structural and ion beam analysis of reactive magnetron …ieomsociety.org/dc2018/papers/124.pdf ·...

Proceedings of the International Conference on Industrial Engineering and Operations Management Washington DC, USA, September 27-29, 2018

© IEOM Society International

Structural and Ion Beam Analysis of Reactive Magnetron Sputtered Titanium Oxynitride Thin Films

Emmanuel Ajenifuja1, 2, 3*, Abimbola P. I. Popoola1, Olawale Popoola2 1Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology,

Pretoria, South Africa. 2Centre for Energy and Electric Power, Tshwane University of Technology, Pretoria, South Africa.

3Center for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria. [email protected], [email protected], [email protected]

Abstract

TiOxNy may combine the advantages of titanium oxides and nitrides in optimal conditions. Due to their physical and chemical versatility, titanium oxynitrides are gaining relevance in numerous applications such as optoelectronics, tribology and catalysis. In this study, titanium oxynitride thin film samples were grown at low sputtering pressure (1.07 Pa) on sodalime glass substrates using 99.99 % purity titanium target with argon working gas, pure nitrogen, background residual oxygen and constant sputtering power of 200 W. While other parameters were fixed at the optimum values, the deposition time was varied from 5 and 25minutes. Rutherford backscattering (RBS) spectrometry was used to determine the stoichiometry and areal density of the films. X-ray diffractometry (XRD) and optical microscopy were used to study the structural and microstructural characteristics of the films. Variations in the elemental concentrations of the films with respect to the N/O ratio were observed based on the thickness and deposition time. Diffraction analysis indicated enhancement in crystallinity of the film with thickness, as shown from the changes in peak intensities at the preferred crystallographic orientation. Stoichiometric results showed transition of the TiNx-Oy thin films from non-metallic oxide (TiOxNy) to metallic nitride (Ti2N) characteristics with increase in N/Ti and N/O ratios.

Keywords Titanium oxynitride; residual oxygen; IBA-RBS; areal density; sputtering pressure

287

mailto:[email protected]





1.0 Introduction Strong interests in transition metal nitrides and oxynitrides are maintained due to their structural uniqueness and

various applications in microelectronics, nanophotonics, corrosion and tribology. Recently, metal oxynitrides have as

well shown great promise in the area of catalysis, especially in water splitting processes, mainly for the liberation of

hydrogen from water. Its catalysis usage is in the direction of providing clean and renewable energy, which is arguably

the most important challenge facing humanity at the moment. As a functional material, metal oxy-nitrides are more

popular due to their physical and chemical adaptability (Shima et al., 1999; Moura et al., 2006; Ludtke et al., 2014).

They are special group of materials that may combine the advantages of oxides and nitrides in optimal conditions, and

recent studies have shown its usefulness in uv-visible light induced photocatalysis such as splitting of water into its

components of hydrogen and oxygen for clean energy generation. In addition, transition-metal oxynitrides have good

electrical conductivities and corrosion resistance, which makes them well suited for catalytic applications. Generally,

oxynitride stabilities in air and moisture are greater than those of the pure nitrides, but with smaller band gaps than

those of comparable oxides. This leads to useful optoelectronic properties. Metal oxinitrides are synthesized as thin

films (Ludtke et al., 2014; Suzuki et al., 2014) and nanoparticles (Armytage & Fender, 1974; Fuertes, 2006; Hitoki et

al., 2002; Zhang et al., 2014), depending on preparatory technique and the targeted aplication (Orhan et al., 2002; Gao

et al., 2011; Schilling et al., 2007).

