Results are reported for work in high-temperature deformatin of dendritic web ribbons, and oxygen measurement in the material

Ast, D. G.

Hyland, S.

English

NASA Technical Reports Server

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ADVAi_CED SILICON SHEET N 87 - ] 6 410 "
CREEP OF RIBBONS
CORNELL ',.iN'*, RSITY
t
S. Hyland a-.: _ ,_. G. Ast "
i
1. Ox.,_;-._"Content
i
" " eep Law
; I
' 3. Mit ".oscopic Mechanisms ,
_' Silicon Sheet Growth and Characterization
(
! -B
OXY_ ¢OI_m'ItP,ATIO_IU(¢M
6. S.
,, I,la|O"4lN*1
'o " hl08_'1 /_*.S Y• I(I0 "¢
/
_.o, / k
4.0.
q 3, ',.
hi'.
II ' ;
2.0. i
|.S. ,
i.0.
_, w|,
• 0,0, ,_._ .,___j,.._.,,_,,_.. , -:_. ,-_ . , ..... , . _ ,
....... w...... v ...... ,
O, 0._ 1.0 I.'_ 2.0 ._.'1 ),_ l.'J 4.0 4.S S,O
_lqIllk%
TEklI_EAI'QKImI OOO(.
P
1987006957-297
https://ntrs.nasa.gov/search.jsp?R=19870006977 2020-03-20T12:13:43+00:00Z
! ADVANCED SILICON SHEET ' -_
IR Transmission Versus WavenJmber for Cz Silicor
91q
"" 50
[O] .-=3.8 pp, a _ Ab'Ttl/'k
_ 49 } /J _"_'/ _ FWHM= ,33 wavenumbers
Z
,'r"
1--
46 j
_, 4S I I I I I.._ J
800 900 I000 I100 1200 1300 J400
: WAVENUMBER (cm"1)
IR Transmission Versus Wavenumber for Low Stress Web
Before and After 850°C, 24-Hour Heat Treatment
O
After Heat Treatment
_, re Heat Treatment
"_" 0
.o_ _ i
• o oom°
_ = 35 wavenumbers
Lo R461-5.7
P- J460 After:
o [O] = 19.9 ppma
o_ FWHM = 35 wavenumbers
/ O
I I I --.I
900.0 1000.0 1100.0 1200.0 1300.0
Wavenumber (c_-1)
"'t 298
k
1987006957-298
ADVANCEDSILICONSHEET
r
9
IR Transmission Versus Wav_number for High Stress Web !
Before and After 850°C, 24-Hour Heat Treatment
ql, all,
o After Heat Treatmer_tF)
U'}
"
c,i
U_
4
°_ _ /\// E01=,_ _mo
o u0 efore:
el
"E o
t-_ _ _ FWHM --- 43 wovenumberso Z025-3.7 _ I ..
; _- J435- \ i After:
o V [O] = 16.8 ppmaa_ FWHM = 35 wavenunlbers
o
E'_ I I I 1
,¢
900.0 1000.0 1100.0 1200.0 1300.0
Wovenumber (cm- 1)
Four-Point Bending Rig at MSEC
/
deflectionprobe
W W
fixedrollers
0o,J / _ .,om_,°/k
t oo_'o_,o".,,¢_ ___
.._ thermocouple$..... sompecombe ____ olechomber
t
_o
"_ ;
:_. 299
1987006957-299
_11_.,_._" L'_,":_" "_':* "_" _'J'
' _ ADVANCED SILICON SHEET
Deflection Versus Time for Web Silicon
Four-Point Bending 6
ZOO8
: z 5 T • J,'_)'c
Sl_ • 16.8 MPa
i
• _
_,_ _ I._w
J
, O0 _ l .. _ I, t i ;,1
0 I 2 3 4 5
• _ TIME (mmules)
• _ 3,0
; Z071 -tl
_, zo_a S2 5 "r.moo'c
' S'_ls • 16.3MI_
_z.o _ ._
:-
_i I , 1O0 .... J -_
0 I 2 3 4 5 6 7 8 ,
TIME (mmules) i!
35
21i/
f.5[ zoo8_I4o_io3T, IO00"C
51tOil • 35 4MISo
00 L , .._.._.____.._ _(_ I 2 _ 4 5 6
T;Mf. (n_,nules)
300
i
1987006957-300
• IP_l_ _ "L._,_
"1
;" ADVANCED SILICON SHEET
C
•:. Preliminary Analysis of Four-Point Bending
o ll"
: _. L___ __8
,m : samDje thickness
- - scm:)]e wadth
: &s = surfoce stroin
;'s = surfoce stress
R --- h/(2%)
"_ .2 i
' _., = R - Rcos[orcsin{i/(2R)t. ] =, //(2R_ r
for Di (( R
" combining: i
, ASSuming a POwer Low Creep
= _o a"n
:nerefore /
, _,,z, = [(Sb;z)/(_oi2]_/_ tt
T_e stress con be Cetermined from the f
sto#e of the cteflection vs. time curve.
T_e moment is
_: obtaine_ from the stress:
t/
[... = 2Bf(sb;)/(;22o]_/_
" [n/(2n+ 1)][h/2](2r_+_)/n
t
so_
L " "
I .
ADVANCED SILICON SHEET
, :_ Preliminary Analysis of Four-Point Bending (Cant'd)
_ _ d
._'_aer elastic loading:
' as = 6lM/kh2B/J '
c'laer plastic loading: _.
'-. _s = 4[M/(h2B)]
K..,e_;¢ uses an intermediate factor of 5.
We will use the plastic factor of 4.
experimentolly,
; = 25 mm
- _); = --_ 0 3 h = 0.153 mm/vW
_,. ieoding to: _o = 8.8x10 -8 sec-1
Creep Low:
= 8.8x10 .8 _3 t
cr in MPo, T = 1000°C
--. {
; Data fromWeb BendingTests _
