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Cover
Title page
Copyright page
Preface
Part 1: Laser Surface Modification and Adhesion Enhancement
1. Chapter 1: Topographical Modification of Polymers and Metals by Laser Ablation to Create Superhydrophobic Surfaces
  1. 1.1 Introduction
  2. 1.2 Wetting Theory
  3. 1.3 Laser Ablation Background
  4. 1.4 Preparation of Superhydrophobic Surfaces by Laser Ablation
  5. 1.5 Summary
  6. References
2. Chapter 2: Nonablative Laser Surface Modification
  1. 2.1 Introduction
  2. 2.2 Part 1 – Nonablative Laser Skin Photorejuvenation
  3. 2.3 Part 2 –Formation of Micro-/Nano-Structures and LIPSS in Materials by Nonablative Laser Processing
  4. 2.4 Part 3 – Nonablative Laser Surface Modification to Alter the Surface Properties of Materials
  5. 2.5 Summary
  6. References
3. Chapter 3: Wettability Characteristics of Laser Surface Engineered Polymers
  1. 3.1 Introduction
  2. 3.2 Lasers for Surface Engineering
  3. 3.3 Laser Surface-Engineered Topography
  4. 3.4 Laser Surface-Engineered Wettability
  5. 3.5 Summary
  6. References
4. Chapter 4: Laser Surface Modification for Adhesion Enhancement
  1. 4.1 Introduction
  2. 4.2 Basic Mechanisms of Laser Surface Modification
  3. 4.3 Laser Induced Surface Modification of Metal Substrates to Enhance Adhesion
  4. 4.4 Laser Induced Surface Modification of Polymers and Composites to Enhance Their Adhesion
  5. 4.5 Summary
  6. References
5. Chapter 5: Laser Surface Modification in Dentistry: Effect on the Adhesion of Restorative Materials
  1. 5.1 Introduction
  2. 5.2 Dental Structures
  3. 5.3 Adhesion of Restorative Materials
  4. 5.4 Laser Light Interaction with the Dental Substrate
  5. 5.5 Dental Structure Ablation and Influence on Bond Strength of Restorative Materials
  6. 5.6 Summary
  7. 5.7 Prospects
  8. References
Part 2: Other Applications
1. Chapter 6: Laser Polymer Welding
  1. 6.1 Introduction to Laser Polymer Welding
  2. 6.2 Theoretical Background
  3. 6.3 Factors Affecting Polymer Laser Welding
  4. 6.4 Practical Applications
  5. 6.5 Testing and Quality Control
  6. 6.6 Future Prospects
  7. 6.7 Summary
  8. Acknowledgements
  9. References
2. Chapter 7: Laser Based Adhesion Testing Technique to Measure Thin Film-Substrate Interface Toughness
  1. 7.1 Introduction
  2. 7.2 Modification of Laser Spallation Technique to Measure Thin Film-Substrate Interface Fracture Toughness
  3. 7.3 Parametric Studies
  4. 7.4 Validation of Dynamic Delamination Protocol
  5. 7.5 Summary
  6. References
3. Chapter 8: Laser Induced Thin Film Debonding for Micro-Device Fabrication Applications
  1. 8.1 Introduction
  2. 8.2 The Mechanism of Laser Induced Debonding (LID)
  3. 8.3 Thin Film Patterning by Laser Induced Forward Transfer
  4. 8.4 GaN Film Lift-Off for High-Brightness LEDs and High Power Electronics
  5. 8.5 Dielectric Passivation Layer Opening for Interconnect Formation in Crystalline Silicon Solar Cells
  6. 8.6 Laser Induced Wafer Debonding for Advanced Packaging Applications
  7. 8.7 Summary
  8. References
4. Chapter 9: Laser Surface Cleaning: Removal of Hard Thin Ceramic Coatings
  1. 9.1 Introduction
  2. 9.2 Chemical Etching of Hard Thin Coatings
  3. 9.3 Typical Experimental Set-Up for Excimer Laser Removal of Thin Coatings
  4. 9.4 Experimental Results on Excimer Laser Removal of Thin Coatings
  5. 9.5 Online Monitoring of Laser Coating Removal Process
  6. 9.6 Discussion of Excimer Laser Coating Removal Mechanisms
  7. 9.7 Finite Element Modelling of Excimer Laser Removal of Thin Coatings
  8. 9.8 Performance Evaluation of Laser Decoated Mechanical Tool
  9. 9.9 Summary
  10. Acknowledgments
  11. References
5. Chapter 10: Laser Removal of Particles from Surfaces
  1. 10.1 Introduction
  2. 10.2 Dry Laser Cleaning (DLC)
  3. 10.3 Steam Laser Cleaning (SLC)
  4. 10.4 Laser Shock Cleaning (LSC)
  5. 10.5 Novel Laser Cleaning Techniques
  6. 10.6 Summary
  7. Acknowledgements
  8. References
Index
End User License Agreement

List of Illustrations

Chapter 1
1. Figure 1.1 The number of publications using the word “superhydrophobic” each year since 1998.
2. Figure 1.2 The local angle of a surface topographical structure with respect to the average surface tangent is shown here as θ_Top. A non-reentrant feature (a) has θ_Top < 90° and only one intersection with the surface normal vector (arrows protruding from surface). Three possible reentrant structures are shown (b-d) which have θ_Top > 90° and intersect with the surface normal vector in at least two places.
3. Figure 1.3 A representation of a liquid pinning on a reentrant surface with a θ⁰ of 70° leading to entrapped air. (a) shows a liquid front advancing on a reentrant surface. In (b), the liquid front maintains a CA of 70° as it advances around the reentrant surface feature. Pinning occurs at the point on the circular surface feature where further wetting forces the CA to deviate from 70°. In (c) the liquid front makes contact with the top of a neighboring structure before the liquid is intruded to the bottom of the pore, causing gas entrapment.
4. Figure 1.4 Scanning electron micrographs depicting the formation of sub-wavelength (800 nm) surface ripples using a 470 fs pulse duration. (a) 9 pulses created ripples with little ablation. As the number of pulses was increased, the ripples became more pronounced (b, c) and eventually broke up into conical structures (d). (Reprinted from [56] with permission of Elsevier).
