The fabrication of nanostructures beyond the diffraction limit has been the focus of nanotechnology research. Scanning probe microscopy (SPM) has attracted the attention of researchers for the detection and manufacture of nanostructures. Here, a nanosecond laser irradiated a cantilevered scanning near-field optical microscopy (SNOM) tip and directly wrote subwavelength nanostructures on Au nano-film, without the assistance of a mask or vacuum atmosphere. This method was stable and reproducible for long-term use. The in situ morphology detection was conducted after the writing process by atomic force microscope (AFM). A feature linewidth of approximately 83.6 nm (< λ/6) was confirmed using scanning electron microscopy (SEM). Linewidth of (167.8 ± 6.6) nm was reproduced stably. Theoretical calculations revealed that the elliptical heat distribution under the SNOM tip generated different linewidths when the tip scanned vertically and horizontally. It also interpreted the influential mechanism of single-pulse energy. The simulated linewidths were consistent with the fabricated linewidths. According to the elemental analysis by energy dispersive spectrometer (EDS), the mechanism of this method can be interpreted as melting of the Au nano-film instead of oxidation. Owing to its high positioning, machining accuracy, and instantaneous energy, this technology is considered convenient and economical for nanostructure fabrication and is proposed to be applied in nanolithography on multiple materials in the future.
Top–down (lithographic) fabrication of nanostructures remains a substantial challenge in nanotechnology. The diffraction limit has become a fundamental barrier that hinders the reduction in the manufacturing dimensions in conventional optical lithography. Electron beam lithography (EBL) provides high spatial resolution for the processing of photoresists [1]; however, it is not applicable to metal nano-films. Scanning probe lithography (SPL), which is based on scanning probe microscopy (SPM), is generally utilized in nanofabrication, including mechanical scratching [2], [3], [4], local anodic oxidation [5], [6], near-field etching [7], [8], [9], and thermal SPL (t-SPL) [10], [11], and so forth. SPL realizes high-resolution nano-pattern fabrication on various materials without the need for expensive masks or vacuum systems used in conventional optical lithography or EBL. The application conditions for each SPL type are unique. Mechanical scratching is only applicable to soft specimens and hard atomic force microscopy (AFM) probes, such as diamond and Si3N4. Local anodic oxidation can be used to fabricate oxide protrusion structures on semiconductors and metallic materials. t-SPL fabricates nano-patterns on a thermally sensitive resist by inducing thermal decomposition.
Scanning near-field optical microscopy (SNOM) can be used for morphology detection and nanofabrication [12]. Cantilevered SNOM tips have also been used for morphology detection [13], [14]. Nanoantenna probes based on metal-coated nanostructures have been used to achieve efficient throughput. The nanoscale aperture of the SNOM tip can be utilized in diverse applications, including near-field microscopy [15], [16], tip-enhanced Raman/photoluminescence spectroscopy [17], [18], fluorescence-based sensing [19], optical tweezers [20], resonance tunability [21], carbon nanotubes (CNTs) growth and catalyst activation [22], [23], and heat generation by light trapping [24].
Near-field enhancement at optical wavelengths, generated from the excitation of surface plasmon polaritons (SPPs) and high-precision constraint of light by the nanoaperture of the tip, provides enormous potential to attain high spatial resolution nanofabrication [25]. Using conventional tapered optical fibers, scanning near-field optical lithography (SNOL) studies have been performed on different materials, such as photoresists [26], [27], [28], [29], conjugated polymers [30], [31], self-assembled monolayers [32], [33], [34], Si [35], [36], [37], [38], and Cr nano-films [39]. In general, SNOL relies on a physical removal process or photochemical reactions between a laser and materials. This overcomes the limitations of the properties of tips and specimens, including hardness and conductivity, and expands the selection range of applicable materials for nanofabrication.
The direct writing of nanostructures on Au nano-films using nanosecond laser-irradiating cantilevered SNOM probes is of interest because noble metals, especially Au and Ag, exhibit strong localized surface plasmon resonance (LSPR) effects. However, detailed investigations into its feasibility and mechanism are unclear and require further study.
