Information of special interest to crystal growers and device physicists now available from monochromatic synchrotron diffraction imaging (topography) is reviewed. Illustrations are taken from a variety of electro-optic crystals. Aspects of the detailed understanding of crystal growth processes obtainable from carefully selected samples are described. Finally, new experimental opportunities now available for exploitation are indicated

Dobbyn, Ronald C.

Kuriyama, Masao

Laor, Uri

Steiner, Bruce

English

NASA Technical Reports Server

r 
. ' *  
, 
4% 
The information 
physicists now avalla 
(topography) Is revie 
trooptic crystals. .s of crY-1 growth 
processes that czn be obizlned from efuily selected samples are 
described. F i n a l l y ,  nev ex7erimental 02 unities DOiJ available for ex- 
Aspects  of t h e  detailed unders 
ploitation are indicazed. 
I. TYPES OF INFORHATION AVAIUIBLE 
In contrast to electron micro- 
scopy, which provides information 03 
the location of 
by synchrotron x-r 
lights irregulariti 
affect performance, 
lattice strains 
contrast in such 
terns in these strains can l e a 3  to a 
detailed underszandlng 05 ~ G Z  they 
arise2. SirtiLarLj-, c r y s r e l i o ~ r q h i c  
dislocations, ei=>er done o r  in 
arrays, a l s o  stark on: Fr; s':.ay COT.- 
bLzsc in t'ne : z s g ~ s  c: :gk q c i - i z y  
crystals, 2 s  in Fi,e.;re 2 .  
Analysis of such I n ? e r f s c z i ~ n s  
can lead not only to a de'"' i o - * € &  
tally of their ? r e s a m e  ar.l 2 i s z r l -  
bution but a l so  ZG an understanc:zt J 
of their origins and cf s;e;s z;?h; 
can be taken to reduce t'neir pre- 
sence. Thus, diffracclon FzsgSng 
provides useful information on the 
imperfections in big:? cualiry crys-  
tals that can be correlaEed wirh 
specific aspects of their perfor- 
mance and can lea improvement in 
this performance ugh guidance on 
desirable modificazion in crystal 
growth parameters. 
Spchrotron storage rings now 
permit far more comprehensive and 
useful realization of these pos- 
- _  . .  -c 
.. 
sibilities than can be achieved with 
Laboratory sources because of two  
characteristics of such 
d t h e i r  high brightness. 
lLnes thils can achieve at least 1 . 5  
arc seco'tld angular resolution, or 
lsss th:: a niicrometer on the OUT- 
fzce of a detector in a typical 
cor.=zgur.zr:o~. . This resolution ci;z 
3s z . i r= r ;e r  Lacreased by the choice 
cf c.z ; :s .  *-zk agropriate optics. 
~sso,c:';:oc of individual Cis- 
L G ~ E C ~ C ~ S  is possible, as in Figure 
3 .  
SZSTEEE 1 r l n s s  - is cenlrral f o  two as- 
p c = s  of c r y s z a l  characterization. 
L :rsc , hi53 brighmess permits 
observazion of diffraction features 
in trarisxrission. The discinctixve 
sigzatures of the dislocations 
observed IC Figure 3 are visible 
only in diffraction in h u e  geometry 
(transmission), with its integration 
of information from the interior of 
a crystal. Moreover, when strsins 
Ere obsemed in trawmission, as in 
Figure 4, differences in their 
direction in various parts of che 
image can be emphasized. In Figure 
C .  
- .  
..: 
' . - *  . .  
n. ,se . .  r,:& brightness achieved in 
C. 
1 
ORIG1NAl PAGE IS 
OF POOR QUALITY 
https://ntrs.nasa.gov/search.jsp?R=19880021043 2020-03-20T05:24:18+00:00Z
L 
#K) of 
j il icon bismuth 
oxi 
Figure 2. Disloca- 
tion patterns in the 
10 keV (040) d i f -  
fraction from an 
indium doped (001)- 
cut wafer of gallium 
srsenide. 
