structural properties of nanocrystalline tin film

7/31/2019 STRUCTURAL PROPERTIES OF NANOCRYSTALLINE TiN FILM

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(Manuscript No: I12725-02)

May 27, 2012/Accepted: June 10, 2012

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STRUCTURAL PROPERTIES OFNANOCRYSTALLINE TiN FILM

A.D. Pogrebnjak *Ukraine Sumy Institute for Surface Modification

P.O.Box 163, 40030Sumy, Ukraine

(Email: [email protected])

.. AhmoodSumy State University,

St.R-Korsakov 2, 40002Sumy(Email: [email protected])

Emad Toma KarashSumy State University

Sumy, Ukraine.Tel: +380 542 334058, Fax: +380 542 334058

(Email: [email protected])

Abstract - The structure and phase composition of nitride-titanic surface ware obtained using scanning electronmicroscopy and X-ray diffraction analysis. Conditions for continuous deposition and ion-plasmous implantationhad higher wear resistance and lower friction coefficient. Also, the influence of pores and particles of drop

friction on the surface's characteristics was investigated. A physical mechanism describing such an influencewas proposed.

Keywords: nanocrystalline structure, nitride-titanic surface, phase composition, scanning electron microscopy,wear resistance friction coefficient.

Introduction

A rapid development in recent years has been seen in the field of nanotechnology due to the existing and/orpotential applications of nanomaterials in a wide variety of technological areas such as electronics, catalysis,ceramics, magnetic data storage and structural components. With reduction in size, the materials exhibit peculiarand interesting mechanical and physical properties, e.g. increased mechanical strength, enhanced diffusivity,higher specific heat and electrical resistivity, compared to the conventional coarse grained counterparts.Nanomaterials include sintered materials with an ultrafine grain structure, loosely aggregated nanoparticles andnanocrystalline thin films [13]. One of the wear-resistant surfaces which are of a great interest for machinebuilding, electronics and microelectronics, is the surface on the basis of titanium nitride. They are widely usedas the firm wear-resistant surfaces for cutting instruments, diffusion barriers in electronics, decorative andcorrosion resisting surfaces etc, because titanium nitride has high solidity, wear resistance and modulus ofelasticity and it is chemically stable. At present time such surfaces are obtained in various types of vacuumsystems, such as Bulat , Plasma copper , Ang-1, etc. All these units differ by the amount and location ofcathode packs, volume of vacuum chambers, force characteristics and heating methods of substrates, also by thedeposition methods (vacuum-arched [4], ion-plasmous [5], condensation with ion bombardment [6-8],magnetron sputtering [9], high-frequency discharge [10]). Therefore it is necessary to study the structural andfunctional properties of surfaces obtained not only in different units, but also in different modes.

The aim of the work is to carry out the complex investigation of tribological properties, structural-phasecomposition and morphology of surfaces and their comparison with TiN surfaces obtained in conditions ofcontinuous deposition or ion-plasmous implantation.


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International Journal Of Structronics & Mechatronics

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METHODS FOR OBTAINING SURFACES AND RESEARCH TECHNIQUE

Polished samples were used as substrates as in FIG.1. They represent flat cylinders with 20 mm diameter and3mm thickness. A stainless steel 12*18H10T was the material of surfaces the material used. Before deposition,the surfaces were purified in the vacuum chamber by means of ion bombardment.

Figure 1: The polished samples

Titanium nitride surfaces were obtained in the vacuum-arched unit Bulat-6. The description of a serial unit isgiven in [2]. At that there were used two modes of deposition: the mode of continuous deposition and depositionmode of ion-plasmous implantation (Plasma-based ion implantation and deposition or PBII&D [6, 7]). In thismode a substrate is plunged in plasma and negative impulse potential is applied. Acceleration of ions occurs in adynamic self-organizing boundary layer, which forms nearby the target surface when the impulse of negativepotential is applied. Surface deposition was conducted in conditions when a constant potential 230 V is given toa substrate simultaneously with negative impulse with amplitude 2kV and impulse spacing frequency 7 kHzwith duration 10 mcs. Arc current was equal to 90 A. The nitrogen pressure during deposition was 10 -4 mm.m.c.The distance between evaporator and substrate was 250 mm. The substrates were heated up to 360 .

