Bridgman growth of NiSb single crystals

Article abstract of DOI:10.1007/s10789-005-0280-0

Structurally perfect NiSb single crystals ?25 mm in diameter and 250 mm in length were grown by the Bridgman method. Polishing etch compositions were selected for the preparation of NiSb substrate surfaces.

Full text of DOI:10.1007/s10789-005-0280-0

Inorganic Materials, Vol. 41, No. 11, 2005, pp. 1162–1165. Translated from Neorganicheskie Materialy, Vol. 41, No. 11, 2005, pp. 1320–1323.
Original Russian Text Copyright © 2005 by Ogarev, Aitkhozhin, Temirov, Palkina, Shchamkhalov, Marenkin.
Bridgman Growth of NiSb Single Crystals
D. A. Ogarev*, S. A. Aitkhozhin**, Yu. Sh. Temirov**, K. K. Palkina*,
K. A. Shchamkhalov**, and S. F. Marenkin*
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
*
*
* Institute of Radio Engineering and Electronics, Russian Academy of Sciences,
Mokhovaya ul. 11, Moscow, 125009 Russia
e-mail: dimoni@mail.ru
Received May 17, 2005
Abstract—Structurally perfect NiSb single crystals ꢀ25 mm in diameter and 250 mm in length were grown
by the Bridgman method. Polishing etch compositions were selected for the preparation of NiSb substrate sur-
faces.
Nickel antimonide belongs to the family of pnic-
According to earlier results [4], nickel antimonide
tides—intermetallic compounds of 3d transition metals melts congruently at 1153°C and has a rather broad
with Group V elements. In nature, nickel antimonide homogeneity range: it dissolves 3 at % Sb and ꢀ4 at % Ni.
occurs as the mineral breithauptite. In recent years,
pnictides have been used in heterostructures composed
Czochralski-grown NiSb single crystals [5] had a
rather low structural perfection and consisted of mosaic
of a ferromagnetic intermetallic compound and semi- blocks. It was of interest to develop a process for the
conductor, which have considerable potential for appli- growth of large, high-quality NiSb single crystals suit-
cation in spintronics [1–3].
able for the fabrication of substrates.
1
01
1
02
1
10
2
01
002
1
03
2
11
2
02
1
12
0
04
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
9
7
2
θ, deg
Fig. 1. XRD pattern of NiSb.
020-1685/05/4111-1162 © 2005 Pleiades Publishing, Inc.
0

BRIDGMAN GROWTH OF NiSb SINGLE CRYSTALS
1163
Fig. 2. Bridgman-grown NiSb crystal.
(
a)
(b)
x
z
z
Sb
y
y
x
Sb
Ni
Ni
Fig. 3. Crystal structure of NiSb projected along the (a) [010] and (b) [100] directions.
The growth charge was prepared from a stoichio- the temperature was raised to the melting point of NiSb
metric mixture of electrolytic nickel and V-5 antimony, (1153°C) at a rate of 30°C/h and then maintained con-
which were sealed in a silica ampule under a vacuum of stant for at least 6 h, followed by furnace-cooling. The
–2
1
0 Pa. The ampule was then mounted in a vertical fur- temperature was monitored with a Pt/Pt–Rh thermo-
nace fitted with a massive steel block for producing a
uniform temperature profile along the length of the
ampule. After heating to 640°C, the temperature was
couple and controlled by a RIF-101 unit.
The resultant samples, pale rose in appearance, were
maintained constant for 3 h, which led to the melting of characterized by x-ray diffraction (XRD) and differen-
antimony and partial reaction between Sb and Ni. Next, tial thermal analysis (DTA).
INORGANIC MATERIALS Vol. 41 No. 11 2005