2 
Figure  3. Indivi. 
reso lved  in 8 keV 
from the Lndium 
vafer of gallium a r s e  
the previous figure, a 
b ,  f o r  example, s:ralr.s i n  t h e  4 0 0 >  
d i r e c t i o n  are c l e a l y  t-LsLbLe i n  
some p a r t s  o f  t h e  crystal vhi ie  
25sent In others 5s: .=Z?SZ: ecLiva- 
Len: In Bragg geoi-,E:ry Z'zser\ra:Lon 
of such d l f f e rezces  s e r r - i z s  cerci-ed 
ar 'alysls of c'ne arocesses l a r c i l z g  CD 
z h e i r  f o m a z i o r , i .  ~ e c c r . ~ ,  :'ne nLgk 
brlghzness of zr s c o r a p t  r l a g  p e r n i t s  
v l c e o  c m e r z  o3ser:iz:or. C: l1zr rac-  
&-on images i n  r e d  ;:me This i n  
r a i  aspeczs of s u b g z z i ~  bouzaary 
structcre and or' large scale cryszal 
S " ' <  a-n. 
The u t i l i t a t i o c  of  a mococnro- 
mator with a synchrozron siorage 
r i n g  can provide imporcant fur ther  
advantages,  although such a combina- 
t i o n  is a v a i l a b l e  i n  the U.S. only 
on our beam l i n e  a t  che h'acional 
Synchrozron Light  Source: . R e  
restriction of d i f f r acz ing  r cd ia t ion  
.. 
* . - c  
r: 
L t , *  --n permits ropic  su;rveyr of  gene- 
t o  a nhrrow speccra l  band subsran- 
t i a l l y  increases  the contrast in an 
image over t h a t  ob ta inable  with a 
vh i t e  beam a s  i n  Figuxe 5 c - 5 ,  The 
i n t e r p r e t a t i o n  of such monochromatic 
images is far s i m p l e r  
c e r t a i n  than the i n t e r p r e  
images formed' v i  th v5i te radi a r i cn. 
h%en asymmetric d i f f r a c t i c n  is 
employed in the monochromator. cwc 
addi t iona l  b e n e f i t s  can be obta ined .  
F i r s t ,  the  beam can be cxpandeC 
seve ra l  f o l d  I n  s i z e  t o  s e v e r s 1  
centimeters i n  he igh t .  With suc'n a 
beam large c r y s t a l s  can be examined 
without scanning. Second, ttre 
paraLlelism of t he  beam i s  increased 
by the  same f a c t o r ,  b r ing ing  the  
reso lu t ion  wel l  under one a r c  sec-  
ond, and approaching a t en th  o f  an 
a rc  second depending on the  pcr-  
t i c u l a r  monochromator crys:al and 
t he  energy o f  the  r a d i a t i o n .  
A l l  of  these  advantages t o -  
gether  are j u s t  now being r e a l i z e d  
on t h e  National Bureau of Standards 
e m  Line a t  the National  
Light  Source a t  Brook- 
n a l  Laborarory. Vet t u r n  
now t o  a b r i e f  survey of i n i t i a l  
r e s u l t s .  
XI. ILLUSTRATIVE 
A c r y s z a ~  conta in ing  d i s t l ~ l c t  
g r a i c s  (w3ick by deflnltlor. differ 
y i e l d s  cozventional x-ray d l f f r a c -  
t i o n  r0ckir.g c u n e s  t h a t  ere Sioad.  
D i f f r ac t ion  inages of  such c rysza l s  
t s i c a l L y  display  SIX^; cor .xas t  
among the var ious g r a l m  . Hovevez, 
even where the d l f f e rence  i n  orleri- 
t a t i o n  approaches a degree,  sinul- 
taneous d i f f r a c t i o n  from more than 
one g ra in  can be observed i f  the 
c r y s t a l  is  s u i t a b l y  o r i en ted  wirh 
r e spec t  to the  beam, as has  been 
done i n  Figure 6 .  Here, f i v e  gra ins  
can be dis t inguished .  I n  such in -  
s t ances ,  t he  p r i n c i p a l  tilt can be 
accurzre ly  determined from the  c l e a r  
&isplacement of che images of the 
i n  c rys t a l log raph ic  o-ie-"" .. - . & " C & * " L . )  - - '  
3 
in ';iuc Cc@ffic:=ry 
(GO!) F:a 
(001) cut 
silicon oxide c ~ r -  
tal shown in Figure 
3 i n  d i f f t ac t io r  i n  
Bragg geometry. 