At continuous deposition of surfaces, the constant potential, arc current, nitrogen pressure in the chamber, the

distance between evaporator and substrate and the temperature of substrates were the same as in impulsedeposition.

The surface thickness, state of the boundary between the base and surface were defined by the means ofscanning electron microscope SEM-106 through fracture pattern at accelerating voltage 20 kV. In addition, themorphology of samples surfaces was studied via scanning electron microscopy.

X-ray diffraction studies of samples were conducted using X-ray diffract meter DRON-2.0 in u-k emission.

Obtained surfaces and samples without covering were tested for wear resistance in friction machine SMC-1bythe surface cylinderschme using technical petrolatum. During the whole testing period the sample was infriction machine. The groove width and its length in the wearing zone were investigated by Brinell microscopeBCH-2, which ensures measurement accuracy 0.025 mm, at magnification 24. The value of volume wear wasdetermined though the formula:

.))2

((2

)2

arcsin(222

aaa

RR

RLV

,

Where the values measured experimentally are the length of wearing zone L and its width a. R is a diameter of acounter body.
http://www.multitran.ru/c/m.exe?t=4057696_1_2http://www.multitran.ru/c/m.exe?t=4057696_1_2


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A.D. Pogrebnjak, .. Ahmood, Emad Toma Karash

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RESULTS AND DISCUSSION

A. TRIBOLOGICAL PROPERTIESFirst of all one shall note that all the surfaces, regardless of obtainment methods, had golden-yellow colorcharacteristic for stoichiometric titanium nitride.

The methodology of tribotechnical testing volume wear allows obtaining graphic charts of the size of wearingarea, volume wear and wearing resistance from time, amount of counter body turns and the length of distancecovered. In fig. 2 dependences of changes of material volume, entrained by a counter body in the testingprocess, from the path length gone by the counter body. The conducted tests over wear resistance showed thatthe covering of surfaces essentially lowered volume wear of the base. During the first 500 turns of the counterbody the entrained volume of substrate material was more than 10 times bigger than the entrained volume ofsurface material. The loss of the substrate material had a catastrophic character (curve 3),[8] whereas thesurfaces did not reach this stage up to the very end of the test. During basic tests at 10000 turns none of thesurfaces wore through and uncovered a substrate. Moreover the loss of the surface material deposited in themode of ion-plasmous implantation was 1.5 2 times less than surfaces obtained during continuous deposition.

Figure 2: The dependences of changes of volume wear V from the length of distance covered by a counter body L for samples with TiNsurfaces obtained in the mode of ion-plasmous implantation (curve 1) and in the mode of continuous deposition (curve 2) and also for

samples without surfaces (curve 3).

The tests measuring surfaces coefficient of sliding friction (the data are given in table 1) also showed the

advantages of surfaces obtained in the mode of ion-plasmous implantation. Thus, the coefficient of slidingfriction for a surface of the second type is proved to be less than the corresponding coefficient of the usualsurface by 10 and 11 % correspondingly while sliding on plastic and polished aluminumother

Processors to do processing on the data assigned to them [28]. For instance, consider an image of size N Nand let the kernel size be K K. Also, let the processor pi be assigned a set of rows of an image starting from jto j + r, for some j > 0, r >0 and j + r N. Processor pi may need the (j _K/2_) th to (j 1) th and (j + r + 1) th

to (j + r + _K/2_) th rows for it to perform computation on its assigned rows. To carry out this processing, in theliterature it is standard practice to allow the processors to communicate among them for the respective dataexchange. This data exchange takes place, concurrently, among the respective pairs of processors [29].However, in the strategies to be proposed here (and adopted in [28]), we assign such additional data required bythe individual processors right at the initial communication phase, before the actual load distribution toindividual processors is carried out. Thereafter, the processors will perform computations on the respectiveportions by utilizing the additionally supplied.


