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Патент USA US2405306

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Aug 9 1%“
J. HILLKER ET AL‘
2,4@»3
' ELECTRONIC MIQROANALYZER MONITORING
Filed Jan. 51, v1944'
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J. HILLIER ETAL,
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ELECTRONIC MICROANALYZER MONITORING
Filed Jan. 51', 1944
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J. HELLIER ETAL.
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ELECTRONIC MICROANALYZER MONITORING
Filed Jan. 51', 1944
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Patented Aug. 6, ices
,
2,45,306
UNITED STATES PATENT QFFICE
2,405,306
ELECTRONIC MICROANALYZER
MONITORING '
James Hillier, Cranhury, and Richard F. Baker,
Princeton, N. J., assignors to Radio Corpora
tion of America, a corporation of Delaware
Application January 31, 1944, Serial No. 520,410
17 Claims. (01. 250-495)
1
2
‘This invention relates generally to electron op-
By means of the improved electron microscope
tics and more particularlyto an improved method
of and means for monitoring the microanalyzing
associated with the analyzer, as described in de
tail hereinafter, the area of the specimen ana
of materials by electron irradiation.
.
lyzed can be observed and monitored at all
The invention is an improvement over the sys- 5 times, so that the relationship of the region ex
tems described in a- copending, U. S. application
amined to the remainder of the specimen can be
of James Hillier, Serial No. 505,572, ?led October
3,
1942,describes
entitledthe“Electronic
which
generation microanalyzer,”
of an electron
determined continuously, independently of and
simultaneously
with the electron velocity anal
ysis.
probe, having extremely minute cross-sectional 10
The apparatus required for electronically
area, which is focused upon a minute area of the
analyzing materials is similar in many respects
electron permeable material to be analyzed.
to the conventional electron microscope.
reflected from the material by the impinging
trons which impinge upon or penetrate the sub—
The
electrons, are subjected to an electrical or mag- 15 stance under observation are subjected to de
netic de?ecting ?eld which de?ects the electrons
?eeting electric or magnetic ?elds whereby they
as a function of their velocities.
The deflected
are deflected amounts proportional to their ve_
electron-s impinge upon a ?uorescent screen for
visual observation of the electron velocity dis-
locities before impingement upon the observation
screen. Accordingly, if desired, the invention
tribution pattern, or the electrons impinge upon 20 may take the form of a relatively simple attach
a photographic plate for providing a permanent
ment for conventional electron microscopes to
record of the pattern. Means are included for
permit microanalysis by electronic methods.
observing upon an auxiliary ?uorescent screen
Furthermore, the electrons which are velocity
the portion of the specimen upon which the
analyzed are those which are scattered in pass
electron probe impinges only during intervals 25 ing through the specimen to some predetermined
when the de?ecting ?eld is not present. Means
angle from the irradiating electron beam axis.
also are provided for adjusting the position of
The thus scattered electrons have lost energy due
the material under observation with respect to
to inelastic collisions with the specimen, hence
the axisof the electron probe.
they are especially suitable for the desired micro
The operation of the electronic microanalyzer 30 analysis, thereby providing improved velocity in
is based on the fact that when electrons pass
through matter some of the energy of the elec-
trons is transformed into X-ray radiation energy.
Since this transformation of energy takes place
dications over the analysis of directly transmit~
ted electrons as described in said ccpending ap~
plication.
Among the objects of the invention are to pro
according to the accepted quantum theory, it 35 vide an improved method of and means for micro
follows that for an electron to excite a photon
analyzing materials permeable to electron irra
of the characteristic X-ray radiation of an elediation. Another object of the invention is to
ment the electron must lose energy in an amount
provide an improved method of and means for
equal to or greater than that contained in the
electronically analyzing minute specimens of
X-ray photon. Thus among the electrons leav~ to materials. A further object of the invention is
ing a specimen containing a certain element there
to provide an improved method of and means for
will be a predominance of those electrons vwhich
electronically analyzing materials by subjecting
have 10st an amount Of Energy equal to or slightly
2. minute area of the material to electron irra
greater than the energy contained in a single
diation, subjecting electrons derived from said
photon of the characteristic X-ray radiation of 45 irradiated area to the effects of a de?ecting ?eld.
that element. The velocity spectrum of the elecand indicating the relative velocities of the elec
trons leaving a point of the specimen will have
trons subjected to said ?eld. Another object is
“lines” corresponding to the important X-ray
to provide improved means for securing a per~
lines of all the elements contained in the area
manent record of the relative velocities of said
of the specimen being examined. Electron mi- 50 electrons subjected to said de?ecting ?eld. A
.croanalysis offers several advantages over orstill further object includes an improved method
dinary methods of microanalysis. Sub-micrm
of and means for subjecting a minute area of ‘a
'scopic regions of a specimen can be analyzed
substance to electron irradiation, subjecting
without removing the region from the specimen
electrons transmitted by said substance to a uni
or withoutchangingitinjany way.
