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Keywords = maskless plasma etching

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9 pages, 3781 KiB  
Article
Effect of Surface Texture on Light Extraction Efficiency for LEDs
by Fu-Der Lai
Crystals 2023, 13(3), 491; https://doi.org/10.3390/cryst13030491 - 12 Mar 2023
Cited by 1 | Viewed by 2386
Abstract
The light extraction efficiency of an LED is dependent on its surface texture. However, the surface of the p-GaN layer is not easy to be etch with inverted hexagonal pyramid structures (IHPS) with small top widths and large depths using existing methods. Therefore, [...] Read more.
The light extraction efficiency of an LED is dependent on its surface texture. However, the surface of the p-GaN layer is not easy to be etch with inverted hexagonal pyramid structures (IHPS) with small top widths and large depths using existing methods. Therefore, it is important to discuss the expected effect of the conditions of thermal annealing and inductively coupled plasma (ICP) reactive ion etching (RIE) for the generation of nano-pin-holes in the photoresist and fabrication of the top surface structure of GaN-based LEDs, in order to enhance the light output power. In this study, the following four items will be discussed: (1) the effect of thermal annealing on the composition of the photoresist; (2) the effect of thermal annealing and ICP RIE on the generation of the nano-pin-holes in the photoresist; (3) the effect of ICP RIE on the IHPS; and (4) the effect of surface texture of the IHPS on the light output power. It has been found that a nano-pin-hole structure in the photoresist etching mask is needed for the fabrication of many IHPS on the LED surface. A maskless via-hole etching technique was used for texturing the photoresist to produce nano-pore structures with diameters of less than 50 nm. The relationship between the light extraction efficiency and the surface texture is discussed in detail. The simulation results show the best light extraction efficiency (LEE) ratio of 358% to be obtained when the distance between two neighboring IHPS patterns (DBNP) is 300 nm. This in turn allowed the formation of IHPS with small top widths and large depths on the LED surface. A LEE ratio of 305% was obtained with the fabrication of IHPS with a top width of 290 nm, a depth of 170 nm and a DBNP of 180 nm on the LED surface. Full article
(This article belongs to the Special Issue Optoelectronics and Photonics in Crystals)
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14 pages, 3191 KiB  
Article
Laser-Patterned Alumina Mask and Mask-Less Dry Etch of Si for Light Trapping with Photonic Crystal Structures
by Jovan Maksimovic, Haoran Mu, Daniel Smith, Tomas Katkus, Mantas Vaičiulis, Ramūnas Aleksiejūnas, Gediminas Seniutinas, Soon Hock Ng and Saulius Juodkazis
Micromachines 2023, 14(3), 550; https://doi.org/10.3390/mi14030550 - 26 Feb 2023
Cited by 4 | Viewed by 2553
Abstract
Ultra-short 230 fs laser pulses of a 515 nm wavelength were tightly focused onto 700 nm focal spots and utilised in opening ∼0.4–1 μm holes in alumina Al2O3 etch masks with a 20–50 nm thickness. Such dielectric masks simplify the fabrication [...] Read more.
Ultra-short 230 fs laser pulses of a 515 nm wavelength were tightly focused onto 700 nm focal spots and utilised in opening ∼0.4–1 μm holes in alumina Al2O3 etch masks with a 20–50 nm thickness. Such dielectric masks simplify the fabrication of photonic crystal (PhC) light-trapping patterns for the above-Lambertian performance of high-efficiency solar cells. The conditions of the laser ablation of transparent etch masks and the effects sub-surface Si modifications were revealed by plasma etching, numerical modelling, and minority carrier lifetime measurements. Mask-less patterning of Si is proposed using fs laser direct writing for dry plasma etching of Si. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2022)
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12 pages, 3175 KiB  
Article
Hydrogel-Assisted 3D Volumetric Hotspot for Sensitive Detection by Surface-Enhanced Raman Spectroscopy
by Soo Hyun Lee, Sunho Kim, Jun-Yeong Yang, ChaeWon Mun, Seunghun Lee, Shin-Hyun Kim and Sung-Gyu Park
Int. J. Mol. Sci. 2022, 23(2), 1004; https://doi.org/10.3390/ijms23021004 - 17 Jan 2022
Cited by 11 | Viewed by 3345
Abstract
Effective hotspot engineering with facile and cost-effective fabrication procedures is critical for the practical application of surface-enhanced Raman spectroscopy (SERS). We propose a SERS substrate composed of a metal film over polyimide nanopillars (MFPNs) with three-dimensional (3D) volumetric hotspots for this purpose. The [...] Read more.