5. Figure 1.5 Scanning electron micrographs of seed holes patterns (1), deeper holes and pores (2) prepared at 0.87 J/cm², and larger corrugations (3) produced at 4.17 J/cm². (1) and (2) were prepared with a laser raster pitch of 7 µm, spot size of 40 µm and a scan speed of 800 µm/s). (Reprinted from [60] with permission of Elsevier).
6. Figure 1.6 Scanning electron micrographs of conical structures formed in silicon (left) and germanium (right) using thousands of 20 ns pulses, λ = 511 nm. (Reprinted from [64] with permission of Springer).
7. Figure 1.7 Cones are formed in a carbon filled acrylic resin by ablation with a 532 nm, 250 mJ/cm², 10 kHz laser (left) and in a triazene polymer with a calcium containing organic additive ablated with a 308 nm excimer laser (right). (Left image reprinted from [69] with permission from Elsevier. Right image reprinted from [65] with permission of Springer).
8. Figure 1.8 Laser ablated PDMS surfaces were found to consist of a polycrystalline silicon region where direct laser incidence occurred surrounded by a carbonaceous deposition field approximately twice the radius of the beam. The images on the left and right are top-down and tilt-angle cross-sectional views, respectively. (Reprinted from [79] with permission of Elsevier).
9. Figure 1.9 Water droplet adhesion force values measured on laser ablated Sylgard^® 184 surfaces were dependent on surface roughness (nm) related to a Cassie-Baxter wetting state. The inset displays the force variation and water droplet images upon approach, contact, and retraction from the surface. (Reprinted from [78] with permission of John Wiley and Sons).
10. Figure 1.10 Surfaces that exhibit large CAs (> 150°) and large sliding angles are described as exhibiting “rose petal” wetting. This schematic demonstrates that, on some surfaces, a change in the volume of air trapped below a water droplet in the Cassie-Baxter state, such as when a droplet is drawn away from the surface, would reduce the pressure within the space increasing the adhesion force between the droplet and the surface. (Reprinted with permission from [80]. Copyright 2013 American Chemical Society).
11. Figure 1.11 Gravitational forces acting on water droplets incident on inclined laser ablation surfaces and sliding resistance forces were found to correlate for untreated PDMS surface (plus symbols and line) and laser ablated PDMS surfaces that exhibited Cassie-Baxter wetting state (open diamond symbols and line). Water droplets persisting in Wenzel wetting state (x symbols and line) did not demonstrate the same correlation. (Reprinted from [79] with permission of Elsevier).
12. Figure 1.12 High-resolution SEM tilt-view images of laser ablation patterned Ultem™ (a) and copolyimide siloxane (b).
13. Figure 1.13 Laser ablated PTFE exhibited entangled fractal fiber structures. (Reprinted from [96] with permission under the Creative Commons Attribution License, license type CC BY).
14. Figure 1.14 Translation of PMMA surfaces through the focal plane of a femtosecond laser resulted in WCA maxima when the surface was located slightly above or below the focal plane. (Reprinted from [107] with permission of AIP Publishing LLC).
15. Figure 1.15 Comparison of WCA to ratios of feature spacing to diameter for laser ablated Kapton surfaces where laser parameters resulted in predominantly cone (a) or rounded protrusions, bumps (b). Lower ratio values indicate greater roughness. (Reprinted from [111] with permission of Elsevier).
16. Figure 1.16 (a) WCA variation with laser wavelength, duration, and fluence [115]. (b) Schematic of ablation process dependence on fluence and pulse duration on polyethersulfone surfaces.
17. Figure 1.17 Comparison between WCA and the fraction of contact area, f, calculated on laser ablated PODR1 surfaces. The gray line is the WCA predicted from a Cassie-Baxter wetting state. (Reprinted from [119] with permission of Elsevier).
18. Figure 1.18 Frequently used silanes for reducing surface free energy.
19. Figure 1.19 CA values for water (filled circles) and hexadecane (open circles) measured on laser ablated, fluorosilanated silicon wafers. (Reprinted with permission from [128]. Copyright 2006 American Chemical Society).
20. Figure 1.20 Progression through different surface features on stainless steel as a function of laser fluence resulted in differences in stability of the Cassie-Baxter wetting state. As surface features within a specific regime became more prominent, the stability of the Cassie-Baxter wetting state increased and the WCA increased. Upon transition to another surface feature regime, this process repeated [130].
21. Figure 1.21 (a) An increase in the pitch (groove spacing) resulted in decreasing WCA for large pitch values indicative of Wenzel wetting. (b) Increasing the pitch resulted in increasing WCA for smaller pitch values indicating development of Cassie-Baxter wetting. (Reprinted from [133] with permission of Elsevier).
22. Figure 1.22 Three-phase contact line (TPCL) transitions for increasing water droplet volumes (from 1.5 µL to 15 µL) on triangle-array laser ablation-patterned and fluorosilanated silicon wafers are shown in a-c as proceeding through a series of steps [138]. The direction of contact line advancement as the volume is increased is determined by differences in free energy change. Water droplets corresponding to these parameters as well as the orientation of the triangle array under the droplet are indicated at the top left corner of each image.
23. Figure 1.23 The CA (left axis) and sliding angle (right axis) were shown to depend on the laser scan speed for laser ablated copper surfaces that were subsequently treated with C₈Si(OMe)₃. The increase in sliding angle and decrease in CA at increasing scan speed are indicative of a transition from a Cassie-Baxter to a Wenzel state. (Reprinted with permission from [142]. Copyright 2015 American Chemical Society).
24. Figure 1.24 The scanning electron micrograph (left) shows hierarchical roughness on a 304L stainless steel surface prepared by ablation with 150 fs pulse duration, 800 nm wavelength, 2.83 J/cm² laser process. The graph (right) shows the time dependence of CA on ablated metal substrates. (Reprinted with permission from [156]. Copyright 2009 American Chemical Society).