Titanium oxynitride as a form of transition-metal oxynitrides is prepared using different techniques such as reactive

sputtering, metal evaporation, vapour deposition, and wet chemical reaction (Rawal et al., 2013; Ajenifuja et al., 2012;

Vaz et al., 2003; Miura et al., 2016; Hovish & Dauskardt, 2016). However, meeting the required stoichiometric

composition in titanium oxynitride thin films is a common challenge (Kazemeini et al., 2000; Trapalis et al., 2007;

Graciani et al., 2007; Braic et al., 2017). Mostly, the strategy is directed towards controlling the nitrogen-oxygen ratio

in the oxynitride system, in order to achieve the required optical and structural properties. Relating to the foregoing,

titanium oxynitride compounds have been shown to possess structure with intermediate properties between metallic

TiNx and insulating TiO2 (Chappe et al., 2006; Rizzo et al., 2009; Braic et al., 2017). Sputtering has shown to be most

resilient technique for film preparations, due to its versatility, controllability and flexibilty. In sputtering, TiOx-Ny is

formed from reactive mixture of nitrogen and oxygen ions in a vacuum chamber containing the titanium target.

Different methods have been used to initiate proper nitrogen-oxygen content in oxynitride films (Martin et al., 2001;

Vaz et al., 2003; Mohamed et al., 2004; Chappe et al., 2006; Rawal et al., 2013). With proper parameter optimization,

TiOx-Ny thin films with different structural and compositional profiles have been synthesized. Braic et al., (2017) and

Hovish and Dauskardt (2016) synthesized TiOxNy and TaOxNy with varied physical properties using vacuum residual

oxygen and atmospheric plasma respectively. More understanding on the use of non-conventional sources of reactive

gases, such as residual oxygen and atmospheric plasma for TiOxNy preparations, and their effect on the film properties

are still desirable. In this work, an optimum vacuum condition with nitrogen and residual oxygen content was utilized

to prepare TiOxNy at varying deposition time. The report is presented on the relationship between the stoichiometric

changes, film thickness and sputtering time based on the vacuum nitrogen-residual oxygen reactive process.

Rutherford backscattering spectroscopy (RBS) was used to determine the thickness and the stoichiometric changes in

288



the sputtered TiOxNy films. The structural changes in the film in relation to the thickness and composition was obtained

through diffraction analysis.

2.0 Materials and Methods TiOxNy thin films on sodalime glass substrates were prepared by reactive magnetron sputtering. A stainless-steel

chamber was evacuated with turbo-molecular pump and a mechanical pump. The chamber was pump down to a

residual vacuum close to 1.33E-3 Pa, before the release of the argon and nitrogen. The substrates were cut into the

required sizes and cleaned successively with the following; methanol, acetone, de-ionized water and finally 20%

HNO3. For plasma generation, high purity argon atmosphere was used and the sputtering target was a 99.99% pure Ti

disc (5 mm thick and of 50.8 mm diameter) positioned at an angle of about 45º relative to the static substrate platform.

Pre-sputtering cleaning for Ti target was carried out in a pure argon, with the shutter placed to shield the substrates

from plasma flow. Thereafter high purity nitrogen gas was released into the chamber to initiate reaction with the

residual oxygen. The deposition parameters used for the preparation are shown in Table 1. The films were left to cool

in the chamber before removal to avoid extraneous oxidation.

Ion beam analysis of the sputtered samples was done using NEC 5SDH 1.7 MeV Pelletron Tandem Accelerator,

equipped with an RF charge exchange ion source to provide proton and helium ions. The measurement using the

Rutherford backscattering spectrometry was performed using the 4He+ ion beam and the incident energy was 2.2 MeV

with the detector energy resolution of 12.0 KeV. The RBS spectra were obtained and the data was used to determine

the stoichiometry, thickness and compositional depth profile of the films using SIMNRA (6.06) analysis software.

The x-ray diffraction analysis was carried out with MD-10 Precision X-Ray Diffractometer. The samples were scanned

at 2θº between 16º and 72º with CuKα radiation, while Profex, an x-ray diffraction analysis software was used to

analyze and determine the crystallographic parameters (Döbelin & Kleeberg, 2015). Optical microscope was used to

study the surface morphology and the microstructure of the films.