In this paper, we report the direct writing of nanostructures onto Au nano-films using a nanosecond-laser-irradiated cantilevered SNOM probe tip. The minimum linewidth of 83.6 nm and repeatable linewidth of approximately (167.8 ± 6.6) nm were obtained on Au nano-film. The direct writing method realized a highly accurate and controllable manufacturing of nanostructures on the Au nanofilm surface without any masks and at a relatively low cost. The single-pulse energy (EL) and polarization (α) were investigated as the two main factors influencing the feature widths of the nanostructure. The simulation results indicate that the influential mechanisms of EL and α reflect the changes in the heat-affected area. According to the energy dispersive spectrometer (EDS) elemental analysis results, the mechanism of this method can be interpreted as melting of the Au nano-film instead of oxidation. Locally excited SPPs generate a high-temperature spot underneath the tip. This hot spot, with high positional accuracy and energy adjustability, provides an excellent nanosized energy source. It can be used in not only high-resolution nanofabrication of various materials but also in nanowelding to precisely illuminate the welding spot.
2. Materials and methods
2.1. Laser-SNOM direct writing system
The laser direct-writing system consists of a nanosecond laser, several optical elements, and an atomic force microscope (AFM) in Fig. 1(a). A 532 nm laser underwent attenuation and polarization control and was focused accurately on the tip aperture. A Nd:YAG laser (Dawa 100, Beamtech Optronics, China) was used in the direct writing process to generate linearly polarized nanosecond optical pulses at a wavelength of 532 nm. The laser pulse width (τ) was 7 ns, the repetition rate was set to 20 Hz, and the EL reached a maximum of 50 mJ. A half-wave plate (HWP) and a polarization beam splitter (PBS) were combined as an attenuator. This attenuator realized continuous and precise regulation of the laser energy and guaranteed that the incident laser polarization along y-axis. A scanning galvanometer was used to accurately manipulate the position of the laser spot with respect to the SNOM tip aperture. A dichroic mirror not only redirected the processing laser but also enabled the monitoring of the laser spot and SNOM tip with the assistance of the charge-coupled device (CCD) system. A 10× objective lens was used to focus the laser and fit the size of the tip aperture. An AFM (Ntegra Spectra II, NT-MDT, Russia) was equipped with the probe and operated in contact mode.
Fig. 1(b) shows a vertical view of the probe (SNOM_C, TipsNano, Estonia). The cantilever and pyramidal tip sizes were 200 μm × 50 μm and 20 μm × 20 μm, respectively. Fig. 1(c) shows the detailed pyramidal-tip structure. It was composed of 500 nm layer of pyramidal hollow SiO2 and 100 nm layer of Al, which was evaporated and deposited on the bottom. Transmission of the laser through the coating layer was negligible because the skin depth of the opaque Al film was approximately 10 nm. The essential nanoaperture of the tip was fabricated using focused ion beam (FIB) milling. The laser was incident vertically from the top into the nanoscale aperture to realize the direct writing of the nanostructures. The width of the tip aperture (w) was 140 nm. The resonant frequency of the probe was maintained at 130 kHz. The spring constant was 16.5 N∙m−1. The probe can be applied in both the direct writing of nanostructures and in situ morphology detection as a normal AFM probe.
The morphology of the fabricated nanostructures was analyzed using scanning electron microscope (SEM) (Sigma 300 VP, ZEISS, Germany), and the elemental type and content in the microarea were analyzed using EDS (ULTIM MAX, Oxford Instruments, UK).
2.2. Sample preparation
Silicon chips were sequentially submerged in an ultrasonic bath of acetone and absolute alcohol for 10 and 5 min, respectively. The Au nano-film (50 nm) was evaporation deposited on the Si substrate at the deposition speed of 0.5 nm∙s−1 using electron beam evaporator (TF500, HHV, UK). The purity of the Au source was 99.999%. The morphology of a 6 μm × 6 μm Au nano-film are shown in Fig. S1 (Appendix A). The roughness average (Ra) and root mean square (Rq) were 1.37 and 1.76 nm, respectively. That is, the substrate surface was sufficiently flat for the direct-writing process.
