US2266082A - Electron microscope - Google Patents

Description

Dec. 16, 1941. UsK I 2,266,082

ELECTRON MICROSCOPE Filed May 2, 19:59

YrnAJ MGA;

Patented Dec. 16, 1941 ELECTRON MICROSCOPE Ernst Ruska, Berlin- Spandau, Germany, assignor to Fides Gesellschaft fiir die Verwaltung und' Verwertung von gewerblichen Schutzrechten mit beschrankter Haftung, Berlin, Germany, a

corporation of Germany Application May 2, 1939, Serial No. 271,420 In Germany May 2, 1938 9 Claims.

This invention relates to a method of investigating chemical reactions by means of a microscope.

-It is known in the art to project the image of an incandescent cathode onto a screen or photosensitive'plate by subjecting the electron rays, emitted from the cathode, to electron-optical lenses so as to produce an electron-optical image of the cathode which allows observing the changes'in intensity and local distribution of the emission of electrons from the surface of the cathode. It has been proposed to influence the electron emission; when taking such observations, by exposing the cathode surface to the action of a gas or'vapor; or by changing the cathode temperature. It is thus possible to determine the capability of substances of emitting electrons under difierentconditions. This method however is not suitable for investigating bodies which are not capable of-emitting electrons. This may only be accomplished by means of a highly magnifying electron microscope, with the aid of whicheven details of 10- -to-10-- mm. may be resolved. It is of particular interest to observe the changes in-distribution, size and shape of thesmallest perceptible bodies, or of individual structures of corresponding fineness in larger bodies, by means of the above-mentioned electron microscope while chemical reactions take place in the substances to be tested. The great resolving power of the electron microscope renders it possible to observe and to photograph details of changes associated with-the chemical reaction, which cannot be made perceptible by any other method, this resolving power now even reaching the range of large, particularly organi 'molecules. Especially in the case of colloidal magnitudes which cannot be resolved by the light microscope, the occurrence of a chemical reaction is largely determined by the surface of the particles.

Consequently, if such particles can be observed by means of an electron microscope, further valuableinformation may be obtained thereby. The majority of the .catalytic processes hitherto insufliciently known mightvalso become explainable as a result of such investigations.

,An object of the present invention is to provide means for making observations of the aforementioned kind, i. e. for effecting chemical reactions of substances within an electron microscope be foreand/or while producing a magnified image of the substancesby subjecting a beam of electron rays modified by the reacting substances to the action of electron-optical lenses and observing or photographically fixing the image. Other,

uum chamber of an electron microscope in order to be exposed to the action of a gas, vapor or a liquid for'the purpose ofobtaining chemical reactions before or while observing the substances.

In the drawing is shown an embodiment of the invention in diagrammatic form. The single figure shows a vertical sectional View of the sluicing device of an electron microscope. The electron ray passes through the sluicing device in the directionas indicated by the arrow 1. 2 denotes the pole shoes of a magnetic lens (objective lens) The sluicing device consists of a rotatable sluicing plug 3 having aconical shape and fitting into a correspondingly shaped bore of the stationary part 4. of the electron microscope. In the plug.

is inserted the object cartridge 5 which is provided at its lower end with an interchangeable object carrier 6. The aperture of this carrier 6 is covered by a foil 28 which is provided .with the substance or object proper to be tested.

Themicroscope according to the invention is;

provided with devices by means of which liquid reagents maybe supplied. from outside into a chamber arranged in the microscope where they,

are evaporated; further with devices with the aid of which solid reagents are sluiced or introduced intothe vacuum chamber where they may be employed for developing gases or vapors; and finally with devices by means of which gaseous or vaporous reagents developed outside the electron microscope may be supplied to the vacuum chamber.

In the stationary part 4 of the microscope is provided a chamber 1 in which vapors may be developed from a liquid reagentby the application of heat. To this end, the lower part of the chamber is provided with a suitable lining 8 consisting, for instance, of a ceramic material. 9 is a supply conduit of glass. It! is a cock and H a con-' tainer for the liquid reagent. By opening the cock ID, the liquid reagent may be supplied to the lower part 8 of the chamber 1. To develop vapors from this liquid, an electric heating coil I2 is provided and supplied with current by the conductors 13. The conductors l3 extend outwardly through a pressure-tight stuffing box 2!).

