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Sensors and Actuators A 221 (2015) 9–14

Contents lists available at ScienceDirect

Sensors and Actuators A: Physical

j ourna l h o mepage: www.elsev ier .com/ locate /sna

n-situ annealing of NiTi thin films at different temperatures

olfgang Tillmann ∗, Soroush Momeni ∗∗

nstitute of Materials Engineering, Technische Universität Dortmund,Leonhard-Euler-Str 2, 44227 Dortmund, Germany

r t i c l e i n f o

rticle history:eceived 26 May 2014eceived in revised form 27 October 2014ccepted 28 October 2014vailable online 5 November 2014

a b s t r a c t

Magnetron sputtered NiTi thin films are usually sputtered at ambient temperature and need a post-annealing treatment to promote crystallization and obtain shape memory effect. However, this treatmentcould adversely affect the microstructure as well as the morphology of the film. Within this study, NiTithin films were generated by annealing during the sputtering process. The effect of the sputtering tem-perature on the morphology of the film, the composition, and shape memory behavior was studied using

eywords:hin filmsputteringnnealinghape memory alloysrecipitation

X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electronmicroscopy (FESEM), and differential scanning calorimetry (DSC).

© 2014 Elsevier B.V. All rights reserved.

. Introduction

NiTi shape memory alloy (SMA) thin films have recentlyttracted great interest for the development of microelectrome-hanical systems (MEMS), such as micro valves [1], micro fluidumps [2], micro wrappers [3], and micro grippers [4]. The mainenefits of MEMS applications for NiTi thin films are for exam-le a large displacement, high damping capacity, large actuationorce, and a low operating voltage. In addition, the shape memoryffect (SME) and the superelasticity (SE) of NiTi thin films can bemployed to engineer surfaces with excellent tribological proper-ies. This is even possible when the material is only present as aurface coating [5,6].

Despite these excellent properties, there are some difficultieso fully integrate NiTi shape memory thin films into MEMS andribological coating systems as their high stoichiometry sensitiv-ty restricts the manufacturability and versatility in MEMS [7]. Inddition, the as-deposited sputtered NiTi thin films are amorphousithout any shape memory effect. In order to promote the shapeemory effect, they need to be crystallized during a post-annealing

rocess (using temperatures of 600 ◦C and higher) [8]. The crys-allization process is a direct consequence of the grain nucleationnd growth at elevated temperatures. As a result, the annealing

∗ Corresponding author. Tel.: +49 231 755 2581.∗∗ Corresponding author. Tel.: +49 231 755 6113.

E-mail addresses: wolfgang.tillmann@udo.edu (W. Tillmann),oroush.momeni@tu-dortmund.de (S. Momeni).

ttp://dx.doi.org/10.1016/j.sna.2014.10.034924-4247/© 2014 Elsevier B.V. All rights reserved.

temperature and time will influence the structure as well asproperty of NiTi thin films and their shape memory behavior. Aconnection between the annealing temperature and phase trans-formation temperatures of NiTi thin films has previously beenreported by Surbled et al. [9]. The effect of annealing parameterson mechanical and shape memory properties of NiTi thin films wasinvestigated by Satoh et al. [10]. Nevertheless, it was noticed thatthe effects of the annealing parameters during the sputtering ofNiTi thin films have not been investigated so far.

The in-situ annealing technique could be more reliable thana post-annealing of NiTi thin films, sputtered at room temper-ature. The most important advantage of this technique is toprevent surface oxidation, polymorphic crystallization, and a film-substrate reaction which can occur during the post-annealingprocess. By employing in-situ annealing treatment, lower tempera-tures (300–450 ◦C) are required to obtain crystallized NiTi thin filmswith good shape memory effects [11]. Thus, it is a cost-efficienttreatment because these required lower crystallization tempera-tures can further be beneficial in terms of conservation of thermalprocessing budgets. Last but not the least, annealing during sput-tering makes it possible to deposit another coating layer on NiTithin films (protective layers) without breaking the vacuum inside ofthe sputtering chamber. As an example, the authors of the presentpaper have already reported the deposition of composite NiTi/TiCNfilms by employing this technique [12]. In spite of the benefits

of the in-situ annealing method, only a few researchers workedon in-situ annealed NiTi SMA thin films [13,14], and the role ofsputtering temperature during deposition has not been preciselyreported.