.55 form magnetic ?eld, and indicating the relative
' ..
2,405,306
3
provide de?ection oi the principal electron beam
velocities of electrons subjected to said magnetic
transmitted by the specimen to an auxiliary
?eld.
Further objects of the invention include an
improved method of and means for electronically
in the specimen chamber but displaced from the
main beam axis. A prism or mirror l2, cooperat
microanalyzing materials permeable to electron
ing with aconven tional lightmicroscope || per
fluorescent screen It, adjustably positioned with
mits an enlarged image of theelectronirradiated
portion of the specimen 4 to be observed con
tinuously, also independently of and simultane
said selected electrons to a de?ecting ?eld, indi- _ , ously with the velocity analysis of the electrons
10
introduced into the deflection chamber l3. Some
cating the relative velocities of said electrons
of the electrons transmitted by the specimen are
subjected to said ?eld and forming an enlarged
scattered or re?ected thereby at angles other than
optical image of the specimen continuously, in
irradiation by irradiating a minute area of said
material, selecting at least a portion of the elec
trons derived from said material,’ subjecting
dependently of and simultaneously with said
the electron beam axis. These scattered electrons
are de?ected by, the de?ecting coils 2|, 2|’, and
are passed into the de?ection chamber to be
velocity analyzed. It therefore will be seen that
electronically microanalyzing materials wherein
an axial portion of the specimen transmitted
electrons derived from a minute‘portion' of said
electrons may be employed for continuously ob
materials are velocity analyzed, and other elec
serving an enlarged image of the specimen, while
trons derived from said material form continu
ously and independently of said velocity analysis 20 other transmitted electrons from the specimen are
electron velocity indications. Another object is
to provide an improved method of and means for
an enlarged visual image of said material, and
velocity analyzed during desired intervals. ~
controlling said visual image by external adjust
It should be understood that the magnetic ?eld
within the de?ection chamber i3 may be estab
lished in any desired manner. It also should be
ment of a light optical lens system.
I .
The invention will be further described by ref
erence to the accompanying drawings of which
understood that the electron lens system described
Figure 1 is a schematic diagram of one embodi
ment thereof, Figure 2 is a schematic diagram of
a second embodiment thereof, Figure 3 is a cross
may be modi?ed in any known manner to provide
a suitable electron probe of convenient cross-sec
tional area for irradiation of the specimen 4, and
sectional elevational view of a preferred embodi
that the third electron lens 8 may be omitted
ment of the invention according to the schematic 30 entirely if the de?ection chamber l3 and image
diagram of Figure 1, Figure 4 is an enlarged frag~
screen Ill are disposed in close relation with the
mentary elevational View of a portion of Figure 3,
specimen
4.
andFigure 5 is a plan view of the devices of Fig
Figure 2 is similar to Figure 1, diiiering in that
ure 4. Similar "reference characters are applied
an electric ?eld is substituted for the magnetic
35
to similar elements throughout the drawings.
field Within the deflection chamber l3 of the de
Referring to Figure 1, an electron source L
vice of Figure 1 for de?ecting the electrons de
which may be provided by a conventional ther
rived irom the specimen 4 in accordance with
mionic cathode which is maintained at a rela
their relative electron velocities. In order to
tively high negative potential with respect to an
provide relatively long electron paths through an
'apertured anode electrode, neither of which are
shown herein, is imaged by a pairof electron
lenses 2, 3 respectively, to irradiate an extremely
'minute area of an electron permeable object 4.
The electron lenses 2, 3, vrespectively, may be of
either the electromagnetic or electrostatic types
electrostatic ?eld, two arcuate concave electrodes
|8, |9, separated by an air gap 20, are disposed
in cooperative relation to provide an arcuate tubu
lar electrostatic de?ecting element which will
cause the de?ected electrons to impinge upon the
, 4.5 screen Hi to provide a velocity distribution pattern
customarily employed in electron optical appa
thereon. A pair of de?ecting coils 2|, 2|’, sym
ratus such as, for example, electron microscopes.
metrically disposed adjacent the specimen 4 be
Ii electromagnetic lenses are employed, as shown
tween the specimen and the deflection chamber
in; the drawings, the focus of said lenses may be 50 |3, provide de?ection of the principal electron
adjusted by means of series resistors 5, 5' con
beam transmitted by the specimen to an auxiliary
nected between one terminal of each of the mag
?uorescent screen I0, which, cooperating with a
netic lenses and an energizing current source
prism or mirror |2 and a, light microscope ||, pro
vides an enlarged image of the electron irradiated
such as, for example, a battery 6.
