Nanostructured ZrO2 and Zr-C-N coatings from chemical vapor deposition of metal-organic precursors

Article abstract of DOI:10.1002/zaac.200400271

Nanocrystalline zirconium carbonitride (Zr-C-N) and zirconium oxide (ZrO₂) films were deposited by chemical vapor deposition (CVD) of zirconium-tetrakis-diethylamide (Zr(NEt₂)₄) and -tert-butyloxide (Zr(OBu^t)₄), respectively. The films were deposited on iron substrates and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Zr-C-N films show blue, golden brown or bronze colours, with colour stability depending upon the precursor composition (pure metal amide or mixed with Et ₂NH). The deposition temperature showed no pronounced effect on the granular morphology of the Zr-C-N films. The XRD data of the films correspond to the formation of carbonitride phase whereas the XPS analyses revealed a strong surface oxidation and incorporation of oxygen in the film. The films deposited using a mixture of Zr(NEt₂)₄ and Et₂NH showed higher N content, better adhesion and scratch resistance when compared to films obtained from the CVD of pure Zr(NEt₂)₄. Subject to the precursor composition and deposition temperature (550-750°C), the microhardness values of Zr-C-N films were found to be in the range 2.11-5.65 GPa. For ZrO₂ films, morphology and phase composition strongly depend on the deposition temperature. The CVD deposits obtained at 350°C show tetragonal ZrO₂ to be the only crystalline phase. Upon increasing the deposition temperature to 450°C, a mixture of tetragonal and monoclinic modifications was formed with morphology made up of interwoven elongated grains. At higher temperatures (550 and 650°C), pure monoclinic phase was obtained with facetted grains and developed texture.

Full text of DOI:10.1002/zaac.200400271

Nanostructured ZrO2 and Zr-C-N Coatings from Chemical Vapor Deposition of
Metal-Organic Precursors
Sanjay Mathur*, Jessica Altmayer and Hao Shen
Saarbrücken/Germany, Leibniz Institute of New Materials, CVD Division
Received July 6th, 2004.
Dedicated to Professor Michael Veith on the Occasion of his 60th Birthday
Abstract. Nanocrystalline zirconium carbonitride (Zr-C-N) and zir-
conium oxide (ZrO2) films were deposited by chemical vapor depo-
sition (CVD) of zirconium-tetrakis-diethylamide (Zr(NEt2)4) and
-tert-butyloxide (Zr(OBut)4), respectively. The films were deposited
on iron substrates and characterized by scanning electron mi-
croscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron
spectroscopy (XPS). The Zr-C-N films show blue, golden brown or
bronze colours, with colour stability depending upon the precursor
composition (pure metal amide or mixed with Et2NH). The depo-
sition temperature showed no pronounced effect on the granular
morphology of the Zr-C-N films. The XRD data of the films corre-
spond to the formation of carbonitride phase whereas the XPS
analyses revealed a strong surface oxidation and incorporation of
oxygen in the film. The films deposited using a mixture of
Zr(NEt2)4 and Et2NH showed higher N content, better adhesion
and scratch resistance when compared to films obtained from the
CVD of pure Zr(NEt2)4. Subject to the precursor composition and
deposition temperature (550Ϫ750 °C), the microhardness values of
Zr-C-N films were found to be in the range 2.11-5.65 GPa. For
ZrO2 films, morphology and phase composition strongly depend
on the deposition temperature. The CVD deposits obtained at
350 °C show tetragonal ZrO2 to be the only crystalline phase. Upon
increasing the deposition temperature to 450 °C, a mixture of tet-
ragonal and monoclinic modifications was formed with mor-
phology made up of interwoven elongated grains. At higher tem-
peratures (550 and 650 °C), pure monoclinic phase was obtained
with facetted grains and developed texture.