r APPLZED STRESS EXPERIMENTAL SZ P0wS_ LAw FrT(kiP^) (Idld/llZN) (lll=l/llZN)
N=3 !
t
27 2 2.8 !
11L3 0.5 0.62
35.4 6 6.3 _ -'
16.8 0.S 0.68
16.8 0.$ 0.6P
13o 0.1 0.3
e WEB WZTH DENDRZTF.,SON AbSUIUZNG1.0AD ZS CARRZEDBY SQUARE
"/ 0irNDRZTE$ ONLY.
r, e,..4
, 7000
- I FROM l:Tr I"o D_TA
i
3O2
' i
1987006957-302
}ADVANCED SILICON SHEET ,
)
Deflection Versus Time for Web Silicon
Four-Poim Bending
2.5 /T = IO00°C 6,
/(111) Fz Silicon
2.0 / Slress =25.2 MPa
"E / tE
"-" 1.5 / Web Silicon without Dendritesz
0 / Stress=27 MPo
C_ 2 -I.5
tdj 1.0
b- t
_J /S _ _ Web Sillco_ with Dr_ J endrites
,. _ J372 - 2.4 ,!
0.0 /-_'_"'-'-'__ I I
0 I 2 3 4 5 ',
TIME (minutes)
Predicted Deflection Versus Time Curve
; 2
Sr = $Z (I'Sl"N '
{ APPROXZMATELY : 0.3 TO 0.36 Sz FOR N = 2,£ " 3 7
i ASSUME THAT THE MATERZAL DOES N0T CHANGE DURZNC THE TF_T. i
l "'_'°"Y . It g =tat,
...... ..... __.i_,'d ;_ d.,;h,L_=J<'_
! _//" ,"1; 1=/ /initioI
V slope. $i
/ time _,'.*.c_ $_,o/> C)J_ _-_-_'_'
.'_
,i
303
!
1987006957-303
• "I ADVANCEDSILICONSHEET
l Analysis of Strain Transition
I
A
PZlastic: Die = [i2/4Eh] Gs ,.
"=-_ G_t (experimentally)Plastic: Dip - 7000 1
?
When does the elastic load distribution
change to a plastic load distribution? ;
t
Dip = N Die
, assume N = 5:
: a) Gs = 27 MPo h = 0.155 mm 5
, = 25mm E(lll)=_.9 x 10 MPo
ttronsition = 15.5 sec
;
b) Ors = 16 MPo "
ttronsition = 44 sec
Th!s order of magnitude seen for
transition from Si to Sf.
Lcod redistribution is responsible for the
transition.
".,.,
p
le :
; 304
1987006957-304
•ADVANCEDSILICONSHEET
Analysis of Strain Bursts
4
"_ _ ' "_ ' _ " ' r;_, 2 <e--., ,
1
There is no stress on a dislocation at
the neutral axis(l).
A dislocation at the neutral axis will
experience a stress due to the long
range stress fields of following
dislocations(2).
If the following dislocations are located
in a port of the sample where they are
under an applied stress(5), they may
generate enough stress on the leading
dislocation to push it through the neutral
axis.
Therefore, if the length of a dislocation ._
pile-up is some fraction of the thickness
of the sample, such as in the case of
Web silicon ribbons, there may be
enough stress on dislocations at the
neutral axis to cause them to move
through, resulting in "strain bursts".
305
1987006957-305
.j 'l_jh_l___ __ ..4 ....
"I_, ADVANCED SILICON SHEET
- flr,_aReferences '/"":;
{.
F
o._
,._ C_ang.e o: misorientation with '
' oeforma_on aue to trapped reaction
._ _rocucts (Oe): d.J.Bactlmann, M.O.Goy
an: R.Tcuremine, Scrip_a Met. 16 (1982)
: 535.
2. influence of coherent twins on
: mechanical behavior (Ni): L.C.Lim, Scripta
I_ Me:. 18 (19bz+) 11..39; L.C.Lim and R.Raj,
Ac_a Met. 32(t984) 727ff and 1183ff.
3. General discuccion on interaction
between grain boundary dislocations and
, ;c:=ice dislocations and their role in
mecnanical properties: L.C.[im and R.Rqj,
.! Journal de Physique Colloque C4 (1985)
i 58!.
4 Reactions between lattice dislocations
cnc _wins studied by TEM (Si):
.:, R..Sleicnmann, M.D.Voudin and D.O.Ast,
Phil. Mag. A 51 (1985) 4-49.
Summary
4-Point Bending
Data consistent with
-transient due to load redistribution
-creep law, at 1000 deg C: _-= q_ Ld_¢" (_;_P_)
Observed creep slower for Web than for Cz
Oxygen Measurements "
High Oxygen content of 20 ppma
Width of IR absorption peak greater for Web
Low stress ribbons-no change with annealing
High stress ribbons-width of beak decreases
with annealing
Appearance of shoulder on IR peak is not predictable
306
1987006957-306


Creep of web ribbons

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