US3435210A - Device for heating,rotating and tilting a specimen in an electron microscope - Google Patents

Description

March 25, 1969 u. VALDRE 3,435,210

DEVICE FOR HEATING ROTATING AND TILTING A SPECIMEN IN AN ELECTRON MICROSCOPE Sheet Filed March 4, 1966 FIG.

March 25, 1969 VALDRE 3,435,210

DEVICE FOR HEATING, ROTATING AND TILTING A SPECIMEN IN AN ELECTRON MICROSCOPE Filed March 4, 1966 Sheet 2 of 3 FlG.2u

March 25, 1969 Filed March 4,

- u. VALDRE 3,435,210 DEVICE FOR HEATING, ROTATING ANI) TILTING A SPECIMEN IN AN ELECTRON MICROSCOPE Sheet 5 of 3 FIG.3

FI'G.4

United States Patent Ofiice 3,435,210 Patented Mar. 25, 1969 Int. of H013 37/26 US. Cl. 250-495 14 Claims ABSTRACT OF THE DISCLOSURE An electron microscope or the like has a device for heating, rotating and tilting a specimen. A specimen cartridge body having a rotatably mounted supporting structure is removably connected to the microscope. A specimen carrier and heater form part of the inner gimbal ring of a cardanic joint, the latter being pivotally mounted on the supporting structure. The rotative position of the specimen carrier is adjusted by transmitting a rotative motion to the supporting structure. An independent adjustment of the tilt axis is made by deflecting a tubular member articulately joined to the inner gimbal ring.

My invention relates to a device, attachable to the object system of an electron microscope, for supporting the specimen.

Known devices of this type permit adjusting the specimen to some extent and generally also performing a single operation such as tilting or heating the specimen.

Some investigations, such as the study of crystalline matter, make it desirable to observe the specimen from virtually all possible directions while simultaneously subjecting the specimen to certain spacial or environmental conditions to promote the manifestation of its peculiar properties.

It is an object of my invention to devise a specimen holding apparatus which affords heating the specimen in the electron microscope to high temperature and also permit tilting the specimen about large angles in all direc tions relative to the electron-optical axis of the microscope, as well as a rotation of the specimen about any desired adjustable axis within the tilting limits.

Another object of the invention is to provide a specimen accommodating device which, although possessing the properties just mentioned, is dimensionally so small that it can be mounted directly in the specimen space of the electron microscope without necessitating appreciable if any structural changes in the microscope apparatus proper.

A further object is to provide a specimen holding device that permits heating and rotating or also tilting the specimen but is readily controllable from the outside of the microscope and which can be introduced into the interior through the opening normally provided for insertion or removal of a conventional specimen holder, without the need for interrupting or appreciably affecting the vacuum within the electron microscope.

Another object of the invention is to permit dark-field microscopy of high resolving power by using only one set of deflecting coils. It is also an object of the invention to devise a specimen holding device satisfying one or more of the foregoing objects which is generally also suitable for orienting the diffraction diagram.

Another significant object of the invention, conjointly with one or more of those mentioned above, is to permit a continuous observation of the specimen, not only in ultimately adjusted positions, but also during its motion from one to another position desired by the attendant, without limiting the observation to a given number of discrete positions, as is the case with some other devices of this general type.

To achieve these and various more specific objects, and in accordance with one of the features of my invention, a device for heating, rotating, and tilting a specimen in an electron microscope comprises a supporting structure, a specimen carrier, heater means for heating the specimen on the carrier, and cardanic joint means universally pivoting the specimen carrier to the supporting structure and having cardanic gimbal bearings of substantially negligible heat conductance mechanically securing the specimen carrier to the supporting structure. The low heat conductance of the gimbal bearings between specimen carrier and the supporting structure is preferably secured by giving the area of engagement between the parts of the gimbal bearings such a small size as to provide for the mechanical connection while maintaining any heat conductance through the preferably point-type bearings at a negligible minimum. As a consequence, the specimen can be heated to a higher temperature than otherwise attainable while requiring for this purpose a reduced supply of heating power, for example only 3 watts for a temperature of 700 C. This is important for preserving the mechanical, magnetical and electron-optical properties of the objective lens despite the adjustability of the specimen carrier. This design of the universal-joint bearings is also valuable because of its slight bearing friction which permits minimizing the forces necessary for the various adjusting movements. This is desirable since the dimensions of the specimen holding and adjusting device must be adapted to the dimensions of the electronic lens system employed.

