Nano femtosecond laser processing in developing nanocrystalline functional materials for multi core orthogonal fluxgate sensor

NANO/FEMTOSECOND LASER PROCESSING IN DEVELOPING NANOCRYSTALLINE FUNCTIONAL MATERIALS FOR MULTI-CORE ORTHOGONAL FLUXGATE SENSOR TAN LI SIRH (B.Eng (Hons.),NUS) A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING NANOSCIENCE & NANOTECHNOLOGY INITIATIVE NATIONAL UNIVERSITY OF SINGAPORE 2009 Acknowledgements ACKNOWLEDGEMENTS I would like to express my utmost sincere and greatest appreciation to my supervisors, Professor Li Xiaoping and Associate Professor Hong Minghui, for their guidance throughout my Master project Their valuable opinions have been utmost importance to me I am also grateful to Dr Seet Hang Li for all his advices and help throughout my project In addition, I would like to thank all members in Neurosensors Lab and Laser Microprocessing Lab for sharing their research experience and helping me in one way or another I would also like to express my heartfelt gratitude to Miss Jasmin Lee from NUSNNI programme, Mr Lim Boon Chow from A-STAR Data Storage Institute (DSI), Miss Li Xue from A-STAR Institute of Materials and Research Engineering (IMRE) and staff at the Advanced Manufacturing Lab (AML) and Materials Science Lab (MSL) for all their kind assistance Lastly, I wish to thank all those who have supported, helped and accompanied me throughout my two years of the Masters course i Table of Contents TABLE OF CONTENTS ACKNOWLEDGEMENTS i TABLE OF CONTENTS ii SUMMARY v LIST OF TABLES viii LIST OF FIGURES ix LIST OF SYMBOLS xv LIST OF PUBLICATIONS xvi Chapter Introduction 1.1 Motivation 1.2 Objectives of Present Study 1.3 Organization of Thesis Chapter Literature Review 2.1 Magnetic Materials and Relevant Theories 2.1.1 Basic Classification of Magnetic Materials 2.1.2 Ferromagnetic Materials and Their Properties 2.1.3 Curie Temperature Tc 2.1.4 Hysteresis 2.1.5 Factors Affecting Magnetic Quality 10 2.1.6 Domain Wall Theories 11 2.1.7 Magnetization Rotation 11 2.1.7.1 Crystalline Anisotropy 12 2.1.7.2 Stress Anisotropy 12 2.1.7.3 Shape Anisotropy 12 2.2 Types of Lasers 13 2.2.1 Nanosecond Laser 13 2.2.2 Femtosecond Laser 14 2.2.3 Effects of Nanosecond and Femtosecond Lasers on Magnetic Materials 18 2.3 Fabrication Methods 21 2.3.1 Template Fabrication 21 2.3.1.1 Conventional Methods 21 2.3.1.2 Laser Micromachining Method .23 2.3.2 Magnetic Material Deposition Methods .24 2.3.2.1 Electrodeposition 24 2.3.2.2 Electron-beam evaporation .25 Chapter Research Approach and Experimental Setup 28 3.1 Research Approach 28 3.2 Materials Development and Fabrication Processes 28 3.2.1 Laser Systems 28 3.2.1.1 355nm Nd:YAG nanosecond laser 28 3.2.1.2 800nm Ti:Sapphire femtosecond laser 29 3.2.2 Deposition Set-up 30 3.2.2.1 Electron-beam Evaporation 30 3.2.2.2 Electrodeposition 31 ii Table of Contents 3.3 Materials Properties Characterization Setup 34 3.3.1 Profilometer 34 3.3.2 Optical Microscope 34 3.3.3 Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) 35 3.3.4 Energy Dispersive X-ray (EDX) 36 3.3.5 X-Ray Diffraction (XRD) 37 3.3.6 Vibrating Specimen Magnetometer (VSM) Setup 39 Chapter Nanosecond Pulsed Laser-assisted Micro-drilling of Templates and Electroplating Deposition of Nanocrystalline Permalloy 40 4.1 Research Approach 40 4.2 Template Fabrication 41 4.2.1 Selection of Machined-drilled or Laser-drilled Templates 41 4.2.2 Methods of Adhesion 43 4.2.3 Fabrication of Single and Stacked Templates 44 4.3 Laser Parameters 45 4.3.1 Laser Fluence Effect 46 4.3.2 Laser Irradiation Time Effect 48 4.3.3 Pulse Number Effect 50 4.3.4 Laser Focal Length Effect 51 4.3.5 Optimization of Laser Parameters 54 4.4 Study of Electrodeposition Parameters 55 4.4.1 XRD Analysis 55 4.4.2 Plating Current Efficiency 57 4.4.3 Plating Current Density 58 4.4.3.1 Composition (Ni%) 58 4.4.3.2 Diameter of Electroplated Wires 60 4.4.3.3 Number of Electroplated Wires 62 4.4.4 Plating Time 64 4.4.4.1 Composition 64 4.4.4.2 Material Structure 67 4.4.5 Template Electrodeposition 68 4.5 Electrodeposited Structures 70 4.5.1 Single Template 70 4.5.2 