Effective hotspot engineering with facile and cost-effective fabrication procedures is critical for the practical application of surface-enhanced Raman spectroscopy (SERS). We propose a SERS substrate composed of a metal film over polyimide nanopillars (MFPNs) with three-dimensional (3D) volumetric hotspots for this purpose. The 3D MFPNs were fabricated through a two-step process of maskless plasma etching and hydrogel encapsulation. The probe molecules dispersed in solution were highly concentrated in the 3D hydrogel networks, which provided a further enhancement of the SERS signals. SERS performance parameters such as the SERS enhancement factor, limit-of-detection, and signal reproducibility were investigated with Cyanine5 (Cy5) acid Raman dye solutions and were compared with those of hydrogel-free MFPNs with two-dimensional hotspots. The hydrogel-coated MFPNs enabled the reliable detection of Cy5 acid, even when the Cy5 concentration was as low as 100 pM. We believe that the 3D volumetric hotspots created by introducing a hydrogel layer onto plasmonic nanostructures demonstrate excellent potential for the sensitive and reproducible detection of toxic and hazardous molecules. Full article
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9 pages, 3765 KiB  
Article
Etching Characteristics of SixNy Film on Textured Single Crystalline Silicon Surface Using Ar/CF4 and He/CF4 Surface-Discharge Plasma
by Toshiyuki Hamada, Shunsuke Masuda, Kazuki Nishida and Soma Yamamoto
Coatings 2020, 10(6), 563; https://doi.org/10.3390/coatings10060563 - 14 Jun 2020
Cited by 6 | Viewed by 3048
Abstract
In this study, we investigated the characteristics of electrode grooves formed by etching silicon nitride (SixNy) films using surface-discharge plasma under Ar/CF4 and He/CF4 gases on the basis of differences in the widths of the electrode grooves [...] Read more.
In this study, we investigated the characteristics of electrode grooves formed by etching silicon nitride (SixNy) films using surface-discharge plasma under Ar/CF4 and He/CF4 gases on the basis of differences in the widths of the electrode grooves etched on the SixNy film. The widths of the grooves etched using Ar as the carrier gas were narrower than those etched using He, and the etching speed achieved using Ar was higher than that achieved using He. Furthermore, the electrode groove created by surface-discharge plasma gradually widened as etching time and applied voltage increased. Full article
(This article belongs to the Special Issue Plasma Surface Engineering)
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13 pages, 2676 KiB  
Article
Black-Si as a Photoelectrode
by Denver P. Linklater, Fatima Haydous, Cheng Xi, Daniele Pergolesi, Jingwen Hu, Elena P. Ivanova, Saulius Juodkazis, Thomas Lippert and Jurga Juodkazytė
Nanomaterials 2020, 10(5), 873; https://doi.org/10.3390/nano10050873 - 1 May 2020
Cited by 11 | Viewed by 4830
Abstract
The fabrication and characterization of photoanodes based on black-Si (b-Si) are presented using a photoelectrochemical cell in NaOH solution. B-Si was fabricated by maskless dry plasma etching and was conformally coated by tens-of-nm of TiO2 using atomic layer deposition (ALD) with a [...] Read more.
The fabrication and characterization of photoanodes based on black-Si (b-Si) are presented using a photoelectrochemical cell in NaOH solution. B-Si was fabricated by maskless dry plasma etching and was conformally coated by tens-of-nm of TiO2 using atomic layer deposition (ALD) with a top layer of CoO x cocatalyst deposited by pulsed laser deposition (PLD). Low reflectivity R < 5 % of b-Si over the entire visible and near-IR ( λ < 2   μ m) spectral range was favorable for the better absorption of light, while an increased surface area facilitated larger current densities. The photoelectrochemical performance of the heterostructured b-Si photoanode is discussed in terms of the n-n junction between b-Si and TiO2. Full article
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9 pages, 1585 KiB  
Article
Highly Sensitive and Selective Nanogap-Enhanced SERS Sensing Platform
by ChaeWon Mun, Vo Thi Nhat Linh, Jung-Dae Kwon, Ho Sang Jung, Dong-Ho Kim and Sung-Gyu Park
Nanomaterials 2019, 9(4), 619; https://doi.org/10.3390/nano9040619 - 16 Apr 2019
Cited by 11 | Viewed by 3995
Abstract
This paper reports a highly sensitive and selective surface-enhanced Raman spectroscopy (SERS) sensing platform. We used a simple fabrication method to generate plasmonic hotspots through a direct maskless plasma etching of a polymer surface and the surface tension-driven assembly of high aspect ratio [...] Read more.
This paper reports a highly sensitive and selective surface-enhanced Raman spectroscopy (SERS) sensing platform. We used a simple fabrication method to generate plasmonic hotspots through a direct maskless plasma etching of a polymer surface and the surface tension-driven assembly of high aspect ratio Ag/polymer nanopillars. These collapsed plasmonic nanopillars produced an enhanced near-field interaction via coupled localized surface plasmon resonance. The high density of the small nanogaps yielded a high plasmonic detection performance, with an average SERS enhancement factor of 1.5 × 107. More importantly, we demonstrated that the encapsulation of plasmonic nanostructures within nanofiltration membranes allowed the selective filtration of small molecules based on the degree of membrane swelling in organic solvents and molecular size. Nanofiltration membrane-encapsulated SERS substrates do not require pretreatments. Therefore, they provide a simple and fast detection of toxic molecules using portable Raman spectroscopy. Full article
(This article belongs to the Special Issue Surface Enhanced Raman Spectroscopy in Nano-World)
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10 pages, 5989 KiB  
Article
Plasma Oxidation Printing into DLC and Graphite for Surface Functionalization
by Tatsuhiko Aizawa, Kenji Wasa and Yoshiro Nogami
C 2019, 5(1), 11; https://doi.org/10.3390/c5010011 - 11 Mar 2019
Cited by 3 | Viewed by 3432
Abstract
A diamond-like carbon (DLC) film, coated on a AISI420-J2 stainless steel substrate and vertically aligned graphite (VAG), was structured by high-density plasma oxidation to work as a DLC-punch for micro-stamping and DLC-nozzle array for micro-dispensing, in addition to acting as a copper-plated thermal [...] Read more.