10 W. Tillmann, S. Momeni / Sensors and Actuators A 221 (2015) 9–14

Table 1Description of sputtering parameters.

Amount of target used 2Gas ArAr flow (ml/min) 320Chamber pressure (mPa) 350

tfitswNep

2

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TD

Table 3The compositions of the deposited NiTi films recorded by EDX.

Sample ID Sputtering time (◦C) Composition (at%) Ni/Ti

A1 80 50.65/49.35A2 305 50.40/49.60

Substrate bias voltage (Kv) −0.075Sputtering power (W) 1400Substrate rotation speed (rpm) 5

The main aim of the present research work is to investigatehe effect of the sputtering temperature on properties of NiTi thinlms as well as their shape memory behaviors. The term of sput-ering temperature in this study refers to the temperature of theample holder in the coating chamber in which the substratesere installed. Moreover, it was observed that employing Ti-richiTi alloy targets can ensure a reproducible production of nearlyquiatomic NiTi thin films and solve the stoichiometry sensitivityroblem.

. Experimental

NiTi thin films were deposited on a silicon (1 0 0) substratey means of a DC magnetron sputtering device (CC800sinox TM,emeCon AG, Germany). Ti-rich NiTi alloy targets (51.8 at% Ti–Ni)ere employed to sputter of the NiTi SMA thin films. In order

o achieve a uniform film composition, the sample holder wasotated on a horizontal table during sputtering. The target toubstrate distance was fixed at approximately 9.5 mm. NiTi thinlms were deposited at four different sputtering temperatures of25 ◦C, 425 ◦C, 305 ◦C, and 80 ◦C by adjusting the heating powerso 25,000 W, 10,000 W, 5000 W, and 0 W, respectively, during theoating processes. Since the maximum applicable heating poweras 10,000 W, an extra heating system was installed inside the

oating chamber which supplied an additional 15,000 W of heat-ng power. By employing this extra heating system, it was possibleo reach the sputtering temperature of 525 ◦C. The deposition athe heating power of 0 W was performed without an intentionaleating of the substrates. However, using the thermocouple, someubstrate heating was detected around 80 ◦C during the deposi-ion process. The temperature of the targets did not exceed 60 ◦Cecause of the water circulating cooling system at the backsidef the targets. Except of the heating power, all of the sputter-ng parameters were kept constant during the deposition of NiTihin films. These parameters are summarized in Table 1.No post-nnealing process was conducted after the deposition of theselms. The detailed description of the deposited thin films is pre-ented in Table 2. The microstructure of the thin films was analyzedy employing X-ray diffraction using Cu K� radiation and a 9◦ inci-ent angle (D8 Advance, BRUKER AXS, Germany). The thin filmorphology and thickness results were analyzed on a fracture

ross-section of coated samples by means of a field emission scan-ing electron microscope (FESEM) (Jeol JXA840, JSM 35, Japan),hile the composition of coatings was determined using energy-

ispersive X-ray spectrometry (EDX) with an electron accelerationoltage of 20 kV and a beam current of 15 nA. All sampling was doney analyzing in areas but not point measurements to investigatehe chemical compositions. Phase transformations of free-standing

able 2escription of specimens.

Sample ID Sputtering time (min) Sputtering temperature (◦C)

A1 180 80A2 180 305A3 180 425A4 180 525

A3 425 50.66/49.34A4 525 50.69/49.31

NiTi coatings were characterized using a differential scanningcalorimeter (DSC 2920 CE from TA Instruments). DSC specimenswith a mass of 20 mg were heated and cooled at the rate of 10 K/minover a temperature range of −150 to 150 ◦C.