Table 1: Sputtering parameters for TiOxNy thin films on glass substrates

Sputtering gas Reactive gases Power (W) Time (min) Base Press. (Pa) Sputtering Press. (Pa) Argon Nitrogen, Oxygen 200 5 - 25 1.33 E-3 1.07

3.0 Results and Discussions

3.1 Ion Beam Analysis The RBS spectra obtained by using 2.2 MeV 4He+ ions are shown in Figs. 1(a) – (e), they were analyzed using the

SIMNRA 6.06 code (Mayer, 2006; Adeoye et al., 2015). Rutherford backscattering method simultaneously provides

information about the stoichiometry, thickness and the areal density of the films. SIMNRA software was used to fit

the simulation over experimental data and give information regarding the stoichiometric compositions and thickness

of the samples. Both the heavy element Ti, and the light elements (N and O) were detected via the backscattering

process, and it is observed that the samples deposited at lowest sputtering time contained highest amount of oxygen.

Due to the lightness of nitrogen and oxygen compared to the incident ion energy (2.2 MeV 4He+), the signal from them

were not as well resolved as that coming from the heavier Ti element. The film thickness was obtained in RBS unit

(1015 atoms/cm2), and the effective composition of the films at different time are given in Table 1. The presence of

289



oxygen in the film was also visually observed from the dark blue colour, characteristic of titanium oxynitride, while

the variations in colour of the films could be noticed in relation to the sputtering time. The colour observation is in

order with recent studies (Naik et al., 2012; Ajenifuja et al., 2016; Braic et al., 2017). Braic et al. (2017) studied the

effect of the level of background residual oxygen on the optical properties of the sputtered titanium oxynitride thin

films. It was shown that TiOxNy samples deposited under high residual oxygen level showed non-metallic (TiO2)

behaviour, while the films deposited when the level of residual oxygen in the background vacuum was low exhibited

metallic (TiN) behaviour. In the present study, since the sputtering chamber was maintained at a relatively low working

pressure, which correspond to lower nitrogen fractional flow. It was observed that the films deposited at lower

sputtering time contained relatively higher amount of oxygen that those films sputtered at longer time, which indicated

higher vacuum residual oxygen at the onset of sputtering. Hence, it was shown that the films prepared at deposition

time of 25 minutes contained negligible amount of oxygen. The thickness (in RBS unit) and chemical composition

results for the deposited TiOxNy films are shown in Table 2. Studies on sputtering of metal nitride and oxynitrides

showed that the most active material at very low sputtering pressure is the ionized metal target atoms (Mao et al.,

2001; Ajenifuja et al., 2016; Braic et al., 2017). Increase in sputtering pressure caused an increase in the fractional

flow of nitrogen, which usually result in decrease in target emission (Mao et al., 2001; Gao et al., 2011; Nirupama et

al., 2010; Ji-Cheng et al., 2009). Specifically, the fixed low sputtering pressure (1.07 Pa) adopted for this experiment

corresponds to the intermediate working pressure with background residual oxygen present in the chamber. From the

stoichiometry of the films, it is observed that titanium ions initially dominated the sputtering chamber. Normally, in

order to increase the content of nitrogen, the fractional flow needs to be increased against the fixed residual oxygen

(Ajenifuja et al., 2016; Ajenifuja et al., 2018). Findings have indicated that the degree of filling of the non-metallic

sub lattice of the nitride increases linearly as the nitrogen content rises, and that is why, time and partial nitrogen

pressure affect the nitrogen content, and usually determine the composition of the nitride film (Fedirko & Pohrelyuk,

1995; Mao et al., 2001; Pohrelyuk et al., 2009). However, as the sputtering time increases, the flow of nitrogen and

its emission intensity improves, while the residual oxygen content diminished in the chamber. It has been shown that

variation of the sputtering time induces changes to the particle fluxes impacting on the substrate surface and it affects

the chemical composition of the films (Roth et al., 1995; Ajenifuja et al., 2018). In this study, as the deposition time

increases, there is a corresponding increase in N2 emission in the plasma. The profile showing the relationship between

the elemental constituents of the film in relation to the thickness is given in Fig. 3. It can be seen that as thickness

increases, the oxygen composition in the films becomes diminished. Hence negligible amount of oxygen was detected

in film deposited at 25 minutes. It indicated that, sputtering time did not only affect the thickness, but also the chemical

composition of the films.