25. Figure 1.25 Scanning electron micrographs of ablated lines (width indicated by b) and spaces (width indicated by a) into stainless steel substrates. In frames (A) through (D), the line pitch (a + b) of the cross-hatch pattern is progressively reduced. The size of unablated regions indicated by the black outlines in each frame shrink as the line pitch is reduced. The sidewalls and redeposited ablation materials create reentrant structures and surface porosity which can lead to air entrapment under an incident liquid droplet. (Reprinted from [158] with permission of Elsevier).
26. Figure 1.26 Four scanning electron micrographs of ablated titanium alloy surfaces are presented. The mark path of the laser with a pitch of Λ₁ is shown in the two images at the left. Microscale ripples with a characteristic wavelength of Λ₂, and LIPS with a characteristic wavelength of Λ₃ can be seen in the two images at the right. The structures become more defined as the number of overlapping pulses is increased from 13 (top images) to 128 (bottom images). These surfaces appear similar to surfaces created by Kietzig et al. [156] (Figure 1.24). (Reprinted from [160] with permission of Elsevier).
27. Figure 1.27 Scanning electron micrographs collected at three magnification levels of microscale conical structures with nanoscale roughness on a titanium substrate. (Reprinted with permission from [161]. Copyright 2011 American Chemical Society).
28. Figure 1.28 Nanocage structures on nickel substrates prepared using femtosecond laser ablation under ethanol. (Reprinted with permission from [162]. Copyright 2015 American Chemical Society).
29. Figure 1.29 An SEM (left) showing reentrant structures created by ablation (100 ns pulse duration, 1064 nm wavelength, 80 kHz repetition rate, 9.8 mm/s scan speed, and 60 passes) and electrodeposition of copper and an SEM image (middle) of a similar, but hierarchical, structure resulting in a CA of 153° (right). (Reprinted from [169] with permission of Elsevier).
30. Figure 1.30 Energy dispersive spectra obtained from an aged, ablated aluminum specimen showing variation in the concentration of aluminum oxide with location around the ablation site. (Reprinted from [170] with the permission of Elsevier Publishing).
31. Figure 1.31 (a) A laser treated silicon shard supporting a water drop. (b) WCA measurement on an ablated and dimethyldichlorosilane (C2SiCl2) treated surface (154° ± 1°). (c) Scanning electron micrograph of an array of conical structures, and (d) a single cone produced at 2.47 J/cm² and 500 pulses. (Reprinted from [173] with permission of John Wiley and Sons).
32. Figure 1.32 Scanning electron micrographs of (a) arrays of cones and (b) arrays of holes on silicon surfaces prepared using the DLIN process. (Reprinted from [176] with permission of AIP Publishing LLC).
Chapter 2
1. Figure 2.1 The structure of human skin.
2. Figure 2.2 Drawing of a cross-section of human skin comparing fractional and non-fractional laser skin resurfacing techniques. The ablative techniques result in removal of tissue by vaporization. The nonablative techniques result in coagulating the affected tissue.
3. Figure 2.3 SEM image of periodic microstructures formed in silicon using a 355 nm wavelength laser with a 10 ps pulsewidth. The laser was scanned over the silicon surface with 4 passes to produce the microstructure surface. The results shown are for an ablative laser process.
4. Figure 2.4 Images of a 150 nm thick Ge₂Sb₂Te₅ sputtered film on a silicon wafer substrate after applying a series of single laser pulses with increasing pulse energy with (a) showing the resulting optical microscope images and (b) the SEM images from the same sample. The laser wavelength was 1064 nm and had a 2.5 µm spot diameter (1/e²). The laser focal point was located +15 µm above the sample surface in order to yield an 8.5 µm effective spot size at the work surface.
5. Figure 2.5 The results of laser direct-writing an L-shaped mark on a 150 nm thick Ge₂Sb₂Te₅ sputtered film on a silicon wafer substrate. The laser had an 8.4 µm effective laser spot diameter at the GST surface and a pulse energy of 0.10 µJ. The laser velocity was selected so there was a 60% overlap between consecutive pulses.
6. Figure 2.6 1064 nm wavelength laser reflectivity measurements on the direct-write L-shaped laser mark shown in Figure 2.5. The results show a hill-shaped reflectivity profile as the laser was scanned between the dark amorphous region and the lighter crystalline region.
Chapter 3
1. Figure 3.1 Typical etch rate/natural logarithm of the fluence plot to estimate the threshold fluence, F_T.
2. Figure 3.2 Typical 3-D profiles of (a) CO₂ laser surface engineered PMMA (50 μm parallel line scan at 7 W, 600 mm/s) and (b) KrF excimer laser surface engineered polyamide 6, 6 (858±91 mJ/cm², 25 Hz and 0.25 mm/s).
Chapter 4
1. Figure 4.1 Summary of methods for surface pretreatment to enhance adhesion.
2. Figure 4.2 Schematic temporal distributions of electron temperature and lattice temperature.
3. Figure 4.3 Optical microscopy image (a) and scanning electron microscopy (SEM) images (b), (c), and (d)) for surface profiles of 316L stainless steel before and after cleaning by femtosecond laser pulses at different magnifications.
4. Figure 4.4 The principle of mechanical interlocking (a) and the schematic micro-trench arrays formed on a substrate (b).
5. Figure 4.5 Schematic laser drilled hole arrays on a material surface in a top-down view (a) and in a cross-sectional view with the axis of a hole normal to the substrate surface (b), or the axis of a hole tilted to the left (c), or the axis of a hole tilted to the right (d), or the axes of holes tilted to the left and right sequentially (e).
6. Figure 4.6 Ripple patterns on 316L stainless steel generated by a pulsed 1064 nm nanosecond laser at very low pulse fluence.
7. Figure 4.7 Evolution of surface morphology of stainless steel 316L on a given location under 532 nm femtosecond laser irradiation as pulse fluence increases from ~1 J/cm² in (a) to >10 J/cm² in (d).
8. Figure 4.8 Scribed lines on stainless steel 316L using a 1064 nm nanosecond pulsed laser at lower (a) and slightly higher (b) pulse fluences.
