Nanocomposite films based on (Nb2Al)N intermetallic nitride have been obtained by the method
of magnetron sputtering. Xray diffraction analysis revealed two stable states of the crystalline structure: (i)
NbN with low amount (within 5 at %) of dissolved Al in a composition close to (Nb2Al)N and (ii) an amor
phous component related to aluminum nitride formed by reactive magnetron sputtering. The substructural
characteristics (grain size and microdeformation level) are sensitive to the current via Al target and exhibit correlation with nanohardness and Knoop hardness of the film, which vary within 29–33.5 and 46–48 GPa, respectively

Dub, S.N.

Ivashchenko, V.I.

Kupchishin, A.I.

Meilekhov, A.A.

Pohrebniak, Oleksandr Dmytrovych

Rogoz, V.N.

Sobol, O.V.

Погребняк, Александр Дмитриевич

Погребняк, Олександр Дмитрович

English

SocioEconomic Challenges Journal (Sumy State University)

ISSN 10637850, Technical Physics Letters, 2015, Vol. 41, No. 7, pp. 697–700. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © V.I. Ivashchenko, A.D. Pogrebnjak, O.V. Sobol’, V.N. Rogoz, A.A. Meilekhov, S.N. Dub, A.I. Kupchishin, 2015, published in Pis’ma v Zhurnal
Tekhnicheskoi Fiziki, 2015, Vol. 41, No. 14, pp. 72–78.
697
Films and coatings based on niobium nitride
(NbN) exhibit many interesting properties, such as
high hardness, electric conductivity, thermal stability,
and chemical inertness [1]. NbN films are used as
cathode material for field electron emission devices in
vacuum microelectronics [2]. It was established that
the introduction of Al atoms into the crystalline lattice
of NbN leads to the formation of Nb1 – xAlxN solid
solutions.
Arcdeposited Nb1 – xAlxN coatings with x < 0.45
are formed predominantly with the cubic B1 (NaCl
type) structure; for x = 0.45–0.71, a mixture of B1 and
B4 structures has been observed, while x > 0.71 favors
the formation of B4 (wurtzite type) structure [3].
Magnetronsputterdeposited Nb–Al–N films also
exhibited B1 (sometimes, with BK–δNbN phase) or
B4 structure, or their mixtures [4–7]. However, nano
composite NbN/AlN films have not been studied until
now. In order to fill this gap, the present study was
aimed at depositing Nb–Al–N films under assump
tion that nanocomposite films would exhibit improved
mechanical properties in comparison to Nb1 – xAlxN
films.
Nb–Al–N films were deposited onto mirrorpol
ished Si (100) substrates by DC magnetron sputtering
of Nb (99.9%) and Al (99.999%) targets with 72 mm
diameter and 4 mm thickness in argon and nitrogen
atmosphere under the following conditions: substrate
temperature Ts = 350°C, substrate bias voltage UB =
⎯50 V, gas flow rates FAr = 40 sccm and FN2 = 13 sccm,
and working pressure PC = 0.17 Pa. The current via Al
target was varied within IAl = 50, 100, 150, 200, 250,
and 300 mA, which corresponded to a discharge power
density of PAl = 2.9, 5.7, 8.6, 11.4, 13.7, and
17.1 W/cm2, respectively. The current via Nb target
was INb = 300 mA, which corresponded to PNb =
17.1 W/cm2. The residual base pressure in the vacuum
chamber was below 10–4 Pa. The distance from targets
to the substrate holder was 8 cm, and the dihedral
angle between targets was ~45°. Prior to being placed
into the vacuum chamber, the substrates were ultra
sonically cleaned of surface contaminations. Prior to
coating deposition, the substrates were ionetched in
hydrogen plasma for 5 min.
The structure of deposited films was studied by
Xray diffraction (XRD) on a DRON3M diffracto
meter using CuK
α
 radiation. Deconvolution of com
plex XRD profiles into components was performed
using an original program. Substructural characteris
tics (grain size and microdeformation) were deter
mined by the line shape analysis with approximation
using the Cauchy function.
The Fourier transform infrared (FTIR) spectra of