290



Figure 1: RBS Spectra for the TiOxNy on sodalime glass substrates (a) GLS, (b) TON-GL5, (c) TON-GL10, (d) TON-GL15, (e) TON-GL20, (f) TON-GL25

291



Table 2: Elemental composition and RBS thickness values of the film on sodalime glass substrates

Sample Deposition Time (mins) RBS (1015 atoms/cm2) Ti N O TON-GL5 5 655.085 0.735 0.143 0.122

TON-GL10 10 930.729 0.723 0.204 0.073 TON-GL15 15 1547.253 0.693 0.255 0.052 TON-GL20 20 2607.366 0.660 0.328 0.012 TON-GL25 25 3103.178 0.652 0.337 0.011

Figure 2: Change in composition of the TiNx film constituents with thickness

3.2 X-Ray Diffraction Analysis The structural details of the magnetron sputtered TiOxNy thin films on sodalime glass at varied times of deposition,

but at a fixed low sputtering pressure in a mixture of argon, nitrogen and the vacuum residual oxygen are shown in

Fig. 3. The XRD parameter values obtained for the films are presented in Table 3. It is shown from the spectra that

relatively thin TiOxNy films sputtered at 5 and 10 minutes barely exhibit any form of crystallinity. Meanwhile, as the

thickness increase, the crystallinity of the films increases remarkably, thus exhibit well resolved peak at intermediate

2θº region (40.17 - 40.41º) corresponding to the plane (111), which is attributed to Ti phase (Glavatskikh & Gorshkov,

1992). It is shown from the sputtered films spectra intensities that (111) is the preferred orientation. A slight shift of

the peaks towards higher 2θº with increase in the film thickness is observed, which is most likely due to the change in

structural properties. This is in agreement with earlier studies which showed that titanium oxynitride films sputtered

at different levels of vacuum residual oxygen exhibited properties ranging from non-metallic (oxide) to metallic (TiN)

nature (Braic et al., 2017). In this work, vacuum residual oxygen level linearly reduces with sputtering time, and thus

influenced the sputtered TiOxNy stoichiometry. In all samples, except TON-GL5, a crystalline phase with (111)

reflection attributed to Ti is the only observable phase. Increase in the films Ti phase crystallization with thickness

could also be linked to packing rearrangement of the impinging particles as they grew farther away from the influence

of the amorphous glass substrate. It is known that substrates do have strong influence on the structural properties of

thin films. The film crystallinity increases could also be related with the oxygen reduction in the film stoichiometry.

292



In addition, it is observed that all the spectra obtained show a broad or diffused peak at the lower 2 theta region (15 -

35º), which might be an indication of an amorphous or nanostructure TiO2 presence. In related studies, similar broad

peaks have been observed for TiO2 nanostructures at low 2θº range, and sharp peak (s) in range assigned to (110)

plane (Tang et al., 2009; Wu et al., 2002; Ranjitha et al., 2013). In line with the RBS results and in agreement with

previous studies, there is an initial formations of TiOxNy reminiscent of non-metallic TiO2 before transition to the

metallic-natured crystalline TiNx-Oy, which is more of mixture of TiNx and Ti phases (Braic et al., 2017; Ajenifuja et

al., 2018). In this study, sputtering time have strong influence on the residual oxygen, nitrogen partial pressure and

sputtering mode, which have resultant effects on the film thickness, stoichiometry and structure as observed (Ajenifuja

et al., 2016; Chandra et al., 2005). The sputtering pressure and time adopted remarkably favours the films transition

from oxide-like TiOxNy to Ti2N with metallic behaviour (Ajenifuja et al., 2012; Ajenifuja et al., 2016; Braic et al.,

2017).