Stacked Templates 74 4.5.3 Single Template with Varying Array Size 75 Chapter Femtosecond Laser Machining of Magnetic Materials 79 5.1 Research Approach 79 5.2 Commercial Vitrovac 6025X 80 5.2.1 Material Removal Rate 81 5.2.2 Morphology of Laser-Machined Channels 82 5.2.3 Study of Laser Fluence Effect on Composition at Ablated and Damaged Areas 83 5.2.4 XRD Analysis 85 5.2.5 Study of Laser Fluence on Magnetic Properties 86 5.2.5.1 Hysteresis 86 5.2.5.2 Coercivity 87 5.2.6 Influence of Different Numbers of Ablated Channels on Magnetic Properties 89 iii Table of Contents 5.2.6.1 Hysteresis 89 5.2.6.2 Coercivity 90 5.3 Electron-beam Deposited Permalloy 91 5.3.1 Surface Morphology of Laser-Machined Channels 91 5.3.1.1 Laser Fluence Effect .91 5.3.1.2 Number of Pulses 95 5.3.2 Study of Laser Fluence Effect on Composition at Ablated and Damaged Areas 97 5.3.3 XRD Analysis 99 5.3.4 Laser Fluence Effect 102 5.3.4.1 Hysteresis 102 5.3.4.2Coercivity .103 Chapter Conclusions and Recommendations 108 6.1 Conclusions 108 6.2 Future Works 113 6.2.1 Methods to improve laser-drilling of templates and electroplating of nanocrystalline Permalloy 113 6.2.2 Method to improve femtosecond laser machining on magnetic materials 115 Reference 117 iv Summary SUMMARY In the development of magnetic sensing elements, the sensitivity of magnetic sensors have been found to increase exponentially when multi-core structures are used as sensing elements These multi-core structures can be achieved by template assisted deposition/electrodeposition or direct processing In this project, multi-core structured functional magnetic materials of extremely high permeability have been successfully developed with the assistance of either nanosecond or femtosecond lasers Methods such as nanosecond laser drilling of polymeric templates for electrodeposition of nanocrystalline nickel-iron wires and femtosecond laser machining of Vitrovac 6025X and nickel-iron thin films are investigated Both methods are found to be suitable to obtain multi-core structures Nanosecond laser-drilled templates selected as smaller hole diameter can be achieved using this approach This would yield high aspect ratio holes for electroplating In addition, there is higher wire density per template, with the template dimensions held constant Laser processing parameters such as laser fluence, laser irradiation time and number of pulses were studied The diameter of the laser-drilled hole and the ablation depth are found to be dependent on the laser fluence An increase in the applied laser fluence will increase both parameters Higher laser irradiation time amplifies the heat affected zones and a threshold number of pulses are required to obtain a clean welldrilled hole Laser-drilled holes are also known to have tapered profile In order to minimize tapering, the focal point is set at the top surface of the template With the achieved templates, electrodeposition was then carried out to fill the drilled holes with Ni-Fe Using XRD, the electroplated Ni-Fe is found to be of FCC structure, with the v Summary lattice constant calculated to be 0.354 nm and having an average crystallite/grain size of 34.5 nm In order to gain an understanding and control of the electrodeposition process, the effect of varying plating current density and plating time on the resulting composition was investigated Experiments were also conducted to investigate the value of the plating current density in order to achieve Permalloy composition for templates with different hole diameters and array sizes (wire number) The results show that the materials composition is independent of both the hole diameters and the array sizes Since mm thick polymeric templates are used, vacuum (for partial removal of air bubbles) and ultrasonic agitation during electroplating are introduced to minimize “blockage” of the laser drilled holes This has been found to be effective in achieving high aspect ratio (1:25) wires If the laser-drilled templates are stacked, the best aspect ratio achieved for deposited nanocrystalline Ni-Fe wires has been found to be 1:50 (pillars of ~ 40 m