1
164
OGAREV et al.
5
HNO + 3HF + 3CH COOH, v = 10 µm/s
3
3
etch
1
HNO + 1HF, v
= 9.125 µm/s
= 1.875 µm/s
= 0.063 µm/s
3
etch
8
0
1HNO + 1HCl, v
3
etch
1Br + 10CH COOH, v
2
3
etch
6
4
2
0
0
0
0
5
10
15
20
25
30
35
Time, s
Fig. 4. Thickness of the layer removed from the NiSb surface as a function of etching time for different etchants.
XRD examination was carried out on a DRON-2
Single crystals were prepared by horizontal Bridg-
diffractometer (CuK radiation, λ = 1.5405 Å, diffrac- man growth in boats made from quartz coated with
α
tion angle from 0° to 55°). The XRD pattern of the pyrolytic carbon, alundum, or graphite.
material (Fig. 1) showed only peaks characteristic of
The best NiSb crystals were grown in a pure hydro-
NiSb. The lattice parameters coincided with those given
gen flow using graphite boats 250–270 mm in length
in the JCPDS PDF.
and 23–25 mm in diameter, which were mounted in a
quartz tube 45–50 mm in diameter. The growth unit
included a 600-mm-long two-zone furnace and a drive
system for translating the furnace along the boat at a
rate of 2–6.5 mm/h. The temperature of the hot zone
was 1200–1220°C. In the second zone, the temperature
profile sloped down with a gradient of 50°C/cm. The
temperature was maintained with an accuracy of
DTA also confirmed that the samples were phase-
pure; the heating curve showed a thermal effect due to
melting at 1136°C, in agreement with earlier results [4].
Mass spectrometry data for NiSb samples
at %
mol %
at %
mol %
±
0.5°ë. One of the NiSb crystals grown under such
Element
sample 1
sample 2
conditions is shown in Fig. 2.
C
0.040
0.0085
0.032
0.0053
0.0023
0.0097
0.013
0.039
0.010
0.0050
0.0026
0.010
The structure of NiSb single crystals was deter-
mined using x-ray intensity data collected on an Enraf-
Nonius CAD-4 automatic four-circle diffractometer
Mg
Al
Si
0.036
(
graphite monochromator, MoKα radiation, λ =
0.042
0.055
0.017
0.7107 Å, θ-scan mode). Absorption correction was
evaluated from transmission curves. All crystallo-
graphic calculations were made using SHELX-93 [6].
The structure was solved by the heavy atom method
and was refined by a full-matrix least squares technique
with anisotropic thermal parameters.
P
0.0005
0.0023
0.010
0.0002
0.0008
0.0045
0.070
0.0004
0.0055
0.0075
0.06
0.0002
0.0020
0.0034
0.0075
0.0003
0.0007
0.0026
0.017
S
K
Ca
Ti
Cr
Mn
Fe
Ni
Co
Cu
Zn
Sb
0.016
0.0005
0.0012
0.0025
0.028
0.0003
0.0008
0.0015
0.018
0.0005
0.0012
0.0042
0.027
The refined lattice parameters of NiSb (hexagonal
symmetry, sp. gr. P6 /mmc, NiAs structure) are a =
3
3
.953 Å and c = 5.141 Å. Figure 3 shows the structure
of NiSb projected along the [010] and [100] directions.
The table presents mass spectrometry data for two
samples cut from a single-crystal NiSb ingot, one from
the first grown portion (sample 1) and the other from
the tail end (sample 2). Note that sample 1 was enriched
in Ni, and sample 2, in Sb as compared to the stoichio-
metric composition. Note also that the effective distri-
bution coefficients of Mg, Al, Si, S, Ca, and Mn are less
than unity, and those of C, P, K, Fe, Cu, and Zn are
greater than unity.
50.50
32.74
49.95
32.25
0.0015
0.0007
0.0005
49.28
0.0010
0.0005
0.0004
67.19
0.0015
0.0006
0.0004
49.82
0.0009
0.0004
0.0003
67.67
Note: Sample 1 was cut from the first grown portion of the crystal,
and sample 2 was cut from the tail end.
INORGANIC MATERIALS Vol. 41 No. 11 2005

BRIDGMAN GROWTH OF NiSb SINGLE CRYSTALS
1165
Fig. 5. NiSb surfaces etched with a 1 : 1 mixture of HNO and HF; 200×.
3
To prepare specimens for microstructural examina-
REFERENCES
tion and NiSb substrates, we used polishing etchants
based on nitric acid. Figure 4 presents 300-K etching
rate data for NiSb substrates and different etchants.
1
2
. Datta, S. and Das, B., Electronic Analog of the Electro-
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netic Semiconductor Heterostructure, Nature (London),
Microstructural analysis (EPIQUANT optical
microscope) revealed a number of defects on the sur-
faces of two samples cut from the tail end of one of the
crystals (Fig. 5), in particular, pores and small-angle
boundaries.
1
999, vol. 402, p. 787.
3
. Gibbs, W., Atomic Spin-offs for the 21st Century, Sci.
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. Sheldrick, G.M., SHELXL-93: Program for the Refine-
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gen, 1993.
4
Thus, using Bridgman growth, we prepared large,
structurally perfect NiSb single crystals. According to
single-crystal XRD results, the lattice parameters of the
5
crystals (hexagonal symmetry, sp. gr. P6 /mmc, NiAs
3
structure) are a = 3.953 Å and c = 5.141 Å. Polishing
etch compositions were selected for revealing struc-
tural defects and for the preparation of substrate sur-
faces.
6
INORGANIC MATERIALS Vol. 41 No. 11 2005