Keywords: Zirconium; Nanostructured thin films; Chemical vapor
deposition; Molecular precursors; Zirconium carbonitride; Zir-
conium oxide
Nanostrukturierte ZrO2 und Zr-C-N Beschichtungen durch chemische
Gasphasenabscheidung von metallorganischen Precursoren
Inhaltsübersicht. Mittels chemischer Gasphasenabscheidung (CVD)
wurden nanokristalline Zirconiumcarbonitrid (Zr-C-N)- und Zir-
coniumoxid (ZrO2)-Schichten aus Zirconium-tetrakis-diethylamid
(Zr(NEt2)4) bzw. Ϫtert-butyloxid (Zr(OBut)4) hergestellt. Die
Schichten wurden auf Eisensubstraten abgeschieden und mit Hilfe
von Rasterelektronenmikroskopie (REM), Röntgendiffraktometrie
(XRD) und X-ray-Photoelektronenspektroskopie (XPS) unter-
sucht. Die Zr-C-N-Schichten zeigen blaue, gold-braune oder bron-
zene Farben, deren Stabilität von der Precursorzusammensetzung
(reines Metallamid oder Gemisch mit Et2NH) abhängt. Außerdem
besitzen sie eine granulare Morphologie, die jedoch keine deutliche
Veränderung in Abhängigkeit von Abscheidetemperatur und Pre-
cursorzusammensetzung zeigt. Die XRD Daten dieser Schichten
entsprechen der Bildung einer kubischen Carbonitridphase. Die
XPS Analysen weisen auf eine starke Oberflächenoxidation sowie
die Sauerstoffeinlagerung innerhalb der Schicht hin. Die Schichten,
die aus einem Gemisch von Zr(NEt2)4 und Et2NH hergestellt wur-
den, haben, im Vergleich zu den durch CVD aus reinem Zr(NEt2)4
erhaltenen Beschichtungen, einen höheren N-Gehalt und zeigen
bessere Haftung sowie eine geringere Rissbildung im Scratch-Test.
Für die Mikrohärte der Zr-C-N-Schichten wurden in Abhängigkeit
von der Zusammensetzung und Abscheidetemperatur (550-750 °C)
Werte zwischen 2,11-5,65 GPa gefunden. Für die ZrO2-Schichten
besteht eine starke Abhängigkeit der Morphologie und Phasenzu-
sammensetzung von der Substrattemperatur. Die bei 350 °C abge-
schiedenen CVD-Filme bestehen ausschließlich aus der tetragona-
len ZrO2-Phase. Bei Erhöhung der Substrattemperatur auf 450 °C
entsteht ein Gemisch aus der tetragonalen und monoklinen Modifi-
kation mit einer faserigen Morphologie. Bei höheren Temperaturen
(550 und 650 °C) wurde eine reine monokline Phase mit facettierten
Teilchen definierter Textur erhalten.
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Nanostructured ZrO2 and Zr-C-N Coatings from Chemical Vapor Deposition
remove any residual water. The 1H and 13C NMR spectra were
Introduction
recorded in benzene-d6 on a NMR spectrometer AC 200 (Bruker).
The compounds zirconium tetrakis-diethylamide (Zr(NEt2)4) and -
tert-butyloxide (Zr(OtBu)4) were prepared following the published
procedures [26Ϫ27]. Zr(NEt2)4 was synthesized by a metathesis re-
action of lithium diethyl amide (prepared from n-BuLi and Et2NH,
eq. (1)) with zirconium chloride (eq. (2)) whereas Zr(OtBu)4 was
obtained by a ligand exchange reaction of Zr(NEt2)4 with excess
ButOH as shown in eq. (3) [26Ϫ28].
The coatings of transition metal oxides, nitrides and car-
bides are finding extensive applications due to their interest-
ing properties such as high melting points, extreme hard-
ness, chemical inertness and electrical conductivity [1Ϫ8].
The high dielectric constant of ZrO2 (ϳ 20, five times that
of SiO2) makes it a potential candidate for gate dielectrics
in metal oxide semiconductor field effect transistors (MOS-
FETs) [7]. Similarly, zirconium nitrides (ZrN) and carbo-
nitrides (Zr-C-N) are being used as decorative and protec-
tive coatings [9] due to their optical and mechanical proper-
ties, respectively [10Ϫ15]. Given the technological potential
of nanostructured coatings, a number of variations of physi-
cal vapor deposition (PVD) and chemical vapor deposition
(CVD) techniques have been used to deposit zirconium ox-
ide, nitride, carbide and carbonitride films [16Ϫ19].
Hexane
Et2NH ϩ BuLi
Ǟ Et NLi ϩ BuH
(1)
(2)
(3)
ᎏᎏᎏ
2
Toluene, THF
ᎏᎏᎏᎏᎏ
4 Et2NLi ϩ ZrCl4
Ǟ Zr(NEt ) ϩ 4 LiCl
2 4
Toluene
ᎏᎏᎏ
Zr(NEt2)4 ϩ 4tBuOH
Ǟ Zr(OtBu) ϩ 4 Et NH
4
2
Both the compounds were purified by distillation under reduced
pressure (Zr(NEt2)4: 80 °C/10Ϫ2 Torr; Zr(OtBu)4: 50 °C/10Ϫ2 Torr).
