Data storage device and system having an optically non transmissive chalcogenide layer

Disclosed is an optical data storage device and system, and a method of doing one or more of entering data into, reading data out of, or erasing data from the device. The optical data storage device is characterized by an encapsulated structure including an optically non-transmissive, chalcogenide, phase changeable layer. The phase changeable layer is sufficiently thick such that the impinging vitrifiying energy pulse does not vitrify all the way through the layer.

FIELD OF THE INVENTION 
The invention disclosed herein relates to data storage devices, where data 
is stored in a material that is switchable between detectable states by 
the application of projected beam energy thereto. 
BACKGROUND OF THE INVENTION 
Nonablative state changeable data storage systems, for example, optical 
data storage systems, record information in a state changeable material 
that is switchable between at least two detectable states by the 
application of projected beam energy thereto, for example, optical energy. 
State changeable data storage material is incorporated in a data storage 
device having a structure such that a layer of data storage material is 
encapsulated between encapsulant layers and supported by a substrate. For 
optical data storage devices the encapsulants include, for example, 
anti-ablation materials and layers, thermal insulation materials and 
layers, anti-reflection materials and layers, reflective layers, and 
chemical isolation layers. Moreover, various layers may perform more than 
one of these functions. For example, anti-reflection layers may also be 
anti-ablation layers and thermal insulating layers. The thicknesses of the 
layers, including the layer of state changeable data storage material, are 
optimized to minimize the energy necessary for state change and optimize 
the high contrast ratio, high carrier to noise ratio, and high stability 
of state changeable data storage materials. 
The state changeable material is a material capable of being switched from 
one detectable state to another detectable state or states by the 
application of projected beam energy thereto. State changeable materials 
are such that the detectable states may differ in their morphology, 
surface topography, relative degree of order, relative degree of disorder, 
electrical properties, optical properties including indices of refraction 
and reflectivity, or combinations of one or more of these properties. The 
state of state changeable material is detectable by the electrical 
conductivity, electrical resistivity, optical transmissivity, optical 
absorption, optical refraction, optical reflectivity, or combinations 
thereof. 
Formation of data storage device is a vacuum process including deposition 
of the individual layes, for example by evaporative deposition, chemical 
vapor deposition, and/or plasma deposition. As used herein plasma 
deposition includes sputtering, glow discharge, and plasma assisted 
chemical vapor deposition. 
Tellurium based materials have been utilized as state changeable materials 
for data storage where the state change is a structural change evidenced 
by a change in reflectivity. This effect is described, for example, in J. 
Feinleib, J. deNeufville, S. C. Moss, and S. R. Ovshinsky, "Rapid 
Reversible Light-Induced Crystallization of Amorphous Semiconductors," 
Appl. Phys. Lett., Vol. 18(6), pages 254-257 (Mar. 15, 1971), and in U.S. 
Pat. No. 3,530,441 to S. R. Ovshinsky for Method and Apparatus For Storing 
And Retrieving Of Information. A recent description of 
tellurium-germanium-tin systems, without oxygen, is in M. Chen, K. A. 
Rubin, V. Marrello, U. G. Gerber, and V. B. Jipson, "Reversibility And 
Stability of Tellurium Alloys for Optical Data Storage," Appl. Phys. 
Lett., Vol. 46(8), pages 734-736 (Apr. 15, 1985). A recent description of 
tellurium-germanium-tin systems with oxygen is in M. Takenaga, N. Yamada, 
S. Ohara, K. Nishiciuchi, M. Nagashima, T. Kashibara, S. Nakamura, and T. 
Yamashita, "New Optical Erasable Medium Using Tellurium Suboxide Thin 
Film," Proceedings, SPIE Conference on Optical Data Storage, Arlington, 
VA, 1983, pages 173-177. 
Tellurium based state changeable materials, in general, are single or 
multi-phased systems (1) where the ordering phenomena include a nucleation 
and growth process (including both or either homogeneous and heterogeneous 
nucleations) to convert a system of disordered materials to a system of 
ordered and disordered materials, and (2) where the vitrification 
phenomenon includes melting and rapid quenching of the phase changeable 
material to transform a system of disordered and ordered materials to a 
system of largely disordered materials. The above phase changes and 
separations occur over relatively small distances, with intimate 
interlocking of the phases and gross structural discrimination, and are 
highly sensitive to local variations in stoichiometry. 