According to another feature of my invention, it is preferable to mount the heating means for the specimen predominantly on the specimen carrier or inner gimbal part which is adjustable in all directions. According to a more specific feature, the heating is effected by a resistance wire made of non-magnetic material wound to the shape of a toroidal spiral or helix in order to prevent the formation of magnetic spurious fields as may impair the image. The current used for heating purposes is supplied by means of silver wires, preferably made of pure silver. It has been found that such a material provides for the desired ductility, also at the high temperatures involved, as well as the required high electrical conductivity and non-magnetic properties of the conductor material. Simultaneously, a good resistance to chemical attack at the operating conditions is secured. The silver wire withstands repeated changes in adjustment of the heating means surrounding the specimen. Since, as a rule, the specimen carrier with the heating means must be adjusted many times, whereas the source of heating power is stationary, the coupling between these respective components must possess particular mechanical and electrical properties; and these can be readily satisfied by using wires of pure silver.

However, it has also been found suitable for the purpose of the invention to use a silver conductor in form of a braided or litz wire of the above-mentioned material, or a wire or braid of pure platinum. According to a preferred embodiment of the invention, the structural components of the universal joint are at least partly made of ceramic material to secure or improve the desired heat insulation.

The rotation of the specimen about an axis perpendicular to the plane of the specimen or specimen carrier is preferably effected by a spur-gear transmission driven from the outside of the microscope through vacuum-tight in-leads. The transmission of the rotational motion onto the cardanic joint is then effected by rotating the supporting structure of the joint, whereas a desired tilting or inclined position of the rotational axis relative to the microscope axis is preferably effected with the aid of an adjustable tubular member ending in a joint component other than the annular supporting structure.

Further properties and advantages of the invention will be apparent from, and will be described in, the following with reference to preferred embodiments of electron-microscope devices according to the invention illustrated by way of example on the accompanying drawings, it being understood that the invention is not limited to the illustrated embodiments.

FIG. 1 is a vertical section of a first device along the line I--I in FIG. 2.

FIG. 2 is a cross section along the line IIII in FIG. 1.

FIG. 2a shows in section a modified portion of FIG. 2 together with an attachment applicable as a component of the device.

FIG. 3 shows partially a vertical section of the same device while omitting several details for explanatory purposes, the section being essentially along the line IIIIII in FIG. 2.

FIG. 4 is a cross section along the line IVIV in FIG. 3.

FIG. 5 represents schematically in vertical section a modification of details in a device otherwise similar to the one shown in FIGS. 1 to 4.

FIG. 6 shows schematically a plan view of another modification of a device otherwise similar to that of FIGS. 1, 2, 3 and 4; and

FIG. 7 illustrates a plan view similar to FIG. 6 but relating to still another embodiment.

As illustrated, the specimen carrier 1 is held by a cardanic joint assembly which comprises a first, inner gimbal .ring 2 (FIGS. 1, 3, 4) and a second, outer gimbal ring 3 coupled with each other by threadably mounted point-type bearing parts 4 and 5 diametrically aligned with each other to define a first girnbal axis, thus permitting the gimbal ring 2 with the specimen carrier 1 to be angularly displaced about this axis. The second gimbal ring 3 is journalled by another pair of point-type bearings 6 and 7 to a supporting structure 8 (FIGS. 1, 4). The inner gimbal ring 2 includes an annular part 9 which has a spherical outer surface and extends coaxially into a tubular member 10 so as to forman articulated connection. The member 10 serves as a guide and is suitable to effect displacement of the specimen carrier 1 about the center of the cardanic assembly. The connections between the component parts of the cardanic joint are such as to involve only slight heat losses and are preferably provided with suitable insulating material such as ceramic or similar heat-resistant material.

Mounted on the inner gimbal ring 2 is a helical resistance wire 11 wound to the shape of a toroidal ring which surrounds the locality of the specimen on the carrier 1 and prevents the formation of spurious magnetic fields as may impair the image formed in the electron micro scope. For this purpose, the material of the resistance wire is not ferromagnetic. It consists of tungsten with a coating of fused or sintered alumina (such as available in the trade under the name Alundum). This resistance heater affords attaining relatively high operating temperatures, such as the above-mentioned temperature of 700 C. or more. Electric insulation is provided between the toroidal resistance 11 and the gimbal bearings.