Table 3: XRD parameters for the sputtered TiOxNy thin films

Sample Interplanar spacing, d(Å) Lattice parameters, a, c (Å) Orientation angle (2θº) TON-GL5 2.240 2.950 4.681 40.330 TON-GL10 2.281 3.002 4.725 40.411 TON-GL15 2.222 2.920 4.661 40.345 TON-GL20 2.302 3.061 4.648 40.171 TON-GL25 2.238 2.934 4.729 40.273

Figure 3: XRD Spectra for the TiOxNy films on sodalime glass substrates at different thickness

293



3.3 Microstructural Analysis Photomicrographs of the film samples at different thicknesses are shown in Figs. 4(a) to (d), representing TON-10 to

TON-25 respectively. The images for samples deposited at lower deposition time, with relatively lower thickness are

shown to be constituted of dispersed particles on the dense background. The grains are believed to be from coalescence

of smaller particle and are evenly distributed on the substrates. Based on studies, at low sputtering pressure, the

sputtered ions possess high mean free path, and thus impinge on the substrate with high kinetic energy which improves

surface agglomeration. Since the sputtering time is increased from one sample to the other, without influencing other

process parameters. Steady increase in the film thickness was obtained, which was as a result of buildup of the larger

grains which makes up the superstructure. Meanwhile, with increase in the sputtering time, a differentiable changes

are observed in the surface morphologies, in terms of micro-particle distribution and population. For example sample

TON-10 consists of highly dispersed globular particles, which is a bit similar to TON-15 shown in Fig. 4(b). For all

the films being sputtered at low pressure, the mean free path of the particles would remain nearly constant in all the

experiments, but the particles accumulation changed with time. Therefore, a linear increase in thickness is shown, but

with changes in the films composition. Due to the instrumental limitation of the microscope, it is not possible to see

beyond the very topmost morphology of most of the samples, hence, an initial formation of first relatively smooth

layer is assumed and then gradual accumulation of the granular crystallites. The main differences identified between

the films based on thickness are the appearance of particles and surface uniformity, such that thicker films

microstructure appears closely parked.

Figure 4: Optical micrograph of the films on glass substrates (a) TON-10, (b) TON-15, (c) TON-20 and (d) TON-25

294



Conclusions

TiOxNy thin films of thickness ranging from 655.085 to 3103.178 x 1015 atoms/cm2 were sputtered on sodalime glass

substrates at relatively low sputtering in the presence of nitrogen and vacuum residual oxygen as reactive gases. With

ion beam analysis, the film thickness and stoichiometry was determined. The lattice parameters, interplanar spacing

and film crystallinity were observed to change with thickness and sputtering time. Meanwhile, sputtered film images

showed evolution in microstructural properties. For relatively thin samples deposited at 5 and 10 minutes, no distinct

crystallographic peak was detected, however, as the thickness increases, the film exhibited strong reflections

corresponding to (111) planar orientation, which as attributed to hexagonal titanium phase. With consistency in the

observed reflection intensity with film thickness, it indicates that it is the preferred orientation for the phase. It is

shown that sputtering time have a strong influence on the residual oxygen, nitrogen partial pressure and sputtering

mode. Hence, the fixed sputtering pressure and the varied time adopted remarkably favours the films transition from

oxide TiOxNy to metallic Ti2N. With proper sputtering time and pressure control, the vacuum residual oxygen was

utilized in a Ti-N system to prepared TiOxNy thin films with different physical and chemical properties.

Acknowledgements The authors acknowledges the support of the following: The World Academy of Science (TWAS) in collaboration with National Research Foundation (NRF), South Africa., and Center for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria. References Adeoye, A. E., Ajenifuja, E., Taleatu, B. A., & Fasasi, Y. A., Rutherford Backscattering

Spectrometry Analysis and Structural Properties of Zn𝑥𝑥Pb1−𝑥𝑥S Thin Films Deposited by Chemical Spray Pyrolysis. Journal of Materials, vol. 2015, pp. 8, 2015.

Ajenifuja, E., Fasasi, A. Y., & Osinkolu, G. A., Sputtering-Pressure Dependent Optical and Microstructural Properties Variations in DC Reactive Magnetron Sputtered Titanium Nitride Thin Films. Transactions of the Indian Ceramic Society, vol. 71(4), pp. 181-188, 2012.

Ajenifuja, E., Osinkolu, G. A., Fasasi, A. Y., Pelemo, D. A., & Obiajunwa, E. I., Rutherford backscattering spectroscopy and structural analysis of DC reactive magnetron sputtered titanium nitride thin films on glass substrates. J Mater Sci: Mater Electron, vol. 27, pp. 335, 2012.