The NMR data (δ, ppm) corresponds to their possible monomeric
The CVD process based on the decomposition of ZrCl4
in the presence of oxygen (ZrO2), nitrogen (ZrN) or carbon
(ZrC) sources requires high temperatures for the chemical
reaction to occur, which restricts the choice of the substrate
materials. The deposition of these phases can be realized at
relatively low temperatures by using PVD techniques, how-
ever it is limited in terms of compositional homogeneity
and conformal coverage on complex geometries. In contrast
to the inorganic precursors (e.g., Zr(NO3)4, ZrX4 (X ϭ Cl,
I)) that generally exhibit low vapor pressure and strong
ionic bonding, the application of metal-organic precursors
in the CVD process is capable of providing uniform films
at reduced deposition temperatures due to the low binding
energy in metal-organic compounds [20]. The formation of
ZrO2 and Zr(C,N) from a variety of zirconium alkoxide and
amide derivatives, respectively has been investigated on sili-
con substrates by thermal or plasma enhanced CVD pro-
cesses [3, 21Ϫ25]. We report here on the low pressure CVD
of zirconium carbonitride and oxide phases from zir-
conium-tetrakis-diethylamide (Zr(NEt2)4) and -tert-bu-
tyloxide (Zr(OBut)4) precursors on steel substrates and the
characterization of the CVD deposits.
1
structures (1 and 3) in the solution (C6D6). Zr(NEt2)4: H NMR:
1.12 t CH3; 3.32 q, CH2. 13C NMR: 16.68, CH3; 43.04, CH2.
Zr(OtBu)4: 1H NMR: 1.31 s, CH3. 13C NMR: 32.47 CH3; 74.69
C(CH3)3.
Chemical Vapor Deposition
The gas-phase decomposition of the metal-organic precursors was
investigated on a cold-wall horizontal CVD reactor [20j] operating
under reduced pressure. The Fe substrate rests in the quartz reactor
on a graphite susceptor, which is heated inductively using a radio
frequency generator. The temperatures were monitored using a
thermocouple attached to the susceptor. The precursors (1:
Zr(NEt2)4, 2: (Zr(NEt2)4 ϩ HNEt2) and 3: Zr(OBut)4) were intro-
duced in the reactor through a glass flange by applying dynamic
vacuum (10Ϫ4 to 10Ϫ6 Torr) and maintaining the precursor reser-
voir at the appropriate temperature (50 °C for 1 and 40 °C for 2
and 3). The thermolysis products were removed through the pump-
ing end of the reactor that was connected to rotary vane and turbo
molecular vacuum pumps.
Experimental
Synthesis of Precursors
The synthesis of Zr(NEt2)4 (1) and Zr(OBut)4 (3) precursors and
further experimental manipulations were performed in a modified
Schlenk type vacuum assembly, taking stringent precautions
against atmospheric moisture. All solvents were purified by stand-
ard methods and stored over appropriate desiccating agents. Anhy-
drous ZrCl4 (Aldrich) was dried in vacuum (100 °C/10Ϫ2 Torr) to
Film Characterization
* Dr. habil. Sanjay Mathur
Leibniz-Institut für Neue Materialien
Im Stadtwald, Geb. 43A
D-66041 Saarbrücken/Germany
Tel: ϩ49-681-9300-274/338
Fax: ϩ49-681-9300-279
Surface morphology and elemental distribution in the films were
recorded on a scanning electron microscope JSM-6400F (JEOL)
coupled with an energy dispersive X-ray facility (EDX). The phase
characterization and texture analysis was done by powder X-ray
diffraction (XRD) analysis performed on a Siemens D-5000 dif-
E-mail: smathur@inm-gmbh.de
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2043

S. Mathur, J. Altmayer, H. Shen
˚
fractometer using Cu Kα (λ ϭ 1.54 A) radiation at room tempera-
ture. The XPS analysis was performed on a Surface Science Instru-
ment SSI-M-Probe using Al Kα radiation. The data were charge
referenced to C 1s peak at a binding energy of 284 eV.