2.3. Near-field multiphysics model
To investigate the laser propagation through the aperture, a three-dimensional (3D) multiphysics model in the vicinity of the SNOM apex was established using COMSOL Multiphysics (Sweden) in Fig. 1(c). The electromagnetic and thermal field distributions within the tip aperture were calculated using the finite-element method (FEM). The width w of the aperture was set to 140 nm. The tip aperture was irradiated with a linearly polarized nanosecond laser beam (λ0 = 532 nm). The incident light was a plane wave (wave vector k0), whose polarization could be set to both α = 0° (transverse magnetic (TM) polarization) and α = 90° (transverse electric (TE) polarization).
In the wave optics module, the electromagnetic field distribution is calculated in the frequency domain using Maxwell’s equation
where E is the electric field and k0 is the wavenumber. ∇ is Hamiltonian. The relative permittivity ɛ(ω) is a complex-valued function of the laser-frequency ω. For nonmetallic materials in the model, such as air, SiO2, and Si, ɛ(ω) was calculated as
where n(ω) and k(ω) are the real and imaginary components of the complex refractive index of the medium, respectively. The optical properties of the air, SiO2, and Si at λ0 = 532 nm are listed in Table S1 (Appendix A).
The optical properties of the metals in the simulation, including Al and Au, were described using the Drude–Lorentz oscillator model [40]. The ɛ(ω) of the metals is expressed as
where ωp is the plasma frequency, and K is the number of oscillators with frequency ωj, strength fj, and lifetime $ 1 / \Gamma_{j} \cdot \Omega_{\mathrm{p}}=\sqrt{f_{0}} \omega_{p}$ is the plasma frequency associated with the intraband transitions, oscillator strength f0, and damping constant . i is imaginary unit and $ j \in \mathrm{~N}^{*}$. The optical parameters of Al and Au in the Drude–Lorentz model are listed in Tables S2 and S3 in Appendix A, respectively.
In the heat transfer module, the thermal distribution on the Au nano-film was simulated in the time domain after obtaining the light-field distribution. The temperature distribution was calculated as follows
where ρ, Cp, and k are the density, specific heat capacity at constant pressure, and thermal conductivity of the material, respectively. T is the temperature, t is the time, and u is the heat flux vector. The heat source Q0 was obtained from the results of the calculated electric field distribution as follows
where c is the velocity of light and ɛ0 is the vacuum permittivity.
The corresponding relationship between the laser power density P and EL is expressed as
$P=\frac{E_{\mathrm{L}}}{s \cdot \tau}$
where s is the area of the focused laser beam and τ is the pulse width of the laser. In this case, s was measured as 2500π μm2, and τ was 7 ns.
According to Eqs. (6), (7), the initial electric field intensity ∣E0∣ in the multiphysics model was set to 7.86 × 107, 8.07 × 107, and 8.28 × 107 V∙m−1 when the EL was 450, 475, and 500 μJ, respectively.
3. Results
Several types of nanostructures, such as nano-lines, nano-letters, and nano-patterns, have been directly written on Au nano-film. During this process, the repetition rate of the laser was set to 20 Hz, and the scanning speed was 0.2 μm∙s−1. The EL was adjusted to 500 μJ. The writing process was executed in contact mode, which ensured sufficient proximity between the tip and nanofilm. The setpoint in the writing process was the same as that in the scanning mode without any extra load, ensuring that the friction force was not sufficiently large to cause mechanical etching of the substrate surface. Fig. 2(a) illustrates the in situ detected morphology of the written lines immediately after processing. The length of the lines is 8 μm, and the spacing between the two lines is 2 μm. Fig. 2(b) is the SEM image of the nano-lines in Fig. 2(a). Notably, the nano-line indicated by the red rectangle in Fig. 2(b) is incomplete. The laser was turned off when that area was processed. This led to the disappearance of approximately 1 μm line. As shown in Fig. 2(a), white areas were observed at the edges of the AFM image. Compared with the conventional AFM tip with an apex radius of a few nanometers, the apex of the cantilevered SNOM tip was not sufficiently sharp. This may have a negative influence on the image quality of the in situ morphology detection in the AFM mode. The SEM images more accurately illustrate the morphology of the nanostructures. Conducting in situ detection is important to ensure the nanostructures, despite the affected image quality. Fig. 2(c) shows a cross-sectional analysis of the white line in Fig. 2(b). The nano-line was V-shaped in cross-sectional view. The widths (distance between the green and red marks in x direction) and depths (distance between the red and blue marks in y direction) of the lines are listed in Table 1. The average linewidth was 167.8 nm as measured using a standard deviation of 6.554 nm. The linewidth was approximately equal to the aperture width w. The laser light, well-confined in the SNOM tip aperture, induced nanostructures at the subwavelength scale. In the vertical direction, the average line depth was 23 nm with a standard deviation of 3.633 nm. According to previously published simulation results [41], the light field intensity decays exponentially at a depth of approximately 20 nm. This explains the experimental depths of approximately 20 nm. Protrusions were observed on both sides of the fabricated nano-lines. We would discuss the reason for the protrusion formation later in this paper.