Y ORIGBNAL PAGE IS 
OF POQW QUALITY 
f 
Figure  5 .  Comparison 
of monochromatic 
l abora to ry  d i f f r a c -  
t i o n  image of i ron  
aluminun c r y s t a l  
with th ree  white 
beam s p c h r o t r o n  
topographs of the  
same c r y s t a l .  
Other types of s t ruc tu re ,  
c l e a r i y  r e l a t ed  t o  s p e c i f i c  aspeczs 
o f  the growrh of a c r y s t a l ,  a r e  
v i s i b l e  i n  dbservat ion o f  i n d i m  
doped gallium arsenide ,  as i n  Figure 
10. Geometrical f ea tu re s  in  a 
c i r c u l a r  region i n  the  cen te r  o f  the  
boule  appear t o  imply f ace t ed  growth 
i n  t h i s  region. This is  surrounded 
by s t r i a t i o n s ,  associaced with 
p e r i o d i c  f luc tua t ion  i n  one o r  more 
growth parameters. 
An image of the c e n t r a l  region 
Various s z r a i n s  an& ocher crys-  
t a l lographic  i r r e g u l a r i r i e s  i n  e l ec -  
t roop t i c  ma te r i a l s  can thus be por-  
trayed by d i f f r a c t i o n  imaging. 
Through such obsen-a t ions  , t he  r o l e  
t h a t  these de fec t s  p lay  can be cor -  
r e l a t e d  with s p e c i f i c  aspec ts  of de- 
v ice  performance. However, a l s o  i n -  
herent  i n  t h i s  technology is  the  i n -  
s i g h t  t h a t  it can provide inco the 
o r i g i n  of the anomalies and the  cor-  
responding p o t e n t i a l  f o r  r h e i r  con- 
5 
trol where suitable samples are 
available. 
An example of this aspect of 
monochromatic synchrotron diffrac- 
tion imaging is a recent s tudy  
carried out on three slices taken 
from a single high quality boule of 
bismuth silicon oxide grown in the 
i 5 0 1 ]  direction as skLowr: in Figure 
i 2 .  ?he three slices were cur and 
- 
Figure 6 .  Xrcage of 
8 keV d i f f r a c t i c n  
from (I 1 10) planes 
of a mosaic (001) 
cut mercuric iodide 
crystal. 
it acquired during growth. 
s i i cc  K 5.5 shorn- in Bragg ("re- 
flection") geometry in Figure 1 and 
in h u e  (transmission) geomezry in 
one orier.=ation in Figure 4 .  Slices 
E and I are shown in Bragg geometry 
in Figures 13 and l b ,  respectlvely. 
Slice I is shown in Lace geometry in 
Figure 1 5 .  Slice K i s  S ~ O L T L  In a 
second orieccaEion in Laue geometry 
6 
-- ripre 7. "Contour 
map" of srrzins i n  
(111) cut slice of 
cadmium telluride, 
recorded by superlm- 
posing diffraction 
from (333)  planes of 
cadmium telluride 
recorded at three 
diffraction angles 
differing by 14Lc arc 
seconds. 
Lmages permits us t o  determine =he 
following sequence of s teps  i n  the 
f a c e t e d  growth o f  the boule. Short- 
l y  af ter  necking, a small near-(001) 
growth plane had been establ ished i n  
t h e  cen te r  of  t he  growing face. 
Four pe r iphe ra l  (iOi) f a c e t s  had 
a l s o  been formed. These a r e  depict- 
ed i n  Figure 17. 