3. Result

3.1. Morphology and composition of thin films

The compositions of the deposited films, measured by EDX, areshown in Table 3. Since the atomic ratios of Ni to Ti in the samplesare all close to 1, it can be concluded that the sputtering temper-ature do not significantly affect the film compositions in this casestudy. It has been previously reported that the sputtering profilesof Ni and Ti atoms from cold and hot targets are different [15]. Nev-ertheless, this result introduces a new approach to compensate thedependency of the sputtering profile on the target temperature byemploying Ti-rich NiTi alloy targets. In fact, this finding can leadto reproducible depositions of NiTi SMA thin films with a nearlyequiatomic composition ratio.

NiTi thin films sputtered at 80 ◦C showed ductile fractures, whilethe other films showed brittle fractures during the sample cross-section preparation. Such ductile fractions can be ascribed to thelack of crystallization in NiTi thin films deposited at a low temper-ature (80 ◦C).

The fracture analysis by means of FESEM reveals variousmicrostructures of NiTi thin films sputtered at different tempera-tures. Fig. 1 shows the FESEM images of the fractured cross-sectionof the deposited thin films. As it can be seen, the NiTi thin filmdeposited at 80 ◦C shows a thick fibrous microstructure. Thin filmsdeposited at 305 ◦C and 425 ◦C exhibit a finely packed fibrous orbamboo-like structure. This structure changes to a densely packedcolumnar structure for the film deposited at 525 ◦C. This differencein microstructures is a direct consequence of the relation betweenthe crystallization temperature, nucleation, and growth. Increas-ing the sputtering temperature to 525 ◦C can enhance the activityof absorbed atoms and promote the migration of atoms to the favor-able energy positions that support the formation of densely packedcolumnar structures. Interestingly, this finding corresponds withthe results obtained in the research work of Zhang et al. [16]. Theyreported that the crystallization of as-deposited NiTi thin filmswas the process of generation and development of columnar struc-tures during post-annealing operation. As a result, during in-situannealing of the NiTi thin films, the increasing of annealing temper-ature leads to the increase of columnar structures (lateral growthof grains) and surface roughness.

One important point regarding the sputtering temperature isits effect on the thickness of the film. Fig. 2 shows the thicknessof NiTi thin films deposited at different temperatures. Generallyspeaking, the thickness of a film during the magnetron sputter-ing can be dominantly affected by the sputtering power and time.Since the processing parameters for the deposition of these thinfilms are the same, the observed variation of the film thickness

could be a consequence of employing different sputtering temper-atures. The NiTi thin films deposited at 80 ◦C possess the lowestthickness (2.73 �m). This can be attributed to the low temperatureof the substrate which cannot adequately provide active spots for

W. Tillmann, S. Momeni / Sensors and Actuators A 221 (2015) 9–14 11

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ttficcsdtpdl

3

atpf2msc

Fa(

Fig. 1. A series of FESEM micrographs of the final microstructure of NiTi thin film

he nucleation and growth of NiTi thin films. Increasing the sput-ering temperature up to 305 ◦C results in a 20% increment of thelm thickness. As it was mentioned, the increased thickness was aonsequence of more nucleation and an increased growth of NiTirystalline materials. The thickness of the thin film deposited atputtering temperatures of 425 ◦C does not show any significantifference compared to those deposited at 305 ◦C. However, thehickness of the film deposited at 525 ◦C shows a 12% decrease com-ared to the films deposited at 305 ◦C and 425 ◦C. This is probablyue to the higher volume diffusion of the deposited atoms, which

eads to a more compacted and even denser microstructure.