A third electron lens 8, which may be energized 55 portion of the specimen continuously in the same
through a third variable resistor 9 by current from
manner as described in Figure 1. Similarly, some
the battery 6, is disposed coaxially with the ?rst
of the electrons transmitted by the specimen but
refracted or scattered from the beam axis, due
and second electron lenses 2, 3.
The electrons transmitted by the specimen 4
to inelastic collisions within the specimen, are de
may be selectively subjected to a magnetic field
?ected by the de?ecting coils 2|, 2|’ to enter the
a 28 between the electrostatic de?ecting ele
within a de?ection chamber l3. The magnetic
ments |8, |5 for the electron velocity analysis de
field will cause the transmitted electrons to fol
low substantially semi-circular paths and impinge
photographic plate M.‘
scribed
heretofore.
Figure 3 is a preferred embodiment of the device
The magnetic field within the de?ection chamber
l3 will deflect the electrons different amounts de
termined by their respective velocities whereby a
described in Figure 1 constructed according to
conventional electron microscope practice. The
velocity distribution pattern will be provided upon
which is supported by a high potential insulator
the image screen Id.
26 and connected to a terminal 21 which is main
‘upon an image screen or
The focus of the pattern
electron source includes a thermionic cathode 25
is controlled by varying the current through the 70 tained at high negative potential. An apertured
anode electrode 28, which is maintained at a high
third lens 8 by adjusting the resistor 9.
A pair of de?ecting coils 2|, 2|’ energized by
positive potential with respect to the thermionic
cathode 25, provides an electron beam having
the battery 6 through an adjustable fourth re
relatively high electron velocity. The ?rst elec
sistor 22 are symmetrically disposed adjacent the
specimen 4 andpbetween the, specimenrand the 75 tron lens 2 is illustrated- asa COHVBhtiOnaléleOl
~deflection chamber |3. The de?ecting coils 2 |-, 2 |"
2,405,306 ‘
tromagnetic electron microscope lens including
port 55v extending between the'walls 31 of‘ they
a winding 29 ‘having a pole piece aperture ‘30.
The second electron lensi3 ‘forms a-unitary strucwithwindingil
the ‘?rst and
electron
lens pole
2 and
includes
ature
second
a second
piece
aper
object o amber, supports two parallel disposed
guide rods 57,. 59 which are journalled in aper
tures in ‘the transverse support 55, and disposed
turei32;
-'~I'he specimen ‘4 is supported by a conventional
specimen supporting element 33 which may be
the specimen 4. The remaining end .of the :‘?rst
guide rod 51 is supported in aperture ‘6| ‘in the
specimen chamber wall 31, and the remainingv
by an external adjusting knob 34 operating 10 a bushing 63 in thespecimen chamber wall 31
adjacent an ‘aperture 36 in the outer wall 31. 0f
ing 63 includes a packing gasket 65 which eifec
the supporting structure. The ‘third electron
tively seals the vacuum within the specimen
lens i8cmay be similar to the ?rst and second elecchamber’. A portion 51 of thesecond guide ‘rod
tron lenses 2, ‘3 respectively, and includes a third 1;, 59 is threaded to receive a complementarily
winding 38 and a relatively large pole piece aperthreaded bushing on the movable support 24
ture 39. A shutter 40, operated by an externally
which carries the light microscope objective lens
controlled knob 4|, is interposed between the
assembly 23, the mirror 12 and ‘the auxiliary
wall of a de?ection chamber 43 which is secured 29 mg knob 50 thereby provides transverse adjust
to .t e supportingstructure of the third electron
ment of the light microscopenobjective 213, the
lens.
a
.
'
'
c
'
A magnetic winding 44, disposed external ‘to
‘
with respect to the central axis of the specimen
the ‘de?ection chamber 43, provides a magnetic
Chamber.
.
aperture 42‘ and for causing them to impinge upon
eye piece
5| of theoflight
is The
supported
onportion
the exterior
themicroscope
specimen
sealed :in
the specimen
37.
or any other structure customarily employed in 30 which
The is
movable
specimen
supportchamber
33 whichwall
is ad
conventional electron microscopes.