9. Figure 4.9 Scribed lines on stainless steel 316L using a 532 nm femtosecond laser at different pulse fluences. From (a) to (d), laser fluence increases from 1 J/cm² to over 10 J/cm² at a fixed scan speed.
10. Figure 4.10 Adhesion strength of 300 µm NiAl coating/10 mm Al AISI 2017 substrate system measured by the pull-off test [46].
11. Figure 4.11 Adhesion strength of 80 µm NiAl coating/1mm Al AISI 2017 substrate system measured by the LASAT adhesion test for samples with holes normal to substrate surface (α = 0) [46].
12. Figure 4.12 Adhesion strength as a function of adhesion area ratio R.
13. Figure 4.13 Results of shear strength and reduction of wetting angle of laser processed samples [66].
14. Figure 4.14 Adhesion strength of PTFE film with different amounts of APE additive irradiated by KrF laser
15. Figure 4.15 Dependence of maximum load in tensile shear tests on PEEK lap joints and water contact angle on PEEK surface on laser irradiation fluence
16. Figure 4.16 Effect of surface treatment on (a) water contact angle on thermoplastic materials (PE, PP and PEEK) and on (b) the adhesion strength between an aluminum thin film and thermoplastic substrates (PE, PP and PEEK)
Chapter 5
1. Figure 5.1 (a) Enamel irradiated with laser with cooling; (b) Enamel irradiated with laser without cooling; (c) Enamel fusion after laser irradiation (asterisks); (d) Irradiated dentine showing surface carbonization.
2. Figure 5.2 (a) Cavity preparation with Er:YAG laser. (b) Irradiated enamel; (c) Irradiated dentine showing irregular surface; (d) Irradiated dentine showing higher intertubular structure removal and protrusion of the peritubular dentine.
3. Figure 5.3 Images of a human tooth emphasizing enamel and dentine structures. (a) Dental structure with enamel demineralization (mineral loss); (b) Different conditions of caries in dentine.
4. Figure 5.4 SEM images of dental enamel. (a) Crystals/prisms dispositions; (b) interprismatic region (asterisks); (c) a closer view of crystals/prisms dispositions.
5. Figure 5.5 SEM images of dentine. (a) Odontoblastic prolongations inside the tubules (grey arrow); (b) Tubules orientation and morphological appearance; (c) From the dentine enamel junction, the dentine has a centripetal orientation toward the pulp chamber.
6. Figure 5.6 Dentinal tubules. (a) Longitudinal cut showing peritubular dentine (asterisks) and intertubular dentine; (b) Transversal cut showing peritubular dentine (asterisks); (c) Arrangement of the network of collagens fibrils inside the tubule.
7. Figure 5.7 Dentinal tubules density. (a) Enamel-dentine junction; (b) Central portion of the coronary dentine; (c) Deeper dentine close to pulp.
8. Figure 5.8 Dental enamel. (a) Enamel surface treated with 37% phosphoric acid. (b) Adhesive interface with enamel.
9. Figure 5.9 Dentine. (a) dentine surface treated with 37% phosphoric acid; (b) dentine surface treated with acidic primer; (c) formation of the hybrid layer (HL) observed at the adhesive interface with etch-and-rinse adhesive system (AL) and composite resin (CR); (d) formation of the hybrid layer observed at the adhesive interface with self-rinse adhesive system.
10. Figure 5.10 Cavity preparation with Er:YAG laser, and restoration with adhesive restorative materials. (a) Initial view-Occlusal caries; (b) Teeth isolated with blue rubber dam; (c) Caries removal with Er:YAG laser; (d) Cavity after enamel removal; (e) Cavity after caries removal with Er:YAG laser; (f) Etch conditioning with phosphoric acid – preparation of surface for adhesive; (g) Application of dental adhesive; (h) Restoration finished; (i) Restoration after occlusal adjustment.
11. Figure 5.11 Irradiated enamel. (a) Melting of enamel; (b) Melting of hydroxyapatite crystals.
12. Figure 5.12 Dentine irradiated with Er:YAG laser. (a) Sound dentine -shows irregular surface with open dentine tubules (circles); (b) Removal of carious lesions with laser. It shows incomplete removal of carious lesion and disorganized tissue (black arrows); (c) Sound dentine. The surface of dentine is scaly with higher ablation in intertubular dentine – closer view.
13. Figure 5.13 Adhesive system on dental surface. (a) Open dentinal tubules after irradiation with Er:YAG laser; (b) Open dentinal tubules after irradiation with Er:YAG laser and etch conditioning with phosphoric acid without protrusion of peritubular dentine; (c) Open dentinal tubules after irradiation with Er:YAG laser and treatment with acidic primer. The deposition of the primer is observed at the entrances of the tubules. (d) Adhesive interface with dentine irradiated with Er:YAG laser employing self-etching adhesive, showing the formation of the hybrid layer.; (e) Adhesive interface with enamel irradiated with Er:YAG laser employing self-etching adhesive.
14. Figure 5.14 Use of the Er, Cr: YSGG laser for cavity preparation. (a) Dentine surface after caries removal and acid etch treatment; (b) Dentine after partial removal of caries; (c) Glass ionomer cement in intimate contact with the irradiated dentine; (d) Dentine surface after cavity preparation.
Chapter 6
1. Figure 6.1 Radiation intensity attenuation by reflection as well as internal scattering and absorption. I/I₀: normalized intensity, R: reflection coefficient, R_i: internal reflection coefficient, S: scattering coefficient, A: absorption coefficient, T: transmission coefficient
2. Figure 6.2 Reflection “R”, transmission “T” and absorption “A” of polycarbonate (PC) at wavelengths between 400 nm and 2,500 nm.
3. Figure 6.3 Temperature dependence of the refractive index for poly (methyl methacrylate) (PMMA), polystyrene (PS) and poly (vinyl chloride) acetate (PVCA) [6]. With increasing temperature the refractive index will decrease, and decrease is more pronounced after the glass transition temperature T_g of the polymer.
