided on said element
connected between said ?rst pair of electrodes for ob
in a direction substantially parallel to an “a” crystal direc
taining an output signal corresponding to the variation
tion thereof.
7
,
3; The invention in accordance with claim 2, wherein 20 in resistance therebetween.
10. The invention in accordance with claim 9, wherein
said element is in the form of a rectangular parallelepiped
having its longitudinal axis substantially parallel to the
F‘c” crystal direction of said element.
.
4. An element of single crystal rutile having an oxy
said second and third pairs of electrodes are disposed so
as to be at substantially the same location with regard
to the “c” crystal direction.
exists between “a” and “0” crystal directions in said ele
ment, a ?rst pair of oppositely disposed electrodes pro
vided on said element in a direction substantially parallel
to the “c” crystal direction thereof, a second pair of op
positely disposed electrodes provided on said element in
11. An element of single crystal rutile having a longi
tudinal axis substantially parallel to the “c” crystal di
rection thereof, said element having an oxygen vacancy
density chosen so that an anisotropy in conduction exists
between “a” and “0” crystal directions in said element,
a pair of oppositely disposed electrodes provided on said
a direction substantially parallel to one “a” crystal direc
element in a direction substantially parallel to the “0”
tion thereof, ‘and a third pair of oppositely disposed elec
trodes provided on said element in a direction substan
provided on said element spaced along the longitudinal
gen vacancy chosen so that an anisotropy in conduction
tially parallel to the other “a” crystal direction thereof.
5. A solid-state electronic device comprising an ele
ment of single crystal rutile having an oxygen vacancy
density chosen so that an anisotropy in conduction exists
in at least two different mutually perpendicular directions
in'said element, means adapted to act on said element so
as to perturb the conduction in said element in a pre
crystal direction thereof, and a plurality of electrodes’
axis thereof.
I
12. The invention in accordance with claim 11 where
in said element is in the form of a rectangular paral
lelepiped and one of the longitudinal faces thereof has
a longitudinal electrode extending substantially the length
thereof, and said plurality of electrodes are longitudinally
spaced on the opposite face from said longitudinal elec
determined direction, and means connected to said ele
ment for obtaining an electrical signal corresponding to
trode.
the iperturbance in conductance occurring in said element
ing an element of single crystal rutile having an oxygen
vacancy density chosen so that an anisotropy; in conduc
tion exists between “a” and “0” crystal directions in said
in said predetermined direction.
,
'
6. A solid-state electronic device comprising an ele
ment of single crystal rutile having an oxygen vacancy’
density chosen so that an anisotropy in conduction exists
between “a” and “c” crystal directions in said element, a
13. A solid-state electronic computer device compris
element, a pair of oppositely disposed electrodes pro
vided on said element in a direction substantially parallel
to the “c” direction thereof, a plurality of electrodes
provided on said element spaced along the “0” crystal
element in a direction substantially parallel to the “c” 50 direction thereof, means applying input signals to said
plurality of electrodes, and circuit means connected to
crystal direction thereof, means adapted to‘ act on said
pair of oppositely disposed electrodes provided on said
element so as to perturb the conduction in said element
said pair of oppositely disposed electrodes for obtaining
in the “c” crystal direction in accordance with an input
signal, and circuit means connected between said elec
‘an output signal corresponding to the variation in the
resistance therebetween.
trodes ‘for obtaining an-outpu't signal corresponding to
the permrbance in conductance occurring in said element
14.‘ A solid-state electronic device comprising an ele
ment of single crystal rutile having an oxygen vacancy
density such that the element acts as a capacitative di
in the “c” direction.
I
electric, a pair of oppositely disposed electrodes on said
7. The invention in accordance with claim 6, wherein
element in a direction substantially parallel to the “c”,
said’ ?rst mentioned means comprises means for applying
an electric ?eld to said element parallel to an “a” crystal 60 direction thereof, means applying an electric field to said
element so that the dielectric constant appearing between
direction thereof, said electric ‘?eld varying in accordance
said electrodes is perturbed, and circuit means connected
with said input signal.
a
between said electrodes ‘for obtaining an output signal
8. A solid-state electronic device comprising an ele
, ment of single crystal rutile’ having an oxygen vacancy (i5 corresponding to' the variation in the capacitance there
density chosen so that an anisotropy in conduction exists
15; A solid-state electronic device comprising an ele
between “a” vand “c” crystal directions in said element,
ment of single crystal rutile having 'an oxygen vacancy
‘a ?rst pair of oppositely disposed electrodes provided on
density such that the element acts as a capacitative di
said element in a direction substantially parallel to the
electric, a ?rst pair of oppositely disposed electrodes pro
between.
.
'
'
_
_“c” crystal direction thereof, a second pair’of oppositely 70 vided on said element in a direction substantially par
disposed electrodes provided on said element in a direct
tion substantially parallel to an “a” crystal ‘direction
allel to the “0” crystal direction thereof, a'second pair
of oppositely disposed electrodes provided on said ele
thereof, ‘means applying an input signal between said sec
ment in a direction substantially parallel to the “a” axis
ond pair of electrodes, and circuit means connected be
tween said ?rst pair of electrodes for obtaining an out
pair of electrodes, and circuit means connected to said
thereof, means applying an input signal to said second
3,100,849
9
?rst pair of electrodes for obtaining an output signal
corresponding to the variation in the capacitance therebetween.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,940,941 '
Dalton _____________ __ June 14, 1960
1t)
2,966,642
De Rudnaj/ __________ __ Nov. 15, 1960
OTHER REFERENCES
Berberiok and Bell, “Dielectric Properties of the Rutile
5 ‘Form of TiOz,” Journal of Applied Physics, vol. 11,
October 1940, pp. 681-692 (page 686 relied on).
Terman: Radio Engineering, McGraw-Hill, N.Y., 1947,
pp. 552-553 relied on.
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