Ajenifuja, E., Popoola, A. P., & Popoola, O., Thickness Dependent Chemical and Microstructural Properties of DC Reactive Magnetron Sputtered Titanium Nitride Thin Films on Low Carbon Steel Cross-section. Journal of Material Research and Technology. In Press, 2018.

Armytage, D., & Fender, B. E., Anion ordering in TaON: A powder neutron diffraction investigation. Acta Crystallogr. Sect. B: Struct. Crystallogr. Cryst. Chem., vol. 30, pp. 809, 1974.

Braic, L., Vasilantonakis, N., Mihai, A., Villar-Garcia, I. J., Fearn, S., Zou, B., . . . Petrov, P. K., Titanium oxynitride thin films with tuneable double epsilon-near-zero behaviour for nanophotonic applications. Appl. Mater. Interfaces, vol. 9(35), pp. 29857–29862, 2017.

Chandra, R., Chawla, A. K., Kaur, D., & Ayyub, P., Structural, Optical and electronic properties of nanocrystalline TiN films. Nanotechnology, vol. 16, pp. 3053–6, 20005.

295



Chappe, J. M., Gavoille, J., Martin, N., Lintymer, J., & Takadoum, J., Water as reactive gas to prepare titanium oxynitride thin films by reactive sputtering. J. Mater. Sci., vol. 41, pp. 5639, 2006.

Döbelin, N., & Kleeberg, R., Profex: a graphical user interface for the Rietveld refinement program BGMN. Journal of Applied Crystallography, vol. 48, pp. 1573-1580, 2015.

Fedirko, V. M., & Pohrelyuk, I. M., Nitriding of Titanium and its Alloys. Kiev: Naukova Dumka, 1995.

Fuertes, A., Prediction of Anion Distributions Using Pauling's Second Rule. Inorg. Chem., vol. 45, pp. 9640, 2006.

Gao, Q., Giordano, C., & Antonietti, M., Controlled synthesis of tantalum oxynitride and nitride nanoparticles. Small, vol. 7, pp. 3334, 2011.

Glavatskikh, S. F., & Gorshkov, A. I., Natural analog of alpha-titanium in the exhalation products of the Great Tolbachik Fissure Eruption (Kamchatka). Doklady Akademii Nauk SSSR, vol. 327, pp. 123 - 127, 1992.

Graciani, J., Fdez Sanz, J., asaki, T., Nakamura, K., & Rodriguez, J., Interaction of Oxygen With Ti N (001): N/O Exchange and Oxidation . Process. J. Chem. Phys., vol. 126, pp. 244713, 2007.

Hitoki, G., Takata, T., Kondo, J. N., Hara, M., Kobayashiand, H., & Domen, K., An oxynitride, TaON, as an efficient water oxidation photocatalyst under visible light irradiation (λ≤ 500 nm). Chem. Commun., vol. 34 pp. 1968, 2002.

Hovish, M. Q., & Dauskardt, R. H., Optical properties of metal oxynitride thin flms grown with atmospheric plasma deposition. J. Phys. D: Appl. Phys., vol. 49, pp. 7, 2016.

Ji-Cheng, Z., Di-Tian, L., You-Zhen, L., & Zheng, L., Effect of sputtering pressure and rapid thermal annealing on optical properties of Ta2O5 thin films. Trans. Nonferrous Met. Soc. China, vol. 19, pp. 359-363, 2009.

Kazemeini, M. H., Berezin, A. A., & Fukuhara, N., Formation of thin TiNxOy films by using a hollow cathode reactive DC sputtering system. Thin Solid Films, vol. 70, 372, 2000.

Ludtke, T., Schmidt, A., Gobel, C., Fischer, A., Becker, N., Reimann, C., . . . Lerch, M., Synthesis and crystal structure of δ-TaON, a metastable polymorph of tantalum oxide nitride. Inorg. Chem., vol. 53, 11691, 2014.