Solid reagents may be introduced into the vacuum chamber according to the invention by providing in the upper portion of the object cartridge 5 an annular channel l5 which is closed by a screen It, for instance, by a platinum netting.

l1 denotes a filling hole provided in the upper end of the cartridge and through which solid reagents may be introduced into the chamber l5. Also in this case an electric heating coil I8 is provided in order to develop, after the cartridge has been inserted, chemical reagents by the application of heat when the electron microscope is in operation. l9 denotes th leads for supplying current to the heating coil, and 20 is the stufiing box for the leads.

In order to supply vapors or gases, developed outside the electron microscope, to the object, two conduits 2|, 22 are provided in the sluicing plug 3. The conduit 2| is connected by means of a cock 23 and a flexible conduit 24 to a gas container 25, whereas the conduit 22 is connected by means of a flexible conduit 26 to a pump '21. By this arrangement the reagents flow along the surface of the object to be tested. If the contain ers for the reagents are connected to a vessel under variable pressure, it is possible to vary the speed withrwhich the reagents issue from the supply containers and therefore the reaction velocity. The wall material of the chambers and channels mustbe adapted to the chemical nature of the reagents. In many cases glass will be sufficient. Instead of using an electric'heating coil for developing reagents, the operation of the vacuum pump 21 sufiices in many cases to cause the reagents to flow to the object to be tested at a given moment and at the desired speed. It is, therefore, favorable to arrange the opening of the exhaust conduit 22 in the immediate neighborhood of the object.

In some cases it may be preferable that such capillaries, in which a liquid reagent is preferably supplied to the object. extend to the outer surface of the vacuum wall in order to come into contact with the outside atmosphere so that the liquid columns of the capillaries separate the vacuum. from the outside atmosphere. However, also an adjustable intermediate pressure may be maintained within the reaction chambers.

Since chemical reactions occurring in the substances are dependent upon the temperature and in many cases occur preferably or only at a definite temperature, it is convenient to know the temperature of the object before or while testing the same -in the electron-optical microscope. To this end, the object carrier foil 28 mayeither be provided with a thermo-couple or microscopically small bodies in the form of Seeger cones and melting at predetermined temperatures may be arranged on the object carrier 6 so as to measure the temperature of the foil. Finely divided wood, metal, tin or the like may, for instance, be employed for this purpose.

What is claimed is: 1. An electron microscope comprising, in combination, an hermetically-closed vessel, means in said vessel for producing-a beamof electron rays, a sluicing devicefor introducing an object into said vessel, an electron-optical lens system for ef fecting-a magnified imageof said object, means for-continuously evacuating said vessel, ,and means for supplying a reactive 'fiuidfrom the outside of said vessel to said sluicing deviceto effect a chemical reaction with said'object during the operation of said lens system, said supply means comprising an outside container for-liquid and a capillary conduit connecting said container with the interior of said sluicing device being capable of holding a liquid column sufficient to seal-the interior of said evacuatedvessel, said fluid supply means and said evacuating means being arranged to communicate with said sluicing device at substantially opposite sides of the object so as to cause the reactive fluid to meet the object when passing from said supply means to said evacuating means.

2. An electron microscope comprising, in combination, a vacuum vessel, a source of electron rays, a sluicing device for inserting an object to be examined into said vessel while maintaining said vessel evacuated, and an electron-optical lens system for producing a magnified image 01 said object, said sluicing device forming a sluice chamber accessible from without when said device is in proper position, an object cartridge detachably arranged in said sluice chamber for holding the object in the path of said rays, said cartridge having a recess disposed outside of said path and forming a storage chamber for reactive substance, and heating means disposed in said sluicing device for heating said reactive substance in said storage chamber in order to eii'ect a'=chemical reaction at said object while producingfsaid image.

