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Hydrogen Induced Etching Features of Wrinkled Graphene Domains
摘要： Wrinkles are observed commonly in CVD (chemical vapor deposition)-grown graphene on Cu and hydrogen etching is of significant interest to understand the growth details, as well as a practical tool for fabricating functional graphene nanostructures. Here, we demonstrate a special hydrogen etching phenomenon of wrinkled graphene domains. We investigated the wrinkling of graphene domains under fast cooling conditions and the results indicated that wrinkles in the monolayer area formed more easily compared to the multilayer area (≥two layers), and the boundary of the multilayer area tended to be a high density wrinkle zone in those graphene domains, with a small portion of multilayer area in the center. Due to the site-selective adsorption of atomic hydrogen on wrinkled regions, the boundary of the multilayer area became a new initial point for the etching process, aside from the domain edge and random defect sites, as reported before, leading to the separation of the monolayer and multilayer area over time. A schematic model was drawn to illustrate how the etching of wrinkled graphene was generated and propagated. This work may provide valuable guidance for the design and growth of nanostructures based on wrinkled graphene.
关键词： graphene,hydrogen etching,wrinkling,CVD synthesis
更新于2025-11-21 11:01:37
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Well‐Defined Cu <sub/>2</sub> O/Cu <sub/>3</sub> (BTC) <sub/>2</sub> Sponge Architecture as Efficient Phenolics Scavenger: Synchronous Etching and Reduction of MOFs in confined‐pH NH <sub/>3</sub> ?H <sub/>2</sub> O
摘要： Fabrication of low-dimensional nano-MOFs as well as nanoparticles/metal-organic frameworks (MOFs) hybrids has sparked new scientific interests but remains a challenging task. Taking Cu3(BTC)2 as a proof of concept, it is demonstrated thats NH3?H2O solution of a confined pH value can readily shape the bulk Cu3(BTC)2 into nanoscale Cu3(BTC)2, beyond the need to control the crystal growth kinetics of MOFs. Adjusting the pH of NH3?H2O within a much small range (10–11) allows fine tuning over the size and shape of nanoscale Cu3(BTC)2. Particularly at pH = 11, NH3?H2O exhibits weak reducibility that triggers a reduction of part of Cu3(BTC)2 into Cu2O, while shaping the other into Cu3(BTC)2 nanowires. Benefiting from the coincidence of reduction and etching effects, the newly generated Cu2O dots can in situ anchor onto adjacent Cu3(BTC)2 nanowires at highly dispersive state, forming a well-defined sponge-like architecture built of Cu2O dots and nano-Cu3(BTC)2. The CuOx derived from annealing of the Cu2O dots/nano-Cu3(BTC)2 hybrid preserves the sophisticated sponge architecture and high porosity, and exhibits promising applications in phenol scavenging, with efficiency outperforming its counterparts and many other Cu-based catalysts reported in literature. It is anticipated that the findings here pave the way for the rational design of intricate nano-MOFs in a more efficient way.
关键词： nanoparticles/MOF,etching and reduction,sponge architecture,synergistic effect,low-dimensional MOFs
更新于2025-11-14 17:03:37
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Casimir-Lifshitz quantum state of superhydrophobic black-silicon surfaces manufactured by a metal-assisted hierarchical nano-microtexturing process
摘要： We investigated superhydrophobic Si nanosurfaces similar to the lotus leaf by performing a hierarchical nanotexturing process on micropyramidal Si surfaces. The process was carried out using a metal-assisted chemical etching process based upon the deposition of Ag nanoparticles. The hierarchical micro-nanosurfaces showed a superhydrophobic character with contact angles of approximately 134～150°. The photon tunnelling also provides a strong light absorption as a black Si. The surface-light emission from broad and sharp photoluminescence was observed in the wavelength ranges of 414.7～440 and 509～516.2 nm. The ?eld-induced tunnelling current on nanosurface shows the formation of quantum surface states. From the analyses of Casimir-Lifshitz quantum state of a photon in vacuum, the superhydrophobic behaviour of water droplet is closely related to the nanosurface and the nanoporous cavity shows the absorption of terahertz energy. Si nanosurface shows the broadband absorption in the spectral range of 800～900 cm?1 corresponding to the energy range of 99.2～111.6 meV with 24～27 THz.
