US 3859535 A
The method of imparting contrast to the surface of an object to be viewed microscopically comprises the steps of introducing the object into a vacuum chamber, connecting the object to the positive pole of a high voltage d.c. source, evacuating the chamber, bombarding the surface of the object with a gas-concentrated electron-ion beam, and feeding into the chamber a gas which reacts chemically with the bombarded object surface. Under the effect of the electron beam and negative or neutralized ions then forms a reaction layer characteristic of the component parts of the object material which layer, after the conclusion of the contrasting process can be observed and evaluated under a microscope.
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Description (OCR text may contain errors)
Unite States Patent 1191 Bartz Jan. 7, 1975  APPARATUS FOR IMPARTING CONTRAST 3,477,936 11/1969 Gillery et al, 204/192 o A MICROSCOPE OBJECT 3,604,970 9/1971 Culbertson et a1. 204/298 X 3,650,930 3/1972 Jones et a]. 204/177 Inventor: Gunter Bartl, Wetzlar, G y 3,704,216 11/1972 Kinstley et a1 204/164  Assignee: Ernst Leitz GmbH, Wetzlar,
Germany Primary Examiner-F. C. Edmundson  F] d J 12 1972 Attorney, Agent, or FirmKrafft & Wells 1e une  Appl. No.: 262,082  ABSTRACT The method of imparting contrast to the surface of an 30 Foreign Application priority Data object to be viewed microscopically comprises the June 21 1971 German 2130605 steps of 1ntroduc1ng the ob ect 1nto a vacuum chamy ber, connecting the object to the positive pole of a high voltage d.c. source, evacuating the chamber,  US. Cl 250/542, 220045126948, 22054/l59321, bombarding the surface of the Object with a g  Int Cl Bolk A61 concentrated electron-ion beam, and feeding into the  Field 56 chamber a gas which reacts chemically with the b0m "556 barded object surface Under the effect of the electron beam and negative or neutralized ions then forms a tion layer characteristic of the component parts of  References Cited mac the ob ect mater1al whlch layer, after the conclus1on UNITED STATES PATENTS of the contrasting process can be observed and evalu- 2,200,909 5/1940 Berghaus 6! al. 204/298 X ated under a microscope 3,308,049 3/1967 Jones et al. 250/531 3,418,229 12/1968 Lakshmanon et a1. 204/164 1 Claim, 1 Drawlng Figure 5/ f7 L a Patented Jan, 7, 1975 3,859,535
if the contrast is to be produced on a non-biological specimen. There are, of course, several methods known by which a contrast may be generated on the surface of a non-biological specimen, however, all these methods have serious disadvantages. There are, for example, the methods of wet etching and of anodic etching for generating colored layers on the specimen. However, these methods are limited to a few particular applications. By the so-called' annealing etching method thin colored oxide layers are produced on the object surface by heating the object in a special oven. But only few objects are suitable for this kind of operation.
Further, a method of producing thin, highly refracting and light-transmissive layers on the object is known, which layers amplify considerably the natural object contrast. The layer is produced by evaporation in a high vacuum. This method, however, is only applicable in scientific research and not in routine investigations,
on account of the great expenditures both of apparaferent erosion of the component parts of the object.
Subsequent oxydization by positive air or oxygen ions will highly amplify the contrast. However, the exact relation between the grey shades or the color and the chemical material is greatly lost by the ion-etching.
It is, therefore, an object of the present invention to provide a simple, effective method of producing contrast, especially color contrast, on the specimen to be examined. It is a further object to provide a method which consumes only little time. And it is a further object to provide a method which may be carried out under microscopic examination so that the user may establish the process and object conditions most favorable for the specific task.
SUMMARY OF THE INVENTION According to the invention, there is provided a method of imparting contrast to a surface portion of an object to be investigated microscopically, comprising the steps of introducing the object into a vacuum chamber, connecting the object to the positive pole of a regulatable high voltage direct current source, at least partially evacuating the chamber, bombarding a surface portion of the object with at least one gasconcentrated electron-ion beam, and feeding into the chamber gas which reacts chemically with the bombarded surface portion of the object.