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B. STRUCTURAL STUDIESX-ray diffraction studies of the phase composition of surfaces obtained in the mode of continuous depositionshowed the presence of only one phase: titanium nitride with face-centered cubic lattice (fcc lattice) of typeNaCl, B1Fm3m [9]. On all X-ray patterns, there were diffraction peaks (111), (200), (220) and (222). The valueof peak intensity indicates that it is the monophase polycrystalline titanium nitride. In surfaces obtained during

ion-plasmous implantation except for all mentioned titanium nitride peaks there was a diffraction peak (101),answering to -Ti and having the size of crystalline grains about 42 nm. However this peak had low intensityand corresponds to the concentration only 2,55 %, that lies within the range of an applied method. The data ofquantitative structural characteristics of surfaces are given in table 1.

Parameter Surface obtained incontinuous deposition

mode

Surface obtained at ion-plasmous implantation

Parameter of crystal lattice, 4.26030.0141 4,25990,0173Lattice deformation, /,

%+0,38 +0,24

The size of coherent

scattering areas, nm 39,62 34,19Diameter of drop fraction,

mcm 0,1310,021 0,180,032

Diameter of surface pores,mcm 0,1530,015 0,3650,032

Pore concentration, 10-4 2.139 3,348

Friction coefficient:on plastic

on polished Al0,420,36

0,380,32

Table 1: The values of experimental parameters for titanium nitride surfaces

The analysis of diffraction maxima intensities denotes the presence of axial texture [111] in titanium nitride forboth deposition modes. The estimation of crystalline grain size showed that the surfaces obtained in the mode ofion-plasmous implantation have the smaller size of grains. The average values of crystalline grain sizes are34 , while at continuous deposition the surfaces had crystalline grain sizes of nearly 40 nm. The obtainedfine-grained structure of surfaces indicates a rather high speed of their depositon.One should note that in both types of samples, there was an increase of TiN crystal lattice parameter (up to0.42603 0.0141 nm for continuous deposition mode and 0.42599 0.0173 nm for ion-plasmous implantation)in comparison with massive titanium nitride for which = 0.4244 nm [9].As compared with massive TiN, the volume of unit cell for surfaces obtained in continuous mode increased by

1,16 % and by 1.12 % for surfaces obtained in impulse mode. This can be explained by the following. Theobtained TiN surfaces are not perfectly stoichiometric as a result of the wide homogeneity region of titaniumnitride. Therefore its properties strongly depend on the amount of nitrogen in nitride. Apparently, there is a lowconcentration of nitrogen in surfaces, that leads to the formation of defective structure conditioned by the lack ofnitrogen atoms in the metal lattice. Moreover, the increase of lattice parameter may indicate a high level of innervoltages. The whole set of these factors influence the elastic, strengthening properties and solidity of obtainedsurfaces.Electron-microscopic investigations showed that the surface morphology of all obtained coverings has the sameform: on the covering surfaces there are both particles of drop fraction and pores. The characteristic form of asurface structure is shown in fig. 3 and 4. It was revealed that particles are present directly on the surface; on theparticles located on the surface and also inside pores.Though the coverings obtained in different modes have different quantitative surface characteristics (table 1).From the data represented in table 1 one can observe that in impulse deposition mode the average values of drop

diameter, average pore sizes and their concentration are higher than at continuous deposition. Exactly, this factexplains the difference of friction coefficients of surfaces obtained under different conditions. In addition, on the


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basis of X-ray diffraction data, one can assume that the sum of particles on the surfaces obtained in impulsemode are the particles of softer phase (-Ti).Surface fractures were studied by scanning electron microscopy. The analysis of fractures showed that theobtained surfaces have good adhesion to substrate: on the " substrate-surface " laundry no extensive pores,cracks, or breaches were observed.

