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6CCVD Research

Surface Nanotexturing of Boron-Doped Diamond Films by Ultrashort Laser Pulses

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2023-02-04
JournalMicromachines
AuthorsMatteo Mastellone, Eleonora Bolli, Veronica Valentini, S. Orlando, Antonio Lettino
InstitutionsNational Research Council - Institute of Methodologies for Environmental Analysis, Delft University of Technology
Citations8
AnalysisFull AI Review Included

Surface Nanotexturing of Boron-Doped Diamond Films by Ultrashort Laser Pulses

Section titled “Surface Nanotexturing of Boron-Doped Diamond Films by Ultrashort Laser Pulses”

Executive Summary

Section titled “Executive Summary”

This study successfully demonstrates controlled surface nanotexturing of polycrystalline Boron-Doped Diamond (BDD) films using femtosecond laser irradiation, focusing on the formation of Laser-Induced Periodic Surface Structures (LIPSS).

  • Controlled Patterning: Two distinct surface patterning regimes were identified: narrow, irregular ripples at low accumulated fluences (less than 14.4 J cm-2) and coarse, highly regular LIPSS at higher fluences.
  • Optimal Periodicity: Highly regular Low Spatial Frequency LIPSS (LSFL) were achieved with a spatial periodicity of 630 nm ± 30 nm, a value attractive for interaction with visible light wavelengths.
  • Structural Alteration: Raman spectroscopy confirmed a significant increase in sp2 (graphitic) carbon content following irradiation, indicating localized graphitization, likely at grain boundaries.
  • Morphological Stability: The depth of the regular LIPSS remained relatively constant at 150 ± 20 nm for high-fluence treatments (144 J cm-2 and above).
  • Roughness Reduction: The laser treatment transformed the surface roughness from randomly distributed to regularly patterned, resulting in an approximate 30% decrease in the roughness average (Ra).
  • Functional Enhancement: The resulting nanostructured BDD surface is proposed for use as efficient solar photo-electrodes due to enhanced optical absorption, and as THz components exploiting the induced metal/dielectric anisotropy.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
BDD Film Thickness4”mPolycrystalline HF-CVD film
B-Doping Level2.8at.%Heavily doped BDD
BDD Resistivity5 x 10-3Ω cmElectrical property
Laser TypeTi:SapphireN/AFemtosecond pulsed laser
Laser Wavelength800nmNear-infrared regime
Pulse Duration100fsUltrashort pulse regime
Single Pulse Fluence (Ίp)1.44J cm-2Fixed parameter for all treatments
Accumulated Fluence Range (ΊA)1.44 to 230.4J cm-2Varied by pulse count (N=1 to 160)
LIPSS Formation Threshold> 14.4J cm-2Minimum fluence for regular LSFL patterning
LIPSS Periodicity (Λ)630 ± 30nmLow Spatial Frequency LIPSS (LSFL)
LIPSS Depth (Peak-to-Valley)150 ± 20nmHigh fluence samples (P100, P160)
Untreated Roughness Average (Ra)113.4 ± 5.0nmInitial surface condition
Treated Roughness Average (Ra)77.3 ± 5.0nmAfter regular patterning
Raman D Band Position (Treated)~1345cm-1Shift indicating sp2 disorder increase
Raman G Band Position (Treated)~1575cm-1Shift indicating sp2 disorder increase

Key Methodologies

Section titled “Key Methodologies”

BDD Film Growth (HF-CVD)

Section titled “BDD Film Growth (HF-CVD)”
  • Seeding: Detonation diamond nanoparticles used for seeding the silicon wafer substrate.
  • Method: Hot-Filament Chemical Vapor Deposition (HF-CVD).
  • Gas Composition: 2.4% CH4/H2 gas ratio (72 sccm CH4 / 3000 sccm H2).
  • Doping Source: 40 sccm trimethylborane (TMB).
  • Substrate Temperature: Approximately 850 °C.

Femtosecond Laser Texturing

Section titled “Femtosecond Laser Texturing”
  • Laser Source: Ti:Sapphire laser (100 fs duration, 800 nm wavelength).
  • Polarization: Linear polarization.
  • Irradiation Environment: High vacuum chamber (pressure less than 5 x 10-7 mbar) to minimize chemical alteration (oxidation/nitridation).
  • Strategy: Single spot impingement (no translational movement) to precisely control the accumulated fluence (ΊA) by varying the number of pulses (N) at a fixed single pulse fluence (Ίp = 1.44 J cm-2).