A hinged
J'Ilstable by means of the specimen-'adjusting-knob
fluorescent screen 46, pivoted adjacent one edge
34 coupled to the Specimen Support '33 through
of the photographic plate 45, may be rotated to
the sylphon 35, supports the magnetic de?ecting
cover the plate 45 for providing a visual image 35 C011 assemblies 2!, 2!’ Which are symmetrically‘
position 41, shown in dash lines, may be observed
offset slightly from the electron beam axis B8.
through a window 48 adjacent to and normal
Thede?ecting coil assemblies 2|, 2l'_ include
therewith.
40 parallel-disposed magnetic pole pieces 69, ‘679',
The auxiliary ‘beam de?ecting coils 2i, 2!’, disWhich support windings ‘H, ‘H’ respectively. Ad
posed within the specimen chamber, may be supjustment of the specimen Support 33 thereby
ported by the adjustable specimen supporting
adjusts the position of the de?ecting coil assem-V
element 33 symmetrically with respect to the
blies 2|, 2|’, and the specimen Simultaneously
specimen 4.. The auxiliary ?uorescent screen It, 45 with respect to the electron beam axis 58.
prism or mirror l2 and the objective lens 23 of the
.
As explained heretofore, the normal electron
specimen chamber on a movable support 24, the
by the de?ecting coils 2|, 2|’ to impinge upon the
position of which may be adjusted by an external
auxiliary ?uorescent screen I 0 for continuous
adjusting knob 50. The remainder of the light 50 observation of the electron-irradiated portion of
ber_wall 31. The details of the preferred em- 60 cidence of the irradiat‘
electrons entering through the aperture 42 and 70 for the electromagnetic de?ecting field ‘of the
position,v as indicated in the drawings. The shut-
Thus the invention described comprises several
ter 40 may then-be opened for a desired interval
modi?cations of an improved method of- and
to expose the photographic‘plate 45.
means for microanalyzing materials by electron
‘ Referring to Figures 4 and 5, a transverse sup- 75 irradiation wherein continuous observation-10f
2,405,306"
a ?uorescent screen for continuously observing
said electron probe irradiation oi’ said object,
the minute electron irradiated portion of the
specimen is provided independently of and, if
desired, simultaneously with'the velocity analysis
means for optically magnifying said image on
said ?uorescent screen and externally a justa‘ble
means for orienting said optical magnifying
of electrons derived from said irradiated speci
means and said ?uorescent screen with respect
men. Improved electron velocity analysis is pro
to said electron irradiated portion of said object.
vided by utilizing electrons scattered within pre
7. 'In an electron microanalyzer including
determined angular limits in passing through
means for providing an electron probe having
the specimen due to inelastic collisions within
extremely minute cross-sectional area, an object
said specimen.
10 substantially permeable to electron irradiation,
. We claim as our invention:
means for irradiating said object by said electron
1. In an electron microanalyzer including
probe, an electron sensitive screen responsive to
means for providing an electron probe having
electrons from said object, and means interposed
extremely minute cross-sectional area, means for
between said screen and said object means pro
supporting an object, means for irradiating said
object by said electron probe, an electron sensi 15 viding a ?eld for de?ecting said electrons derived
from said object as a function of their velocity
tive screen responsive to electrons from said ob
as a function of their velocity to provide an elec
tron velocity distribution image on said screen,
to provide an electron velocity distribution image
on said screen, the improvement comprising elec
tronic means for continuously providing a visible
image of said electron probe irradiated portion
of said object independently of and simultane
the improvement comprising electronic means for
ously with said de?ection of said electrons.
ject, and means-interposed between said screen
and said object means providing a ?eld for de
?ecting said electrons derived from said object
8. In
continuously providing a visible image of said
an
electron
,
microanalyzer - including
means for providing an electron probe having
electron probe irradiated portion of said object
means independently of and simultaneously with 25 extremely minute cross-sectional area, means for
supporting an object substantially permeable to
said de?ection of said electrons.
electron irradiation, means for irradiating said
2. An electron microanalyzer including elec
object by said electron probe, an electron sensitive
tron beam generating means and electron beam
focusing means for providing an electron probe
screen responsive to electrons from said object,
means for supporting an object, means for irra
said object means providing a magnetic ?eld for
de?ecting said electrons derived from said object
having extremely minute cross-sectional area, 30 and means interposed between said screen and
diating said object by said electron probe, an
electron sensitive screen responsive to electrons
from said object, means interposed between said
providing a ?eld
, screen and said object means
for de?ecting said electrons derived from said
object as a function of their velocity to provide
as a function of their velocity to provide an elec
tron velocity distribution image on said screen,
the improvement comprising means for con
tinuously providing a second electron image of
said electron probe irradiated portion of said ob
ject means independently of and simultaneously
an electron velocity distribution image on said
screen, and electronic means for continuously
with said de?ection of said electrons.