coatings were measured at room temperature in a
400–4000 cm–1 range on a TSM 1202 (Infraspek Ltd.)
spectrometer. The Knoop hardness (HK) was mea
sured using a Micromet 2103 (Buehler Ltd.) micro
hardness tester at a 100mN load. The film thickness
The Effect of Al Target Current on the Structure and Properties 
of (Nb2Al)N Films with an Amorphous AlN Phase
V. I. Ivashchenkoa, A. D. Pogrebnjakb*, O. V. Sobol’c, V. N. Rogozb, 
A. A. Meilekhovc, S. N. Dubd, and A. I. Kupchishine
a Institute for Problems in Materials Science, National Academy of Sciences of Ukraine, 03680 Kyiv142, Ukraine
b Sumy National University, 40007 Sumy, Ukraine
c National Technical University Kharkiv Polytechnic Institute, 61002 Kharkiv, Ukraine
d V. Bakul Institute for Superhard Materials, 04074 Kyiv, Ukraine
e Abai Kazakh National Pedagogical University, Almaty, 050010 Kazakhstan
*email: alexp@i.ua
Received January 20, 2015
Abstract—Nanocomposite films based on (Nb2Al)N intermetallic nitride have been obtained by the method
of magnetron sputtering. Xray diffraction analysis revealed two stable states of the crystalline structure: (i)
NbN with low amount (within 5 at %) of dissolved Al in a composition close to (Nb2Al)N and (ii) an amor
phous component related to aluminum nitride formed by reactive magnetron sputtering. The substructural
characteristics (grain size and microdeformation level) are sensitive to the current via Al target and exhibit
correlation with nanohardness and Knoop hardness of the film, which vary within 29–33.5 and 46–48 GPa,
respectively.
DOI: 10.1134/S1063785015070214
698
TECHNICAL PHYSICS LETTERS  Vol. 41  No. 7  2015
IVASHCHENKO et al.
was determined with the aid of a MicronGamma pro
filometer. The thicknesses of Nb–Al–N coatings
ranged within d = 0.7–0.9 μm and were weakly depen
dent on IAl in the interval studied.
Figure 1a shows the XRD patters of Nb–Al–N
coatings deposited at various IAl, where the indicated
reflections refer to the B1 structure of NbN [8]. In
addition, the interval of diffraction angles 2θ = 28°–
30° revealed a halolike diffraction component due to
an amorphous phase. Based on the results of previous
investigations, this component can be identified with
the amorphous aluminum nitride. As can be seen, the
sputtering at all IAl values and a relatively small con
stant substrate bias voltage of –50 V leads to the for
mation of grains with predominant growth direction
[100] perpendicular to the surface, which results in a
relative increase in the (200) reflection intensity for all
samples (see Fig. 1a). At a minimum value of IAl =
50 mA (Fig. 1a, curve 1), the XRD pattern exhibits a
complicated profile corresponding to various planes,
while higher currents lead to the appearance of asym
metry of diffraction lines on the side of greater angles.
The results of deconvolution showed the presence of
two characteristic periods (Fig. 1b). The first is close to
0.438–0.439 nm, which is characteristic of NbN lat
tice with a small amount of substitutional Al impurity.
The second period is about 0.428–0.429 nm, which is
characteristic of Nb–Al–N system with a Nb : Al =
2 : 1 atomic ratio in the lattice that corresponds to
Nb0.67Al0.33N formula as determined using the Vegard
rule for different radii of substituted atoms in crystal
lattices of the same type [9]. The base lattice parame
ters for B1–NbN and B1–AlN were selected to be
0.4393 and 0.4120 nm, respectively [5].
For the intermediate interval of currents, IAl =
150–250 mA, the phase ratio is close to
90
6000
0
5000
4000
3000
2000
1000
I,
 a
.u
.
80706050403020 100
1
2
3
4
5
(1
11
)
(2
00
)
(3
11
)
(4
00
)
140
I,
 a
.u
.
95908580 10
1
2
3
4
2θ, deg
20
0
120
100
80
60
40
(a)
(b)
Fig. 1. (a) XRD patterns of Nb–Al–N coatings deposited at various IAl (mA): (1) 50, (2) 100, (3) 150, (4) 250, and (5) 300;
