Nanostructured substrate effects on diamond-like Carbon films properties grown by pulsed laser deposition

ARTICLE IN PRESS SCT-21535; No of Pages 6 Surface & Coatings Technology xxx (2016) xxx–xxx

Contents lists available at ScienceDirect

Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat

Nanostructured substrate effects on diamond-like Carbon films properties grown by pulsed laser deposition S.A. Hevia a, b, * ,1 , F. Guzmán-Olivos c , I. Muñoz a , G. Muñoz-Cordovez a , S. Caballero-Bendixsen a , H.M. Ruiz d , M. Favre a, b a

Instituto de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile Centro de Investigación en Nanotecnología y Materiales Avanzados CIEN-UC, Av. Vicuña Mackenna 4860, Santiago,Chile c Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Blanco Encalada 2008, Santiago, Chile d Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso, Chile b

A R T I C L E

I N F O

Article history: Received 9 April 2016 Received in revised form 25 August 2016 Accepted 27 August 2016 Available online xxxx Keywords: DLC PLD Nanostructured substrate Carbon nanodots AFM Raman

A B S T R A C T A study on the effect of using a nanostructured substrate in the growth of a diamond-like carbon (DLC) film by pulsed laser deposition (PLD) has been carried out. It was found that the deposition on a nanoporous substrate gives origin to a film with a lower ratio of the sp3 to sp2 hybridizations of carbon atoms bondings as compared to a film deposited on a flat substrate under the same conditions, namely flat Silicon (Si) or Aluminum (Al) foil. This could be a consequence of a local stress relaxation during the growing process induced by the nanoporous structure of the substrate, suggesting that it might not be possible to obtain a high content of tetrahedral amorphous carbon when that kind of substrates is used. Motivated by previous investigations of nanodots growth using a nanoporous alumina substrate, a low pressure Argon background was used during the deposition process, in order to achieve different values of the sp3 content. © 2016 Published by Elsevier B.V.

1. Introduction Diamond-like carbon (DLC) thin films have attracted the attention of scientists and engineers due to their wide range of applicability [1–9]. Of particular interest in this context is the hydrogenfree, tetrahedral amorphous carbon (ta-C) form of DLC, with a high content of sp3 bonds, with characteristics close to those of diamond, such as a high mechanical hardness, chemical inertness and wide band gap [10–12]. Several methods have been employed to deposit ta-C films, including pulsed laser deposition (PLD) [13–16], magnetron sputtering with ion implanting [17], mass selected ion beams [18], or filtered cathodic vacuum arc [19], among others. However, regardless of the technique, the fraction of sp3 bonding in the ta-C films depends mainly on the ion energy used in the deposition process, observing a maximum close to 85% for an ion energy around

* Corresponding author at: Instituto de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile. E-mail address: samuel.hevia@fis.puc.cl (S. Hevia). 1 Now at Center for Energy Research, University of California, San Diego, La Jolla, CA 92093, U.S.A.

100 eV [10,19,20]. A relevant issue to be considered in the use of ta-C films is the compressive stress generated during the growing process, as it causes poor adherence and limits the maximum thickness of the film [11]. Previous studies have shown that the existence of this stress is due to the mechanism of sp3 bond formation in the film [10]. Several strategies have been proposed to reduce the stress in as-deposited DLC film, such as the incorporation of metals or multilayers [21–23], or a post deposition annealing treatment that has been found to reduce dramatically this stress, without affecting the sp3 content of the film [24,25]. Recently DLC has been fabricated in the form of nanostructure, expanding the application range of this material. DLC nanodots are fabricated by filtered cathodic arc plasma or PLD using a porous membrane as an evaporation mask [26–29], or by using electron beam lithography [30]. However a question appears naturally: Is it possible to grow nanostructures of ta-C? In this work we show experimental results that contribute to give an answer to this question. In particular, a comparative study of the effect of a nanostructured substrate on the DLC film properties is presented. The films were deposited with a PLD system on a nanoporous anodic aluminum oxide (AAO), used as a nanostructured substrate, and also on flat substrates. As it is shown below, employing the AAO as a substrate reduce significantly the fraction of sp3 bonds in the

http://dx.doi.org/10.1016/j.surfcoat.2016.08.083 0257-8972/© 2016 Published by Elsevier B.V.