Complex nano-patterns were obtained using this method. Figs. 3(a) and (b) depict the AFM and SEM images of the nano-letters “XJTU,” respectively. The widths of the vertical and horizontal lines are shown in Fig. 3(b). The average width of vertical lines was 162.7 nm with a standard deviation of 7.84 nm, close to the values measured in Fig. 2(c). However, the average width of the horizontal lines increased to 220.6 nm, with a standard deviation of 22.46 nm. Our theoretical calculations revealed that the increase in width was affected by the polarization and scanning direction. The thermal distribution on the surface after irradiation with a single laser pulse is interpreted in Fig. 3(c). The polarization was along the y direction. The heat distribution was slightly larger than that at the tip aperture (black squares). The shape of the heat peak on the nano-film surface was approximately elliptical, the major axis of which was along the polarization direction. The polarization is guaranteed to be parallel to the vertical direction by the PBS in the optical system. The direct writing process is a combination of melting and reshaping of the surface material. The heat-peak area, which was above the melting point of Au (Tm = 1337 K), melted and generated grooves. Fig. 3(d) shows the temperature distribution along the lines x = 0 nm and y = 0 nm. The width of the heat-affected area along the minor axis of the ellipse was approximately 163 nm. Meanwhile, the width of the heat-affected area along the major axis exceeded approximately 240 nm. These calculation results were close to the experimental values. When the tip was scanned vertically (parallel to the polarization), the fabricated linewidth approximated the minor axis of the ellipse. The linewidth increased toward the major axis of the ellipse when it was scanned horizontally (perpendicular to the polarization). The nano-lines manufactured in the inclined and horizontal directions were shallower than those manufactured in the vertical direction. The difference in depth under various polarizations was caused by the interaction time between the laser and material. The elliptical heat-affected area led to different interaction times. Under the same scanning speed, the interaction time of the vertical scan (major axis) was obviously longer than those of the horizontal (minor axis) and inclined scan directions. The material was irradiated by more laser pulses when the scanning direction was parallel to polarization. The expansion of the interaction time between the material and laser deepened the nano-lines.
An EDS analysis was conducted to investigate the elemental composition. The elemental content analysis was executed at four points, and one yellow line in the nanoletters, as shown in Fig. 3(b). Points 1 and 2 are in the written nano-lines, and points 3 and 4 are in the unaffected area. The EDS spectra of the four points and lines are shown in Fig. S2 (Appendix A). The weight percent of elements (wt%) are shown in Fig. 3(e). The main elements in the substrate were Au, Si, C, and O. The sample surface randomly adsorbed organic substances in the air during its preparation and transportation, resulting in the existence of C and O. The weight percentage of Au at points 1 and 2 (approximately 45%) was lower than that at points 3 and 4 and the line average (approximately 55%). This situation was reversed for Si. Fig. 3(f) illustrates the elemental distribution along this line. At the position of the two fabricated nano-lines, the Si spectrum (red line) protruded, and the Au spectrum (green line) became a valley. The O content barely changed during this process. This implied that the protrusions were not formed by oxidation. We attribute the mechanism of direct writing using this novel technology to the local melting and reshaping of the Au nano-film. The Au melted in the laser-affected area restricted to the tip aperture. Melted Au accumulated on both sides of the grooves, generating protrusions.
