A low-cost, flexible, high-pressure (600 psi) system for crystal growth and related thermophysical properties measurements was designed, assembled, and tested. The furnace system includes a magnetically coupled translation mechanism that eliminates the need for a high-pressure mechanical feedthru. The system is currently being used for continuing crystal growth experiments and thermophysical properties measurements on several material systems including Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te, and Hg(1-x)Zn(x)Se

Cobb, S. D.

Gillies, D. C.

Lehoczky, S. L.

Szofran, F. R.

English

NASA Technical Reports Server

NASA
Technical
Memorandum
NASA TM-108430
N/ A
//,/-- "/G
lop
INITIAL DEVELOPMENT OF A HIGH-PRESSURE CRYSTAL
GROWTH FACILITY -- CENTER DIRECTOR'S
DISCRETIONARY FUND FINAL REPORT
(PROJECT NO. 87-25)
By F. R. Szofran, S. L. Lehoczky, S. D. Cobb, and D. C. Gillies
Space Science Laboratory
Science and Engineering Directorate
November 1993
(NASA-TM-IO8430) INITIAL
DEVELOPMENT OF A HIGH-PRESSURE
CRYSTAL GROWTH FACILITY: CENTER
DIRECTOR'S DISCRETIONARY FUND Fina]
Report (NASA) 10 p
National Aeronautics and
Space Administration
George C. Marshall Space Flight Center
G3/T6
N94-21807
Unclas
01q8121
MSFC- Form 3190 (Rev. May 1983)
https://ntrs.nasa.gov/search.jsp?R=19940017334 2020-06-16T18:59:50+00:00Z

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
November 1993 Technical M _morand.m
4. TITLE AND SUBTITLE S. FUNDING NUMBERS
Initial Development of a High-Pressure Crystal Growth
Facility -- Center Director's Discretionary Fund Final
Report (prgject No. 87-25)
6. AUTHOR(S)
F. R. Szofran, S. L. Lehoczky, S. D. Cobb, and D. C. Gillies
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
George C. Marshall Space Flight Center
Marshall Space Flight Center, AL 35812
9. SPONSORING/MONITC)RING AGENCY NAME(S) AND ADDRESS(E S)
National Aeronautics and Space Administration
Washington, D.C. 20546
8. PERFORMING ORGANIZATION
REPORT NUMBER
10. SPONSORING / MONITORING
AGENCY REPORT NUMBER
NASA TM-108430
11. SUPPLEMENTARY NOTES
Prepared by Space Science Laboratory, Science & Engineering Directorate.
12a. DISTRIBUTION/AVAILABILITY STATEMENT
Unclassified--Unlimited
12b. DISTRIBUTION CODE
13. ABSTRACT (Maximum 200words)
A low-cost, flexible, high-pressure (600 psi) system for crystal growth and related
thermophysical properties measurements was designed, assembled, and tested. The furnace
system includes a novel, magnetically coupled translation mechanism that eliminates the need
for a high-pressure mechanical feedthru. The system is currently being used for continuing
crystal growth experiments and thermophysical properties measurements on several material
systems including Hgl.xCdxTe, Hg].xZnxTe, and Hg]_xZnxSe.
14. SUBJECT TERMS
High-Pressure Crystal Growth Furnacel
Thermophysical Properties Measurements
17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION
OF REPORT OF THIS PAGE
Unclassified Unclassified
NSN 7540-01-280-5500
19. SECURITY CLASSIFICATION
OF ABSTRACT
Unclassified
15. NUMBER OF PAGES
9
16. PRICE CODE
NTIS
20. LIMITATION OF ABSTRACT
Unlimited
Standard Form 298 (Rev. 2-89)