The electric leads 12 and 13 (FIGS. 3, 4) for supplying heating current to the resistor 11 consist of silver wire or litz, preferably pure silver of highest feasible electrical conductivity. Such leads permit repeatedly changing the positional adjustment of the specimen carrier without danger of breaking. The leads 12 and 13 are connected to respective slip rings 112 and 113 (FIGS. 1 and 3), which receive heating current through brush contacts 14 and 15 (FIGS. 2, 3) with the aid of pressure contacts 16, 17 through respective counter contacts 18, 19 and through respective external connecting wires 20 and 21.

The supporting structure 8 is rigidly joined with a spur gear 22 (FIGS. 1, 3) rotatably mounted on a stationary part 23 which is connected by screw bolts 25 with the body 24 (FIG. 1) of the specimen cartridge of the device. A pinion 26, meshing with spur gear 22, permits rotating the structure 8. Pinion 26 is rigidly joined with a coaxial spur gear 27 (FIGS. 1, 2) meshing with a spur gear 28 which can be rotated by means of a worm gear 29 (FIG. 2). A flexible drive shaft, to be actuated from the outside, is connected with the worm gear 29 through a clutch 30. The spur gear 28 is rotatably mounted on the fixed ringshaped part 31 of the electron microscope serving to receive the specimen-accommodating device. The spur gears 28 and 27 become disengaged from each other when the cartridge-type device is being removed by pulling it upwardly out of its seat formed by the microscope part 31; conversely, the gears 27 and 28 enter in mutual meshing engagement when the device is being inserted, in either case without the necessity of touching or actuating the drive means from the outside.

FIGS. 6 and 7 illustrate modified forms of the coupling between the spur gear 28 and the external drive means, the engagement between the spur gear 28 with the gear 27 (FIG. 1) being established or released simply by inserting and removing respectively the specimen cartridge as described above.

In the embodiment of FIG. 6, the worm gear 129 is driven from the drive shaft through a pair of conical spur gears 32. In the embodiment of FIG. 7, the same purpose is served by a universal joint 33.

As shown in FIG. 1, the tubular member 10 is joined with a spherical member 34 which is seated in a spherical seat formed by the cartridge body 24. Springs 35 and 36 (FIG. 2) press the tubular member 10 in two directions perpendicularly related to each other against two small pistons and 136. These permit adjusting the tubular member 10 by tilting motion about the center of the spherical seat at part 34 in opposition to the forces of springs 35 and 36. The springs 35 and 36 are housed in respective sleeves 37 and 38 and act upon the same core portion 39 for the tubular member 10 as the counter pistons 135 and 136. The piston 135 is driven by rotating a screw 40 which acts upon one arm of a bell crank lever 41 whose other arm presses upon a tappet and is held against the tappet by a spring 43. The tappet 42 pushes against the piston 135.

The second piston 136 is driven by axial displacement of a screw 44. The two screws 40 and 44 are connected with flexible external drive shafts through plug- type couplings 46 and 45 respectively.

Such a device is very compact. The drives for orthogonal displacement of the pistons 135, 136 afford a better utilization of the space in the middle of the specimen table so that the environment of the specimen table remains available for other control or actuating means.

An anti-contamination element 54 is insertable into the pole shoe bore 55 in the lower portion of the device (FIG. 1).

To facilitate shifting the clutches 30, 45 and 46 into active and inactive position, the device is shown provided with an auxiliary guide member illustrated in FIG. 2a. It comprises a guide block 47 with parallel bores 48, 49 and 50 within which the ends of the plug-type clutches are located. Rotational wedges or latches 51 and 52, also mounted in the guide block 47, permit blocking the clutches. The clutches are released for operation by opening the rotational wedges.

Shown in FIG. 5 is a particular embodiment of the point-type bearing parts 53 of the cardanic joint. In this case the bearing pins or points are produced by cutting lugs into the material and bending the lugs to obtain a bearing structure corresponding to that comparable with the point-type bearing pins 4, 5, 6, 7 according to FIG. 4.