Results and Discussion
Film Growth
The precursors, Zr(NEt2)4 and Zr(OBut)4, were chosen due
to their high vapour pressures, gas phase stability and the
presence of pre-formed Zr-O and Zr-N σ-bonds that should
favour the formation of ZrO2 and ZrN solid-state phases at
low processing temperatures. Moreover, the use of a single
molecular source in the CVD process simplifies the growth
parameters and allows a precise control over the phase,
composition and particle size in the deposits [20]. In ad-
dition to neat amide precursor, a mixture of Zr(NEt2)4 and
Et2NH (1:1, w/w) was also employed in order to obtain
nitrogen-rich deposits through a matrix assisted chemical
vapor deposition (MA-CVD). The three precursor systems
are denoted as Zr(NEt2)4 (1), Zr(NEt2)4 ϩ HNEt2 (2) and
Zr(OBut)4 (3), in the following text. The thermal decompo-
sition of the precursor systems was investigated in a cold-
wall CVD reactor described in our earlier publications [20].
The films obtained from 1 and 2 showed blue, yellowish
brown or gold colour depending upon the deposition tem-
perature whereas the coatings produced using 3 were grey.
Figure 1 XRD patterns (Cu Kα) of Zr-C-N films obtained from 1
and 2 at 550 °C.
Phase Identification and Composition
The X-ray diffraction profiles (Fig. 1) of films deposited
using 1 and 2 on steel substrates showed broad peaks in-
dicative of small particle size and/or poor crystallinity of
the coatings in the temperature range 550-750 °C. The ob-
served diffraction patterns correspond to the reported data
for cubic zirconium carbonitride phase with highest inten-
sity observed in our samples for the (111) peak [29]. The
energy dispersive X-ray (EDX) analysis of the films ob-
tained by the CVD of both 1 and 2 showed the presence of
Zr, C, N and significant amount of O. The X-ray photoelec-
tron spectra (Fig. 2) of the as-deposited film (from 1)
showed the presence of Zr, C and O with a small amount
of N. The elemental composition determined after Arϩ
sputtering performed to remove the oxidized surface, re-
veals higher nitrogen content in the film demonstrating the
surface oxidation of the films. However, the films contained
even after sputtering significant amount of oxygen, which
indicates that the oxidation zone is larger in ZrN films de-
posited on steel [9, 14]. The presence of carbon even after
several sputtering steps rules out its presence as organic
residue and suggests the formation of a carbonitride phase
(Zr-C-N) [30]. The similar values of lattice parameters for
cubic ZrC (469 pm), ZrN (458 pm) and Zr(CxNy) (459 pm
for x ϭ y) phases prevent an unambiguous determination
of stoichiometry and phase identification. Since the precur-
sor did not possess Zr-C bonds, the formation of pure ZrC
Figure 2 XPS overview spectra of Zr-C-N (derived from 1 and 2)
and ZrO2 films (3) deposited at 550 °C.
phase is less probable, particularly in view of the rather low
deposition temperatures. It is more likely that the presence
of N-C units in the amide groups favours the formation of
carbonitride composition as also suggested by the XRD
and XPS studies (Figs. 1 and 2). This is confirmed by the
observed chemical shift of C1s in the XPS spectra (285 eV)
while the peak corresponding to the zirconium carbide
phase is expected at ϳ 282 eV [6]. As expected, the ZrO2
films contain only minor amount of residual carbon in the
films (Fig. 2), which was found to be present mainly on the
film surface.
Given the fact that the precursor is devoid of oxygen and
the films were grown under low pressure conditions, the
oxygen mainly originate from an ex situ surface oxidation
of the film that is likely due to the weaker Zr-N bonds and
the higher reactivity of nanostructured surface towards at-
mospheric oxygen. The replacement of nitrogen by oxygen
or incorporation of additional oxygen is visible in the col-
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Nanostructured ZrO2 and Zr-C-N Coatings from Chemical Vapor Deposition
(a)
our change from blue (as deposited) to brownish yellow
(after 48 h). This stoichiometric variation influences the free
electron concentration of the metal (Zr) that is responsible
for the reflectivity and colour of nitride films [14]. It has
been shown that the degree of oxidation is restricted to a
few monolayers on Si substrates, whereas the oxidation
zone is much deeper in the case of Fe substrates [9] as found
in this study (vide supra). The higher affinity of zirconium
towards oxygen is a well-known limitation in the fabrication
of nitride films, and it has been demonstrated [31] that reac-
tive sputtering of metallic zirconium in N2-O2 atmosphere
with a nitrogen content of 80 % produced pure films of
monoclinic ZrO2. According to thermodynamic consider-
ations, these observations are supported by the higher
Gibbs free energy for ZrO2 (ϳ Ϫ1020 kJ/mol) when com-
pared to ZrN (ϳ Ϫ315 kJ/mol) which makes ZrO2 more
stable under standard conditions.