Please cite this article as: S. Hevia, et al., Nanostructured substrate effects on diamond-like Carbon films properties grown by pulsed laser deposition, Surface & Coatings Technology (2016), http://dx.doi.org/10.1016/j.surfcoat.2016.08.083

ARTICLE IN PRESS 2

S. Hevia, et al. / Surface & Coatings Technology xxx (2016) xxx–xxx

DLC film, giving a limit to the maximum value of sp3 contained in a DLC, apparently due to a stress relaxation during the growing process induced by the nanoporous structure of the substrate.

2. Experimental details The PLD was performed in a vacuum chamber, with a base pressure of 3 • 10 −5 Torr, using an external, single pulse, Nd:YAG laser source generating 3.5 ns pulses of 380 mJ, at 1.06 lm, focused at ∼45◦ onto a graphite target (purity higher than 99.99% ), with a characteristic fluence of 6.7 J/cm2 . To obtain a homogeneous deposit over a surface of ∼1 cm2 , the substrates were placed at 50 mm from the laser spot. The exposure time was 120 s, with the laser operating at 10 Hz. Based on previous results [15], and in order to investigate the relationship between the plasma carbon ions energy distribution and Carbon plasma species on the properties of the resulting films, an Argon background was used, with pressures ranging from 8 to 340 mTorr. To perform this study two type of flat substrates were used, n-type Si(100) wafers and high purity Al sheets (99.997%) with a native oxide layer on top (without porous). On the other hand, porous alumina membranes were used as nanostructured substrates. These AAO membranes were fabricated from high purity aluminum foils (99.997%), 0.1 mm thick, by the two-step anodization process [31]. Before anodization, the foils were washed with detergent and then successively with acetone and deionized water. After that, the aluminum sheets were annealed at 350 ◦ C in Argon flow at atmospheric pressure for 60 min, and then were mechanically polished with alumina suspensions, first using a fine grade of 0.3 lm and then of 0.05 lm, applied successively with polishing cloth, in a 25 min process. Finally, the foils were washed twice in deionized water using an ultrasonic bath. The anodizations were carried out at 40 V using a 0.3 M oxalic acid solution as electrolyte, which was cooled at 5 ◦ C. The first anodization was carried out during 4 h, which was then followed by 150 min of etching treatment (5% H3 PO4 and 1.8% H2 Cr2 O4 ) in order to obtain an ordered pre-pattern. The second anodization was performed during 13 h and 20 min, in order to obtain a AAO layer of 40 lm thickness on an aluminum sheet. The AAO membranes were subjected to an etching treatment using a 5 wt.% phosphoric acid solution at room temperature that was carried out for 50 min. With this treatment the pores are widened without affecting the order of the membranes. Fig. 1-(a) shows a top view of an AAO used as substrate. This micrograph was obtained with a Scanning Electron Microscope, operated with an accelerating voltage of 5 kV. Fig. 1-(b) shows an histogram of the dimensions of the pores, as observed in the micrograph. The histogram data was obtained from the image, which was processed and analyzed by using Image J [32] processing software. Considering that the pores have an elliptical shape, average values of 81.3 ± 7.0 nm and 68.9 ± 4.3 nm were obtained for the major and minor axis, respectively. From this analysis, the porosity of the membranes was estimated around 47%. A topographic surface characterization of the DLC films was carried out using atomic force microscope (AFM), from JPK instruments, model NanoWizard 3 BioScience. In order to determine the binding state of the carbon atoms in the films, a Raman micro-analysis was performed employing a LabRam010 Spectrometer with a 632.8 nm laser excitation and X-ray photoemission spectroscopy was carry out by using an XPS from from Physical Electronic, model 1257. The laser produced plasma was characterized by optical emission spectroscopy (OES), in order to determine the Carbon plasma species. The spectra were obtained with a Spectra Pro 275 (1200 g/mm) spectrometer, with a gated avalanche diode array, with 20 ms exposure time, and averaged over twenty shots. The Carbon plasma emission was collected with a lens array optically coupled with a fiber