.2. Crystalline structure of thin films

Fig. 3(a) and (b) shows XRD spectra of deposited NiTi thin filmst low sputtering temperatures. The film deposited at 80 ◦C shows aypical amorphous spectrum with no recognizable peaks. The XRDattern of the film deposited at 305◦ shows that it has not beenully crystallized during the sputtering process. The broad peak at

◦

� within a range of 36–51 is characteristic for an amorphousatrix containing tiny NiTi nanocrystallites. However, there is a

harp peak at 2� of 67◦ which shows that the film was partiallyrystallized. The position of this peak correlates with (2 0 0) peak

2,73

3,43 3,43,04

0

0,5

1

1,5

2

2,5

3

3,5

4

Sample A1 Sample A2 Sample A3 Sample A4

Thic kne ss (µ m)

ig. 2. Film thickness of NiTi SMA thin films deposited at the sputtering temper-tures of 80 ◦C (sample A1), 305 ◦C (sample A2), 425 ◦C (sample A3), and 525 ◦Csample A4).

sited at sputtering temperatures of (a) 80 ◦C (b) 425 ◦C (c) 305 ◦C, and (d) 525 ◦C.

of the austenite phase. This is perhaps due to the initial stacking ofthe austenite B2 NiTi phase onto the (h 0 0) planes.

Fig. 4(a) and (b) shows XRD profiles of NiTi thin films depositedat high sputtering temperatures. The XRD pattern of the filmdeposited at 425 ◦C shows three obvious diffraction peaks at2� = 42.3◦, 62◦, and 78.2◦, respectively, which correspond withthe (1 1 0), (2 0 0), and (2 1 1) lattice orientations of austenite B2structure of NiTi thin films. The existence of a weak and broadNi4Ti3 peak at 2� = 37.8◦ implies slight non-equilibrium precipi-tation reactions during sputtering. The presence of other Ni4Ti3peaks such as (2 0 2) at 2� = 41◦ and (1 2 2) at 2� = 43◦ was notconfirmed because of an intense B2 (1 1 0) peak at 42.3◦ and theabsence of fully crystalline and large precipitates. The NiTi thin filmdeposited at 525◦ shows diffraction patterns similar to that of thefilms deposited at 425 ◦C with 2� = 42.3◦, 62◦, and 78.2◦, indexedas (1 1 0), (2 0 0), and (2 1 1), respectively. However, an extra peakin the XRD pattern of this film appears at 2� = 38.0◦. There are twohypotheses for this phenomenon: the first hypothesis is a silicideformation close to the film–substrate interface as a result of anincreasing sputtering temperature. The second hypothesis is theformation of Ni4Ti3 precipitations. The small Ni4Ti3 peak observedfor the film deposited at 425 ◦C appears also with an increasedintensity and width for the film deposited at 525 ◦C. By increasingthe sputtering temperature, diffusion becomes more active, whichcauses the precipitates to form and grow at a higher rate. This leadsto the formation of larger and more crystalline precipitations andconsequently increases the intensity and width of the Ni4Ti3 peak.Based on this hypothesis, it can be assumed that the small peak at2� = 55◦ belongs to the (2 3 2) diffraction pattern of these precipi-tates. Furthermore, the broadening of the austenite NiTi peaks at2� of 62◦ and 78◦ could be a consequence of their overlapping withthe (4 2 2) and (5 3 2) peaks of the Ni4Ti3 precipitates. This was alsoreported by Ho et al. [17] that the depositions of NiTi thin filmsfrom a cold target to a hot Si substrate with temperatures of 500 ◦Cand 600 ◦C could intensively promote the growth of precipitates.