By t he  t i m e  t h a t  the boule had 
grown t o  the  l o c a t i o n  o f  s l i c e  E ,  
t h e  (011) f a c e t  vas growing more' 
r a p i d l y  than the o t h e r s ,  causLng i z  
t o  decrease i n  area as i l l u s x a t e d  
i n  Finure 18. MeaRwhile, the cen- 
d 
Figure 8 .  Sharp 
bounda-ries separa-  
t i n g  suberains d i f -  
f e r i n g  i n  o r i e n t a -  
t i o n  by a b o u t  2 a r c  
seconds,  shown i n  8 
keV d i f f r a c t i o n  from 
( 2 2 4 )  planes of  a 
(001) c u t  undoped 
gal Lium a r sen ide  
wafer ( # 3 ) .  ALSO 
visible are curved 
regions of s t r a i n  
that  produces c u m -  
e d ,  continuously 
vary ing  c o n t r a s t .  
t r a l ,  near-(001) f a c e t  w a s  growing 
nonuniformly. 1:s growch race was 
g r e a t e r  i n  proximity t o  the  r a p i d l y  
growing (011) f a c e t ,  causing the  
c e n t r a l  near-(001) f a c e t  t o  dev ia t e  
from a p rec i se  (001) o r i e n t a t i o n ,  
observed as s t r a i n  f r i n g e s  i n  t h e  
c e n t r a l  par: o f  Figure 13.  
Between t h e  growth of s l i ce  E 
and t h a t  of s l i c e  I ,  the  r a t e  o f  
growth of t h e  (0x1) f a c e t  slowed, 
while the  growth of the  (101) f a c e t  
i nc reased ,  causing a corresponding 
change il: =he shape of  t h e  r e l aced  
f a c e r s  as a ' r s r rac ted  i n  f i g u r e  1 9 .  
Figure 9 .  icter- 
a c t i n g  d i s l o c a t i o n s  
observed in  10 keV 
d i f f r a c t i o n  i n  Laue 
geometry (trans - 
mission) from (220) 
planes of  (001) Cut 
undoped g a l  1 ium 
a r sen ide  crystal 
( $ 5 ) .  
. 
. 
‘i 
. 
c0103 t c 1001 
Figure 10. Image o f  
Bragg d i f f r a c t i o n  at 
8 keV from ( O O L )  
crystal planes of  
t he  (001) c u t  indium 
doped gall ium a r -  
sen ide  v a f e r  shoLn 
i n  Figures  2 and 3 
i n  Laue geometry. 
The change i n  the  o r i e n t a t i o n  of the 
c e n z r a l  f r inges  indica:es t h a t  the 
s lope  of t he  c e n t r a l  near-(001) face 
underwent a corresponding change. 
By the  t i m e  t h a t  t h e  center o f  
t h e  boule had grown t o  pos i t i on  K, 
however, growth of the (101) f ace t  
had ceased completely, causing a 
d i s t i n c t i v e  shape i n  high scrain 
regions i n  both s l i c e s  I and K ,  and 
a s s o c i a t e d  w i t h  f u r t h e r  change i n  
t h e  o r i e n t a t i o n  of t he  cen t r a l  
s t r a i n  f r i n g e s ,  Figures 19 and 20 ,  
S ? e c l f l c  aspects  o f  th is  non 
respeczLve:y. 
c0nstar.t f a c e t e d  growzh modei  a r e  
v e r i f i e d  i n  magnified po r t ions  o f  
the  d i f f r a c t i o n  images, Figures 2 1  
and 22.  Figure 2 1  i l l u s t r a t e s  con- 
t i n u i t y  between f r i n g e s  observed i n  
the c e n t r a l  reg ion  and t h e  p e r i -  
pheral  s t r i a t i o n s ,  support ing the  
f ace t ed  growth model wi th  growch o f  
t h e  c e n t r a l  facet a t  an angle t o  t h e  
(001) plane.  Cessat ion i n  the  
growth of the (101) facet  while the 
(011) f a c e t  continued t o  grow i s  il- 
l u s t r a t e d  i n  Figure 2 2 .  
A rnathemacical model t h a t  suc- 
c e s s f u l l y  p r e d i c t s  flow & ~ r i n &  sza-  
Figure 11. v,F;.i - 
f i e d  p o r t i o n  of 
image of  d i f f r a c t l o n  
i n  h u e  geometry at 
10 keV from (040)  
planes  of  the (001) 
cut indium doped 
gal l ium arsenide 
crystal shown i n  F i -  
gures 2,3, and 10. 