3. In an electron microscope having, in combi=- nation, a vacuum vessel, a source of electron'rays, a sluicing device for inserting an object in said vessel While maintaining said vessel evacuated;

and an electron-optical lens system for producinga magnified image of said object,in combination, said sluicing device having a stationary body and movable sluice member associated with said body for opening and closing the device, said "sta' tionary body having a chamber communicating with said vessel and disposed for receiving re-' active substance, a supply conduit disposed insaid body, said conduit opening into said cha n ber and extending outside of said vacuum vessel for supplying reactive substance to said chamber, and heating means associatedwith said'body forevaporating said substance in said chamber, whereby a chemical reaction is effected atfsaid' obiect while producing said magnified imag'eI 4. An electronic microscope comprising avacg uum vessel, a source of electron rays in saidfvs sel, a sluicing device for inserting an object to'b'e examined into said. vessel while maintaining -said vessel evacuated, an object holder in said's'luicing device for holding the object in the path of said electron rays, electron-optical lens means for producing a magnified image of said object, means for supplying a chemically reactive substance to said object while producing said image,

a said supply means being associated with said sluicing device and arranged between said source of electron rays and said object, heating means associated with said sluicing device, and exhaust means for continuously evacuating said vessel during the operation of said lens means and said simply means, said exhaust meanshaving an ex.- haust duct opening into said sluicing device, L

5. A sluicing device for electron-opticalmicroiscopes, comprising a stationary body having .an axial bore for the passage of an electron beam and a transversal bore, .a .revolvable cock body arranged insaid transversal bore and having. a sluice chamber extending in the direction of said axial bore when in proper position, a removable, object holder in said chamber, means for supply.- ing chemically reactive substance to the. object, saidsupply means having a duct in one of said bodies connecting said chamber with the outside,, and evacuating means comprising a suction duct, in said cock body opening into said chamber and.

extending through a front face of said cock body.

6. A device for electron-optically observing chemical reactions by means of electron rays in an electron-optical microscope, comprising in combination a stationary body having an axial bore forming a passage for said rays, a movable sluicing member associated with said body and having a sluice chamber forming when in proper position an intermediate section of said bore,

holding means in said chamber for exposing a substance to said rays, said stationary body forming a receptacle for the reception of another substance, said receptacle being arranged concentrically to said passage and in open communication with said axial bore, conduit means in said stationary body for supplying said other substance to said receptacle, and an exhaust conduit opening into said axial bore whereby said other substance is caused to contact said first substance when passing from said receptacle to said exhaust conduit.

7. In an electron microscope having a vacuum vessel which comprises a vessel portion enclosing th electron beam to be passed through the object to be studied, a second vessel portion for causing the beam modified by the object to produce a magnified image, and a third vessel portion disposed intermediate said first and second vessel portions, said third vessel portion forming a sluicing device and comprising a sluice chamber,,a removable apertured object cartridge in said chamber, means for selectively connecting said sluice chamber either with the interior of said first and second vessel portions for passing said electron beam through the aperture of said object cartridge or with the outside atmosphere for inserting and removing said cartridge, means disposed outside of the microscope for controlling the gas and pressure conditions in said chamber, and fluid-conduit means opening directly into said sluice chamber and connecting it with said outside means.

8. In an electron microscope having a vacuum vessel which comprises a vessel portion enclosing the electron to be passed through the object to be studied, a second vessel portion for causing the beam modified by the object to produce a magnified image, and a third vessel portion disposed intermediate said first and second vessel portions, said third vessel portion forming a sluicing device and comprising a sluice chamber, a removable apertured object cartridge in said chamber, means for selectively connecting said sluice chamber either with the interior of said first and second vessel portions for passing said electron beam through the aperture of said object cartridge or with the outside atmosphere for inserting and removing said cartridge, evacuating means, and conduit means communicating directly with said sluice chamber and connecting it with said evacuating means.

9. In an electron microscope having a vacuum vessel which comprises a vessel portion enclosing the electron beam to be passed through the object to be studied, a second vessel portion for causing the beam modified by the object to produce a magnified image, and a third vessel portion disposed intermediate said first and second vessel portions, said third vessel portion forming a sluicing device and comprising a sluice chamber, and means for selectively connecting said sluice chamber either with the interior of said first and second vessel portions for passing said electron beam through the aperture of said object cartridge or with the outside atmosphere for inserting and removing said cartridge, an object holder removably arranged in said sluice chamber for holding the object in the path of said beam, a container for reactive substance, and conduit means connecting said container with said sluice device for supplying reactive substance to said sluice chamber during the operation of the microscope.

ERNST RUSKA.

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