In addition to the above steps the divergence of the impinging ion beam may be varied during the process and different gases may be introduced into the chamber successively. However, the gases may also be introduced simultaneously as a mixture. Further, it is possible to bombard the object simultaneously with the beams of several ion sources. And finally, a relative movement between the object and the impinging beam may be generated.
BRIEFDESCRIPTION OF THE DRAWING 'The invention will be more readily comprehended from the following description when taken in conjunction with the appending drawing which shows an appa ratus for performing the invented method.
DESCRIPTION OF THE PREFERRED EMBODIMENT For carrying out the method, a vacuum chamber I is used, which is provided with an object carrier 2, which is connected electrically to the positive pole of a high voltage direct current source 3 and to earth. The object 4 is mounted on the carrier 2. The vacuum chamber 1 is provided with an ion gun 5 of the gas discharge type, which is connected on the one hand with the negative pole of the source 3, on the other hand with a regulatable gas source 6. The vacuum chamber has an inlet 7 through which reagent gas is supplied, and an outlet 8 connected to a vacuum pump 9. After the object 4 is mounted on the object carrier 2 and the vacuum chamber 1 is closed, an underpressure of for example 10 Torr is generated in the vacuum chamber by means of the vacuum pump 9 and maintained. Now the ion gun 5 is operated by switching on the high tension and the gas supply from the source 6. There forms a gasconcentrated beam, the boundaries of which light up. The focussing of this beam is controlled in each case according to magnitude of the surface portion of the object, which is to be irradiated by the fine regulation of the gas supply from the source 6, for example by means of a needle valve. Simultaneously a gas reacting with the. object in a chemical way is supplied via the inlet 7. Under the effect of the electron beam and negative or neutralized ions, a reaction layer characteristic of the component parts of the object material then formsfwhich after conclusion of the contrasting process can be observed under a microscope and evaluated.
Instead of using, as shown, an indiyidual inlet 7 for the reaction gas, it is possible to feed the gas directly via the ion gun 5. Also, a mixture of different gases may be fed into the chamber during the bombardment of the object.
In order to protect objects against impermissible heating during the reaction, the object carrier may be equipped with a suitable cooling device of known kind. Conversely, it may be desirable to increase the reaction speed and this can be achieved, for example, by heating the object. For this purpose, the object carrier may be provided with a corresponding heating device.
The reaction layers display, in direction towards the object parts not irradiated, a contrast falling off towards the edge. In order to counteract this, means may be provided to effect relative movement between object and beam, which secure an uniform bombardment of all desired object surface portions.
The object may be bombarded simultaneously by beams derived from a plurality of electron-ion-beam sources. The respective beams may then be directed towards the object from different directions and can be arranged to impinge on different surface portions of the object.
[t is possible to provide one or more stops or masks in the path of the or each bombarding beam, which cause an exact limiting of the bombarded region.
What is claimed is:
1. An apparatus for imparting contrast to the surface portion of an object to be investigated microscopically, the apparatus comprising: i
a. a non-grounded vacuum chamber (1);
b. an object carrier (2) inside the vacuum chamber for disposing an object thereon, the carrier being connected to one wall of the chamber;
0. a high voltage D.C. source (3) outside the vacuum chamber, the positive pole of the DC. source being connected to the object carrier and to the ground;
d. a combined electron-ion gun ('5) of the gas discharging type mounted in the wall of the vacuum chamber opposite from the object carrier, the cathode of said combined electron-ion gun being connected to the negative pole of the DC. source and means for supplying a reagent gas into the vacuum chamber;
f. means for evacuating the vacuum chamber; and g. switching means located between said negative pole and said electron-ion upon closing of which the voltage between the object an d the electron-ion gun causes an electron-ion beam to impinge on the object where a layer characteristic of the component parts of the object material is formed.