Mao, D., Tao, K., & Hopwood, J., Ionized physical vapour deposition of titanium nitride: plasma and film characterization. J. Vac. Sci. Technol. A, vol. 20 (2), pp. 379–387, 2001.

Martin, N., Banakh, O., Santo, A. M., Springer, S., Sanjines, R., Takadoum, J., & Levy, F., Correlation between processing and properties of TiOxNy thin films sputter deposited by the reactive gas pulsing technique. Appl. Surf. Sci., vol. 185, pp. 123–133, 2001.

Mayer, M., SIMNRA version 6.06. Max-Planck-Institut fur Plasmaphysik . Garching, Germany: Max-Planck-Institut fur Plasmaphysik . Retrieved from www.rzg.mpg.de/~mam, 2006.

Miura, A., Rosero-Navarro, C., Masubuchi, Y., Higuchi, M., Kikkawa, S., & Tadanaga, K., Nitrogen-Rich Manganese Oxynitrides with Enhanced Catalytic Activity in the Oxygen Reduction Reaction. Angew. Chem. Int. Ed., vol. 55, pp. 7963 –7967, 2016.

Mohamed, S. H., Kappertz, O., Niemeier, T., Drese, R., Wakkad, M. M., & Wuttig, M., Effect of heat treatment on structural, optical and mechanical properties of sputtered TiOxNy films. Thin Solid Films, vol. 468, pp. 48–56, 2004.

Moura, C., Carvalho, P., Vaz, F., Cunha, L., & Alves, E., Raman Spectra and Structural Analysis in ZrOxNy Thin Films . Thin Solid Films, vol. 515, pp. 1132, 2006.

296



Naik, G. V., Schroeder, J. L., Ni, X., Kildishev, A. V., Sands, T. D., & Boltasseva, A., Titanium Nitride as A Plasmonic Material for Visible and Near-infrared Wavelengths. Opt. Mater. Express, vol. 2, pp. 478-489, 2012.

Nirupama, V., Gunasekhar, B., Sreedhar, B., Effect of oxygen partial pressure on the structural and optical properties of dc reactive magnetron sputtered molybdenum oxide films. Curr. Appl. Phys., vol. 10, pp. 272-278, 2010.

Orhan, E., Tessier, F., & Marchand, R., Synthesis and energetics of yellow TaON. Solid State Sci., vol. 4, pp. 1071, 2002.

Pohrelyuk, I. M., Fedirko, V. M., Yas’kiv, O. I., Lee, D.-B., Tkachuk, O. V., & Li, C.,. Influence of the nonstoichiometry of titanium nitride TiNx on the degree of its modification with oxygen. Materials Science, vol. 45(4), 2009.

Ranjitha, A., Muthukumarasamy, N., Thambidurai, M., Balasundaraprabhu, R., & Agilan, S., Effect of annealing temperature on nanocrystalline TiO2 thin films prepared by sol–gel dip coating method. Optik - International Journal for Light and Electron Optics, vol. 124(23), pp. 6201 - 6204, 2013.

Rawal, S. K., Chawla, A. K., Jayaganthan, R., & Chandra, R., Effect of power variation on wettability and optical properties of co-sputtered titanium and zirconium oxynitride films. Bull. Mater. Sci., vol. 36 (3), pp. 403–409, 2013.

Rizzo, A., Signore, M. A., Mirenghi, L., & Di Luccio, T., Synthesis and characterization of titanium and zirconium oxynitride coatings. Thin Solid Films, vol. 517, pp. 5956, 2009.

Roth, R., Schubert, J., Martin, M., & Fromm, E., Effect of process parameter changes on the composition of magnetron sputtered and evaporated TiN and AlN films measured by UHV in-situ techniques. Thin Solid Films, vol. 270, pp. 320-324, 1995.

Schilling, H., Stork, A., Irran, E., Wolff, H., Bredow, T., Dronskowski, R., & Lerch, M., Angew. Chem. Int. Ed., vol. 46, pp. 2931, 2007.