8 
ble Ctochralski 
interface is illust r: 2 3 .  Extension 
tures of this 
the manufacture of 
that regions of the c 
duced. 
337. RITURE DIRECTIONS 
sonochroma- 
tic radiation removes ambiguity as- 
sociated with diffraction by photons 
with the range of wavelengths in 
white ra&Larion, another ambiguity 
In the interpretarion nevertheless 
remains. Contrast in a monochroma- 
tic image can be caused either by 
variation in latrice parameter or by 
variation in orientation of the 
crystal lattice. Diffraction from a 
surface defect surrounded by a per- 
fect. crystal is illustrated schemat- 
ically In Figure 26, in which spa- 
tial confusion in the diffracted 
image is shown to be traceable to 
dissimilar diffraction angles. A 
principal consequence of these dif  - 
fering angles is that radiation from 
such a defect is displaced in the 
image from the locazion of the image 
of the immediately surrounding un- 
disturbed region. Separation of the 
diffracted radiation from the two 
E 
I 
K 
Figure 12. Relative positions of 
slices taken from a single high 
q u a l i t y  8 mm b o d e  of blsnruz3 
silicon oxide. 
sources, defecr an& s u r r o u n c i ~ g  r e -  
gion, and resoua: of the hmbL,l;ir~: 
in the source cap. be accoiqLlskeC 
by " o u t  s=a:e analysis," t'nroq':: 
placing a ~ .  adciltionai diffraczxg 
crystal so as to intercept :ne G L f -  
fracted image, as illustrs=ec ir. 
Figure 27. 
Examples of the results of such 
"out state analysis" are shown ir. 
Figures 28 and 29, which picture 
images of the central region of the 
indium doped gallium arsenide crys- 
tal previously shown in conventions1 
diffraction images Figures 2, 3, and 
10. 
When the analyzer crystal is 
set to pass "perfect crystal" dif- 
fraction, the. conzrasz between dif- 
9 
f r a c c i n g  anc n o 3  d i f f r a c t i n g  regions 
i s  r e l z z i v e l y  h i g h .  This high  
co-:=ras: is ca-sec by che aSsence o f  
kzerferL:.g 1Lffraczion from de- 
f e c c s .  ";.en the azzlyzer cq-s ta l  i s  
se: t o  liscrFrr.in,=te aga ins t  t h L s  
"?"rfec: C T ~ S Z E L ~ '  ciz=rzcrio~, ~ h e  
denscry of  tne image i s  reduced by 
-. - -  
-L L.,e lo:-ereC Cffz'rGctea briS3tness at 
IT G f c I I  ar.gle. ~ n z . l > - s i s  of sucn 
s i i cp l i f i ed  inages s h o c l d  prove :o be 
more direc: and thus iess subject t o  
Zhe models employed cnan I s  cne 
analys is  or' convenrionai d i f f r a c t i o n  
images . 
Another opportunity with 5y-1- 
c h r o t r o n  radiazion no t  yec f u l l y  
e x p l o i t e d  is  t h e  c b i l i t y  t o  carry 
o u t  ExperimEnts i n  r e a l  time v'nile 
observat ions a r e  made r i c h  a video 
canera.  One exzmple whose f e i s i b i l -  
i r y  has been proved is the  observa- 
Figure 13. D i f f r ac -  
t i o n  image i n  Era&& 
geometry of ( O O i  ) 
cut s l i ce  E of  
bismuth s i l i c o n  
oxide from (006) 
planes a t  8 keV. 
. ,-. 
Figure 1 4 .  D l f f r a c -  
tion image i n  Eragg 
geometry of (001) 
cut s l i c e  I of  
b i smu th silicon 
oxide from (0 0 10) 
planes at 8 keV. 
Figure 16. D i f f r a c -  
tion image i n  h u e  
geomerry of bismuth 
silicon oxide s l i c e  
at 
crystal is shown in 
Bragg geometry in 
Figure 1 and in 
another orientation 
in Laue geometry in 
Figure 4. 
f 
Figure 18. Abstraction of faceted 
Figure 17. Abstraction of face of growth of bismuth silicon oxide 
growing bismuth silicon oxide boule boule while slice E was; being 
shortly after initial necking. f onned. 