Fig. 1. (a) SEM micrograph of a PAM used as substrate. (b) Histogram of the pore dimensions obtained from the image, considering that the pores have an elliptical shape. The average values of the major and minor axis are 81.3 ± 7.0nm and 68.9 ± 4.3nm respectively.

optic arrangement, from a sampling region of ∼3 mm characteristic diameter, centered on the plasma plume axis. Spectral resolution of the spectrometer is 0.2 nm at 500 nm. The intensified diode detector array has a sensitivity of 2800 photons/count and a maximum gain of 2000 photoelectrons/count. 3. Results In order to unveil the effect of the substrates on the morphological properties of Carbon films, an AFM characterization was performed. Fig. 2 shows AFM images of DLC films deposited on AAO (left hand side) and Silicon (right hand side), as a function of Argon background pressure. Fig. 2-(a) corresponds to a topographic image of DLC deposited at base pressure using AAO as a substrate. The films show a regular pattern that corresponds just to the observed in the bare AAO, reported in a previous work [26]. The geometrical pattern observed in Fig. 2-(a, b, c) indicates that at low pressure, Carbon deposition is almost conformal to the topography of the surface. However, as background pressure increases the formation of carbon nanoclusters takes place on top of the pattern, in a similar way to that with Silicon substrates, shown in the right hand side images. The DLC films deposited on Silicon at base pressure, Fig. 2-(g), is smooth with

Please cite this article as: S. Hevia, et al., Nanostructured substrate effects on diamond-like Carbon films properties grown by pulsed laser deposition, Surface & Coatings Technology (2016), http://dx.doi.org/10.1016/j.surfcoat.2016.08.083

ARTICLE IN PRESS S. Hevia, et al. / Surface & Coatings Technology xxx (2016) xxx–xxx

(a)

53 nm

200 nm

(g)

200 nm

0 nm (b)

200 nm

(c)

200 nm

(d)

200 nm

(e)

43 nm

0 nm 42 nm

0 nm 35 nm

0 nm (h)

10 nm

200 nm

0 nm (i)

6 nm

200 nm

0 nm (j)

11 nm

function of background pressure. Typically Raman spectra of amorphous carbon present two main peaks, labelled as D, at ∼1350 cm −1 , and G at ∼1510 cm −1 , which can be fitted by Lorentzian and BreitWigner-Fano (BWF) functions, respectively, as shown in Fig. 3. Both, the G peak position and the relative intensity of D and G peaks, allow the relative content of sp2 and sp3 bonds to be quantified [33,34]. In the curves that correspond to the samples growth at base pressure, the sp3 content is the highest for each sample. This is inferred from the fact that the fitting can be done mainly by a BWF shape. The relative intensity of resonance D increases as the background pressure increases. However, the evolution as a function of the pressure is different for both substrates. In the case of AAO, a notorious change in the spectra is observed between 17 mTorr and 85 mTorr (see Fig. 3). In the case of the Silicon substrate, this transition is also observed, but the pressure range shifts to between 250 mTorr and 340 mTorr. A quantitative analysis of these Raman spectra can be carried out in order to determined the ratio of sp3 to sp2 C–C bonds. This analysis can be done under the frame of the “Three-Stage Model” proposed by Ferrari et al. [33,34], in combination with XPS spectroscopy. With this purpose Fig. 4 shows the C1s peak of the XPS spectra of Carbon films grown over AAO, on the left hand side, and Silicon, on the right. As it is known, XPS carbon spectra present a peak at 284.5 eV, which corresponds to a C1s core level. As in DLC films both, sp2 and sp3 bonds are present, it is necessary to fit four peaks for the corresponding binding energies, 284.4 eV for the sp2 bond (black curve), 285.2 eV for the sp3 bond (red curve), 286.5 eV and 290 eV for C–O (green) and O–C=O (magenta curve) bonds, respectively [35,36]. The small contributions of C=O and O–C=O are attributed to surface contamination of the samples by air-exposure