A serious limitation to the rate of data storage is the slow ordering or 
erasing time. Ordering or erasing occurs by the crystallization of 
vitrified or written spots. However, a layer of phase changeable material 
thin enough to provide first fringe reflection is so thin that 
vitrification or writing of the spot occurs substantially all the way 
through the layer. For most active layer compositions, when the spot 
crystallizes on erasure, it does so from the sides, where there is some 
unvitrified material to serve as nucleation sites. Thus, the erase time 
depends, in part, on the diameter of the spot. 
SUMMARY OF THE INVENTION 
According to the invention herein contemplated, there is provided a data 
storage device having an optically nontransmissive chalcogen data storage 
medium layer, a substrate supporting the medium, and dielectric films 
encapsulating the chalcogenide data storage medium. By "optically 
nontransmissive" is meant an optical transmissivity of less than 
approximately 5% in the non-ordered, or vitrified, state. The optical 
thickness of the chalcogenide layer should be thick enough to provide an 
optical transmissivity of less than 5% in the non-ordered or vitrified 
state. 
According to the invention herein contemplated, the chalcogenide layer must 
also be thick enough that the projected beam energy does not vitrify the 
material all the way through the layer, but only through a top portion, 
which may be well-shaped. Thus, for energy pulses of comtemplated duration 
and energy density, the thermal thickness should be such to avoid 
vitrification all the way through the chalcogenide layer. Underneath the 
well of vitrified material is material in a crystallized or ordered state. 
We have found that the depth of the vitrified spot of phase change material 
is typically three to ten times smaller then the diameter of the vitrified 
spot and that crystallization ratio is independent of spot size. Using 
this finding we have prepared devices with a thicker layer of phase change 
material then heretofore thought optimal. In this way we have been able to 
attain a significantly higher crystallization rate then that heretofore 
observed in similar chalcogenide films of 800 to 1200 Angstroms thickness. 
Microscopic examination of data storage devices with the herein 
contemplated thick chalcogenide films shows that this is accomplished by 
providing seeds or nucleation sites through a phenomenon we refer to as 
"back growth". By "back growth" we mean that crystals nucleate and 
crystallization proceeds from unvitrified chalcogenide material in the 
layer behind and adjacent to the vitrified chalcogen material but remote 
from the source of vitrifiying energy, i.e., that crystallization proceeds 
from a region below the vitrified spots. 
As herein contemplated the thickness of the chalcogenide layer, that is, 
the layer of phase change material, must be thick enough that transient 
heat transfer from the vitrifying or writing pulse of projected beam 
energy out of the vitrified spot is low enough to avoid complete 
vitrification all the way through the layer. That is, the projected beam 
energy does not penetrate all the way through the layer of phase change 
chalcogenide material. 
It is believed that crystallization proceeds from the state-state 
interface, i.e., the vitrified state-crystallized state interface, with 
the uncycled crystals serving as nucleation sites. Back growth proceeds 
much more quickly than the side growth of the prior art, because the axis 
of growth is perpendicular to the largest dimension of the spot size, 
instead of parallel to it. As herein postulated back growth proceeds 
through only about the 0.1 micron depth of the spot rather than through 
approximately 1 micron radius of the spot as in the case of side growth. 
The invention herein contemplated provides self-alignment of the two states 
along the state-state interface. In the prior art crystallization proceeds 
through a layer-layer boundary. According to the present invention, 
crystallization proceeds through a phase-phase boundary of the same 
material, and new, growing crystals will be properly aligned with the 
unvitrified crystals. As a result, crystal growth is far less likely to 
exhibit undesirable patterning and concommitant residual signed upon 
erasure caused by irregularities in previous growth patterns. 
It is believed that back growth results in better control of the size, 
orientation, volume fraction, and growth rate of the crystals. Thus, it is 
believed that the optically nontransmissive, crystalline, chalcogenide 
layer provides consistent, and even preferred orientations, and reduces 
the time for switching from the less ordered detectable state to the more 
ordered detectable state. 
Moreover, it is believed that the invention reduces the cycle history 
dependent change in the order of the ordered material. This is because the 
seeds or nucleation sites are themselves not subject to cycling or state 
change and as a result the phase change material crystallizes consistently 
at each cycle. This results in a great improvement in stability and cycle 
history invariance. 
