Development
of atom resolution electron microscopy
and future
H.Hashimoto
Okayama University of Science, l-l, Ridai-Cho, Okayama 700-0005, Japan
Rapid development of electron microscopy has made it possible to observe the images of
atomic processes of many materials in various critical. conditions. In this paper some contributions
related to the present author in the past 54 years and future prospect are presented.
1. Dynamical electron diffraction theory for crystal lattice images/in-situ
observation
of Chemical Reaction and Atomic Process by TV System
Our universal electron diffraction microscope(UEDM) in 1953 enable us to understand the
relation between EM image contrast and electron diffraction, Fig. 1. shows the images of moire pattern
formed by the superposition of rotationary superimposed
two crystals, one of which contains
dislocations in (a)(1957) and in between of which there is a dislocation net work in (b) (1978). Two
beams dynamical theory of electron diffraction was applied to understand the image contrast of crystal
lattice, moire pattern and Fresnel fringes in 1958-1962. By fitting the UEDM with a specimen heating
and gas reaction cartridge (1956) and made newly designed two more elecrton microscopes with gas
reaction specimen chamber (1959,1968), growth and evaporation process of oxides and sulfides were
recorded using tine film (1958) and TV orthicon cameras (1978) and observed drops formation (1958)
which was completely different from the dislocation mechanism at that time(Fig.2). Dark field and
bright field images of the decomposition of Th-pyromerite chain molecules and coagulation to Th02
crystals on graphite film under 1OOkv electron beam irradiation were recorded in 1971 and 1978
respectively as shown in Fig.3 and 4. Around 1978, we are able to obtain our first leliable atomic
resolution images of defects in metals. Applying spherical Aberration Free Focus condition and modified
current TV camera, we have recorded the movement of atoms in crystals with a speed of 0.03,~~ per
frame (Fig.5). This technique was successfully used by Cambridge group in 1983 and commercialized
in 1985 and now producing useful observations in the industry of metals and ceramics . [ l]
2.Formation
Process
of Defects by 400kV -1SMeV
Elections Irradiation
Using TV system and 400kV atom resolution electron microscope, in situ observation of the
formation process of dislocation loop was carried out in 1985-1989 (Fig.6) and the mature of defects
was determined from the mode of growth and the image contract calculations. Stacking fault tetrahedra
(SET) formed in Au by the irradialion of 2MeV electrons was observed by 1OOkV EM(Fig.7). Various
sizes of SIT down to single vacancies were observed.[2]
3.Simultaneous
Display
of Atomic Images and Their Fourier Transform
Fast Fourier transform(FFT) of observed crystal structure atomic images on fluorescent
screen and TV screen was carried out and displayed together with moving atomic images in two
monitors in 1980(Fig.8). Combination of the moving atom images and their FFT some times gave
useful information’s. Selected area down to the unit cell areas could be realized. Image processing in
Fourier space was also carried out, which is now utilized rather widely.[3]
4.Characterized
Atom Image Using Core Loss Electrons
Using Ca-L23 (350-346eV) shell loss electrons, high resolution images of high Tc
superconductors containing single and double Ca atomic columns were recorded with 6eV energy width.
JEOL 200KV FE-electron microscope with GIF and drift free goniometer was used. The image recorded
with 60s~ exposures showed heavy quantum noise. The images was improved by using the successive
superposition of selected areas and also by eliminating the noises in Fourier space. Images of Ca atoms
arranged with 0.32nm and 0.38nm were revealed. Some future prospects will be discussed.
References
[l].Hashimoto H. Proc.Roy. IVIicr.Soc.18/5(1983) 298 [2].Hashimoto H. et al.,proc Electronmicros.(l98O)vo14,240
[3].Hashimoto H. et al.,Proc.Electronmicros.(1980)voll,ll8,Yokota
et al.Ultramicros.6(1981)313.
p
/;.
~1~11~
2Onm
r
Fig.lMoire
(a)dis-
Fig.Z.Crystals.
Fig.3.DF
location in a crystal.
growing i?om
@)Th02aystal.
CuS
drop ofW-oxide.
interval 0.083s.
0, )dislocation
images
(a)Th-atomic
(c)Coagwation
chains.
Fig.4.BF
process.
molecules
of
Fig.h.Radiation
damag ,e Fig.7.SF.r
ofSi 400kV A(lOO),
Au under 2MeV
irradiation(a)
twin band Au.
B(lll),C(311)
irradiation.
shown in(b).
structure
image ofhigh
Tc Hg1223.
Fig.lO.Core-loss
image
formed by using G-L23
loss elecfJons E=6eV,60sec.
of atoms,
10 sec.
formed in Fig.X.Au film under 1OOkV electron beam
atoms at the tip of
Fig.9.Atomic
A ,cryetals B, smooth
area C, (b) movement
internal
network in ZnS
Fig.S.Movement
images. (a)coagulated
Fig. 11 .Processed
FFT ofselected
area ABC are
image of Fig. 10 by superposition
Fourier space. Bright spots are Ca atom image.
and in