200 nm

0 nm 71 nm

200 nm

0 nm (k)

43 nm

200 nm

0 nm (f)

7 nm

3

0 nm

124 nm (l)

95 nm

200 nm

200 nm

0 nm

0 nm

Fig. 2. Characteristic AFM images of Carbon films growth over different substrates, as a function of Argon background pressure. (a) to (f) are AFM images of DLC films deposited on AAO, and (g) to (k) correspond to equivalent films deposited on Silicon substrate.

some clusters on top. The background pressure increment promotes the growth of Carbon clusters, as seen in Fig. 2-(h–k). For the higher pressure used, 340 mTorr of Argon, the films consists of a collection of clusters regardless of the deposition substrate. As previously mentioned, a relevant characteristic of DLC films is their content of sp3 C–C bonds. In order to evaluate this feature, micro-Raman spectroscopy was performed on DLC films grown on AAO and Silicon substrates. The spectra are show in Fig. 3 as a

Fig. 3. Micro-Raman spectra of Carbon films growth over AAO and Silicon, as a function of Argon background pressure. Characteristic peaks D and G are fitted by Lorentzian and Breit-Wigner-Fano (BWF) functions, respectively.

Please cite this article as: S. Hevia, et al., Nanostructured substrate effects on diamond-like Carbon films properties grown by pulsed laser deposition, Surface & Coatings Technology (2016), http://dx.doi.org/10.1016/j.surfcoat.2016.08.083

ARTICLE IN PRESS 4

S. Hevia, et al. / Surface & Coatings Technology xxx (2016) xxx–xxx

DLC/Si

Intensity (a .u.)

DLC/AAO

Binding energy (eV) Fig. 4. XPS spectra of DLC films growth on AAO (left) and Silicon (right) substrates, at different Argon pressures. The C1s peak is fitted using four different peaks, corresponding to the sp2 bond (black curve), the sp3 bond (red curve), and the C–O (green curve) and O–C=O (magenta curve) bonds. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

and during the preparation process. This fitting procedure shows a notorious trend. In fact, when the Argon background pressure goes up, the area of the curve associated with the sp2 bonds increases, and at the same time, the one associated with the sp3 bonds decreases. The area difference between that of the curve associated with the sp3 bonds in AAO and Silicon substrates is observed to be significant at low pressures, becoming less pronounced when the Argon pressure reaches 350 mTorr. By measuring the areas below these curves it is possible to quantify the ratio of sp3 to sp2 C–C bonds contained in the DLC films. In the case of samples grown over Silicon substrates the content of sp3 C–C bonds change from ∼50% to ∼15%, and in the case of films grown over AAO substrates a change from ∼35% to ∼15% is observed. These values are consistent with the quantitative analysis of the I(D)/I(G) ratio and the position of G peak in the Raman spectra, shown in Fig. 5. On the light of these observations arises the question if these changes in DLC content are due to the substrate morphology or the atomic structure of the surface. In order to clarify this point, we grew films on an Aluminum foil with and oxide layer on top (without porous), under same conditions, namely Argon background pressure and deposition time, of those previously described. The results of the characterization of these films are also summarized in Fig. 5, where the values of characterization parameters of Carbon films deposited on porous membrane (AAO), Aluminum (Al) foil and Silicon (Si), are shown as a function of Argon background pressure. The position of peak G and I(D)/I(G) peak ratio, obtained from Raman