Additionally, the thicker, optically nontransmissive chalcogen layer is 
internally reflecting. In the prior art, the thickness of approximately 
the thinner chalcogen layer had to have a thickness of Lambda/2n, where n 
was the index of refraction and Lambda the wave length in order to 
maximize contrast, i.e., minimize vitrified reflectivity and maximize 
crystallize reflectivity, where contrast equals R.sub.crystalline 
-R.sub.amorphous. 
In the internally reflecting phase change material herein contemplated, 
incident light is reflected back from both the front (light incident) 
interface and the vitrified state-crystallized state interface, rather 
than from the chalcogenide layer-dielectric layer interface. Thus, 
thickness of the thick, optically nontransmissive layer may be fairly 
nonuniform as long as certain thicknesses, i.e., the thermal penetration 
thickness and the optical thickness are exceeded. By way of contrast the 
thin film chalcogenide structures of the prior art depends critically on 
the thickness of the active chalcogenide layer. The greater tolerance of 
layer thickness variation of the present invention results in far fewer 
manufacturing and quality control problems. 
Because of the increase in crystallization rates due to the more favorable 
geometry of the thick layer structure, chalcogen compounds which are more 
stable and concomitantly have slower intrinsic switching times may be 
utilized and still yield good results. Under the prior art, a fast 
switching chalcogen, such as, for example, Te.sub.83 Ge.sub.5 Sn.sub.6 
O.sub.6-8, might be used. Te.sub.83 Ge.sub.5 Sn.sub.6 O.sub.6-8, however, 
has a crystallization temperature of about 80.degree. C. This relatively 
low crystalization temperature means that the material may be relatively 
unstable over time in the amorphous state. With the present invention, the 
fast switching time of the low crystallization temperatures thin layer 
material is obtained with a thicker layer of a compound such as 
Te.sub.87-88 Ge.sub.5 Sn.sub.6 O.sub.3-4, which has a crystallization 
temperature of 1OO.degree. C., and is, accordingly, more stable over time. 
According to one exemplification of the present invention, there is 
provided a data storage device comprising a first substrate, a first 
dielectric layer deposited atop the substrate, and an optically 
nontransmissive chalcogen phase changeable data storage medium layer 
deposited atop the first dielectric layer. The optically nontransmissive, 
chalcogen, phase changeable, data storage medium layer has an ALPHA x D 
product greater then or equal to 3, where 
EQU T=TO EXP(-ALPHA.times.D), 
and 
ALPHA=optical absorption coefficient, 
D=active chalcogenide layer thickness, 
T=transmitted light intensity, and 
TO=intensity of light entering the active layer. 
Deposited atop the layer of state changeable material may optionally be a 
second dielectric layer. With the herein contemplated thick chalcogenide 
layer structure, the second dielectric layer may be unnecessary. A second 
substrate is located atop that. The resultant device exhibits dynamic 
tester cycle-history invariance through more than at least 17,000 cycles 
with contrast of about 40 or more decibles, with complete erasability. 
In a further exemplification, there is provided a data storage system 
comprising a data storage device containing nontransmissive, chalcogenide, 
phase changeable data storage medium, a means for imparting relative 
motion thereto, projected energy beam means, means for determining the 
state of the memory material, and controller means for synchronizing the 
projected beam energy means and the relative movement means. 
In a further exemplification, one or more of writing data into a data 
storage device, reading data out of the data storage device, or erasing 
data from the data storage deivce is performed. The method comprises 
writing data into the data storage medium with electromagnetic energy of a 
first energy density and duration, reading the state of the data storage 
medium with electromagnetic energy of a second energy density and 
duration, and erasing data from the data storage medium with 
electromagnetic energy of a third energy density and duration. 
Exemplary chalcogenide compositions useful in providing the chalcogenide 
data storage medium include tellurium, for example, where the tellurium is 
present with a cross linking agent or agents. The chalcogenide composition 
is reversibly switchable between detectably different states. 
Suitable cross linking agents are elements of groups IIIB, IVB, and VB of 
the Periodic Table. These include boron, aluminium, indium, and gallium 
from Group IIIB, silicon, germanium and tin from Group IVB, nitrogen, 
phosphorous, arsenic, antimony, and bismuth from Group VB, as well as 
combinations thereof. Exemplary cross linking agents from Groups IIIB, 
IVB, and VB of the periodic table include silicon, germanium, tin, 
arsenic, antimony, and mixtures thereof, expecially silicon, and/or 
germanium, either alone or with one or more of tin, arsenic, or antimony. 