Figure 3: Microphotographs of the surface (, b) and fracture (c, d) of TiN-surface, obtained at continuousdeposition.

It was estableshed that regardless of the deposition modes there were pores in surfaces. These pores may be oftwo types: open pores located on the surface and closed pores distributed inside the coverings. The throughpores reaching a substrate were not revealed. It should be noted that in open surface pores there is oftenobserved an oriented growth of surface particles. This fact illustrates electron microphotographs given in fig. 3and 4.In our opinion, the pores play a definite role in provision of tribological properties of surfaces.It can beexplained by the following. The presence of surface pores in coverings provides free volumes, which play atwo-fold role in tests for wear resistance. In the first place these pores are filled by a lubricant providing easiersliding in friction pair: in the second place, the surface particles of drop fraction do shift in them, which arestripped by a counterbody in testing process. The closed pores inside the surfaces play the role of peculiar

voltage relaxation, since they possess considerably lesser compressibility than the surface material. Thereforethe pores inside surfaces perform the role of dampers providing the continuous wear resistance of coverings.


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figure 4: Microphotographs of the surface (, b) and fracture (c) and crosscut fracture (d) of TiN-surface,obtained in the mode of ion-plasmous implantation.

Conclusion

In the mentioned deposition modes obtained nanocrystalline surfaces of titanium nitride were obtained withface-centered cubic lattice. The obtained surfaces have good adhesion to substrates and serve as a reliabledefence. The comparison of surface characteristics showed that the mode of ion-plasmous implantation providestwo phase fine-dispersed crystal structure of surfaces, which in turn show higher characteristics of wearresistance and lesser coefficient of sliding friction. The particular role here is played both by the surface poresand pores located inside the coverings.

References

1. B. Major, R. Ebner, T. Wierzchon, W. Mroz, W. Waldhauser,R. Major, and M. Wozni ak, Thin layers ofTiN fabricated on metallic titanium and polyurethane by pulsed laser deposition,Annals of Transplantation 9(1A), (Suppl.)(2004).

2. D.B. Chrisey and G.K. Hubler, Pulsed Laser Deposition of Thin Films, John Wiley & Sons, 1994.

3. B. Major, Ablation and Deposition with a Pulsed Laser,Wydawnictwo Naukowe Akapit, Krakw, 2002, (inPolish).

4. J.M. Lackner; Industrially-scaled Hybrid Pulsed Laser Deposition at Room Temperature, Orecop sc.,Cracow, 2005.

5. B. Major, W. Mrz, T. Wierzchon, W. Waldhauser, J.M. Lackner, and R. Ebner, Pulsed laser deposition ofadvanced titanium nitride thin layers, Surf. Coat. Technol. 180181, 580584 (2004).

6. D. Buerle,Laser Processing and Chemistry, (third edition),Springer-Verlag, Berlin, Heidelberg, 2000.

7. R. Major and P. Lacki, Computers and structures in Book of Abstract of the Third M.I.T Conference onComputational Fluid and Solid Mechanics, Boston, 242 (2005).


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8. R. Major, P. Lacki, J.M. Lackner, and B. Major, Modelling of nanoindentation t o simulate thin layerbehaviour,Bull. Pol.Ac.: Tech. 54, 191200 (2006).

9. D. Rather, A.S. Hoffman, F.J. Schoen, and J.E. Lemons, Biofilms, biomaterials and device-relatedinfections, B.Costerton, G. Cook, M.Shirliff, P. Stoodley M. Pasmore (eds.),Biomaterials Science, in AnIntroduction to Materials inMedicine, Elsevier Inc., 345354 (2004).

10. G.E. Wnek, G.L. Bowlin, Shih-Horng Su et al., Surface Coatings,S.L. McArthur, K. McLean, Surfacemodification;Encyclopedia of Biomaterials and Biomedical Engineering 2,14121431 (2004).

structural properties of nanocrystalline tin film

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