diameter and 2mm in length), with a composition of 83% nickel and 17% iron When multiple holes of different array sizes on the same template are placed in the electrolyte, composition of nickel-iron varies due to the ions distribution in the cell varied along the electrolyte Femtosecond laser (direct) processing of magnetic materials were successfully carried out on Vitrovac 6025X foils and electron-beam evaporated Ni-Fe thin films The results showed that femtosecond laser processing is a feasible way to fabricate multicore sensing elements For multi-core Vitrovac 6025X, no composition distribution of the ablated magnetic foils were observed across the entire surface profile, suggesting no diffusion process took place during ablation Hysteresis loops, obtained from samples ablated using different laser fluences as well as specimens with different numbers of ablated channels, show that the overall anisotropy of the magnetic foils vi Summary before and after femtosecond laser processing did not change significantly and that the magnetic property of the specimens (i.e coercivity) did not deteriorate significantly, even when a significant amount of the magnetic materials was ablated For multi-core Ni-Fe thin films, it is observed that there is a 5% increment in terms of coercivity for fully ablated channels However, the results show that femtosecond laser irradiation can be manipulated to modify the properties of Ni-Fe Surface modification was observed Ripples formation, tilted to an angle to the direction of the beam, was observed when different laser fluences were applied to the nanocrystalline films When the polarization state of the laser beam was changed to 90°, shorter ripples (parallel to beam’s scanning direction) were formed As the number of ablative pulses increased, formation and collapse of ripples occurred earlier than that of the threshold laser fluence at single pulse XRD analysis suggests that rapidquenching effect changes the surface layer from nanocrystalline to amorphous and that the average crystallite/grain size decreases upon ripples formation After laser ablation, regardless of the value of the laser fluences, anisotropy has shifted towards the easy axes of the films The appearance of ripples marks the point when coercivity of the magnetic material begins to decrease It appears that there is a laser fluence threshold for both average crystallite/grain size and coercivity to decrease to a minimum, beyond which coercivity will increase at a gradual rate vii List of Tables LIST OF TABLES Table 2.1: Summary of classification of magnetic properties 7  Table 2.2: Types of anisotropy 12  Table 3.1: List of fabrication equipment used in this project 28  Table 3.2: List of characterization equipment used in this project 28  Table 3.3: Electrolyte solution content 32  Table 4.1: Calculations from XRD results 56  Table 4.2: Summary of grain size results 57  Table 4.3: Summary of current efficiency results 58  Table 4.4: Summary of hole diameter, plating area, plating current in relation to a constant current density 62  Table 5.1: Composition of Ni-Fe (%) after laser ablation at non-ablated and ablated areas 99  Table 5.2: Calculations from XRD results 100  viii List of Figures LIST OF FIGURES Figure 2.1: A typical hysteresis curve 10 Figure 2.2: Process of magnetization 11 Figure 2.3: Nanosecond laser processing 13 Figure 2.4: SEM image of an ablated metal channel created by a nanosecond laser 14 Figure 2.5: SEM image showing minimum amount of re-deposited material after femtosecond laser ablation 15 Figure 2.6: Nanosecond laser processing 16 Figure 2.7: Easy axis M-H loops (a) before and (b) after fabrication of grooves parallel to the as-deposited hard axis in FeN monolayer 19 Figure 2.8: Hysteresis loops of Finemet: (a) sample non-treated by laser, (b) laser treated sample with small density dotted lines, and (c) laser treated sample with high density of dotted lines 20 Figure 2.9: XRD analysis of amorphous alloy ribbon before and after laser micromachining 20 Figure 2.10: Photograph showing patterned template on developed negative