Especially preferred is germanium, either alone, or with tin. 
Additionally, other chalcogens, as selenium and sulphur, may be present. 
Exemplary chalcogenide compositions include the chalcogen e.g. tellurium, 
and a cross linking agent, e.g. silicon and/or germanium, or silicon 
and/or germanium with another cross linking agent in the medium sufficient 
to form a stable chalcogenide. Additionally oxygen, or a switching 
modulator, as Ni, Pt, or Pd, may be present. Generally, the atomic ratio 
of the cross linking agent to total composition is from about 1 percent to 
about 20 atomic percent. 
The data storage medium may be formed by depositing the materials to form a 
deposit thereof. The deposit may be more than 2000 Angstroms thick.

DETAILED DESCRIPTION OF THE INVENTION 
According to the invention described herein, there is provided a projected 
beam storage device having a thick layer of data storage medium. The layer 
of medium is substantially optically non-transmissive and a portion 
thereof is switchable between detectable states by the application of 
projected beam energy thereto. 
The layer of phase changeable chalcogenide material herein contemplated is 
thicker then the "optical thickness" and "thermal penetration thickness" 
thereof. The thermal penetration thickness is the maximum distance into 
the phase changeable chalcogenide, measured from the projected energy beam 
incident side, that is heated to a temperature high enough to cause 
vitrifiction by the projected energy beam. The chalcogenide phase change 
material beyond the thermal penetration thickness is not vitrified by the 
projected energy beam. It may, however, be crystallized directly by the 
beam. 
The thermal penetration thickness is a function of the projected energy 
beam's energy, wavelength and duration. It is also a function of the 
thermal conductivity, k, and the specific heat, C.sub.p of the 
chalcogenide material, and of the maximum temperature, T.sub.m, attained 
by the projected energy beam incident side of the chalcogenide phase 
change. 
An approximate theoretical calculation of the thermal penetration thickness 
may be made using the methods described in William H. McAdams, Heat 
Transmission, Third Edition, McGraw-Hill Book Company, Inc., New York, NY 
(1954), at Chapter 3, "Transient Conduction", page 39, "Semi-infinite 
Solid", in R. Byron Bird, Warren E. Stuart, and Edwin N. Lightfoot, 
Transport Phenomena, John Wiley & Sons, Inc., New York, NY (1960), at 
Chapter 11, "Temperature Distributions With More Then One Independent 
Variable", Example 11.1-1, "Heating of a Semi-Infinite Slab", at page 
353-354, and in H.S. Carslaw and J.C. Jaeger, Conduction of Heat In 
Solids, Second Edition, Oxford University Press (1959), all of which are 
incorporated herein by reference. 
Using the methods described in the above incorporated texts, the thermal 
penetration thickness, d, may be calculated by assuming (1) a maximum 
temperature, T.sub.m, at the thermal penetration thickness, d, less then 
or equal to the melting temperature of the chalcogenide phase change 
material, (2) a maximum temperature, T.sub.s, at the projected energy beam 
incident surface of the chalcogenide phase change material, and (3) an 
initial temperature, To, of the chalcogenide phase change layer, e.g. 
ambient temperature. These temperatures may be related through a reduced 
dimensionless "unaccomplished temperature change", Y, which is defined by: 
##EQU1## 
The physical properties of the chalcogenide phase change material are 
related through the dimensionless number Z, which is defined as 
##EQU2## 
Using the above mathematic models and assumed temperature limitations, and 
following the procedures described in the above incorporated texts, and 
the graphical solutions, the theoreticaly predicted thermal energy 
penetration thickness for a 200 nanosecond pulse is about 2000 Angstroms. 
Actual experimental observations have shown that for record pulse widths of 
about 200 nanoseconds, and record powers of about 1 to 5 milliwatts, a 
chalcogenide phase change layer thickness of above about 2000 to 2500 
Angstroms is adequate to provide back crystallization, with greater 
thicknesses being desirable to provide a substantial absence of optical 
transmissivity through the chalcogenide phase change layer and to act as 
an encapsulant and/or dielectric. 