9. In an electron microanalyzer including
providing a visible image of said electron probe 40
means for providing .an electron probe having
irradiated portion of said object means inde
extremely minute cross-sectional area, means for
pendently of and simultaneously with said de?ec
supporting an object substantially permeable to
tion of said electrons as a function of their
electron irradiation, means for irradiating said
object by said electron probe, an electron sensitive
screen responsive to electrons from said object,
tron beam generating means and electron beam
and means interposed between said screen and
focusing means for providing an electron probe
said object means providing an electrostatic ?eld
having extremely minute cross-‘sectional area,
means for supporting an object substantially per 50 for de?ecting said electrons derived from said
object as a function of their velocity to provide
meable to electron irradiation, means for irradi
an electron velocity distribution image on said
ating said object by said electron probe, an elec
screen, the improvement comprising electron
tron sensitive photographic screen responsive to
optical means for continuously providing a visible
electrons from said object, and means inter
image of said electron probe irradiated portion
posed between said screen and said object means
of said object means independently of and simul
providing a ?eld for de?ecting said electrons de
taneously with said de?ection of said electrons.
rived from said object as a function of their
10. Apparatus of the type described in claim 2
velocity to provide an electron velocity distribu
including an externally operable shutter inter
tion image on said screen, the improvement com
prising electronic means for continuously provid SD posed between said object supporting means and
ing a visible image of said electron probe irra
said screen for controlling the electron exposure
diated portion of said object means independ
time for said screen, said object second image
ently of and simultaneously with said de?ection
means being independent of said shutter.
of said electrons as a function of their velocity.
vll. The method of electron microanalyzing a
4. Apparatus of the type‘described in claim 1
material comprising generating an electron probe
including means disposed within said de?ecting
of minute cross-sectional area, electron irradiat
means selectively providing a visual image of said
ing said material by said electron probe, sub
jecting electrons derived from said object to a
5. Apparatus of the type described in claim “3
?eld to de?ect said electrons as a function of
characterized in that said image means includes
electron velocity, indicating the relative velocities’
a ?uorescent screen for-continuously observing
of said derived electrons, and forming con
said electron probe irradiation of 'said obj‘ect,.and
tinuously and electron optically a visual image of
means for optically magnifying said image von
velocity.
4."
'
3. In an electron microanalyzer including elec
screen.
'
t
'
said electron irradiated portion of said material,
_6. Apparatus of the type described in claim 3 75 said image formation being independent of ‘said
characterized in that said image means includes
said ?uorescent
screen.
,
~
‘
v
‘
‘
>
V
'
'
2,405,306
electron de?ection as a function of electron
velocity.
12. The method of electron microanalyzing a
material comprising electron irradiating aminute
I
10
screen
responsive to electrons
de?ected from said
object for continuously providing a visible image
of said electron probe irradiated portion of said
object means independently of and simultane
cross-sectional area of said material, indicating 5 ously with said de?ection of said electrons as a
the relative velocities of the electrons derived
function of their velocity.
from said area of said material in response to said
15. Apparatus of the type described in claim 3
irradiation and continuously forming electron
characterized in that said image means includes
indications an enlarged visual image of said 10“ said electron probe irradiation of said object,
irradiating
said object
by responsive
said electron
an
respect to said electron irradiated portion of said
electron
sensitive
screen
to probe,
electrons
object.
from said object, means interposed between said
16. The method of electron microanalyzing a
screen and said object means providing a ?eld for 20 material comprising electron irradiating a minute
between said object supporting means and said’ 25 and which have been scattered between predeter
and
portion
simultaneously
of said object
withmeans
said de?ection
independently
of said
of
means
17. Inforanproviding
electron an
microanalyzer
electron probeincluding
having
electrons as a function of their velocity.
30 extremely minute cross-sectional area, means for
14 An electron microanalyzer mcludmg elec-
supporting an object, means for irradiating said
posed between said screen and said object means 40 in?! means interposed between Said Object means
prising magnetic beam de?ecting means inter_ 45
JAMES HILLIER.
posed between said object supporting means and
RICHARD F, BAKER.
‘
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