(b)
The presence of an additional nitrogen source in 2 (in the
Figure 3 SEM images of Zr-C-N films deposited from (a) 1 and
(b) 2.
form of free Et2NH) was employed to obtain N-rich films
and to reduce the incorporation of carbon. As expected, the
partial pressure of diethyl amine produced coatings with
increased N content and reduced carbon percentage (Fig.
2). Further, the films deposited using Zr(NEt2)4ϩEt2NH
precursor system were stable towards oxidation (no evident
colour change) and showed visibly better reflectivity. How-
ever the X-ray diffractograms of the films deposited at 550,
650 and 750 °C exhibit patterns similar to those observed
for films deposited using 1 as precursor, which shows
that phase composition did not change significantly, and
zirconium carbonitride composition is also present in the
film obtained from 2. Although oxygen is evident in the
XPS analysis, the formation of an oxide overlayer is not
indicated in the X-ray diffraction patterns of the films. It is
possible that the oxidized overlayer in the Zr-C-N films do
not have a definite structure.
Figure 4 (a-c) In-plane SEM images of ZrO2 obtained at 450, 550
and 650 °C. (d) Cross-sectional SEM image of a ZrO2 film on iron
substrate (at 650 °C).
Morphology and Microstructure
The Zr-C-N films obtained using 1 and 2 exhibited a granu-
lar morphology made up of spherical particles of nano-
metric dimensions. The deposition temperature did not
show any remarkable change in the morphological features,
in both cases. The high-resolution scanning electron
micrographs (Fig. 3) of the Zr-C-N films show a smooth
surface for the films obtained from 1, whereas a nanostruc-
tured surface is observed in the case of 2. In contrary to
the Zr-C-N films, the ZrO2 films exhibited characteristic
morphology (Fig. 4) at different temperatures (350-650 °C).
For instance, the film deposited at 450 °C shows a dense
microstructure formed by cross-linked elongated grains
(Fig. 4a). At higher deposition temperatures (550 and
650 °C), the grains exhibit a facetted morphology (Fig. 4b
and c). The observed morphology change is also associated
with a structural change as shown by the X-ray diffraction
studies of these films (see later). The cross-sectional SEM
image (Fig. 4d) of a ZrO2 film (at 650°C) showed a dense
and columnar microstructure.
The as-obtained ZrO2 deposits were crystalline in the
temperature range 350-650 °C (Fig. 5). The X-ray diffrac-
tion pattern of the film deposited at 350 °C revealed a nan-
ocrystalline deposit of tetragonal (t) ZrO2. The average
grain size calculated from the X-ray diffraction data
(Scherrer Formula) was found to be 6 nm. At 450 °C, both
monoclinic (m) and t-ZrO2 phases coexist indicating a tem-
perature dependent t-to-m phase transformation. At higher
deposition temperatures (550 and 650 °C), the phase tran-
sition is complete and only monophasic m-ZrO2 is ob-
tained. Although tetragonal phase is a high temperature
phase among the ZrO2 phases (monoclininc: stable up to
1205 °C; tetragonal: 1205-2377 °C and cubic: 2377 to the
melting point at 2710 °C), its preferred formation at 450 °C
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S. Mathur, J. Altmayer, H. Shen
(a)
(b)
(c)
Figure 5 XRD patterns (Cu Kα) of ZrO2 films deposited at 350,
450, 550 and 650 °C.
can be due to the lower surface energy of nanocrystalline t-
ZrO2. This was proposed by Garvie [32] who predicted that
ZrO2 particles with a critical size (< 10 nm) can be stabil-
ized in the tetragonal form whereas particles larger than the
critical size would undergo t-to-m transformation. This has
been recently confirmed by Chraska et al. [33] using a sim-
ple thermodynamic model that suggests that even larger
grains could be stable as tetragonal if they directly nucleate
in the tetragonal modification. The analysis of the XRD
data of the CVD deposits obtained at higher temperatures
(> 450 °C) suggests that ZrO2 nucleates on the substrate
surface in the tetragonal phase but transforms gradually to
monoclinic phase presumably due to increasing grain size.