Structural and Morphological Characterization

Section titled “Structural and Morphological Characterization”
  • Surface Imaging: Field-Emission Gun Scanning Electron Microscopy (FEG-SEM) and Atomic Force Microscopy (AFM) in tapping mode.
  • Periodicity Quantification: 2D Fast Fourier Transformation (2D-FFT) applied to SEM images (30 x 30 ”m2 area) to determine LIPSS spatial periodicity and homogeneity.
  • Depth and Roughness: AFM line profiles and roughness parameter calculations (Ra and Rms) performed on 25 ”m2 sampling areas.
  • Chemical Analysis: Confocal Micro-Raman Spectroscopy (532 nm laser) performed at the center of the irradiated spots to assess sp2 (graphitic) content evolution.

Commercial Applications

Section titled “Commercial Applications”

The ability to precisely control the surface morphology and induce localized sp2 graphitization on BDD opens several high-value engineering applications:

  • Solar Photo-Electrodes: The LIPSS structure enhances optical absorption in the visible-IR range, allowing BDD to function as an efficient photo-electrode for solar-driven chemical processes (e.g., CO2 reduction or water splitting).
  • Electrochemical Sensing: The nanostructured surface and altered surface chemistry (sp2 content) improve the sensitivity and selectivity of BDD electrodes, crucial for advanced bio-sensing and electro-catalytic applications.
  • THz Components: The periodic structure creates an anisotropic metal/dielectric pattern (graphite sp2 regions acting as metallic inclusions within the diamond sp3 matrix), enabling the implementation of BDD plates as THz components.
  • Microelectromechanical Systems (MEMS): Surface functionalization via laser texturing can tune the mechanical and surface energy properties of BDD components used in harsh environments.
  • Supercapacitors: Increased effective surface area due to nanotexturing can enhance the charge storage capacity and performance of diamond-based supercapacitors.
View Original Abstract

Polycrystalline boron-doped diamond (BDD) films were surface nanotextured by femtosecond pulsed laser irradiation (100 fs duration, 800 nm wavelength, 1.44 J cm−2 single pulse fluence) to analyse the evolution of induced alterations on the surface morphology and structural properties. The aim was to identify the occurrence of laser-induced periodic surface structures (LIPSS) as a function of the number of pulses released on the unit area. Micro-Raman spectroscopy pointed out an increase in the graphite surface content of the films following the laser irradiation due to the formation of ordered carbon sites with respect to the pristine sample. SEM and AFM surface morphology studies allowed the determination of two different types of surface patterning: narrow but highly irregular ripples without a definite spatial periodicity or long-range order for irradiations with relatively low accumulated fluences (<14.4 J cm−2) and coarse but highly regular LIPSS with a spatial periodicity of approximately 630 nm ± 30 nm for higher fluences up to 230.4 J cm−2.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2014 - Boron Doped Diamond Biotechnology: From Sensors to Neurointerfaces [Crossref]
  2. 2016 - Diamond-Based Supercapacitors: Realization and Properties [Crossref]
  3. 2015 - Porous Diamond with High Electrochemical Performance [Crossref]
  4. 2013 - Photo-Illuminated Diamond as a Solid-State Source of Solvated Electrons in Water for Nitrogen Reduction [Crossref]
  5. 2016 - Diamond Electrochemistry at the Nanoscale: A Review [Crossref]
  6. 2020 - Nanostructured Boron Doped Diamond Electrodes with Increased Reactivity for Solar-Driven CO2 Reduction in Room Temperature Ionic Liquids [Crossref]
  7. 2018 - Laser-Induced Periodic Surface Structures (LIPSS) on Heavily Boron-Doped Diamond for Electrode Applications [Crossref]
  8. 2016 - Black Diamond for Solar Energy Conversion [Crossref]
  9. 2021 - Strain-Tuning of the Electronic, Optical, and Vibrational Properties of Two-Dimensional Crystals [Crossref]
  10. 2022 - Diamond Semiconductor and Elastic Strain Engineering [Crossref]

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