4. Figure 6.4 Influence of optical penetration depth on the processing result for polyamide (PA6) using CO₂- and Nd:YAG-laser radiations with same processing parameters, sample thickness “s” is 2 mm [6].
5. Figure 6.5 Transmission” T” of PMMA, PA6, PP and PC in the wavelength range from 800 nm to 1,200 nm (sample thickness 2mm).
6. Figure 6.6 Absorption spectra of PMMA, PA6 and PP Increasing absorption is caused by C-H group oscillations.
7. Figure 6.7 (a) Surface absorption with low optical penetration depth a* compared to sample thickness s and (b) volume absorption with high optical penetration depth of laser radiation in thermoplastic polymers [6].
8. Figure 6.8 Temperature calculation according to equation (6.20) for high optical penetration depth “a” (left) and low optical penetration depth (right) with spot size of 1 mm on the surface of the target and different radiation powers and interaction times. T₀: starting temperature, T_m: melting temperature, T_d: decomposition temperature, z_m: melting depth [6].
9. Figure 6.9 Reptation model of a macromolecular chain in the molten state in its initial cage in the first layer near the interface to the second layer at starting time t₀, moving minor chains out of the cage at different times t₁ and t₂ shorter than the reptation time t_r with increasing transition through the surface into the second layer [6].
10. Figure 6.10 Interdiffusion process of macromolecular chain segments between the two molten layers. The depth X of the interdiffusion zone will increase with increasing interaction time t at constant temperature T as well as a constant interaction time t with increasing temperature T [6].
11. Figure 6.11 Micro-swirls caused by the squeezing process. Layer 1 is transparent and layer 2 is absorbing for laser radiation [6].
12. Figure 6.12 Examples of butt joint welding with laser. CO₂-laser radiation has a low optical penetration depth at high density polyethylene (HDPE) resulting in surface absorption with low melting depth (left); diode laser has a high optical penetration depth resulting in volume absorption and welding the entire poly(methyl methacrylate) (PMMA) sample of thickness 3 mm [6].
13. Figure 6.13 Through-transmission laser welding process. Laser radiation is transmitted through the transparent layer to the absorbing layer. In the absorbing layer, the laser radiation is converted into process heat which heats the transparent layer by heat conduction. Mechanical fixing supports the mixing of molten materials of the two surfaces [6].
14. Figure 6.14 Principle of contour laser welding [6].
15. Figure 6.15 Correlation of achievable weld strength and applied line energy, left side shows a process diagram with achievable weld strength as a function of laser line energy with indication of the parameter settings 1–4. The parameter settings correspond to the four cross sections on the right side. Sample 1 is of low weld strength, sample 2 of optimal weld strength and samples 3 and 4 are overheated having low weld strengths [25].
16. Figure 6.16 Principle of quasi-simultaneous laser welding [6].
17. Figure 6.17 Heating process in quasi-simultaneous laser welding. The temperature increase is shown based on constant laser interaction time with 1, 5, 20 and 40 repetition scans. As more scans in the same time are applied, more homogeneous is the heating process [26].
18. Figure 6.18 Squeeze flow of the melt during quasi-simultaneous laser welding [6].
19. Figure 6.19 Principle of simultaneous laser welding with four direct emitting laser sources having line shaped laser radiation geometry [6].
20. Figure 6.20 Beam shaping optics for generating a circular beam pattern by diffractive optical elements for simultaneous laser welding; left shows the optical device, right the schematic setup [28].
21. Figure 6.21 Principle of mask laser welding [29].
22. Figure 6.22 Principle of TWIST laser welding, a linear motion with relatively low speed is added to a high speed circulation of the focused laser beam (left), a zigzag motion (middle) and complex motion geometry (right) to generate a homogeneous heating process [31].
23. Figure 6.23 Globo laser welding of an automotive lamp housing [6].
24. Figure 6.24 Principle of IR-hybrid laser welding, superposing laser radiation and NIR-radiation in a combined spot [32].
25. Figure 6.25 Laser welded electronic car key with carbon black as laser absorbing additive in the plastic housing. The material for the key buttons is made from a soft plastic as laser transparent part with black visible color [6].
26. Figure 6.26 Color corrected laser transparent and absorbing PETG components (marked with tapes) using an organic dye in the absorbing component [6]
27. Figure 6.27 (left) Principle of through-transmission laser welding using absorbing layer at the joint interface. (right) Contour laser welded PMMA sample using Clearweld coating supplied by Crysta-Lyn, Binghamton, NY, as an absorbing layer [34].
28. Figure 6.28 Laser welded micro-fluidic mixer device made of PA using focused laser radiation from a 1,550 nm fiber laser [41].
29. Figure 6.29 Laser welded parts in automotive application [6].
30. Figure 6.30 Laser welded parts in consumer goods [6].
31. Figure 6.31 Laser welded parts in electronic application [6].
32. Figure 6.32 Laser welded parts in medical application [6].
33. Figure 6.33 Quality monitoring and control techniques for laser welding of thermoplastic components [6].
34. Figure 6.34 Options for process monitoring during laser welding of thermoplastics [6].
Chapter 7
1. Figure 7.1 Schematic of the laser spallation technique adapted to measure interface strength of a thin film deposited on a substrate.
2. Figure 7.2 Schematic showing the similarity between the laser spallation experiment and the Newton’s cradle. The laser loading is analogous to the impact of the leftmost sphere and the spallation of the thin film from the substrate is similar to the detachment of the rightmost sphere.
3. Figure 7.3 Examples of experimental high velocity and hypervelocity impact craters (left column) generated by Aluminum projectiles in copper targets showing surface (on the backside of the target) and half-section views (right column) at impact velocities indicated: (a) 1.08, (b) 2.64, (c) 4.4, (d) 6.01 km/s. The conventions for measuring crater geometries are illustrated in (b) for u₀ = 2.64 km/s along with the concept of the impact axis shown dotted with arrows. Note spall crack in (c) at arrow. (Figure reproduced from Ref. 53).