In a particularly preferred exemplification of the invention, the energy 
profile of the projected energy beam means is established or controlled to 
provide a laterally uniform thermal penetration depth such that 
crystallization and vitrification occur only within a distance d* of the 
projected energy beam incident side of the phase change chalcogenide 
layer. The distance d* is defined by 
EQU d*=Lambda/4n. 
Lambda is the wavelength of the projected energy beam, and n is the index 
of refraction of the vitrified phase change chalcogenide material. The 
thickness d* gives the maximum contrast between written and erased states. 
FIGS. 1 and 2 show a projected beam data storage device 1 of the invention, 
having a substrate, for example a plastic substrate 11, a first 
encapsulating dielectric layer 21, for example a first germanium oxide 
encapsulating layer, a chalcogenide data storage medium layer 31, a second 
dielectric layer 41, e.g., a second germanium oxide layer 41, and a second 
substrate, e.g., plastic substrate 51. 
FIG. 2 shows a section of the data storage device 1 of FIG. 1 in greater 
detail. As there shown, the substrate 11 is a polymeric sheet, for example 
a polymethyl methacrylate sheet. The substrate 11 is an optically 
invariant, optically isotropic, transparent sheet. The preferred thickness 
of the substrate 11 is from about 1 mm to about 1.5 mm. 
Atop the substrate 11 is a film, sheet, or layer 13, e.g., a 
photoinitiated, polymerized acrylic epoxide sheet. Polymerized, molded, or 
cast into the polymeric sheet 13 may be grooves. When grooves are present 
they may have a thickness from about 500 to about 1000 Angstroms. The 
film, sheet, or layer 13 may act as an adhesive, holding the substrate 11 
to the encapsulants. It has a thickness of from about 30 to about 200 
microns and preferably from about 50 to about 100 microns. 
Deposited atop the photo-polymerized sheet 13 is a dielectric barrier layer 
21. The dielectric barrier layer 21, for example, of germanium oxide, is 
from about 500 to about 2000 angstroms thick. The dielectric barrier layer 
21 has one or more functions. It serves to prevent oxidizing agents from 
getting to the chalcogen active layer 31 and prevents the plastic 
substrate from deforming due to local heating of the chalcogenide layer 
31, e.g., during recording or erasing. The barrier layer 21 also serves as 
an anti-reflective coating, increasing the optical sensitivity of the 
chalcogenide active layer 31. 
Other dielectrics may provide the encapsulating layers 21, 41. For example, 
the encapsulating layers may be silicon nitride, layered or graded to 
avoid diffusion of silicon into the chalcogenide layer 31. Alternatively, 
the encapsulating dielectric layers 21, 41 may be silica, alumina, or 
other dielectric. Alternatively, the chalcogenide layer may be thick 
enough to be self encapsulating. 
The chalcogenide data storage medium 31 has a thickness 
(1) of at least d, where d is the thermal penetration depth described 
above, 
(2) greater than about d* where Lambda is the wave length of the projected 
beam energy, and n is the index of refraction of the crystalline data 
storage medium, and 
(3) an optical thickness great enough to be substantially optically 
non-transmissive as described above and internally reflecting. The 
thickness of the layer of chalcogenide data storage medium is at least 
about 2000 Angstroms and preferrably from about 2000 to 4000 Angstroms. 
Atop the chalcogenide layer 31 and in contact with the opposite surface 
thereof is a second dielectric layer 41, e.g., a germanium oxide layer. 
The second dielectric layer 41 when present, may, but need not be of equal 
thickness as the first layer 21. However, because the herein contemplated 
thick chalcogenide layer 31 is a good thermal barrier, the second 
dielectric layer 41 may be omitted. A second photopolymer layer 49 and a 
second substrate layer 51 are in contact with the opposite surface of the 
encapsulating layer 41. 
The polyacrylate layers 13, 49, are cast or molded in place. These layers 
13, 49 can be photo-polymerized in place, e.g., by the application of 
ultra-violet light. The barrier layers 21, 41, are deposited, by 
evaporation, for example, of germanium and germanium oxide materials, or 
by sputtering, including reactive sputtering where the oxygen content of 
the reactive gas used in reactive sputtering is controlled. The 
chalcogenide film 31 may be prepared by evaporation, or by sputtering, or 
by chemical vapor deposition. 