photoresist layer 21 Figure 2.11: FESEM image of developed bi-layered photoresist after single exposure 22 Figure 3.1: Schematics of the laser drilling setup 29 Figure 3.2: Schematic representation of the laser set-up for cutting magnetic foils 30 Figure 3.3: Schematics of the electrodeposition setup 31 Figure 3.4: Diamond tip-wafer surface interaction 34 Figure 3.5: Set of atomic planes in a crystal, at an angle θ from the incident beam 38 ix Chapter Conclusions and Recommendations absence of Si and B elements as established by EDX analysis Hysteresis loops obtained from samples ablated using different laser fluences as well as specimens with different numbers of ablated channels show that the overall anisotropy of the magnetic foils before and after femtosecond laser processing did not change significantly and that the magnetic property of the specimens such as the coercivity did not deteriorate significantly, even when a significant amount of the magnetic materials was ablated Averaged composition for electron-beam deposited nanocrystalline Ni-Fe remains similar to that of as-deposited XRD analysis suggests that rapid-quenching effect changes the surface layer of the material to be amorphous and the average crystallite/grain size decreases upon ripples formation After laser ablation, regardless of the value of the laser fluences, anisotropy has shifted towards the easy axes of the films It is proposed that femtosecond laser processing has induced anisotropy to be towards the longitudinal axe of the magnetic films which is accrued to the changes in crystallinity and removal of non-magnetic phase or voids The appearance of ripples marks the point when coercivity of the magnetic material begins to decrease It appears that there is a laser fluence threshold for both average crystallite/grain size and coercivity to decrease to a minimum, beyond which coercivity will increase at a gradual rate In the development of magnetic sensing elements, the sensitivity of magnetic sensors have been found to increase exponentially when multi-core structures are used as sensing elements In this project, multi-core structured functional magnetic materials of extremely high permeability have been successfully developed with the 111 Chapter Conclusions and Recommendations assistance of either nanosecond or femtosecond lasers Methods such as nanosecond laser-drilling of polymeric templates for electrodeposition of nanocrystalline Ni-Fe wires and femtosecond laser machining of Vitrovac 6025X and nanocrystalline Ni-Fe thin films are investigated Both methods are found to be suitable to obtain multi-core structures For stacked laser-drilled templates, the best aspect ratio achieved for electroplated nanocrystalline Ni-Fe wires is 1:50 (pillars of ~ 40 m diameter and 2mm in length), with a composition of 83% nickel and 17% iron For the second method using femtosecond laser on Vitrovac 6025X foils and electron-beam evaporated Ni-Fe thin films, the results showed that femtosecond laser processing can be used to fabricate multi-core sensing elements In addition, for fabrication of multicore nanocrystalline Ni-Fe thin films, it is observed that there is a 5% increment in terms of coercivity for fully ablated channels However, experiments show that laser irradiation can be used to modify magnetic materials such that the material becomes softer 112 Chapter Conclusions and Recommendations 6.2 Future Works To further improve the current project, the following ideas are proposed 6.2.1 Methods to improve laser-drilling of templates and electroplating of nanocrystalline Permalloy Femtosecond laser drilling on polymeric template can be considered Femtosecond laser drilling to obtain deep and high quality holes in metal without any postprocessing or special gas environment had been demonstrated by G Kamlage et al [73] Laser fluence well above the ablation threshold was selected for initial drilling process to acquire higher ablation rate Low fluence was then chosen for the finishing in order to minimize any possible surface damage The SEM images of the drilled holes in 1mm thick