Fig. 5. Structural features of Carbon films deposited on PAM (AAO), Aluminum (Al) foil and Silicon (Si), as a function of Argon background pressure. Both, position of peak G and I(D)/I(G) peak ratio, are obtained from Raman spectroscopy, whereas the sp3 content is inferred from XPS measurements. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)

spectroscopy, and the sp3 content inferred from XPS measurements, are presented. A remarkable result that can be highlighted from Fig. 5 is the fact that films grown on Silicon (data in black circles) and on Aluminum foil (data in red down-triangles) shows very similar values of the characterization parameters, which are different from the values obtained from the analysis of the films grown on AAO (data in blue up-triangles). This observation strongly suggests that the substrate morphology plays a crucial role in determining the actual sp3 content of the resulting film. We have previously investigated the temporal and spatial scales for the Carbon plasma plume in PLD to change from a carbon iondominated plasma to one where C2 molecules dominate [37]. In order to correlate the DLC films properties with the Carbon plasma properties generated in the PLD chamber, we further investigated the expanding plume by OES. We have found in previous investigations of Carbon nanodots grow by PLD that the dominant species in the laser produced plasma is C2 Carbon molecules. To improve our characterization of the laser Carbon plasma deposition process we have registered the optical emission of a free expanding laser plasma and also on stagnation onto the deposition substrate, as a function of Ar background pressure. This is shown in Fig. 6, for both conditions. Light is collected from a region at 50 mm from the laser target, which also coincides with a position which is tangent to the deposition substrate. Argon pressures correspond to those at which structural data is presented in Figs. 2 to 6. At base pressure the only prominent feature in the spectra at both conditions is the line at 426.7 nm, which corresponds to single ionized Carbon (CII). As Argon background pressure is increased, the spectra show to be fully dominated by emission corresponding to vibrational states of the d3 P g → a3 Pu

Please cite this article as: S. Hevia, et al., Nanostructured substrate effects on diamond-like Carbon films properties grown by pulsed laser deposition, Surface & Coatings Technology (2016), http://dx.doi.org/10.1016/j.surfcoat.2016.08.083

ARTICLE IN PRESS S. Hevia, et al. / Surface & Coatings Technology xxx (2016) xxx–xxx

5

Fig. 6. Emission spectra of laser plasma at 50mm from laser target, for different base and Argon pressures. a) Free expanding laser plasma, and b) laser plasma stagnating on the substrate surface.

higher pressures again no differences are observed between the free expanding and surface stagnated Carbon plasmas. 4. Discussion The AFM images shown in Fig. 2 highlight the effect of an increasing Ar background pressure on the morphological properties of the deposited films. In fact, as Ar pressure increases from base pressure to 340 mTorr, a marked growth in grain size is observed, leading to a progressive nanostructuration of the films. The analysis of the Carbon films properties presented in the previous section provides

no substrate silicon substrate AAO substrate alumina substrate

5x105

Molecular Density (a.u.)

Swan bands (Dm = 2, Dm = 1, Dm = 0, Dm = −1), of the neutral C2 molecule [38] and, to a lesser extent, vibrational states from the B1 Pu → X 1 Sg+ Swing system, of the neutral C3 molecule [39], seen as a wide emission band around 400 nm. Similar features of the C2 emission dependence on Ar background pressure have been observed in pulsed laser assisted deposition of single wall carbon nanotubes [40]. As in our case C2 emission is strongly dominant, it precludes single ionized carbon lines to be intense enough to attempt a quantitative characterization of the Carbon plasma, using either Stark broadening or Boltzmann plot, to infer plasma density and temperature, in local thermodynamic equilibrium (LTE) conditions. As all spectra have been collected under the same conditions of detector sensitivity and integration time, a noticeable fact is that for Argon pressures between 8 and 85 mTorr, light emission is slightly higher in the case when the laser plasma stagnates over the deposition substrate. Light intensity emitted per unit volume by a plasma species at a given wavelength is proportional to the number density of the plasma species. Based on this we have performed a numerical integration of the visible emission of the laser plasma as shown in Fig. 6, as a function of pressure, for the different conditions mentioned above, i.e., free expanding laser plasma, and plasma stagnating over AAO, Aluminum foil, and Silicon substrate. The spectra used in the numerical integration were collected at the same position of those in Fig. 6. The result is presented in Fig. 7. The numerical integration was performed, after background subtraction, over the wavelength range from 450 to 525 nm, which includes the two most prominent emission bands of the C2 molecule. No significant differences are observed for pressures below 50 mTorr, with a monotonic increase in density for all conditions. A clear distinctive behavior is observed in the range from above 50 mTorr to 200 mTorr, in which the characteristic molecular density of the free expanding Carbon plasma is about half of that seen when the Carbon plasma stagnates over a surface, regardless of the particular surface, AAO, Al foil, or Si. At