1 2  
- 
. 
7 
1 -  
.- - - - __ -. __--- 
Figure 1 9 .  Abs t rac t ion  of faceted 
growth of bismuth s i l i c o n  oxide 
boule while s l i c e  I w a s  being 
f onned. 
ACKNOWLEDGEMENTS 
The authors  acknowledge the s u p p o r t  
o f  t he  U. S .  Department o f  Commerce 
and of the Nat ional  Aeronauzics and 
Space Adminis t ra t ion,  through the  
F igure  20. Abstraction of faceted 
growth of bismuth s i l icon  oxide 
boule  while s l ice  K was being 
formed. 
Figure 21. Magnification o f  reg ion  
ad jacent  co che center. in t,F..e [loo! . 
d i r e c t i o n ,  of  a (006) d i f f r a c t i o n  of  
sl ice I i n  Bragg geometry at 8 keV. 
This s e c t i o n  shovs the boundary be- 
tween the  c e n t r a l  rec+cangular near  
(001) f a c e t  grovth reg ion  conta in ing  
f r i n g e s  and the perFphera1 (101) 
f a c e t  grovrh. 
REFERENCES 
1. Present  address:  Vuclear Research 
Center ,  Beer Sheva. 
2 .  Bruce S t e i n e r ,  U r i  Laor,  Xaszo 
Kuriyiima, Gabr ie l le  G .  Long, and 
13 
I 
Figure 23. Mathematical model of 
flow in the bismuth silicon oxide 
melt for stable flat interface Czo- 
chralski growsh. 
- .  
- 1  
Figure 2 2 .  K a p i f i -  
cation of t t ie Ill[;,  
corner rcy,ion of a 
( 0 6 0 )  d i f f r n c L i o : ,  
im3ge of slice 11 i:. 
h u e  GeonrcBtq 2: 
i r l  the [OlO] direc- 
tion, -and thereby 
t f .e  cessation in the 
6:~vth of one of the 
facets while an ad- 
jacent facet contin- 
ued to grov. 
on Rndiation to X:ittsrials 
ience: Diffraction Imaglrlg (Top- 
ograph) and Kicroradiography, in 
Advanced Techniques for Microstruc- 
z u r e  Characterizatiori-, " 1988. 
5 .  V. J .  Boettinger, H. E. Surde 
and X. Kuriyama, '%?hit@ Beam 
i 
! I 
Figure  24. Hodel of flow in the 
bismuth silicon oxide melt for 
faceted interface Czochralski 
growth. CompetLtion bemeen the two 
melt curents cacses chaages In the 
relative rotes of growth of z5e 
vaiious facers. 
. .  -- 
ORffilMAL 
OF POOR 
PAGE ts 
QUALln 
Figure 2 8 .  K z p i  - 
f i e d  po-t ion of 
( 0 0 4 )  diffraction 
image of ccn:ral 
p o r t i o n  of  (001) C U E  
indium doped gal l i iun 
a rsen ide  wafer a s  
d i f f r a c t e d  by a 
s i l i c o n  c r y s t a l  
o r i e n t e d  t o  pass  the 
" p e r f e c t  c r y s t a l "  
d i f f r a c t i o n  and t o  
d i sc r imina te  aga ins t  
d e f e c t s .  
Figure 29. Magni- 
f i e d  p o r t i o n  of  
(004) d i f f r a c t i o n  
image of c e n t r a l  
p o r t i o n  o f  (001) c u t  
indium doped gal l lurr  
a rsen ide  w a f e r  2s 
d i f f r a c t e d  by E 
s i l i c o n  cry5 t Z L  
o r ien teL t o  ? a s s  
diffraczlon fr0ir 
de fec t s  and t o  d L s -  
cr lmina te  a g a i r s z  
"perfec: cr]..scal 
d i f f r a c t i o c .  
1 6  


X-ray diffraction imaging (topography) of electroopticcrystals by synchrotron radiation

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server