stainless steel and the replicas are shown in Figure 6.1 Figure 6.1: SEM images of the drilled holes and their replicas [73] S Nolte et al [74] have also reported that the polarization state of the laser radiation also affects the quality of the drilled hole Figure 6.2 shows the SEM image of the exit of a hole produced in 1mm thick steel plate using diffractive optical element without 113 Chapter Conclusions and Recommendations any changes to the polarization state Undesired deformations on the shape of the circular hole were observed The non-circular hole is due the polarization-dependent reflections occurring at the walls inside the hole which led to a non-uniformity intensity distribution Figure 6.2: Exit of a hole produced in mm thick steel plate using diffractive optical element without any change in the polarization state [74] By rotating a half-waveplate during the drilling process, linear polarization was converted into circular polarization to minimize the effects of reflection A circular hole as seen in Figure 6.3 was obtained Figure 6.3: Exit of a hole produced in mm thick steel plate using diffractive optical element and polarization trepanning technique [74] 114 Chapter Conclusions and Recommendations 6.2.2 Method to improve femtosecond laser machining on magnetic materials Currently, the 150nm thick magnetic thin films are deposited by electron beam evaporation with an averaged composition of 83% nickel and 17% iron Alternative deposition method would be to use sputtering Sputtering is carried out by energized gas particles hitting the target with sufficient energy that result in the ejection of one or more atoms to be sputtered on the substrate Therefore, consider the sputtering of a NiFe target where CNi and CFe represent nickel and iron concentrations respectively The concentrations are represented by C Ni = n Ni n and C Fe = n Fe n where nNi and nFe are the numbers of Ni and Fe atoms with sputtering yields SNi and SFe The ratio of the sputtered atom flux, JNi and JFe , is given by J Ni S Ni C Ni = J Fe S Fe C Fe (6.1) If ng is the number of argon gas atoms hitting the target, the numbers of atoms ejected from the target will be ngCNiSNi and ngCFeSFe As a result, surface concentration of the target will be changed to ' C Ni (1 − n g S Ni / n) C Ni = ' C Fe (1 − n g S Fe / n) C Fe (6.2) If the sputtering yield SNi is higher than that of SFe, the target surface will be enriched in Fe atoms, and then the Fe atoms will begin to sputter more That is, C Ni (1 − n g S Ni / n) J Ni S Ni C Ni' = = ' J Fe S Fe C Fe C Fe (1 − n g S Fe / n) (6.3) 115 Chapter Conclusions and Recommendations The surface composition of the target will continue to change until the ratio of sputtered flux reached to 81:19, which is the original composition of the target Hence, sputtering would be able to deposit Ni-Fe thin film at a strict stoichiometric of 80:20 The composition is ideal for magnetic sensor applications as the coercivity and saturation magnetization would be at its minimum 116 Reference Reference Phan, M.-H., and Peng, H.-X., "Giant magnetoimpedance materials: fundamentals and applications," Progress in Materials Science, 2008, Vol 53, No 2, pp 323-420 Chiriac, H., Herea, D.-D., and Corodeanu, S., "Microwire array for giant magneto-impedance detection of magnetic particles for biosensor prototype," Journal of Magnetism and Magnetic Materials, 2007, Vol 311, No.1, pp 425428 Li, X.P., Fan, J., Ding, J., and Qian, X.B., "Multi-core orthogonal fluxgate sensor," Journal of Magnetism and Magnetic Materials, 2005, Vol 300, No.1, pp e98-e103 Lenz, J., and Edelstein, S., "Magnetic sensors and their applications," IEEE Sensors Journal, 2006, Vol 6, No.3, pp 631-649 Al-Mawlawi, D., Liu, C.Z., and Moskovits, M., "Nanowires formed in anodic oxide nanotemplates," Journal of Materials Research, 1994, Vol 9, No 4, pp 1014-1018 Su, Y.-W., Wu, C.-S., Chen, C.-C., and Chen, C.