FIGS. 3a and 3b illustrate the difference in growth pattern between crystal 
growth in an erased spot in a thin film medium of the prior art and in the 
thick film medium of the present invention. In FIG. 3a, the thickness of 
the data storage medium layer is on the order of 1000 Angstroms. At this 
thickness, the incident erasing energy beam vitrifies a spot through 
substantially the whole thickness of the layer. When the spot 
recrystallizes, crystal growth will proceed from unvitrified crystals 
which can serve as nucleate sites at the edges the spot. This results in 
an inward moving crystallization front, i.e., edge growth. With this edge 
growth pattern, crystallization time will be slow because growth must 
proceed through the whole diameter of the erased spot. 
FIG. 3b, the layer of chalcogenide material is much thicker, on the order 
of 2000 to 5000 Angstroms. The incident vitrifying pulse vitrifies a spot 
only partially through the layer, leaving a back layer of crystals 
surrounding and beneath the well of vitrified material. As the spot 
recrystallizes, this back layer provides nucleation sites. Since crystal 
growth is in a direction perpendicular to the diameter of the relatively 
shallow erased spot, the spot will recrystallize much more quickly. In 
addition we have found that the orientation of the crystals in the back 
layer 41 may be controlled such that they all have the same orientation 
with th tellurium c-axis oriented from film front to back. The orientation 
of back layer crystals within the chalcogenide film 41 may be controlled 
techniques, for example, by providing composition gradiants in the phase 
change material layer 41 whereby to provide a graded crystallization 
temperature, or by providing a seeding layer. For example the 
crystallization temperature remote from the projected energy beam may be 
higher then the crystallization temperature on the energy beam incident 
side of the phase change material layer 41. The gradiant may be linear, or 
discrete. 
The concomitant improvement in erasure time is illustrated by FIGS. 4a and 
4b where the erase time of thin and thick film phase change layers are 
shown. In these graphs, the erase pulse width, i.e., time in microseconds, 
is plotted against the contrast for various record powers. The spot is 
considered to be erased when the contrast maximizes and levels out. In 
FIG. 4a, where edge growth was the mechanism of erasure in film of phase 
change material the point of erasure did not occur until between 1 and 
about 9 microseconds had elapsed. In FIG. 4b, where back growth was the 
postulated mechanism in a 4000 Angstrom thick film, the point of erasure 
was reached before 0.5 microseconds, and the rise and leveling out pattern 
could not be detected. The erase time was below the ranges ordinarily 
observed with films 800 to 1200 Angstroms thick. 
According to a further exemplification of the invention shown in FIG. 7, 
there is provided an optical data storage system adapted for use with the 
optical data storage device shown in FIGS. 1 and 2 and having an optically 
non-transmissive, chalcogenide, phase changeable data storage medium layer 
therein. The system includes means for imparting relative motion to the 
disc 1, as turntable means 111 driven by motor means 113. 
The system has projected energy beam means for writing data into the phase 
changeable chalcogenide data storage medium, reading data out of the phase 
changeable chalcogenide data storage medium, and erasing data from the 
phase changeable chalcogenide data storage medium. The projected energy 
beam means includes recording or writing means for vitrifying a cell of 
the phase changeable chalcogenide data storage medium to a relatively 
disordered state, erasing means for crystallizing a cell of the phase 
changeable chalcogenide data storage medium, and reading means for 
determining that state of the phase changeable chalcogenide data storage 
medium. 
The projected beam energy means, e.g., laser means 121 and 123 are 
controlled by controller means 151 and encoding means 153 when in the 
"write" and "erase" or "vitrify" and "crystallize" modes. When in the 
"read" mode the projected beam energy means utlizes photodetector means 
131 and decoder means 155, controlled by the controller means, to 
determine the state of the cell of phase change memory material. 
The controller means 151 also includes tracking means for synchronizing the 
projected beam energy means, the turntable means 111, and the motor means 
113. 
Utilizing the relatively thick film, substantially optically 
non-transmissive, phase changeable, chalcogenide data storage medium of 
the invention, it is possible to do one or more of enter data into, read 
data out of, or erase data from an optical data storage device of the type 
described hereinabove. While the invention has been described with respect 
to certain preferred exemplifications and embodiments thereof it is not 
intended to be bound thereby but solely by the claims appended hereto.