4x105 3x105 2x105 1x105 0

0

100

200

300

400

Argon Pressure (mTorr) Fig. 7. Relative molecular Carbon density at 50mm from the laser target, for a free expanding plasma and stagnating over different deposition substrates.

Please cite this article as: S. Hevia, et al., Nanostructured substrate effects on diamond-like Carbon films properties grown by pulsed laser deposition, Surface & Coatings Technology (2016), http://dx.doi.org/10.1016/j.surfcoat.2016.08.083

ARTICLE IN PRESS 6

S. Hevia, et al. / Surface & Coatings Technology xxx (2016) xxx–xxx

strong evidence that employing a nanoporous membrane as a substrate instead a flat surface alters significantly the fraction of sp3 bondings, particularly when it is deposited at base pressure condition, where the highest percentage of sp3 bondings is achieved. This is in contrast with the fact that plasma conditions over the deposition substrate, as inferred from the relative molecular Carbon density shown in Fig. 7, do not change, within the error bars of the data, for the different deposition substrates investigated. In order to give an explanation to this observation, the deposition mechanism of the DLC film on a substrate should be reviewed. Several authors have attempted to explain this mechanism. Lifshitz et al. [41] proposed, on the base of Auger analysis of the depth profiles of medium energy C ions incident on Nickel substrates, that the DLC film growth takes place in the sub-surface region of the substrate. This process of low energy sub-surface implantation was called “subplantation”. McKenzie [42] and Davis [43] have proposed that the formation of sp3 bonding is mediated by a compressive stress in the film, generated by ion beam impact, which moves the film above the Berman-Simon line and so stabilizes the high pressure diamond phase. This explanation relays on the idea that the amorphous carbon (a-C) is under quasi-thermodynamic equilibrium, so the stability of sp2 and sp3 bonding in a-C follows the phase diagram of crystalline carbon. Therefore, to obtain sp3 bonding a minimum amount of pressure above the Berman-Simon diamond-graphite equilibrium line [44] is needed. While several simulations appear to confirm the idea of subplantation [45–48], a full understanding is still missing. This growth mechanism has been reviewed by Robertson [10], who has proposed that only a sub-surface growth in a restricted volume is needed to get sp3 bonding. Although a strong correlation between the fraction of sp3 bonding and macroscopic stress of DLC films has been observed, particularly for ta-C, Ferrari et al. [49] showed that while stress may be necessary to stabilize the sp3 phase during the film growth, it is not longer needed once the sp3 phase is formed. In fact, Ferrari et al. [25] critically analyzed the origin of stress in taC and claim that the usually quoted stress vs. sp3 correlation is an unfortunate consequence of the existing deposition procedures, and they conclude that macroscopic stress is not necessary to produce a film with a high sp3 content. In this context, it is particularly interesting to compare the images (a) vs. (g) of Fig. 2 and to correlate them with the fraction of sp3 bonding. In the case of Fig. 2-(a), due to the nanostrutured substrate, it was not possible to obtain a continuous film, and instead of that, a pattern of DLC triangles surrounding the pores with dimension around 50 nm was obtained. In this condition a continuous stress across the Carbon film is not possible due the clusterization inferred from the images. On the other hand, in the case of Fig. 2-(g) a continuous film resulted, and the highest fraction of sp3 bonding was achieved.