4. Figure 7.4 (a) Schematic illustrating the dynamic thin film-substrate interface adhesion test protocol. Laser-induced acoustic compressive pulses are launched from the backside of the substrate. The starter crack for the adhesion test results from the normal spallation of the weak adhesion region. (b) The kinetic energy trapped/accumulated in the thin film stack above the weak adhesion layer is channeled to the film-substrate interface leading to a controlled interfacial delamination with final crack extension of Δa.
5. Figure 7.5 Steps involved in the bi-shadow mask technique to fabricate thin film patterns with weak adhesion layers.
6. Figure 7.6 Details of thin film dynamic adhesion test sample geometry.
7. Figure 7.7 Evolution of (a) Al/Si interface stress and (b) kinetic (K) and strain (U) energy stored in 4 µm-thick Al film on a Si substrate subjected to the compressive pulse shown in the inset of (a).
8. Figure 7.8 Envelopes of kinetic (K) and strain (U) energy components as a function of Al/Si interface stress. The right vertical solid line represents the Al/Si interface adhesion strength measured using normal laser spallation test. The kinetic energy stored in the thin film at the onset of interface spallation is denoted by a square symbol at intersection of the interface strength line with the envelope. The effect of weak interface layer is visualized by the intersection of the dashed vertical line (circular symbol), corresponding to the adhesion strength of the weak adhesion layer with the envelope.
9. Figure 7.9 Al film patterns (2.8 µm thick and 310 µm wide) after dynamic delamination from a Si (100) substrate. The final delamination lengths of ca. 6, 9 and 12 mm develop from a 380 µm- long initial pre-crack (weak adhesion layer) for Nd:YAG laser fluences, 51, 59.5 and 68 mJ/mm², respectively.
10. Figure 7.10 (a) Experimentally measured substrate stresses profiles of the two dynamic adhesion tests, differentiated by continuous and dashed lines, conducted at low Nd:YAG laser fluence (51 mJ/mm²) to demonstrate experimental repeatability. (b) Envelopes of kinetic energy stored in the thin film stack at the Au/Al interface as a function of Au/Si interface stress under the action of the substrate stresses plotted in (a). The kinetic energy available for delamination is marked by circles at the intersection of the curves with the vertical line drawn at the Au/Si interface strength.
11. Figure 7.11 Schematic summarizing the various factors that can be varied to achieve control over the dynamic delamination event.
12. Figure 7.12 (a) Kinetic energy versus interface stress envelopes for various Al film thickness values considered in the parametric study. (b) Peak magnitudes of interface stress and kinetic energy as a function of Al film thickness. All the simulations were carried out using a 12 ns Gaussian substrate stress pulse with a magnitude of 1 GPa.
13. Figure 7.13 (a) Kinetic energy versus thin film-substrate interface stress envelopes for five Gaussian substrate stress pulses with magnitudes varying from 1 GPa to 3 GPa. (b) Peak magnitudes of Al/Si interface stress and kinetic energy as a function of the amplitude of the substrate stress pulse.
14. Figure 7.14 (a) Details of the β functions used in the substrate shape influence study. (b) Kinetic energy versus Al/Si interface stress envelopes corresponding to the β functions plotted in (a) showing the effect of the shape of the substrate pulse.
15. Figure 7.15 Kinetic energy versus interface stress envelopes for three different materials, Al, Cu and Au, under the influence of a Gaussian-shaped substrate stress pulse with a magnitude of 1 GPa. The effect of thin film thickness for different materials is also shown for comparison. The numbers represent the corresponding thin film thicknesses in μm.
16. Figure 7.16 Kinetic energy versus interface stress envelopes for different Au thicknesses ranging from 100 nm to 500 nm. The dashed and solid curves are for Au placement at the bottom and top, respectively, on a 3 µm thick Al film. Au deposition increases inertia by adding mass to the thin film.
17. Figure 7.17 (a) Schematic of the setup used to determine interface crack speed history during the dynamic delamination event. (b) Top view of the experimental sample showing how the Ti resistors are placed on top of the test thin film. (c) Comparison of thin film delaminations, with and without Ti resistors, after the delamination test under similar loading conditions. (d) Crack speed and crack tip location histories obtained for the dynamic delamination experiment.
18. Figure 7.18 Evolution of energy components associated with the dynamic fracture problem of a 4.3 μm-thick Al film with a 330 μm-long pre-crack subjected to an initial peel velocity V_o of 147 m/s: Kinetic energy (K), fracture energy (F), potential energy (U) and total energy which is sum of K, F and U.
19. Figure 7.19 Comparison between experimental results and numerical simulations for the crack tip evolution (a) and the crack speed history (b). The simulations are performed for different values of the thin film-substrate interfacial fracture toughness G_c.
Chapter 8
1. Figure 8.1 The two simplest thin film structures: (a). A transparent thin film on an opaque substrate; (b). An opaque thin film on a transparent substrate. (c). Laser induced thin film delamination. The ablation site is also the source of pressure generated stress wave (acoustic source) as labeled in a) and b). Reproduced from [5]. Courtesy of Wiley-Scrivener Publishing LLC.
2. Figure 8.2 Optical images showing laser induced delamination along the laser scribed lines in a semiconductor device wafer.
3. Figure 8.3 Scanning Electron Microscopy (SEM) images showing laser induced chipping along the laser scribed lines in a semiconductor device wafer.
4. Figure 8.4 Scanning Electron Microscopy (SEM) images of cross sections normal to laser scribed lines in a semiconductor device wafer.
5. Figure 8.5 Schematic illustrations of four major LIFT processes, namely direct laser transfer (a), hydrogen-assisted transfer (b), sacrificial layer assisted laser transfer (c), and the matrix-assisted pulsed laser evaporation-direct-write (MAPLE-DW) (d).
6. Figure 8.6 Schematic illustrations of the conventional LED configuration (a) and the vertical LED configuration (b)
7. Figure 8.7 Schematic of lift-off process for transferring GaN devices from a sapphire substrate onto a conductive substrate
8. Figure 8.8 Single-pulse laser liftoff of GaN from sapphire at 248 nm laser wavelength (one pulse covers nine dies). Reproduced from [50]. Courtesy of SPIE.