-D., "Fabrication of twodimensional arrays of CdSe pillars using e-beam lithography and electrochemical deposition," Advanced Materials, 2003, Vol 15, No 1, pp 49-51 Tebble, R.S., and Craik, D.J., "Magnetic Materials," John Wiley & Sons Ltd, 1999 Li, X.P., Zhao, Z.J., Ang, S., Oh, T.B., Song, T.W., Ng, W.C., Koh, S.J., and Lee, J.Y., "Effect of current density on the magnetic properties of 117 Reference electroplated NiFe layers," Materials Science Forum, 2003, Vol, 437-438, pp 61-64 Seet, H.L., See, S.H., Li, X.P., Lee, J.Y., Lee, K.Y.T., Teoh, S.H., and Lim, C.T., "Study of the parameters of the electroplating of ferromagnetic materials in relation to material permeability," Materials Science Forum, 2003, Vol 437-438, pp 475-478 10 Zele áková, A., Kollár, P., Vértesy, Z., Ku mi ski, M., Ramin, D., and Rieheman, W., "Influence of small circular holes on the coercivity and domain structure of nanocrystalline finemet," Scripta Materialia, 2001, Vol 44, No 4, pp 613-617 11 Semerok, A., Chaléard, C., Detalle, V., Lacour, J.-L., Mauchien, P., Meynadier, P., Nouvellon, C., Sallé, B., Palianov, P., Perdrix, M., and Petite, G., "Experimental investigations of laser ablation efficiency of pure metals with femto, pico and nanosecond pulses," Applied Surface Science, 1999, Vol 138-139, pp 311-314 12 http://en.wikipedia.org/wiki/Nickel [Assessed on 30 November 2008] 13 http://en.wikipedia.org/wiki/Iron [Accessed on 30 November 2008] 14 http://en.wikipedia.org/wiki/Ferromagnet [Assessed on October 2008] 15 http://en.wikipedia.org/wiki/Diamagnetism [Assessed on October 2008] 16 http://en.wikipedia.org/wiki/Paramagnetism [Assessed on October 2008] 17 Boll, R., "Soft Magnetic materials: fundamentals, alloys, properties, products, applications," Henyden & Son Ltd, London, 1979 18 Neelakantha, P.S., "Handbook of electromagnetic materials: monolithic and composite versions and their applications," CRC Press, Florida, 1995 118 Reference 19 http://hyperphysics.phy-astr.gsu.edu/hbase/solids/ferro.html [Assessed on October 2008] 20 Kovacs, G.T.A., "Micromachined transducers sourcebook," McGraw-Hill, Boston, 1998 21 http://www.geo.umn.edu/orgs/irm/hg2m/hg2m_c/hg2m_c.html [Assessed on 11 October 2008] 22 http://www.clark-mxr.com/Industrial/Handbook/Chapter3.htm [Assessed on 11 October 2008] 23 Liu, X., Du, D., and Mourou, G., "Laser ablation and micromachining with ultrashort laser pulses," IEEE Journal of Quantum Electron, 1997, Vol 33, No 10, pp 1706-1716 24 Chichkov, B.N., Momma, C., Nolte, S., Alvensleben, F.von., and Tünnermann, A., "Femtosecond, picosecond and nanosecond laser ablation of solids," Applied Physics A, 1996, Vol 63, No 2, pp 109-115 25 Hirayama, Y., and Obara, M., "Heat effects of metals ablated with femtosecond laser pulses," Applied Surface Science, 2002, Vol 197-198, pp 741-745 26 Korte, F., Nolte, S., Chichkov, B.N., Bauer, T., Kamlage, G., Wagner, T., Fallnich, C., and Welling, H., "Far-field and near-field material processing with femtosecond laser pulses," Applied Physics A, 1999, Vol 69, No 7, pp S7-S11 27 Herman, P.R., Marjoribanks, R.S., Oettl, A., Chen, K., Konovalov, I., and Ness, S., "Laser shaping of photonic materials: deep ultraviolet and ultrafast lasers," Applied Surface Science, 2000, Vol 154-155, pp 577-586 119 Reference 28 Gall, H.L., Gouzerh, J., Youssef, J Ben., Koshkina, O., Guitonni, J., Desvignes, J.M., Fessant, A., Spenato, D., Gieraltowski, J., and Loaëc, J., "Two-dimensional arrays of magnetic stripes and dots patterned by laser ablation," Journal of Applied Physics, 1997, Vol 81, No 8, pp 4727-4729 29 Jia, W., Peng, Z., Wang, Z., Ni, X., and Wang, C., "The effect of femtosecond laser micromachining on the surface characteristics and subsurface microstructure of amorphous FeCuNbSiB alloy," Applied Surface Science, 2006, Vol 253, pp 1299-1303 30 Lazare, S., and Tokarev, V., "Recent experimental and theoretical advances in microdrilling of polymers with ultraviolet laser beams," Proceedings of SPIE, 2004, pp 221-231 31 Masmiati, N., and Philip, P.K., "Investigations on laser percussion drilling of some thermoplastic polymers," Journal of Materials Processing Technology, 2007, Vol 185, No 1-3, pp 198-203 32 Serfetinides, A.A., Makropoulou, M.I., Skordoulis, C.D., and Kar, A.K., "Ultra-short pulsed laser ablation of