Fig. 4(a) illustrates the feature linewidths fabricated using different EL. The linewidth was detected to be 83.6, 125.3, and 167.1 nm under EL1 = 450 μJ, EL2 = 475 μJ, and EL3 = 500 μJ, respectively. With a decrease in EL, both the line width and depth gradually decayed. The nanoline was too shallow to be observed by SEM when EL was too small. In addition, the tip of the SNOM tends to get damaged at a significantly high laser intensity. Therefore, the laser energy control is significant in this technology. Fig. 4(b) shows the calculated thermal distribution along the x direction for different EL. The widths of the heat-affected areas along the minor axis of the ellipse were approximately 71, 124, and 163 nm. This was consistent with the results shown in Fig. 4(a). Figs. 4(c) and (d) show the fabrication of the nano-patterns. The laser was turned off in the red rectangular area. No discernible features were produced, which eliminated mechanical scratching as a direct writing mechanism.
4. Discussion
The minimum feature width of the nanostructures by the laser direct-writing process is about 83.6 nm (less than λ/6), which is over the diffraction limit. The direct writing process is stable and repeatable to achieve controllable manufacture of nano-patterns with linewidth of approximately (167.8 ± 6.6) nm on Au nano-film. The difference in the line width and depth caused by the vertical and horizontal scanning is explained by the elliptical heat distribution beneath the SNOM tip. Both the line width and depth decayed with decreasing EL. Controlling the EL is necessary to fabricate clear nano-lines and prevent damage to the SNOM tip. EDS elemental analysis indicated that the mechanism was melting of the Au nano-film instead of oxidation. Theoretical simulation results verified the mechanism and clarified the influence of the polarization α and EL on the fabricated linewidth.
SNOL on Au nano-film technology was compared with other SPL methods mentioned in Section 1. The mechanism, feasibility, and resolution of each method are listed in Table 2. The advantages and disadvantages of these techniques are summarized below. In summary, SNOL overcomes the limitations of the properties of tips and specimens, such as hardness and conductivity and expands the selection range of applicable materials. This avoids chips caused by mechanical forces. Unlike the near-field etching method, laser polarization in SNOL is not necessarily P-polarization. However, the feature sizes are affected by the aperture size of the SNOM probes. Hence, based on the influential mechanisms of various parameters, we proposed optimization approaches to improve the feature resolution, aspect ratio, and processing throughput.
We considered two approaches for improving the feature size. The first is to decrease the aperture size of the SNOM tip. This restricted the laser to a smaller area to improve the resolution. However, a smaller aperture induced transmission decay. Hence, when considering both resolution and transmission, the aperture width should be optimized. The second is the application of a bowtie-ridge aperture instead of a square aperture at the SNOM tip. The gap between the bowtie ridges could be tens of nanometers, which would lead to a higher resolution of the feature size.
This suggests that a higher single-pulse energy of the laser EL process results in deep trenches. However, this would also broaden the nano-lines simultaneously, making an increase in their aspect ratio difficult. Moreover, extremely high EL damaged the SNOM tip. Extending the scanning time or reducing the scanning speed extended the reaction time between the near-field laser and nanofilm. The line depth increased with increasing thermal diffusion time. However, the deepening effect was limited by the near-field-affected area. Repeated scanning of the nano-lines assists in deepening the trench. As the SNOM tip works in the contact mode, it drops to the bottom of the nano-line in the second scanning process. The direct writing process begins again from the bottom of the nano-line.
Application of a high laser repetition and high scanning speed is recommended to improve the processing throughput. High repetition significantly increases the number of laser pulses at a certain time. Moreover, a high scanning speed improves processing speed. Here, we can replace the laser device with a new device with high repetition. The scanning speed of 0.2 μm∙s−1 is considerably below the scanning speed limit of the AFM system.
