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6CCVD Research

Femtosecond Laser-Induced Periodic Surface Structures in Titanium-Doped Diamond-like Nanocomposite Films - Effects of the Beam Polarization Rotation

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2023-01-13
JournalMaterials
AuthorsS.M. Pimenov, E.V. Zavedeev, B. Jaeggi, Beat Neuenschwander
InstitutionsBern University of Applied Sciences, Prokhorov General Physics Institute
Citations7
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research investigates the precise control of laser-induced periodic surface structures (LIPSS) and resulting nanoscale friction on hard Titanium-doped Diamond-like Nanocomposite (Ti-DLN) films using femtosecond (fs) laser ablation.

  • Friction Control: Demonstrated the ability to tailor nanoscale friction properties by rotating the orientation of the LIPSS nanogratings relative to the scanning direction.
  • LIPSS Orientation: All Low Spatial Frequency LIPSS (LSFL) are oriented strictly perpendicular to the electric field (E) vector of the linearly-polarized laser beam, allowing synchronous rotation of the nanostructure via polarization control.
  • Periodicity Variation: The LSFL period is not constant, increasing gradually from 360 ± 5 nm (ripples parallel to scanning direction) to 420 ± 10 nm (ripples perpendicular to scanning direction) as the polarization angle rotates from 0° to 90°.
  • Tribological Anisotropy: The ratio of friction forces (A = FLIPSS/Ffilm) decreases significantly as the LIPSS rotate from perpendicular (high friction) to parallel (low friction) relative to the AFM tip movement.
  • High-Speed Processing: Ti-DLN films maintain a constant ablation depth across high pulse frequencies (100 kHz to 2 MHz), supporting high-throughput manufacturing, although processing must be limited to sub-MHz rates to avoid surface cracking and excessive graphitization.
  • Mechanism Insight: The observed LSFL periods (360-420 nm) are smaller than predicted for surface plasmon polaritons (SPP) excited at the air/graphitized carbon (GC) interface (~470 nm), suggesting non-normal beam incidence and complex dielectric changes in the laser-excited nanocomposite layer.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Film MaterialTi-DLN (a-C:H:Si:O)-Titanium content 17-18 at.%
Film Hardness22-23GPaNanoindentation hardness
Laser Wavelength (λ)515nmVisible fs-laser
Pulse Duration (τ)320fsUltra-short pulse regime
Peak Fluence (F)0.32J/cm2Used for ablation and LIPSS formation
Ablation Threshold (Fth)~0.3J/cm2Single-pulse threshold
Pulse Frequency Range (f)100 kHz - 2MHzTested range
Effective Pulse Number (Neff)~28-Maintained constant via Vs/f = 0.5 ”m pitch
Ablation Depth1.5 - 1.65”mStable across 0.1-2 MHz frequency range
LSFL Period (A) Range360 ± 5 to 420 ± 10nmVaries with polarization angle (0° to 90°)
LSFL Grating Depth130 - 210nmMeasured via AFM
AFM Tip Load (Fload)200nNUsed for Lateral Force Microscopy (LFM)
Friction Coefficient (”gr)0.55-Laser-graphitized surface (derived from fit)
Friction Coefficient (”0)0.69-Original Ti-DLN film surface (derived from fit)

Key Methodologies

Section titled “Key Methodologies”
  1. Ti-DLN Film Synthesis: Films were grown on Si substrates using Plasma-Assisted Chemical Vapor Deposition (PACVD). The carbon-silicon matrix was derived from polymethylphenylsiloxane (PMPS) vapor plasma, while titanium doping (17-18 at.%) was achieved via simultaneous magnetron sputtering of a Ti target.
  2. Femtosecond Laser Setup: A linearly-polarized fs-laser (515 nm, 320 fs) was focused onto the film surface at normal incidence (F = 0.32 J/cm2). A galvanometer scanner controlled the beam velocity (Vs) to produce 10 ”m wide microgrooves.
  3. High-Frequency Testing: Pulse repetition rates (f) were tested from 100 kHz up to 2 MHz. Vs was adjusted proportionally to f to maintain a constant scanning pitch of 0.5 ”m, ensuring a consistent effective pulse number (Neff ~ 28) for comparison.
  4. Polarization Rotation: The direction of the electric field vector (E) was rotated relative to the beam scanning direction (Vs) in 30° increments (0°, 30°, 60°, 90°) to control the orientation of the resulting LIPSS.
  5. Structural Analysis: Surface morphology and LIPSS periodicity were characterized using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). LIPSS periods were quantified using two-dimensional Fast Fourier Transform (FFT) analysis of the images.
  6. Nanofriction Measurement: Nanoscale friction was measured using contact-mode AFM in Lateral Force Microscopy (LFM) mode. Wear-resistant diamond-coated Si probes (Rtip ~ 100 nm) were used at a constant load of 200 nN to minimize capillary forces and tip wear.
  7. Modeling: Numerical simulations of the friction ratio (A = FLIPSS/Ffilm) were performed based on the measured sinusoidal ripple profile (maximum slope angle 60°) to derive the friction coefficients (”gr and ”0) of the laser-graphitized and original surfaces.