polymers," Applied Surface Science, 2001, Vol 180, No 1, pp 42-56 33 Pham, D., Tonge, L., Cao, J., Wright, J., Papiernik, Harvey, E., and Nicolau, D., "Effects of polymer properties on laser ablation behaviour," Smart Material Structure, 2002, Vol 11, pp 668-674 34 Ohring, M., "Materials science of thin films deposition and structure," Academic Press, San Diego, second edition, 2002 35 http://www.me.mtu.edu/~microweb/chap4/ [Assessed on 11 October 2008] 120 Reference 36 Vassie, L.H., Roach, R.J., Tyrer, J.R., and Sharp, B.L., "Fumes generated during laser processing of polyninyl chloride (PVC)," Optics and Laser Technology, 1995, Vol 27, No 1, pp 31-37 37 Lippert, T., "Laser application of polymers," Advances in Polymer Science, 2004, Vol 168, pp 51-246 38 Liu, Z.Q., Feng, Y., and Yi, X.-S., "Coupling effects of the number of pulses, pulse repetition rate and fluence during laser PMMA ablation," Applied Surface Science, 2000, Vol 165, pp 303-308 39 Rose, I., and Whittington, C., "Nickel plating handbook," OM Group, Espoo, 2002 40 Bari, G.D., "ASM Handbook Vol 5," ASM International, OH, 1994 41 Krause, T., Arulnayagam, L., and Pritzkert, M., "Model for nickel-iron alloy electrodeposition on a rotating disk electrode," Journal of Electrochemical Society, 1997, Vol 144, No.3, pp 960-969 42 Brenner, A., "Electrodeposition of alloys," Academic Press, New York, 1963 43 Zech, N., Podlaha E.J., and Landolt D., "Anomalous codeposition of iron group metals I Experimental results," Journal of The Electrochemical Society, 1999, Vol 146, No 8, pp 2886-2891 44 Yeo, S.H., Choo, J.H., and Sim, K.H.A., "On the effects of ultrasonic vibrations on localized electrochemical deposition," Journal of Micromechanics and Microengineering, 2002, Vol 12, pp 271-279 45 Prasad, P.B.S.N.V., Vasudevan, R., Seshadri, S.K., and Ahila, S., "The effect of ultrasonic vibration on nickel electrodeposition," Materials Letters, 1993, Vol 17, pp 357-359 121 Reference 46 Zhu, X., Villeneuve, D.M., Naumov, A.Y., Nikumb, S., and Corkum, P.B., "Experimental study of drilling sub-10 µm holes in thin metal foils with femtosecond laser pulses," Applied Surface Science, 1999, Vol 152, No 3-4, pp 138 - 148 47 Hirayama, Y., and Obara, M., "Heat-affected zone and ablation rate of copper ablated with femtosecond laser," Journal of Applied Physics, 2005, Vol 97, pp 064903(1)-(5) 48 Brinbaum, M., "Semiconductor surface damage produced by ruby lasers," Journal of Applied Physics, 1965, No 36, pp 3688 - 3689 49 Borowiec, A., and Haugen, H.K., "Subwavelength ripple formation on the surfaces of compound semiconductors irradiated with femtosecond laser pulses," Applied Physics Letter, 2003, Vol 82, No 25, pp 4462-4464 50 Zhao, Q.Z., Malzer, S., and Wang, L.J., "Self-organized tungsten nanospikes grown on subwavelength ripples induced by femtosecond laser pulses," Optics Express, 2007, Vol 15, No 24, pp 15741-15746 51 Regelskis, K., Račiukaitis, G., and Gedvilas, M., "Ripple formation in the chromium thin film during laser ablation," Applied Surface Science, 2007, Vol 253, No 15, pp 6584-6587 52 Vorobyev, A.Y., Makin, V.S., and Guo, C., "Periodic ordering of random surface nanostructures induced by femtosecond laser pulses on metals," Journal of Applied Physics, 2007, Vol 101, Issue 3, pp 034903 53 Shimotsuma, Y., Kazansky, P.G., Qiu, J., and Hirao, K., "Self-organized nanogratings in glass irradiated by ultrashort light pulses," Physical Review Letters, 2003, Vol 91, No 24, pp 247405 122 Reference 54 Wellershoff, S.