5. Conclusions
We realized the laser direct writing of complex nanostructures beyond the diffraction limit on Au nano-films with a cantilevered SNOM tip. The mechanism of this novel technology was interpreted using both theoretical calculations and experiments. The SNOM tip was capable of confining the laser to an aperture size and generating a high-temperature spot to melt the Au nano-film. Finally, we emphasize that this method for nanostructure fabrication is convenient and economical and can potentially be applied in nanolithography on multiple materials, and even in nanowelding.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was supported by the National Key Research and Development Program of China (2023YFB4605100), the Shaanxi Provincial Key Research and Development Program (2019ZDLGY01-09 and 2021ZDLGY10-02), and the State Key Laboratory of Solidification Processing (SKLSP202203).
SteinmannP, WeaverJMR.Nanometer-scale gaps between metallic electrodes fabricated using a statistical alignment technique.Appl Phys Lett2005; 86(6):063104.
[2]
GengYQ, YanYD, ZhaoXS, HuZJ, LiangYC, SunT, et al.Fabrication of millimeter scale nanochannels using the AFM tip-based nanomachining method.Appl Surf Sci2013; 266:386-394.
[3]
SunY, YanY, LiangY, HuZ, ZhaoX, SunT, et al.Effect of the molecular weight on deformation states of the polystyrene film by AFM single scanning.Scanning2013; 35(5):308-315.
[4]
Ramiaczek-KrasowskaM, PrazmowskaJ, SzyszkaA, PaszkiewiczR, TlaczalaM.Application of afm microscope as a nanolithography tool.In: Proceedings of the 2010 International Students and Young Scientists Workshop "Photonics and Microsystems; 2010 Jun 25–27; Szklarska Poreba, Poland. Piscataway: IEEE; 2011. p. 69–72.
[5]
LiuX, ChenKS, WellsSA, BallaI, ZhuJ, WoodJD, et al.Scanning probe nanopatterning and layer-by-layer thinning of black phosphorus.Adv Mater2017; 29(1):1604121.
[6]
TelloM, GarcíaF, PhysicsR.Linewidth determination in local oxidation nanolithography of silicon surfaces.J Appl Phys2002; 92(7):4075-4079.
[7]
YinH, DongX, WangX, CuiJ, WangW, MeiX.Advanced mechanism of multiphysics fields tip enhancement induced withvaried laser power to fabricate pattern-transformable subdiffraction limit nanostructures.Appl Opt2021; 60(36):11018-11026.
[8]
YinH, ZhangJ, WangX, CuiJ, WangW, MeiX.Recent progress in near-field tip enhancement: principles and applications.Phys Status Solidi-RRL2022; 16:2100456.
[9]
ChimmalgiA, ChoiTY, GrigoropoulosCP, KomvopoulosKJAPL.Femtosecond laser aperturless near-field nanomachining of metals assisted by scanning probe microscopy.Appl Phys Lett2003; 82(8):1146-1148.
[10]
WolfH, RawlingsC, MenschP, HedrickJL, CoadyDJ, DuerigU, et al.Sub-20nm silicon patterning and metal lift-off using thermal scanning probe lithography.J Vac Sci Technol B2015; 33(2):02B102.
[11]
Conde-RubioA, LiuX, BoeroG, BruggerJ.Edge-contact MoS2 transistors fabricated using thermal scanning probe lithography.ACS Appl Mater Interfaces2022; 14(37):42328-42336.
[12]
LoS, WangH.Near-field photolithography by a fiber probe.In: Proceedings of the 2001 1st IEEE Conference on Nanotechnology; 2001 Oct 30–30; Maui, HI, USA. Piscataway: IEEE; 2002. p. 36–9.
[13]
Schürmann RooijG, NoellW, StauferU, deNF .Microfabrication of a combined AFM–SNOM sensor.Ultramicroscopy2000; 82:33-38.
[14]
StopkaM, DrewsD, MayrK, LacherM, EhrfeldW, KalkbrennerT, et al.Multifunctional AFM/SNOM cantilever probes: fabrication and measurements.Microelectron Eng2000; 53(1–4):183-186.
[15]
ShiX, Coca-LópezN, JanikJ, HartschuhA.Advances in tip-enhanced near-field Raman microscopy using nanoantennas.Chem Rev2017; 117(7):4945-4960.