Commercial Applications

Section titled “Commercial Applications”
  • High-Performance Tribological Coatings: Manufacturing hard, wear-resistant Ti-DLN coatings with engineered surface textures for reduced friction and improved durability in mechanical systems.
  • Anisotropic Micro/Nano-Devices: Creating surfaces with directional friction or wetting properties for use in microfluidics, seals, and advanced micro-electromechanical systems (MEMS).
  • High-Speed Manufacturing: Utilizing the demonstrated stability of ablation depth at high pulse frequencies (up to 500 kHz) for rapid, high-throughput production of structured functional surfaces.
  • Optical and Sensing Surfaces: Fabricating robust, high-resolution diffraction gratings or structured surfaces for optical components and sensors, leveraging the precise control over LIPSS orientation and period.
  • Biomaterials and Implants: Developing DLC-based coatings for medical devices where controlled surface topography and friction are necessary to manage cell interaction or reduce wear in articulating joints.
View Original Abstract

We study the properties of laser-induced periodic surface structures (LIPSS) formed on titanium-doped diamond-like nanocomposite (DLN) a-C:H:Si:O films during ablation processing with linearly-polarized beams of a visible femtosecond laser (wavelength 515 nm, pulse duration 320 fs, pulse repetition rates 100 kHz-2 MHz, scanning beam velocity 0.05-1 m/s). The studies are focused on (i) laser ablation characteristics of Ti-DLN films at different pulse frequencies and constant fluence close to the ablation threshold, (ii) effects of the polarization angle rotation on the properties of low spatial frequency LIPSS (LSFL), and (iii) nanofriction properties of the ‘rotating’ LIPSS using atomic force microscopy (AFM) in a lateral force mode. It is found that (i) all LSFL are oriented perpendicular to the beam polarization direction, so being rotated with the beam polarization, and (ii) LSFL periods are gradually changed from 360 ± 5 nm for ripples parallel to the beam scanning direction to 420 ± 10 nm for ripples formed perpendicular to the beam scanning. The obtained results are discussed in the frame of the surface plasmon polaritons model of the LIPSS formation. Also, the findings of the nanoscale friction behavior, dependent on the LIPSS orientation relative to the AFM tip scanning direction, are presented and discussed.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1991 - Amorphous solid systems: Diamond-like carbon, carbides, films and multilayer structures [Crossref]
  2. 1992 - Diamond-like nanocomposites (DLN) [Crossref]
  3. 1992 - Diamond-like nanocomposites: Electronic transport mechanisms and some applications [Crossref]
  4. 2001 - Thermostable resistors based on diamond-like carbon films deposited by CVD method [Crossref]
  5. 2004 - Electron transport in W-containing amorphous carbon-silicon diamond-like nanocomposites [Crossref]
  6. 2006 - Superconductivity in W-containing diamond-like nanocomposite films [Crossref]
  7. 2008 - IR spectroscopy of diamondlike silicon-carbon films [Crossref]
  8. 2009 - Electrochemical behavior of amorphous metal-silicon-carbon nanocomposites based on titanium or tungsten nanophase [Crossref]
  9. 2011 - Microstructural design for fabrication of strain sensor utilizing tungsten-doped amorphous carbon coatings [Crossref]
  10. 2018 - Structure of diamond-like silicon-carbon films alloyed by vanadium [Crossref]

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