关键词： Metal-assisted etching,hierarchical nano-microstructure,Ag nanodot deposition,superhydrophobic nanosurface
更新于2025-11-14 15:14:40
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Interfacial Contact is Required for Metal-Assisted Plasma Etching of Silicon
摘要： For decades, fabrication of semiconductor devices has utilized well-established etching techniques to create complex nanostructures in silicon. The most common dry process is reactive ion etching which fabricates nanostructures through the selective removal of unmasked silicon. Generalized enhancements of etching have been reported with mask-enhanced etching with Al, Cr, Cu, and Ag masks, but there is a lack of reports exploring the ability of metallic films to catalytically enhance the local etching of silicon in plasmas. Here, metal-assisted plasma etching (MAPE) is performed using patterned nanometers-thick gold films to catalyze the etching of silicon in an SF6/O2 mixed plasma, selectively increasing the rate of etching by over 1000%. The catalytic enhancement of etching requires direct Si-metal interfacial contact, similar to metal-assisted chemical etching (MACE), but is different in terms of the etching mechanism. The mechanism of MAPE is explored by characterizing the degree of enhancement as a function of Au catalyst configuration and relative oxygen feed concentration, along with the catalytic activities of other common MACE metals including Ag, Pt, and Cu.
关键词： nanofabrication,MACE,silicon processing,reactive ion etching,metal assisted etching
更新于2025-09-23 15:23:52
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Improved galvanic porous silicon fabrication using patterned electrodes
摘要： On-chip porous silicon can be fabricated in a number of ways, but perhaps the simplest is a galvanic method that requires no external power supply. While this etch process is relatively simple, the etch is highly dependent on the surface area ratio (SAR) of a backside precious metal and frontside silicon surface, which respectively act as the cathode and the anode of an electrochemical cell. The SAR controls the etch current density, and therefore local variations can create high current densities that have detrimental effects on the quality of the final porous silicon film. The present study investigates the use of patterned backside platinum electrodes with the galvanic etch technique. The use of a patterned backside electrode that mimics the silicon pattern on the frontside, provides a more consistent etch current throughout the entire sample, and thus a more uniform porous silicon film. A triangular shape porous silicon film was tested in this work for comparison to a previous study utilizing an unpatterned electrode. With patterned electrodes, an etch depth variation percentage was observed throughout the length of the film of 8%. This is a considerable improvement over a 108% depth variation observed with a similar frontside silicon pattern and an unpatterned backside electrode.
关键词： porous silicon,electrochemical etching,mesoporous,galvanic etching
更新于2025-09-23 15:23:52
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Anomalous shape evolution of Ag2O2 nanocrystals modulated by surface adsorbates during electron beam etching
摘要： An understanding of nanocrystal shape evolution is significant for the design, synthesis and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with high spatial resolution. Here, we report the anomalous shape evolution of Ag2O2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag2O2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag2O2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag2O2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Our findings provide critical insights into the modulatory function of surface adsorbates on shape control of nanocrystals.
关键词： surface adsorbates,Ag2O2 nanocrystal,shape evolution,In situ TEM,electron beam etching
更新于2025-09-23 15:23:52
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Nanoparticle Emissions from Metal-Assisted Chemical Etching of Silicon Nanowires for Lithium Ion Batteries
摘要： As one of the most promising anode materials for high-capacity lithium ion batteries (LIBs), silicon nanowires (SiNWs) have been studied extensively. The metal-assisted chemical etching (MACE) is a low-cost and scalable method for SiNWs synthesis. Nanoparticle emissions from the MACE process, however, are of grave concerns due to their hazardous effects on both occupational and public health. In this study, both airborne and aqueous nanoparticle emissions from the MACE process for SiNWs with three sizes of 90 nm, 120 nm, and 140 nm are experimentally investigated. The prepared SiNWs are used as anodes of LIB coin cells, and the experimental results reveal that the initial discharge and charge capacities of LIB electrodes are 3636 and 2721 mAh g-1 with 90 nm SiNWs, 3779 and 2712 mAh g-1 with 120 nm SiNWs, and 3611 and 2539 mAh g-1 with 140 nm SiNWs. It is found that, for 1 kW h of LIB electrodes, the MACE process for 140 nm SiNWs produces a high concentration of airborne nanoparticle emissions of 2.48 × 109 particles/cm3; the process for 120 nm SiNWs produces a high mass concentration of aqueous particle emissions, with a value of 9.95 × 105 mg/L. The findings in this study can provide experimental data of nanoparticle emissions from the MACE process for SiNWs for LIB applications, and can help the environmental impact assessment and life cycle assessment of the technology in the future.