(b) deconvolution of the XRD profile of the coating deposited at IAl = 150 mA into components: (1) NbN (400) reflection,
(2) Nb0.67Al0.33N (400) reflection, (3) sum of components, and (4) points of the initial data array.
TECHNICAL PHYSICS LETTERS  Vol. 41  No. 7  2015
THE EFFECT OF Al TARGET CURRENT 699
3.5 NbN/Nb0.67Al0.33N. The corresponding substruc
tural characteristics, which have been determined by
the approximation of two orders of diffraction reflec
tions for the (200)–(400) pair, are presented in Fig. 2.
As can be seen, an increase in IAl is accompanied by
growth of the grain size and microdeformation level in
the direction of [100] texture axis. The growth in
deformation is probably explained by increasing disso
lution of aluminum atoms in niobium sublattice,
which leads to a strong distortion of the lattice. A sharp
decrease in the grain size and microdeformation level
at the maximum Al target current (IAl = 300 mA) may
be related to both the annealing and the ordering of
defect structure with the formation of new boundaries
via a grainpolygonizationtype process.
We have also deposited AlN coatings at various IAl
values and analyzed the corresponding XRD patterns.
The results (not presented here) showed that all AlN
films were amorphous (aAlN). However, their FTIR
spectra were indicative of the improvement of Al–N
bonds with increasing IAl (a line at 667 cm–1 related to
Al–N bond vibrations [10, 11] became more pro
nounced).
Figure 3 shows the results of nano and microin
dentation of the obtained (Nb2Al)N nanocomposite
films. The Knoop hardness (HK) of Nb–Al–N films
was higher than that of NbN and AlN films. The
mechanical strength of nanocomposite films was also
better than that of Nb1 – xAlxN films. It was noted that
the Knoop microhardness is about 50% greater than
the nanohardness, which may be related to the fact
that nanoindentation proceeds in a dynamic regime,
while the Knoop hardness is measured in a static
regime.
Thus, we have found two stable crystalline states in
nanocomposite films: (i) NbN with low amount
(within 5 at %) of dissolved Al in a composition close
to (Nb2Al)N and (ii) an amorphous component
related to aluminum nitride formed by reactive mag
netron sputtering. The substructural characteristics
are sensitive to the current via the Al target and exhibit
correlation with the nanohardness and Knoop hard
ness of the film. The good mechanical properties of
the obtained nanocomposite films allow them to be
50
80
0
70
60
50
40
30
20
10
100 150 200 250 300
L
, 
n
m
1
2
(a)
50
5.0
1.0
100 150 200 250 300
ε
, 
%
1
2
(b)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
IAl, mA
Fig. 2. Dependences of the substructural characteristics–
(a) average grain size L and (b) microdeformation level ε–
on Altarget current IAl for the crystalline components of
(1) NbN and (2) Nb0.67Al0.33N (or (Nb2Al)N).
300
48
250200150100
IAl, mA
44
40
36
32
28
H
, 
H
K
, 
G
P
a
H
HK
300
340
250200150100
IAl, mA
330
320
310
300
E
, 
G
P
a(a) (b)
Fig. 3. Plots of (a) nanohardness (H) and Knoop hardness (HK) and (b) elastic modulus (E) vs. Altarget current IAl for magne
tronsputterdeposited Nb–Al–N films.
700
TECHNICAL PHYSICS LETTERS  Vol. 41  No. 7  2015
IVASHCHENKO et al.
recommended as wearresistant and protective coat
ings. 
Acknowledgments. This study was supported in part
in the framework of a State Complex Research Pro
gram, projects nor. 0112U001382 and 0113U000137c.
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Translated by P. Pozdeev


The effect of Al target current on the structure and properties of (Nb2Al)N films with an amorphous AlN phase

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The effect of Al target current on the structure and properties of (Nb2Al)N films with an amorphous AlN phase

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