Shima, Y., Hasuyama, H., Kondoh, T., Imaoka, Y., Watari, T., Baba, K., & Hatada, R., Mechanical properties of silicon oxynitride thin films prepared by low energy ion beam assisted deposition. Nucl. Instrum. Methods B, vol. 148, pp. 599–603, 1999.

Suzuki, A., Hirose, Y., Oka, D., Nakao, S., Fukumura, T., Ishii, S., . . . Hasegawa, T., Low temperature epitaxial growth of anatase TaON using anatase TiO2 seed layer. Chem. Mater., vol. 26, pp. 976, 2014.

Tang, X., Qian, J., Wang, Z., Wang, H., Feng, Q., & Liua, G., Comparison of low crystallinity TiO2 film with nanocrystalline anatase film for dye-sensitized solar cells. J. Colloid Interf. Sci., vol. 330, pp. 386-391, 2009.

Trapalis, C., Giannakopoulou, T., Todorova, N., Anastasescu, C., Anastasescu, M., & Gartner, M., Optical and Microstructural Properties of Sol-Gel TiOxNy Thin Films. Semiconductor conference. International, vol. 2, pp. 303. Sinaia, Romania, 2007.

Vaz, F., Cerqueira, P., Rebouta, L., Nascimento, S. M., Alves, E., Goudeau, P., & Riviere, J. P., Structural, optical and mechanical properties of coloured TiNxOy thin films. Surf. Coat. Technol., vol. 174–175, pp. 197–203, 2003.

Wu, M., Lin, G., Chen, D., Wang, G., He, D., Feng, S., & Xu, R., Sol-Hydrothermal Synthesis and Hydrothermally Structural Evolution of Nanocrystal Titanium Di‐oxide. Chem. Mater., vol. 14, pp. 1974-1980, 2002.

Zhang, P., Zhang, J., & Gong, J., Tantalum-based semiconductors for solar water splitting. Chem. Soc. Rev., vol. 43, pp. 4395, 2014.

297



Biographies Emmanuel Ajenifuja is currently on TWAS-NRF Postdoctoral Research Fellowship in the Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria, South Africa. He is also a Research Fellow in Center for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria. He earned his M.Sc. and Ph.D. in Engineering Physics from Obafemi Awolowo University, Ile-Ife, Nigeria. He has published journals and conference papers. Dr. Ajenifuja has worked extensively on thin films material for tribology and optoelectronic applications, and also on natural ceramics for environmental applications. His current research interests is on Co-based superalloys fabrication and nitride oxidation resistant layer for superalloy surface protection. Abimbola Patricia I. Popoola is a Full Professor, and the Leader, Advanced Engineering Materials and Surface Technologies Group in the Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria, South Africa. With a combination of qualifications that encompasses all areas of Metallurgical and Materials Engineering, she holds a National Diploma in Materials Technology, which deals with the study of Metals, Polymers, Ceramics, Glass and Cement Technology. She has a BSC (honours) degree in Metallurgical and Materials Engineering; Master’s and Doctoral degrees in Metallurgical Engineering. She worked on the Quantitative Analysis of Cementitious Materials using Non-destructive Ultrasonic Testing. She completed her Doctoral degree in Physical Metallurgy/Laser Materials Deposition at TUT. Prof Popoola has published a total of 220 peer-reviewed journal papers. Until date, she has made a lot of impact with her publications, which have been acknowledged both locally and internationally, her works has attained high viewership and citations by different authors within the research field /community. Her research collaborations transverse both local and international space. Olawale Popoola is a Senior Lecturer and the Director, Centre for Energy and Electric Power, Faculty of Engineering and the Built Environment Tshwane University of Technology, Pretoria, South Africa. He has published journals and conference papers. Dr Olawale Popoola has published several peer-reviewed journal papers and conference proceedings. He has made a lot of impact with his publications, which have been acknowledged both locally and internationally, and his works has attained high viewership and citations by different authors within the research field. His research collaborations transverse both local and international space. His skills and expertise include the following among others, material characterization, mechanical properties, renewable energy technologies and power electronics.

298

structural and ion beam analysis of reactive magnetron …ieomsociety.org/dc2018/papers/124.pdf ·...

Documents