关键词： Lithium ion batteries (LIBs),Metal-assisted chemical etching (MACE),Nanoparticle emissions,Silicon nanowires (SiNWs)
更新于2025-09-23 15:23:52
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Fabrication of octagonal and dodecagonal single crystal Si micropyramids via etching without using a pre-patterned mask
摘要： Surface texturing of Si has attracted signi?cant attention over the past decades as micro/nano patterns allow for preferred opto-electronic and electrochemical properties. Here a new fabrication method, based on etching in aqueous NaOH-polyethylene glycol solution is presented, which allows the formation of novel eight and twelve sided Si micropyramids. Particularly, the presence of NaOH resulted in the formation of four sided facets along intersecting {111} planes, while with continuous etching the high molar mass polyethylene glycol resulted in the formation of four additional facets identi?ed to be (212) planes producing octagonal pyramids. Further etching of these octagonal pyramids lead to the formation of twelve-sided pyramids. Eight-faceted (octagonal) pyramids have been reported in the literature, but only through the use of photolithography, while twelve-faceted (dodecagonal) pyramids have not been observed for any type of crystal.
关键词： Pyramids,Octagon,Si patterning,Etching,Polyethylene glycol,Dodecagon
更新于2025-09-23 15:23:52
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Uniform position-sensitivity verification of novel electrochemically-etched panorama mega-size polymer ion image detectors
摘要： Recent novel applications of mega-size polycarbonate ion image detectors processed in mega-size electrochemical etching chambers have raised concerns on uniform position-sensitivity and consistency in ion energy responses of detectors with different effective areas. In this context, the uniform position-sensitivity, detection efficiency and track diameters of alpha particles over a broad energy range in detectors of different effective areas; i.e. small size (2 × 2 cm2), medium sizes (17 × 17 cm2) and (22.6 × 22.6 cm2), as well as large (33 × 33 cm2) were investigated in order to make them independent of the detector effective area. Alpha particles of 6 different energies from ~0.3 to ~3.0 MeV at a fluence of ~1.0 × 104 alphas·cm?2 were studied applying 50 Hz – HV field conditions. As an example, 36 positions on 6 rows and 6 columns of a 33 × 33 cm2 detector were studied. By having the same efficiency and mean track diameter only at ~0.8 MeV alpha energy in different detector effective areas under the conditions applied, it is concluded that: (1) position-sensitivity, efficiency and alpha energy responses are consistently uniform independent of the detector effective areas for particles with dE/dX)particle ≥ dE/dX)alpha at ~0.8 MeV, but (2) a "voltage compensation factor" (Vc) commensurate with each detector effective area and type of particle should be applied for particles with dE/dX)particle < dE/dX)alpha at ~0.8 MeV for efficient, consistent and uniform ion detection.
关键词： Electrochemical etching,Polycarbonate track detectors,Effective detector area,Position-sensitivity,Voltage compensation factor
更新于2025-09-23 15:23:52
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Formation of 45° Silicon (110) Surface Using Triton X- <i>n</i> Surfactants in Potassium Hydroxide for Infrared Applications
摘要： Silicon (Si) micromirrors are an integral feature for many micro-optomechanical systems (MOEMS). Such mirrors are generally wet etched in alkaline solution at elevated temperature. For 90? beam steering applications, 45? slanted Si (110) plane is the prime choice fabricated with the incorporation of tensioactive surfactants. Here, Triton-Si and Triton-hydroxide (OH?)/H2O interaction using varying hydrophilic chain length Triton (X-45, X-100 and X-405) were investigated. The surfactant concentration was varied from 0 to 1000 ppm in potassium hydroxide (KOH). Triton molecules were shown to adsorb preferentially on (110) than on (100) surface. Longer chain length Triton hampered OH? access to Si surface resulting in slower etch rate. In contrast, contact angle measurement suggested that shorter Triton interfaced better with Si surface. Later, Si wafers etched in Triton 10 ppm – KOH were examined. The measured output for (110)X-45, (110)X-100, (110)X-405 and polished Si wafer reference (Rq < 5?) mirrors were 0.58, 0.76, 0.72 and 1.25 mW, respectively. Subsequently, Si-SiO2 thin film in [HLHL]2-substrate configuration was fabricated. Broadband micromirror for use in 3.0–5.5 μm spectrum range was experimentally realized with reflected efficiency of 73%.
关键词： wet etching,optical measurement,Silicon micromirrors,Triton X-n,surface roughness,potassium hydroxide,surfactants
更新于2025-09-23 15:23:52