TABLE OF CONTENTS
Page
OBJECTIVES AND BACKGROUND OF THE PROJECT ................................ 1
APPROACH AND DESCRIPTION OF THE APPARATUS .............................. 1
RESULTS ..................................................................................................................... 2
SUMMARY .................................................................................................................. 5
REFERENCES ............................................................................................................. 5
PI_It)ING PAGE BLANK NOT FK.MED
IolUl
LIST OF ILLUSTRATIONS
Figure Title Page
1 Schematic drawing of the high-pressure part of the furnace excluding
the translation mechanism .......................................................................................... 2
2 Furnace thermal profile suitable for growing Hg0.zCd0.sTe ................................. 3
3 Overall schematic diagram of the high-pressure furnace system ........................ 4
iv
TECHNICAL MEMORANDUM
INITIAL DEVELOPMENT OF A HIGH-PRESSURE CRYSTAL GROWTH
FACILITY -- CENTER DIRECTOR'S DISCRETIONARY FUND FINAL
REPORT (PROJECT NO. 87-25)
OBJECTIVES AND BACKGROUND OF THE PROJECT
This project initiated the development of a high-pressure facility for future flight experi-
ments and commercial scale crystal growth to facilitate the measurement of thermophysical
properties and growth of larger diameter crystals of semiconducting compounds having a
very high vapor pressure at the growth temperature. Many of the compound semiconductors
currently being developed to meet unique photonic and electronic materials requirements have
vapor pressures of tens of atmospheres at the growth temperatures. These materials include
all of the important narrow band-gap solid solution semiconducting alloy systems such as
Hg I xCdxTe, Hgj xMnxTe, Hg I _Zn_Te, and related compounds which are the subjects of
seve-ral approved-space flight experiments. Most III-V compounds such as GaAs, also the
subject of a flight experiment, and InP and their alloys also have high vapor pressures. The
crystal growth of any of these materials in commercially viable sizes can be done more ef-
ficiently, if at all, in a high-pressure furnace. For example, Hgl.xCdxTe alloys are typically
grown in fused silica ampoules in diameters up to about 1.5 cm, but the vapor pressure pro-
hibits growth of larger-diameter material in ambient pressure apparatus. Requirements are
projected for diameters 4 to 5 times larger than the capabilities provided by presently avail-
able apparatus, and the long lead times for developing such apparatus require that develop-
ment begin as soon a_ possible. Such a facility is being considered for inclusion in the Space
Station Furnace Facility being developed for use on Space Station Freedom.
APPROACH AND DESCRIPTION OF THE APPARATUS
A high-pressure furnace in which the furnace shell is also the pressure vessel has been
described by Ciszek and Evans [1]. A modified version of that furnace, shown in Figure 1,
has been constructed. All necessary instrumentation is included for pressure control, tem-
perature control, translation, and temperature measurement to carry out experiments in the
furnace including crystal growth by directional solidification (Bridgman) or the quench-an-
neal method and differential thermal analysis for phase diagram determination of II-VI Hg
compounds such as Hg_._Zn_Te and Hgl_xZnxSe which are materials being investigated in a
current flight project.
The furnace has high- and low-temperature zones, a gradient zone, and a booster heater
at the high-temperature end of the gradient zone to enable the achievement of higher tempera-
ture gradients. The actual bore diameter is 22 mm which will permit sample containers to be
used with outside diameters up to 20 mm. This, in turn, will allow the growth of ingots up
to 18 mm in diameter. An example temperature profile used to grow Hg 08Cd02Te is shown
in Figure 2. An additional feature of the design is that the furnace core and insulation package
are modular so that replacing the core to achieve additional thermal profiles is straightforward
and nondestructive. Thus, additional cores could be constructed and easily interchanged as
required for different experiments.