3.3. Phase transformation analysis of thin films

Fig. 5(a) and (b) shows DSC curves of the NiTi thin filmsdeposited at 80 ◦C and 305 ◦C. It can be clearly seen thatno thermal events happen when cooling the samples from

12 W. Tillmann, S. Momeni / Sensors and Actuators A 221 (2015) 9–14

Fig. 3. A series of XRD patterns of NiTi thin films deposited at sputtering temperatures of (a) 80 ◦C and (b) 305 ◦C.

sited a

1aTl

Fig. 4. A series of XRD patterns of NiTi thin films depo

20 ◦C to −60 ◦C. However, a weak endothermic peak started

t 9 ◦C during the heating process and stopped at 48 ◦C.his might be attributed to the non-uniform partial crystal-ization of the films, either through the thickness or radially

Fig. 5. A series of DSC thermographs of NiTi thin films deposite

t sputtering temperatures of (a) 425 ◦C and (b) 525 ◦C.

which is in agreement with the XRD results in Fig. 3(a) and

(b).

The DSC curve of the film deposited at a sputtering temperatureof 425 ◦C is shown in Fig. 6(a) In this measurement, exothermic

d at sputtering temperatures of (a) 80 ◦C and (b) 305 ◦C.

W. Tillmann, S. Momeni / Sensors and Actuators A 221 (2015) 9–14 13

posite

asraifpwtssuifp

setaatefepttaewifitNat

Ftca(

Fig. 6. A series of DSC thermographs of NiTi thin films de

nd endothermic peaks can be clearly observed at the marten-itic and reverse martensitic transformation on cooling and heating,espectively. It was shown that the transformation into the parentustenitic phase starts (As) at −2.2 ◦C and completes transformingnto austenite (Af) at 55.7 ◦C. As the temperature decreases, a trans-ormation back into the martensite phase starts (Ms) at 53.7 ◦C. Thehase transformation into martensite (Mf) is completed at 25.8 ◦Chile cooling down the coating. The DSC plot uncovered that the

ransformation to austenite is a two-step transformation. The firsttep begins at the austenite start (As) temperature of −2.2 ◦C and theecond step at 28 ◦C. In order to simplify labeling, (As) and (Af) aresed to indicate the temperature of the first appearance of austen-

te and the completion of the transformation. The two argumentsor a two-step transition are a type of R-phase and the presence ofrecipitates [12].

The first hypothesis concerning the R-phase formation corre-ponds with a DSC measurement that was conducted by Miyazakit al. [18]. They found such a two-step curve for a Ti-51.9 at% Ni alloyhin film that was sputtered at room temperature and subsequentlyged at 500 ◦C for 1 h. They called the first and second peaks A*nd RA*, representing the reverse transformation from a martensiteo a R-phase and from a R-phase to austenite, respectively. How-ver, the R-phase is more commonly found before the transitionrom austenite to martensite. Based on the second hypothesis, thelongated transition could be due to the Ni4Ti3 precipitates. Theserecipitates can elongate the transition temperatures and cause awo-peak transition. Fan et al. [19] demonstrated that polycrys-alline alloys with a low Ni supersaturation (50.6 at%) showed anbnormal two-stage transformation. In these alloys, Ni4Ti3 pref-rentially precipitated only at the grain boundary (GB) regions,here nucleation barriers were low compared to those of grain

nteriors (GIs), resulting in a localized two-stage B2-R-B19′ trans-ormation near the GBs and a one-stage B2–B19′ transformationn the GIs. This could be the reason for the observed DSC curve ofhe film deposited at 425 ◦C, as the EDX result shows its slightlyi-rich (50.6 at%) composition. Nevertheless, more investigationsre needed to exactly clarify the reason of the two-step martensiticransformations.