9. Figure 8.9 A conventional screen-printed silicon solar cell with full-area aluminum backside contact film (a) and a passivated-emitter-and-rear-cell (PERC) solar cell with dielectric rear passivation and aluminum point contacts to silicon base (b).
10. Figure 8.10 The threshold fluence for silicon melting (F_th,melt) and for breaking dielectric layer (F_th,break) on the spatial distribution of a focused Gaussian beam
11. Figure 8.11 Laser induced debonding of thermal silicon oxide on silicon at a low fluence (a, optical image), at an intermediate fluence (b, optical image), and at a high fluence (c, SEM image). Reproduced from [63]. Courtesy of SPIE.
12. Figure 8.12 Schematics of mechanical debonding (a) and laser-induced debonding (b)
Chapter 9
1. Figure 9.1 Schematic of a typical optical set-up used for excimer laser decoating process.
2. Figure 9.2 Schematic illustration of experimental set-up for laser decoating of TiN from coated tungsten carbide plates.
3. Figure 9.3 Variation of ablation rate with fluence for TiN coating and WC substrate.
4. Figure 9.4 Effect of linear scan speed on ablation depth observed during laser decoating of 2 mm thick TiN coating from WC substrate (fluence = 2 J/cm² and frequency = 25 Hz).
5. Figure 9.5 SEM image (a) and depth profile (b) of the TiN coated WC substrate after laser decoating (fluence = 2 J/cm², frequency = 25 Hz and scan speed = 0.02 mm/s). (a) SEM image showing the laser decoated and original coated surfaces (b) Depth profile along the laser decoated interface.
6. Figure 9.6 EDX spectra observed over TiN coated WC substrate, before (point A) and after laser decoating (point B) (inside image shows the region of EDX analysis). (a) Before laser decoating (b) After laser decoating (fluence = 2 J/cm², scan speed = 0.5 mm/s, frequency = 50 Hz and laser beam overlap = 80 %).
7. Figure 9.7 Laser decoated WC insert (fluence = 2 J/cm², scan speed = 0.5 mm/s, frequency = 50 Hz and laser beam overlap = 80 %) (a) Photographic image of decoated (TiN) insert (b) SEM image of laser decoated insert edge.
8. Figure 9.8 TiN coated WC micro-tool used for laser decoating experimentation.
9. Figure 9.9 Schematic illustration of experimental set-up for the laser decoating of TiN from coated WC micro-tool.
10. Figure 9.10 Surface morphology of the TiN coated WC micro-tools before and after laser decoating. (a) Before laser decoating (b) After laser decoating (fluence = 2 J/cm², frequency = 25 Hz and rotational speed = 10 rpm).
11. Figure 9.11 EDX spectra observed over TiN coated WC micro-tools, before (point A) and after laser decoating (point B) (inside image shows the region of EDX analysis). (a) Before laser decoating (b) After laser decoating (fluence = 2 J/cm², frequency = 25 Hz and rotational speed = 10 rpm).
12. Figure 9.12 Variation of ablation rate with fluence for TiAlN coating and WC substrate (frequency = 25 Hz and number of pulses = 250).
13. Figure 9.13 Surface morphology (left) and depth profile (right) of laser ablated samples (fluence = 2 J/cm², frequency = 25 Hz and number of pulses = 250). (a) TiAlN coated WC substrate (b) Uncoated WC substrate.
14. Figure 9.14 Effect of number of pulses on ablation depth observed during laser decoating of 2 mm thick TiAlN coating from WC substrate (fluence = 2 J/cm² and frequency = 25 Hz).
15. Figure 9.15 Effect of laser scan speed on ablation depth observed during laser decoating of 2 mm thick TiAlN coating from WC substrate (fluence = 2 J/cm² and frequency = 25 Hz).
16. Figure 9.16 SEM image (top) and depth profile (bottom) of the TiAlN coated WC substrate after laser decoating (fluence = 2 J/cm², frequency = 25 Hz and linear scan speed = 0.1 mm/s). (a) SEM image showing the coated and decoated regions (b) Depth profile along laser decoated track.
17. Figure 9.17 Surface morphology of the TiAlN coated WC substrate after laser decoating, with various beam overlaps.
18. Figure 9.18 Effect of laser beam overlap on surface roughness (Ra) during laser decoating of 2 µm thick TiAlN coating from WC substrate (fluence = 2 J/cm² and frequency = 25 Hz).
19. Figure 9.19 EDX spectra of the TiAlN coated WC substrate before (point A) and after laser decoating (point B) (inside image shows the region of EDX analysis). (a) Before laser decoating (b) After laser decoating (fluence = 2 J/cm², laser beam overlap = 93.7 %, scan speed = 1.6 mm/s and frequency = 25 Hz).
20. Figure 9.20 Cross-sectional SEM back-scattered images of TiAlN coated WC substrate, showing (a) as-received coated, (b) fully decoated and (c) interface of decoated and as-received coated sample. 1 = substrate, 2 = coating, 3 = resin mount.
21. Figure 9.21 Variation of ablation rate with fluence for CrTiAlN coating and steel substrate (frequency = 25 Hz and number of pulses = 200).
22. Figure 9.22 Effect of fluence and number of pulses on ablation depth of CrTiAlN (number on line contour indicates depth in µm).
23. Figure 9.23 Effect of fluence and number of pulses on ablation depth of steel (number on line contour indicates depth in µm).
24. Figure 9.24 Depth profiles (left) and SEM images (right) of CrTiAlN coated steel substrate after laser decoating.
25. Figure 9.25 Optical microscopy images showing the surface textures of CrTiAlN coated steel substrate after laser decoating for various scan speeds and laser beam overlaps.
26. Figure 9.26 EDX spectra of the CrTiAlN coated steel substrate before (point A) and after laser decoating (point B) (inside image shows the region of EDX analysis). (a) Before laser decoating (b) After laser decoating (fluence = 2 J/cm², laser beam overlap = 90 %, scan speed = 4.2 mm/s and frequency = 100 Hz).