ToTranslation
Mechanism
Sample -_.
HeaterWinding
Insulation
PressureVessel _,_
x • ,
'AV-/
High-Temperature
Zone
BoosterHeater
GradientZone
Low-Temperature
Zone
The furnace system includes a
novel translation mechanism that uses
magnetic coupling and which elimi-
nates the need for a high-pressure
mechanical feedthru. The translation
rate range is determined by a combi-
nation of a dc motor and gear reduc-
tion box connected to a ball lead
screw. Thus, any translation rate of
interest for crystal growth can be
achieved.
The argon gas handling system
was safety tested up to 1100 psi but
pressures above 600 psi will not be
needed in the laboratory. The pres-
sure inside the furnace is under
closed-loop control and can be pro-
grammed to follow a pressure profile
such as the pressure inside an am-
poule during the temperature profile
imposed during crystal growth or
thermophysical properties measure-
ments. A schematic diagram of the
furnace control functions is shown in
Figure 3. The pressure system has
been used successfully during several
Hg0.sCd02Te crystal growth experi-
ments.
Figure 1. Schematic drawing of the
high-pressure part of the furnace
excluding the translation mechanism.
RESULTS
For a modest overall cost, a highly functional and safe high-pressure furnace system has
been designed, assembled, and tested. In addition to the individual tests of the thermal and
pressure subsystems, two Hg08Cd0.2Te ingots have been directionally solidified in the fur-
nace as a system test. The temperature profile is shown in Figure 2 and the pressure profile
was designed to equalize the pressure on either side of the ampoule wall. The pressure in-
side the ampoule was calculated from the known pressure over Hg08Cdo2Te [2] and is ap-
proximately one-third the equilibrium vapor pressure of pure mercury. Other parameters are
given in the following table.
TestNo.
HP-1
14-1
Ampoule
o.d./i.d.
(mm)
12/8
Translation Rate
(mm/lw)
0.35
Length
Grown
(mm)
33
14/8 0.35 129
14-2a 14/8 0.36 50
14-2b 14/8 0.29 48
Temperature (°C)
900
8OO
700
60O
5OO
4OO
30O
f
zonell
0 10 15 20 25 3O
Position relative to bottom of furnace (cm)
35 4O
Figure 2. Furnace thermal profile suitable for growing Hgo2CdosTe.
F]owmeter
Upper
Magnetically Coupled
Translation
Translation
Tube
in Protective
Bulkhead
MasterControl
Typical Zone Control
Zone 1 Slave m_l
Control
a I=11
l!I
Ammeter
Solid I 0-140 V
State ___ Variac
Switch
Zone 2 Controls
Zone 3 Controls
Flowmeter
Jacket
Flowmeter
Lower End
Drain
Cooling Water
Inlet
Drive
Position
Sensor
) Water Pressure
k. Regulator
1800:1
Gearbox
_ Water Filte_
Pressure __
Transducer
r-.-i
High Pressure IMI
Ramp Control
!1 r Main R_gutat°r
!i_/Electronics
SO psi
Main Regulator
0-1,500 psi
S
= Drive Motor
Speed Sensor
3000
I DSl
"_,',.'k<_.e,.
Reg.
Figure 3. Overall schematic diagram of the high-pressure furnace system.
4
SUMMARY
The project has shown that a low-cost, flexible, high-pressure system for crystal g.rowth
and related thermophysical properties measurements can be assembled. The system is cur-
rently being used for continuing crystal growth experiments and thermophysical properties
measurements on several material systems including Hgl._CdxTe, Hgl.xZnxTe, and
Hgl.xZnxSe. A pending proposal would use the system for Hgl.xMnxTe.
.
.
REFERENCES
Ciszek, T. F., and Evans, C. D., presented Seventh American Conference on Crystal
Growth, Monterey, CA, July 12-17, 1987.
See, for example, Kelly, J. D., Martin, B. G., Szofran, F. R., and Lehoczky, S. L.,
J. El¢¢trochem. Soc., 129, 2360 (1982) (and references therein).
"pA__III_LLY BLANK
APPROVAL
Initial Development of a High-Pressure Crystal Growth Facility --
Center Director's Discretionary Fund Final Report (Project No. 87-25)
•By
F. R. Szofran, S. L. Lehoczky, S. D. Cobb, and D. C. Gillies
This report has been reviewed for technical accuracy and contains no information
concerning national security or nuclear energy activities or programs. The report, in its
entirety, is unclassified.
.......
Gfegor_S._Vilson
Director, Space Science Laboratory
'I_ U,S. GOVERNMENT PRINTING OFFICE 1993 533--108/80146
PRt_ld)tNt; PAGE BLANK NOi FK._Et._



Initial development of a high-pressure crystal growth facility: Center director's discretionary fund

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