The DCS curve of the film deposited at 525 ◦C is shown inig. 6(b). In the cooling cycle, the forward transformation into

he martensite phase started at a temperature of 36.1 ◦C and wasompleted at 14.8 ◦C. In the reverse transformation on heating,ustenite start and finish temperatures were determined as 33.2 ◦CAs) and 63 ◦C (Af), respectively. It can be obviously seen that there

d at sputtering temperature of (a) 425 ◦C and (b) 525 ◦C.

are not two-peak transitions in the thermal transformation behav-ior of the NiTi thin film. This phenomenon is probably due to thecoherency strains associated with the Ni4Ti3 precipitate forma-tion within NiTi grains. It is well known that coherency strainfields around precipitates can spread the transformation over arange of temperatures or cause multiple-stage transformations[20,21]. Although the initial Ni4Ti3 precipitates are coherent withthe NiTi matrix, increasing the sputtering temperature to up to525 ◦C causes the precipitates to grow in size and to lose theircoherency. Consequently, the inhomogeneity of the stress distribu-tion between these precipitates and the surrounding NiTi matrix isremoved. This, in turn, can prevent two-stage transformations frommartensite to austenite. The formation of larger Ni4Ti3 precipitatesis also in agreement with the XRD pattern of this film in Fig. 4(b).

The existence of a small transformation temperature hysteresisfor the films deposited at 425 ◦C and 525 ◦C is an excellent propertyfor applications in microelectromechanical systems (MEMS). It isparticularly beneficial when a short response time is required fora fast cyclic microactuation. However, it will be very interesting tocomplement the present results with further investigations con-cerning a mechanical and tribological analysis of these thin films.Such an investigation is in progress by the authors of the presentwork to clarify the effect of the sputtering temperature on mechan-ical as well as tribological properties of NiTi thin films.

4. Conclusion

In this study, nearly equiatomic NiTi thin films were depositedby means of magnetron sputtering of a Ti-rich NiTi alloy. Theeffect of the sputtering temperature (temperature inside the coat-ing chamber) on the microstructure and shape memory behaviorof NiTi films was investigated. The thickness of the deposited filmswas about 3 �m and shows a variation of 12–20% upon changingthe sputtering temperature. In addition, the following points arehighlighted:

1. Employing a Ti-rich NiTi target can compensate the discrepancyin the angular flux distribution of Ni and Ti atoms from cold and

hot targets.

2. NiTi thin films deposited for 180 min at various temperaturespossess different microstructures. The films deposited at 80 ◦Care fully amorphous, while films deposited at 305 ◦C are partially

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4 W. Tillmann, S. Momeni / Senso

crystallized. A deposition at a sputtering temperature above 425◦

leads to a fully crystallized formation of NiTi thin films.. NiTi thin films deposited at 425 ◦C show two-stage transforma-

tion behavior upon heating due to the formation of a R-phaseor Ni4Ti3 precipitates, while the films deposited at 525 ◦C showone-stage transformation upon heating and cooling.

. NiTi thin films deposited at 425 ◦C and 525 ◦C possess very smalltransformation temperature hysteresis which can enable themto show fast frequency response.

eferences

[1] K. Otsuka, T.K. Sawamura, Shimizu crystal structure and internal defects ofequiatomic TiNi martensite, Phys. Sat. Sol. A 5 (1971) 457–470.

[2] D.Y. Li, X.F. Wu, T. Ko, The effect of stress on soft modes for phase transition inTi–Ni alloy, Philos. Mag. A 63 (1991) 585–603.

[3] J.J. Gill, D.T. Chang, L.A. Momoda, G.P. Carman, Manufacturing issues of thin filmNiTi micro wrapper, Sens. Actuators. A 93 (2001) 148–156.

[4] M. Nishida, T. Honma, Electron microscopy studies of the all-round shape mem-ory effect in a Ti-51.0 atm% Ni alloy, Scr. Mater. 18 (1984) 1293–1296.

[5] D.S. Grummon, S. Nam, L. Chang, Effect of super elastically deforming NiTi sur-face microalloys on fatigue crack nucleation in copper, Proc. Mater. Res. Soc.246 (1992) 259–264.

[6] Li. Hou, D.S. Grummon, Transformational superelasticity in sputteredtitanium–nickel thin films, Scr. Mater. 33 (1995) 989–995.