BerneschiS, BarucciA, BaldiniF, CosiF, QuercioliF, PelliS, et al.Optical fibre micro/nano tips as fluorescence-based sensors and iInterrogation probes.Optics2020; 1(2):213-242.
[20]
KotsifakiDG, ChormaicSN.Plasmonic optical tweezers based on nanostructures: fundamentals, advances and prospects.Nanophotonics2019; 8(7):1227-1245.
[21]
HeydarianH, YazdanfarP, ShahmansouriA, RashidianB.Tunable wide-band graphene plasmonic nano-color-sorter: application in scanning near-field optical microscopy.J Opt Soc Am B2019; 36(2):435-442.
[22]
YazdanfarP, HeydarianH, RashidianB.Controlled optical near-field growth of individual free-standing well-oriented carbon nanotubes, application for scattering SNOM/AFM probes.Nanophotonics2022; 11(21):4671-4686.
[23]
YazdanfarP, HeydarianH, RashidianB.Photothermal heating using a near-field plasmonic probe, application in NFO–CVD.In: Proceedings of the 2018 Fifth International Conference on Millimeter-Wave and Terahertz Technologies (MMWaTT); 2018 Dec 18–20; Tehran, Iran. Piscataway: IEEE; 2018. p. 94–6.
[24]
YazdanfarP, HeydarianH, RashidianB.Modal control of thermoplasmonic behavior of nanostructures based on excitation of perfect absorption resonances.J Opt Soc Am B2020; 37(8):2238-2247.
[25]
WangX, CuiJ, YinH, WangZ, HeX, MeiX.Fabrication of nanostructure on Au nano-film by nanosecond laser coupled with cantilevered scanning near-field optical microscopy probe.Nanotechnology2023; 34(7):075301.
[26]
AghaeiSM, YasrebiN, RashidianB.Characterization of line nanopatterns on positive photoresist produced by scanning near-field optical microscope.J Nanomater2015; 2015:936876.
[27]
NaberA, KockH, FuchsH.High-resolution lithography with near-field optical microscopy.Scanning1996; 18(8):567-571.
[28]
LinY, HongMH, WangWJ, LawYZ, ChongTC.Sub-30 nm lithography with near-field scanning optical microscope combined with femtosecond laser.Appl Phys A2005; 80(3):461-545.
[29]
RoszkiewiczA, JainA, TeodorczykM, NasalskiW.Formation and characterization of hole nanopattern on photoresist layer by scanning near-field optical microscope.Nanomaterials2019; 9(10):1452.
CacialliF, RiehnR, DownesA, LatiniG, CharasA, MorgadoJ.Fabrication of conjugated polymers nanostructures via direct near-field optical lithography.Ultramicroscopy2004; 100(3–4):449-455.
[32]
SunS, LeggettGJ.Matching the resolution of electron beam lithography by scanning near-field photolithography.Nano Lett2004; 4(8):1381-1384.
[33]
SunS, ChongKSL, LeggettGJ.Nanoscale molecular patterns fabricated by using scanning near-field optical lithography.J Am Chem Soc2002; 124(11):2414-2415.
[34]
SunS, LeggettGJ.Generation of nanostructures by scanning near-field photolithography of self-assembled monolayers and wet chemical etching.Nano Lett2002; 2(11):1223-1227.
HeitzJ, YakuninS, StehrerT, WysockiG, BäuerleD.Laser-induced nanopatterning, ablation, and plasma spectroscopy in the near-field of an optical fiber tip. R. Vilar, O. Conde, M. Fajardo, L.O. Silva, M. Pires, A. Utkin (Eds.), XVII International Symposium on Gas Flow, Chemical Lasers, and High-power Lasers, Bellingham, WA, USA (2009), p. 71311W
RakiADć, DjurisicAB, ElazarJM, MajewskiML.Optical properties of metallic films for vertical-cavity optoelectronic devices.Appl Opt1998; 37(22):5271-5283.
[41]
WangX, CuiJ, YinH, WangZ, HeX, MeiX.Mechanism of nanostructure processing on Au and Ag nano-film by a nanosecond laser illuminating cantilevered scanning near-field optical microscopy tip.Appl Opt2022; 61(33):9773-9780.
PDF
(2476KB)