5. Conclusions The aim of this work was to unveil the effect of use a nanostructured substrate in the growth of a DLC film. We have established that the deposition on a nanostructured substrate gives origin to a film with a lower sp3 to sp2 ratio as compared to a flat substrate deposited on the same conditions. We consider that this result contributes to achieve a better understanding of the growth mechanism of the DLC film. Nevertheless, independent of the mechanism that induce this reduction of the sp3 hybridization contained in the film, which, on base of our observations, could be a consequence of a limitation of the maximum stress induced in the film due the nanostructuration, our results are relevant from the technical point of view, as they indicate that it could exist a limit in the maximum value of sp3 contained in a DLC film which can be achieved when these kind of substrates are used.

Acknowledgments This work has been funded by projects FONDECYT Nos. 1161614 and 1141119, and CONICYT PIA No. ACT1108. F. Guzmán-Olivos acknowledges postdoctoral project FONDECYT No. 3140565.

References [1] R. Hauert, Tribol. Int. 37 (2004) 991. [2] M. Alaluf. M, J. Appelbaum, L. Klibanov, D. Brinker, D. Scheiman, N. Croitoru, Thin solid films, 256 (1995) l. [3] J.K. Luo, A.J. Flewitt, S.M. Spearing, N.A. Fleck, W.I. Milne, Appl. Phys. Lett. 85 (2004) 5748. [4] J.P. Sullivan, T.A. Friedmann, K. Hjort, MRS Bull. 26 (2001) 309. [5] C. Casiraghi, J. Robertson, A.C. Ferrari, Mater. Today 10 (2007) 44. [6] Y. Wu, Y. Lin, A.A. Bol, K.A. Jenkins, F. Xia, D.B. Farmer, Y. Zhu, P. Avouris, Nature 472 (2001) 74. [7] X. Jiang, G. Wu, J. Zhou, S. Wang, A.A. Seng, Z. Du, Nanoscale Res. Lett. 6 (2011) 518. [8] K. Bewilogua, D. Hofmann, Surf. Coatings Technol. 242 (2014) 214. [9] F.T. Thema, P. Beukes, B.D. Ngom, E. Manikandan, M. Maaza, J. Alloys Compd. 648 (2015) 326. [10] J. Robertson, Mat. Sci. and Eng.: R: Reports 37 (2002) 129. [11] M.P. Siegal, D.R. Tallant, N. Provencio, D.L. Overmyer, R.L. Simpson, L.J. Martinez-Miranda, Appl. Phys. Lett. 76 (2000) 3052. [12] M.P. Siegal, D.R. Tallant, J. Martinez-Miranda, J.C. Barbour, R.L. Simpson, D.L. Overmyer, Phys. Rev. Lett. B 61 (2000) 10451. [13] A.A. Voevodin, M.S. Donley, Surf. Coating Technol. 82 (1996) 199. [14] M. Jelínek, T. Kocourek, J. Remsa, J. Miksovský, J. Zemek, K. Smetana, B. Dvoránková, T. Luxbacher, Appl. Phys. A 101 (2010) 579. [15] F. Guzmán, M. Favre, H.M. Ruiz, S.A. Hevia, L.S. Caballero, E.S. Wyndham, H. Bhuyan, M. Flores, S. Mändl, J. Phys. D: Appl. Phys 46 (2013) 215202. [16] S.S. Yap, C.H. Nee, S.L. Yap, T.Y. Tou, J. Nanomaterials (2015)731306. [17] J. Schwan, S. Ulrich, H. Roth, H. Ehrhardt, S.R.P. Silva, J. Robertson, R. Samlenski, R. Brenn, J. Appl Phys. 79 (1996) 1416. [18] A.A. Voevodin, M.S. Donley, J.S. Zabinski, Surf. Coat. Technol. 