27. Figure 9.27 Cross-sectional SEM back-scattered images of CrTiAlN coated steel substrate.
28. Figure 9.28 Schematic illustration of the experimental setup of the probe beam reflection (PBR) system used for online monitoring of coating removal.
29. Figure 9.29 Change in normalized reflected intensity observed during TiN coating removal from WC micro-tool for various number of pulses per spot and laser fluences.
30. Figure 9.30 Schematic illustration of the experimental setup of the laser plume emission spectroscopy (LPES) system used for online monitoring of coating removal.
31. Figure 9.31 Emission spectra observed during TiN coating removal from WC micro-tool for various numbers of laser pulses per spot.
32. Figure 9.32 Calculated thermal history over the TiAlN surface for a single laser pulse (fluence = 2 J/cm²).
33. Figure 9.33 High speed camera images showing TiAlN coating removal (ejected particles shown inside the circle).
34. Figure 9.34 SEM image showing re-deposited TiAlN material at the laser decoated interface.
35. Figure 9.35 Geometry used for finite element analysis (dimensions in µm).
36. Figure 9.36 Temperature contour (K) observed over TiN coated WC substrate during laser decoating for various numbers of pulses per position (fluence 2 J/cm² and frequency = 25 Hz).
37. Figure 9.37 Contour profiles of stress and strain observed over TiN coated WC substrate during laser decoating (number of pulses = 250, fluence 2 J/cm² and frequency = 25 Hz).
38. Figure 9.38 Effect of various decoating techniques on surface roughness of the TiN coated WC insert.
39. Figure 9.39 Effect of various decoating techniques on the wear rate parameter during mechanical turning process
40. Figure 9.40 Effect of various decoating techniques on surface roughness of the mechanically turned surface.
41. Figure 9.41 Effect of various decoating techniques on the energy footprint for removing 1 cm³ by mechanical turning.
42. Figure 9.42 Effect of input voltage on power consumption and laser output energy (frequency = 50 Hz).
43. Figure 9.43 Comparison of energy footprints for different manufacturing process steps.
Chapter 10
1. Figure 10.1 An optical microscope image of silicon wafer with 500-nm polystyrene (PS) particles; before (top) and after DLC (bottom).
2. Figure 10.2 Various cases of SLC using (a) ultraviolet, (b) near-infrared(NIR), and (c) mid-infrared(MIR) irradiation.
3. Figure 10.3 Concept of LSC.
4. Figure 10.4 Force diagram showing the particle removal mechanism by LSC.
5. Figure 10.5 Optical microscope images of silicon wafer with 300, 500, 1000 nm PS particles; (a) before and (b) after LSC.
6. Figure 10.6 Scanning electron microscope images of silicon wafer with 50-nm Al₂O₃ particles; (a) before and (b) after liquid-assisted LSC.
7. Figure 10.7 Atomic force microscope images of silicon wafer contaminated with 10-nm gold particles; (a) before and (b) after DOC.

List of Tables

Chapter 2
1. Tabel 2.1 Laser wavelengths and types used for laser-based skin treatment.
Chapter 3
1. Table 3.1 Literature data detailing various laser surface engineered polymeric materials and the data pertaining to the variations in surface roughness and topography.
2. Table 3.2 Literature data detailing various laser surface engineered materials, the main surface engineering results and associated contact angle.
Chapter 4
1. Table 4.1 Effect of substrate surface treatment on the adhesion strength of cold sprayed Al coating on Al substrate [32]
2. Table 4.2 Laser process conditions used in [50].
3. Table 4.3 T-peel adhesion test results [50].
4. Table 4.4 Summary of test results for adhesively bonded AA2024-T3 alumium alloy sheet joints [52].
5. Table 4.5 Laser process conditions and maximum lap shear load of glass fiber reinforced polyisocyanurate resin composite [70]
Chapter 5
1. Table 5.1 Lasers Employed in Operative Dentistry
2. Table 5.2 Classification of currently employed adhesive systems.
3. Table 5.3 Classification of currently employed adhesive systems.
Chapter 6
1. Table 6.1 Optical penetration depth “a” for some typical thermoplastic polymers. The penetration depth for near-infrared radiation (e.g. diode lasers) is much higher compared to the penetration depth of mid-infrared radiation (e.g. CO₂-laser). PC: polycarbonate, PMMA: poly (methyl methacrylate), PVC: poly (vinyl chloride), LDPE: low density polyethylene, PA 6: polyamide, PP: polypropylene
2. Table 6.2 Characteristic C-H group oscillations in the wavelength range between 1,200 and 2,500 nm [6].
3. Table 6.3 Oscillation types of atoms and atom groups within a molecular chain and their spectroscopic terms [6].
4. Table 6.4 Structure and group oscillations of polymer chains in the range of the CO₂-laser wavelength. Oscillation frequencies are given in wavenumbers (cm⁻¹) [6].
5. Table 6.5 Dimensions of scattering structures in polymers and their effect on NIR- and MIR-radiations [6].
6. Table 6.6 Bond strength values of laser welded joints compared with material tensile strength of amorphous and semi-crystalline polymers.
7. Table 6.7 Quality monitoring techniques and their main applications for polymer laser welding processes as well as online process control used for industrial applications [6]
Chapter 9
1. Table 9.1 Surface roughness of the laser decoated steel substrate (coating = 2 µm thick CrTiAlN, frequency = 100 Hz and fluence = 2 J/cm²)
Chapter 10
1. Table 10.1 Major adhesion forces.
2. Table 10.2 Effects of main process parameters on DLC.
3. Table 10.3 Previous studies on DLC.
4. Table 10.4 Effects of main process parameters on SLC.
5. Table 10.5 Previous studies on SLC.
6. Table 10.6 Effects of main process parameters on LSC
7. Table 10.7 Previous studies on LSC
8. Table 10.8 Previous studies on novel laser cleaning techniques
9. Table 10.9 Size limitation of the developed laser cleaning techniques

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Adhesion and Adhesives: Fundamental and Applied Aspects

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