A diamond-like carbon (DLC) film, coated on a AISI420-J2 stainless steel substrate and vertically aligned graphite (VAG), was structured by high-density plasma oxidation to work as a DLC-punch for micro-stamping and DLC-nozzle array for micro-dispensing, in addition to acting as a copper-plated thermal spreader, respectively. Thick DLC films were micro-patterned by maskless lithography and directly plasma-etched to remove the unmasked regions. Thick VAG (Ca plates were micro-patterned by screen-printing and selectively etched to activate the surface. Raman spectroscopy as well as electric resistivity measurement proved that there was no degradation of VAG by this surface activation. Wet plating was utilized to prove that copper wettability was improved by this surface treatment. Full article
(This article belongs to the Special Issue Plasma Processing for Carbon-based Materials)
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12 pages, 4924 KiB  
Article
Separated Type Atmospheric Pressure Plasma Microjets Array for Maskless Microscale Etching
by Yichuan Dai, Man Zhang, Qiang Li, Li Wen, Hai Wang and Jiaru Chu
Micromachines 2017, 8(6), 173; https://doi.org/10.3390/mi8060173 - 1 Jun 2017
Cited by 11 | Viewed by 6266
Abstract
Maskless etching approaches such as microdischarges and atmospheric pressure plasma jets (APPJs) have been studied recently. Nonetheless, a simple, long lifetime, and efficient maskless etching method is still a challenge. In this work, a separated type maskless etching system based on atmospheric pressure [...] Read more.
Maskless etching approaches such as microdischarges and atmospheric pressure plasma jets (APPJs) have been studied recently. Nonetheless, a simple, long lifetime, and efficient maskless etching method is still a challenge. In this work, a separated type maskless etching system based on atmospheric pressure He/O2 plasma jet and microfabricated Micro Electro Mechanical Systems (MEMS) nozzle have been developed with advantages of simple-structure, flexibility, and parallel processing capacity. The plasma was generated in the glass tube, forming the micron level plasma jet between the nozzle and the surface of polymer. The plasma microjet was capable of removing photoresist without masks since it contains oxygen reactive species verified by spectra measurement. The experimental results illustrated that different features of microholes etched by plasma microjet could be achieved by controlling the distance between the nozzle and the substrate, additive oxygen ratio, and etch time, the result of which is consistent with the analysis result of plasma spectra. In addition, a parallel etching process was also realized by plasma microjets array. Full article
(This article belongs to the Special Issue Microplasma Devices)
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10 pages, 7163 KiB  
Article
Fabrication of SiNx Thin Film of Micro Dielectric Barrier Discharge Reactor for Maskless Nanoscale Etching
by Qiang Li, Jie Liu, Yichuan Dai, Wushu Xiang, Man Zhang, Hai Wang and Li Wen
Micromachines 2016, 7(12), 232; https://doi.org/10.3390/mi7120232 - 14 Dec 2016
Cited by 8 | Viewed by 10426
Abstract
The prevention of glow-to-arc transition exhibited by micro dielectric barrier discharge (MDBD), as well as its long lifetime, has generated much excitement across a variety of applications. Silicon nitride (SiNx) is often used as a dielectric barrier layer in DBD due [...] Read more.
The prevention of glow-to-arc transition exhibited by micro dielectric barrier discharge (MDBD), as well as its long lifetime, has generated much excitement across a variety of applications. Silicon nitride (SiNx) is often used as a dielectric barrier layer in DBD due to its excellent chemical inertness and high electrical permittivity. However, during fabrication of the MDBD devices with multilayer films for maskless nano etching, the residual stress-induced deformation may bring cracks or wrinkles of the devices after depositing SiNx by plasma enhanced chemical vapor deposition (PECVD). Considering that the residual stress of SiNx can be tailored from compressive stress to tensile stress under different PECVD deposition parameters, in order to minimize the stress-induced deformation and avoid cracks or wrinkles of the MDBD device, we experimentally measured stress in each thin film of a MDBD device, then used numerical simulation to analyze and obtain the minimum deformation of multilayer films when the intrinsic stress of SiNx is −200 MPa compressive stress. The stress of SiNx can be tailored to the desired value by tuning the deposition parameters of the SiNx film, such as the silane (SiH4)–ammonia (NH3) flow ratio, radio frequency (RF) power, chamber pressure, and deposition temperature. Finally, we used the optimum PECVD process parameters to successfully fabricate a MDBD device with good quality. Full article
(This article belongs to the Special Issue Microplasma Devices)
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