-S., Hohlfeld, J., Güdde, J., and Matthias, E., "The role of electron-phonon coupling in femtosecond laser damage of metals," Applied Physics A, 1999, Vol 69, No 7, pp S99-S107 55 Siwick, B.J., Dwyer, J.R., Jordan, R.E., and Miller, R.J.D., "An atomic-level view of melting using femtosecond electron diffraction," Science, 2003, Vol 302, No 5649, pp 1382-1385 56 Varlamova, O., Costache, F., Ratzke, M., and Reif, J., "Control parameters in pattern formation upon femtosecond laser ablation," Applied Surface Science, 2007, Vol 253, No 19, pp 7932 - 7936 57 Wang, J and Guo, C., "Ultrafast dynamics of femtosecond laser-induced periodic surface pattern formation on metals." Applied Physics Letter, 2005, Vol 87, Issue 25, pp 251914 58 Kaganov, M.I., Lifshitz, I.M., and Tanatarov, L.V., ZH Eksp Teor Fiz 31, 232 (1996) [Sov Phys JETP 4, 173 (1957)] 59 Wellershoff, S.S., Gudde, J., Hohlfeld, J., Muller, J.G., and Matthias, E., "The role of electron-phonon coupling in femtosecond laser damage of metals," Proceedings of SPIE, 1998, Vol 3343, pp 378 60 Dufour, C., Paumier, E., and Toulemonde, M., "Electron-phonon coupling and the sensitivity of metals to irradiation with swift heavy ions," Nuclear Instruments and Methods in Physics Research B, 1997, Vol 122, No 3, pp 445-448 61 Wagner, R., Jens Gottmann, J., Horn, A., and Kreutz, E.W., "Subwavelength ripple formation induced by tightly focused femtosecond laser radiation," Applied Surface Science, 2006, Vol 252, Issue 24, pp 8576-8579 123 Reference 62 Trelenberg, T.W., Dinh, L.N., B.C Stuart, B.C., and Balooch, M., "Femtosecond pulsed laser ablation of metal alloy and semiconductor targets," Applied Surface Science, 2004, Vol 229, Issue 1-4, pp 268-274 63 Liu, B., Huang, R., Wang, J., Widatallah, H.M., Lu, H., Zhang, J., and Liu, J., "Mössbauer investigation of Fe–Ni fine particles," Journal of Applied Physics, 1999, Vol 85, No 2, pp 1010 64 Sin, K., Wang, C.T., Wang, S.X., and Clemens, B.M., "Effects of lamination on soft magnetic properties of FeN films on sloping surfaces," Journal of Applied Physics, 1997, Vol 81, No 8, pp 4507 65 Viala, B., Minor, M.K., and Barnard, J.A., "Microstructure and magnetism in FeTaN films deposited in the nanocrystalline state," Journal of Applied Physics, 1996, Vol 80, Issue 7, pp 3941 66 Satio, N., Fujiwara, H., and Sugita, Y., "A new type of magnetic domain structure in negative magnetostriction Ni-Fe films," Journal of the Physical Society of Japan, 1964, Vol 19, pp 1116-1125 67 Chen, J.S., Lau, S.P., Zhang, Y.B., Sun, Z., Tay, B.K., and Sun, C.Q., "Deposition of permalloy films by filtered cathodic vacuum arc," Thin Solid Films, 2003, Vol 443, Issue 1-2, pp 115-119 68 Gavrila, H., and Ionita, V., "Crystalline and amorphous soft magnetic materials and their applications - status of art and challenges," Journal of Optoelectronics and Advanced Materials, 2002, Vol 4, No 2, pp 173 - 192 69 Černý, R., Cháb, V., Ivlev, G., Gatskevich, E., and P ikryl, P., "Modeling the phase-change processes in pulsed laser-irradiated InSb," Physical Review B, 1999, Vol 59, Issue 16, pp 10685-10690 124 Reference 70 Herzer, G., "Grain size dependence of coercivity and permeability in nanocrystalline ferromagnets," IEEE Transactions of Magnetics, 1990, Vol 26, No 5, pp.1397-1402 71 Pfeifer, F., and Radeloff, C., "Soft magnetic Ni-Fe and Co-Fe alloys - some physical and metallurgical aspects," Journal of Magnetism and Magnetic Materials, 1980, Vol 19, Issue 1-3, pp.190-207 72 Chi, G.C., Mogab, C.J., Burtherus, A.D., and Lehner, A.G., "The magnetoresistivity, structure, and magnetic anisotropy of RF sputtered and Ebeam evaporated NiFe film," Journal of Applied Physics, 1981, Vol 52, No 3, pp 2439-2441 73 Kamlage, G., Bauer, T., Ostendorf, A., and Chichkov, B.N., "Deep drilling of metals by femtosecond laser pulses," Applied Physics A, 2003, Vol 77, No 2, pp 307 - 310 74 Nolte, S., Kamlage, Gunter., Korte, F., Bauer, T., Wagner, T., Ostendorf, A., Fallnich, C., and Welling H., "Microstructuring with femtosecond laser," Advanced Engineering Materials, 2000, Vol 2, No 1-2, pp 23-27 125 ... Unlike nanosecond laser machining, processing of magnetic materials using femtosecond laser does not create any domain pinning effects [10] In addition, A Semerok et al has shown that femtosecond laser. .. either nanosecond or femtosecond lasers Methods such as nanosecond laser drilling of polymeric templates for electrodeposition of nanocrystalline nickel-iron wires and femtosecond laser machining... Introduction 1) Utilizing nanosecond laser and optimizing laser processing parameters in approaches to achieve the desired structures, in particular, optimizing laser process parameters for laser assisted