[7] A. Ishida, V. Martiniv, Sputter-deposited shape-memory alloy thin films: prop-erties and applications, MRS Bull. 27 (2) (2002) 111–114.

[8] J.J. Kim, P. Moine, D.A. Stevenson, Crystallization behavior of amorphous NiTialloys prepared by sputter deposition, Scr. Metall. 20 (1986) 243–248.

[9] P. Surbled, C. Clerc, B.L. Piofle, M. Ataka, F. Fujita, Effect of composition andthermal annealing on the transformation temperatures of sputtered TiNi shapememory alloy thin films, Thin Solid Films 401 (2001) 52–59.

10] G. Satoh, A. Birnbaum, Y.L. Yao, Effect of annealing parameters on the shapememory properties of NiTi thin films, in: ICALEO 2008 Congress Proceedings,Poster presentation gallery, 100–167.

11] Y.Q. Fu, H.J. Du, Effects of film composition and annealing on residual stressevolution for shape memory TiNi film, Mater. Sci. Eng. A 342 (2003) 236.

12] W. Tillmann, S. Momeni, Deposition of superelastic composite NiTi based films,Vacuum 104 (2014) 41–46.

13] K. Gisser, G.D. Busch, A.D. Johnson, A.B. Ellis, Oriented nickel–titanium shapememory alloy films prepared by annealing during deposition, Appl. Phys. Lett.61 (14) (1992).

14] A. Kumar, S.K. Sharma, S. Bysakh, S.V. Kamat, S. Mohan, Effect of substrate andannealing temperatures on mechanical properties of Ti-rich NiTi films, J. Mater.Sci. Technol. 26 (11) (2010) 961–966.

15] K. Ho, K.K. Mohanchandra, G.P. Garmen, Examination of the sputtering profileof NiTi under target heating conditions, Thin Solid Films 413 (1–2) (2002) 1–7.

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16] L. Zhang, C. Xie, J.W., Effect of annealing temperature on surface morphol-ogy and mechanical properties of sputter-deposited Ti–Ni thin films, J. AlloysCompd. 424 (2007) 238–243.

17] K.K. Ho, G.P. Carman, Sputter deposition of NiTi thin film shape memory alloyusing a heated target, Thin Solid Films 370 (2000) 18–29.

18] S. Miyazaki, A. Ishida, Martensitic transformation and shape memory behaviorin sputter-deposited TiNi-base thin films, Mater. Sci. Eng. A 273–275 (1999)106–133.

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Biographies

Soroush Momeni received his B.Sc. in Textile Engineering(Textile Chemistry and Fiber Science) from the Azad Uni-versity of Tehran, Iran. He gained his M.Sc. in AdvancedMaterials (Nanomaterials) in February 2012 from the Uni-versity of Ulm, Germany. Since April 2012, he is pursuinghis PhD degree under the direction of Professor Wolf-gang Tillmann at the Institute of Materials Engineering,Technical University of Dortmund, Germany. His researchinterest currently focuses on magnetron sputtering phys-ical vapor deposition techniques, binary and ternary NiTishape memory alloy thin films, self-healing coating sys-tems, antibacterial magnetron sputtered coatings, wearresistance hard coatings as well as cavitation erosion resis-

tance coatings.

Wolfgang Tillmann got his PhD degree in 1992 in thefield of joining engineering ceramics from the MaterialScience Institute (MSI), Aachen University of Technology,Germany where he was a chief engineer subsequentlyafter his graduation until 1996. After that he started work-ing as the head of Materials and Mechanics department attechnical center Hilti Corp, Principality of Liechtensteinfrom 1997 to 2000. From 2001 to 2002, he was a man-aging director of the business unit diamond tools at Hilti

Germany ltd. Since November 2002, he is a full Professor atthe Institute of Materials Engineering, Technical Univer-sity of Dortmund. His research interests include brazingtechnology, powder metallurgy, thermal Spraying, and

magnetron sputtering physical vapor deposition techniques.