52 (1997) 42. [19] P.J. Fallon, V.S. Veerasamy, C.A. Davis, J. Robertson, G.A.J. Amaratunga, W.I. Milne, Phys Rev. B 48 (1993) 4777. [20] N. Koukhunthot, C. Euaruksakul, P. Photongkam, P. Wongpanya, J. Met. Mat. and Minerals 23 (2013) 35. [21] K. Okuri, T. Arai, Surf. Coat. Technol. 47 (1991) 710. [22] M. Chhowalla, Y. Yin, G.A.J. Amaratunga, D.R. Mckenzie, T. Frauenheim, Appl. Phys. Lett. 69 (1996) 2344. [23] M. Chhowalla, Diamond Rel. Mater. 10 (2001) 1011. [24] T.A. Friedmann, J.P. Sullivan, J.A. Knapp, D.R. Tallant, D.M. Follstaedt, D.L. Medlin, P.B. Mirkarimi, Appl. Phys. Lett. 71 (1997) 3820. [25] A.C. Ferrari, S.E. Rodil, J. Robertson, W.I. Milne, Diamond Rel. Mater. 11 (2002) 994. [26] S.A. Hevia, P. Homm, F. Guzmán, H.M. Ruiz, G. Munoz, L.S. Caballero, M. Favre, M. Flores, Surf. Coat. Technol. 253 (2014) 161. [27] C. Li, P.X. Yan, X.C. Li, E.M. Chong, Phys. E. 42 (2010) 1343. [28] C. Li, X.C. Li, E.M. Chong, P.J. Zhang, X.Y. Fan, P.X. Yan, Appl. Surf. Sci. 254 (2008) 2544. [29] G. Muñoz, P. Homm, F. Guzmán, H.M. Ruiz, L.S. Caballero, M. Favre, M. Flores, S.A. Hevia, J. Phys: Conf. Series 591 (2015) 012047. [30] T. Djenizian, E. Balaur, P. Schmuki, Nanotechnology 17 (2006) 2004. [31] S.A. Hevia, P. Homm, A. Cortes, V. Nunez, C. Contreras, J. Vera, R. Segura, Nanoscale Res. Lett. 7 (2012) 342. [32] J. Tony, Collins, Biotechniques 43 (2007) 25. [33] A.C. Ferrari, J. Robertson, Phys. Rev. B 61 (2000) 14095. [34] A.C. Ferrari, J. Robertson, Phys. Rev. B 64 (2001) 075414. [35] J.I. Wilson, J. Walton, G. Beamson, J. Electron Spectros. Relat. Phenomena 121 (2001) 183. [36] R. Haerle, E. Riedo, A. Pasquarello, A. Baldereschi, Phys. Rev. B 65 (2001) 32. [37] H.M. Ruiz, F. Guzmán, M. Favre, H. Bhuyan, H. Chuaqui, E.S. Wyndham, Plasma Sources Sci. Technol 21 (2012) 034014. [38] G.B. Donati, Astron. Nachr. 62 (1882) 375. [39] W. Huggins, Proc. Roy, Soc. 33 (1882) 1. [40] D.E. Motaung, M.K. Kisten, E. Manikandan, N.J. Coville, J. Appl. Phys. 141 (2010) 034308. [41] Y. Lifshitz, S.R. Kasi, J.W. Rabalais, W. Eckstein, Phys. Rev. B 41 (1990) 10468. [42] D.R. McKenzie, J.V.a.c. Sci, Technol. B 11 (1993) 1928. [43] C.A. Davis, Thin Solid Films 226 (1993) 30. [44] R. Berman, F. Simon, Z. Elektrochem 59 (1955) 333. [45] H.P. Kaukonen, R.M. Nieminen, Phys. Rev. Lett. 68 (1992) 620. [46] S. Uhlmann, T. Frauenheim, Y. Lifshitz, Phys. Rev. Lett. 81 (1998) 641. [47] H.P. Kaukonen, R.M. Nieminen, Phys. Rev. B 61 (2000) 2806. [48] K. Kohary, S. Kugler, Phys. Rev. B 63 (2001) 193404. [49] A.C. Ferrari, B. Kleinsorge, N.A. Morrison, A. Hart, V. Stolojan, J. Robertson, J. Appl. Phys. 10 (1999) 7191.

Please cite this article as: S. Hevia, et al., Nanostructured substrate effects on diamond-like Carbon films properties grown by pulsed laser deposition, Surface & Coatings Technology (2016), http://dx.doi.org/10.1016/j.surfcoat.2016.08.083