New 500 kv Electron Microscope

Transcription

1 New 500 kv Electron Microscope B. T ADANO, H. KIMURA, S. KATAGIRI, M. NISHIGAKI Hitachi Central Research Laboratory, Kokubunji, Tokyo and R. UYEDA, Y. SAKAKI, S. MARUSE, K. MIHAMA, Y. KAMIYA Nagoya University, Chikusa-ku, Nagoya, Japan [Reprinted from Journal of Electron Microscopy Vol. 14, No.2, 1965]

2 ORIGINAL ( 6) JOURNAL OF ELECTRONMICROSCOPY VoL 14, No.2, 88-92, 1965 New soo kv Electron Microscope B. TADANO, H. KIMURA, S. KATACIRI, M. NISHIGAKI Hitachi Central Research Laboratory, Kolmbunji, Tokyo and R. UYEDA, Y. SAKAKI, S. MARUSE, K. MIHAMA, Y. KAMIYA Nagoya University, Chikusa lw, Nagoya, Japan (Received February 11, 1965) A new hlgh voltage electron microscope is completed. A lo stage electron gun with a Cockcroft Walton type of accelerator of the same stages is enclosed in a pressure tank of 3 kg/cm 2 Freon gas. The maximum accelerating voltage is 500 kv. The magnification is higher than 100,000 and the resolution better than 15 A. The construction of the new instrument and some photographs taken by this microscope are shown. IT was known for many years that thick specimens would be studied by elevating the accelerating voltage of electron micro scope ll. Several attempts were made before 1950 with no significant results, mainly be cause of technical difficulties. Recently, many good electron micrographs taken at high voltages were published ) and also the decrease of absorption coefficient with increasing accelerating voltage was quantitatively studied Besides the high penetration. several advantages of high voltage electron microscope have been proved. The damage of specimens due to electron irradiation is reduced, making easy the study of materials quickly deteriorated by irradiation". The short wavelength of electrons enables to obtain the diffraction pattern from a very small selected area 6 ). The effect of inelastic scattering is small, resulting in good dark field images free from chromatic aberration 3 ). The present 500 kv electron microscope was designed specially for routine work, based upon the data obtained with the previous instrument7) and taking into account recent developments')s). The external view and cross sectional diagram are shown in Fig. 1 & 2, respectively. The accelerating tube and the high voltage source are enclosed in a tank filled with Freon gas a t the pressure of 3 kg/cm2. The enclosed system is appropriate for stable operation. The filament of the electron gun can be exchanged by device A of Fig. 1. After pulling tube A down to the position shown in Fig. 2, the space above the filament assemble is brought to atomospheric pressure. The filament is ready to be taken out through the tube. The loss of Freon gas by the pro cedure is negligible. In order to minimize induced voltages, a symmetric Cockcroft-Walton circuit is adopted. The power is supplied by a 1.5 kc generator. The accelerating voltage can be set at 200, 350 and 500 kv. The filament is heated by another 100 kc power supply. Ten stage ac celeration, which makes 50 kv at maximum per stage, is most effective for stable operation. With the use of a negative feed back system, stability 2 x 1O-6/min is obtained at 500 kv. The high voltage source disclosed by removing the tank cover and the connection diagram of electric circuit are shown in Fig. 3 & 4, respectively. The lens system consists of double condensers, objective, intermediate and double

3 ( 7 ) New 500 kv Electron Microscope AODO ,,~ 2800 II ~ 2600 fig. 1. scope. Exlernal view of new 500 kv eleclron micro projection lenses. Double projection lenses are applied to give magnification as high as ' ,000 times and also effective speci.11en plate distance of selected area diffraction as 1800 large as 2,000 mm. The objective lens is excited by 12,000 Ampereturns. The focal 1600 length, spherical aberration constant and chromatic aberration constant are estimated 1400 to be 5.5 mm. 5.0 mm and 4.0 mm, respectively. Two sets of magnetic deflectors are used for 1200 the adjustment of illuminating beam. The specimen chamber and adapters (tilting, heating and cooling) are similar to those of 1000 HU llb. The inside of the column on which direct 800 or scattered electrons fall is lined with aluminum. The illuminating system is shielded by lead cover of 20 mm thick. The X-ray radiations outside the instrument are everywhere less than 0.5 mr/hr under the Fig. 2, Seclional diagram of a new microscope. normal operating condition. Electron micrographs taken at 500 kv are '

4 90 B. T ADANO et al. (8 ) by a dial gauge. Fig. 6 is an example of a pair of bright and dark field images. Fig. 7 shows that the resolution is as high as to show parallel lines of spacing about 10 A This work is partly supported by Toyo Rayon Foundation for the Promotion of Science and Technology. to whom we would like to express deep appreciation. Fig. 3. tank cover. Fig. 4. High voltage Source disclosed by removing C 20 C, ~A9 -A IO Connection diagram of high voltage source. reproduced in Figs Fig. 5 shows an example of high penetration. The sample is molybdenite of 3 mm x 1 mm in area with nearly uniform thickness which was measured References 1) V. E. COSSLETT: J. Royal Microscopical Soc. 18, 1 (1962) 2) HASHIMOTO, H., TANAKA, K., KOBAYASHI, K., SUITO, E., SHiMADZU, S. & lwanaga M.: j. Phys. Soc. Japan 17, Supplement B Il 170 (1962) H. HASHIMOTO: j. Appl. Phys. 35, 177 (1964) 3) Dupouy G. & PERRIER F.: C. R. Acad. Sc. 253,2435, (1961) j. de Microscopie 1, 167, (1962) Ann. Phys. 8, 251, (1963) J. de Microscopie 3, 233 (1964) 4) KOBAYASHI, K., SUITO E. & SHIMADZU S.: Proc. 4th lnt. Conf. Electronmicroscopy 165 (1958) KOBAYASHI, K., HASHIMOTO, H., SVlTO, E., SHiMADZU S. & IWANAGA M.: Japanese J. Appl. Phys. 2, 47 (1963) 5) Dupouy, G., PERRIER, F., UYEDA, R., AYROLES R. & MME A. MAZEL: Preprint of Prague Conference 105 (1964) 6) DupoUY, G., PERRIER, F., UYEDA, R., AYROLES R. & BOUSQUET A.: C.R. Acad. Sc. 257, 1511 (1963) 7) TADANO, B., SAKAKI, Y., MARUSE S., & MORITO N.: j. Electronmicroscopy 4, 5 (1956) TADANO, B., KATAGIRI, S., lchlge, K., SAKAKI Y. & MARUSE S.: Proc. 4th lnt. Conf. Electronmicroscopy 166 (1958) 8) DupoUY, G., PERRIER F. & FABRE R.: C.R. Acad. Sc. 252, 627 (1961)

5 (9) New 500 kv Electron Microscope.91 Fig. 6. Bright and dark r,,,ld images of Capper-Tin Allay Alm_ (500 kv)

6 92 B. T"n"NO et al. (10) Fig. 5. Molybdenite (about 2 micron thick, 500 kv) Fig. 7. Moire pattern of Gold-Nickel 111m with spacing of 9.2 A (500 kv)