研究目的
Improving the spatial resolution in nanofabrication using two-photon-absorption induced polymerization to achieve sub-diffraction-limit resolution.
研究成果
A resolution of ~36 nm (λ/21) is achieved in nanofabrication using two-photon-absorption induced polymerization by combining high laser intensity with fast scanning speeds. This approach allows for the fabrication of stable 3D microstructures with sub-diffraction-limit resolution, demonstrating the effectiveness of the developed optical setup and process parameters.
研究不足
The resolution is limited by factors such as laser intensity, exposure time, and scanning speed. Micro-explosions can occur at high intensities, and very thin fibers may not survive the development process or SEM observation. The distance between voxels must be less than 2 μm for suspended fibers to form. The custom setup may have alignment and stability constraints.
1：Experimental Design and Method Selection:
The study uses a systematic nanofabrication process with a femtosecond laser at 780 nm wavelength. It involves fabricating polymerized voxels, nano-lines, and suspended nano-fibers to investigate factors like laser intensity, exposure time, and scanning speed. The method leverages nonlinear optical effects for high resolution.
2：Sample Selection and Data Sources:
A photoresist based on methyl-methacrylate monomer is used, prepared as a mixture with specific components (MMA monomer, DPE-6A cross-linker, sensitizer, initiator). Samples are fabricated on glass substrates.
3：List of Experimental Equipment and Materials:
Equipment includes a Ti:sapphire femtosecond laser (Mai Tai, Spectra Physics), objective lens with NA 1.4, piezoelectric stage (P-517.2CL, SN110024792, Multi-Axis Piezo Scanner), CCD camera, attenuator, beam expander, dichroic mirror, shutter, and field-emission scanning electron microscope (FEI FEG 450 SEM). Materials include methyl methacrylate monomer, DPE-6A cross-linker, 2-Benzyl-2-(dimethylamino)-4′-morpholino-butyrophenone sensitizer, benzil initiator, and ethanol for washing.
4：4, piezoelectric stage (P-2CL, SN110024792, Multi-Axis Piezo Scanner), CCD camera, attenuator, beam expander, dichroic mirror, shutter, and field-emission scanning electron microscope (FEI FEG 450 SEM). Materials include methyl methacrylate monomer, DPE-6A cross-linker, 2-Benzyl-2-(dimethylamino)-4′-morpholino-butyrophenone sensitizer, benzil initiator, and ethanol for washing. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The laser beam is focused into the resin using a high NA objective lens. The sample is moved using a piezoelectric stage for XY positioning and a motorized objective lens for Z scanning. Voxels are created by single spot irradiation, nano-lines by continuous scans, and suspended fibers by translating between voxels at fixed speeds. After fabrication, samples are washed in ethanol and analyzed with SEM.
5：Data Analysis Methods:
SEM images are used to measure voxel diameters, line widths, and fiber resolutions. Data is analyzed to determine dependencies on laser intensity and exposure time, with linear and exponential fits applied.
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Field-emission scanning electron microscope
FEI FEG 450 SEM
FEI
Used to observe and analyze the fabricated micro/nanostructures.
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Ti:sapphire femtosecond laser
Mai Tai
Spectra Physics
Used as the light source for two-photon absorption polymerization, providing high peak power pulses.
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Objective lens
Tightly focuses the laser beam into the photoresist with high numerical aperture.
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Piezoelectric stage
P-517.2CL
Positions and moves the sample in the XY plane with high precision.
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Charge-coupled device camera
CCD camera
Enables precise control of the focal spot position and in situ fabrication monitoring.
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Attenuator
Attenuates the laser power dose for precise control in the polymerization process.
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Beam expander
Expands the laser beam for better focusing.
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Dichroic mirror
Directs the laser beam and allows for imaging with the CCD camera.
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Shutter
Controls the exposure of the laser beam to the sample.
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