A device according to the invention, in any of the modifications described, permits displacing the specimen carrier in space toward any desired direction within the limits determined by the particular design. By acting upon the drives for the pistons 135 and 136, the specimen carrier can be adjusted with respect to the direction of its rotational axis. The rotation of the specimen carrier about this adjusted axis is effected by the above-described system of spur gears. Consequently, the specimen can be rotated about any inclined axis. The cooperative action of the drive imparts to the axis of the rotating object carrier an essentially conical travel path.

To those skilled in the art, it will be obvious, however, that various details can be readily substituted by equivalent means and that the invention permits a variety of modifications other than particularly illustrated and described herein, without departing from the essential features of my invention and within the scope of the claims annexed thereto.

Iclaim:

1. A device for heating, rotating and tilting a specimen in an electron microscope or the like, comprising a specimen cartridge body, means for connecting said body to the microscope, a supporting structure connected with said body and rotatable about the axis of the microscope, a specimen carrier, cardanic joint means universally pivoting said carrier to said structure and having an inner ring structure and an outer ring structure, said inner ring structure holding said carrier and having first bearing parts jounalling said inner ring structure to said outer ring structure and defining a first gimbal axis, second bearing parts journalling said outer ring structure to said supporting structure and defining a second gimbal axis, said first and second bearing parts being of substantially negligible heat conductance, means for rotating said supporting structure with said cardanic joint means and said carrier, specimen heater means mounted on said first ring structure, and tilting means for tilting said inner ring structure together with said carrier, said tilting means comprising a tubular member substantially coaxial with the microscope axis and having one end orientably supported within said cartridge body, the other end of said tubular member being articulately joined with said inner ring structure, said tilting means further comprising control means engageable with said tubular member between said two ends.

2. In a device according to claim 1, said inner ring structure comprising an annular part having a spherical outer surface and said spherical surface 'being in engagement with said other end of said tubular member.

3. In a device according to claim 1, said gimbal bearing parts being point-type bearings whose efiective cross section is small relative to that of said carrier, whereby heat conductance through said bearings is substantially suppressed.

4. In a device according to claim 1, said bearing parts consisting of bearing pins having a screw thread and being removable by unscrewing.

5. In a device according to claim 1, said cardanic joint means comprising an annular member having two inwardly projecting and diametrically aligned protuberances which for-m respective bearing pins and are in pivotal engagement with said outer ring structure.

6. In a device according to claim 5, said cardanic joint comprising an outer gimbal having two inwardly projecting and diametrically aligned protuberances which form respective bearing pins and are in pivotal engagement with said outer ring structure.

7. In a device according to claim 1, said cardanic joint comprising component parts of heat insulating ceramic material.

8. In a device according to claim 1, said means for rotating said supporting structure comprising a gear transmission having actuating means extending vacuum-sealed to the outside and being in driving connection with said supporting structure.

9. In a device according to claim 8, said gear trans mission comprising a gear train having two gears meshing with each other and being axially displaceable relative to one another for disengaging them from each other.

10. In a device according to claim 1, said tubular member being orientably supported within said body by having a spherical seat on said body at a locality spaced from said cardanic joint means, whereby said tubular member is tiltable about the center of said seat, and said control means being actuable from the outside and in controlling connection with said tubular member for setting it to a desired position of tilt.

11. In a device according to claim 1, said device having a pole piece with a bore, said cardanic joint means extending into said pole-piece bore, an anti-contamination shield, said bore having an inner surface adjacent to which said shield is placed.

12. A device according to claim 1, comprising flexible electric leads connected to said heater means for supplying heating current thereto.

13. In a device according to claim 12, said leads consisting of silver.

14. A device according to claim 12, comprising brush contacts, said supporting structure having coaxially mounted slip rings, said brush contacts being in pressure contact with said slip rings respectively, and said leads being respectively connected to said slip rings.

References Cited UNITED STATES PATENTS 3,151,241 9/1964 Herrmann et al. 25049.5 3,179,799 4/1965 Valdre 25049.5 3,240,934 3/1966 Watanabe et al 25049.5 3,297,869 1/1967 Ozasa et al. 25049.5

WILLIAM F. LINDQUIST, Primary Examiner.

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