The primary nuclei formed in the CVD process rapidly
grow through different phenomena such as coalescence and
adsorption of new adatoms on the existing nuclei, which
can be governed by the substrate temperature and gas phase
supersaturation. The intensity of observed peaks and ab-
sence of other reflections in XRD patterns suggest a pre-
ferred growth orientation for the grains. This texture effect
can be discerned from the scanning electron micrographs of
the ZrO2 films (Fig. 4).
Figure 6 SEM images of scratch traces performed on Zr-C-N ((a)
1 and (b) 2) and (c) ZrO2 films.
Microhardness and Adhesion Test
Figure 7 Hardness of Zr-C-N (1 and 2) and ZrO2 films deposited
at 550 °C.
The adhesion of the coatings was investigated using a dia-
mond indenter (radius, 2 µm) that was pressed in the film
with a given vertical load (Fz) and moved on the surface
in a horizontal direction. The vertical load was gradually
increased to enhance the horizontal friction drag (Fy) up to
a critical load value (Lc) where the coating will be removed.
The Lc values for the Zr-C-N films obtained at 550 °C from
1 (0.08 N) and 2 (0.1 N) suggest that the adhesion of films
obtained from 2 is better than that obtained from 1. The
scanning electron micrographs (Fig. 6) of the scratch re-
gions for the films obtained from 1, 2 and 3 reveal that the
films do not show characteristic spalling typically observed
in ceramic films. Apparently, small amount of pyrolytic car-
bon is also present in the film that leads to an enhanced
plasticity at the expense of hardness [34]. Indeed, the micro-
hardness (Hk) values for the Zr-C-N films (Fig. 7) obtained
by the CVD of 2 at 550, 650 and 750 °C show a gradual
decrease with Hk values of 5.65, 3.68 and 2.11 GPa, respec-
tively. It can be envisaged that higher deposition tempera-
tures promotes the decomposition of amine molecules in
the gas phase resulting in a higher incorporation of residual
carbon in the films, which can lower the hardness values
[34]. The Hk value of 4.98 GPa in the films obtained by the
CVD of 1 at 550 °C was lower than the hardness value in
films deposited at same temperature using 2 as precursor.
This lowering in Hk value can be ascribed to the stronger
oxidation of the films obtained from 1. Further studies, re-
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Z. Anorg. Allg. Chem. 2004, 630, 2042Ϫ2048

Nanostructured ZrO2 and Zr-C-N Coatings from Chemical Vapor Deposition
acknowledges Prof. H. Schmidt for providing the necessary infra-
quired to validate these findings, are currently underway.
The Hk value of a ZrO2 film deposited at 550 °C was found
to be 4.64 GPa (Fig. 7). The scratch test results on ZrO2
films deposited at 550 °C showed the films to be strongly
adherent to the substrate (Lc ϭ 0.1 N).
structure facilities. This study was supported in part by the NATO-
CLG Program (No. 979756). Thanks are also due to the German
Science Foundation (DFG) for supporting this work in the frame
of the priority program on nanomaterials Ϫ Sonderforschungsbe-
reich 277 Ϫ operating at the Saarland University, Saarbrücken,
Germany.
Conclusions
References
Zirconium carbonitride (Zr-C-N) and zirconium oxide
(ZrO2) films were deposited using Zr(NEt2)4 and Zr(OBut)4
precursors, respectively in a low pressure cold wall CVD
reactor. The Zr-C-N films obtained using pure Zr(NEt2)4
easily oxidize under ambient conditions. The atmosphere
oxidation is accompanied by a change in the colour of as-
deposited films. The XPS analysis revealed a strong incor-
poration of oxygen at the surface, which is associated with
lowering of nitrogen content in the surface layers. A
decreasing oxygen concentration is observed away from the
film surface but still significant amount of oxygen was
found in the film bulk. In order to obtain N-rich films,
Zr(NEt2)4 was mixed with Et2NH and used in the CVD
process. The bronze-coloured films obtained from this pre-
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oxygen content, although the overall phase composition
and morphology did not show any considerable change.
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temperatures (450-650 °C) whereas the precursor flux influ-
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(10 nm) beyond which transformation to monoclinic phase
occurs. This was supported by the XRD analysis of films
deposited at 550 and 650 °C, which revealed monophasic
m-ZrO2 with average particle sizes of 34 and 40 nm, respec-
tively.
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