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Nanofluidic and monolithic environmental cells for cryogenic microscopy
摘要： We present a device capable of combining nanofluidics and cryogenic transmission electron microscopy (cryo-TEM) to allow inspection of water-soluble samples under near-native conditions. The devices can be produced in a multitude of designs, but as a general rule, they consist of channels or chambers enclosed between two electron-transparent silicon nitride windows. With the appropriate design, those devices can allow screening of multiple samples in parallel and remove the interaction between the sample and the environment (no air–water interface). We demonstrate channel sizes from 80 to 500 nm in height and widths from 100 to 2000 μm. The presented fabrication flow allows producing hollow devices on a single wafer eliminating the need of aligning or bonding two half-cavities from separate wafers, which provides additional resistance to thermal stress. Taking advantage of a single-step through-membrane exposure with a 100 keV electron beam, we introduced arrays of thin (10–15 nm) electron-transparent silicon nitride membrane windows aligned between top and bottom (200–250 nm) carrier membranes. Importantly, the final devices are compatible with standard TEM holders. Furthermore, they are compatible with rapid freezing of samples, which is crucial for the formation of vitreous water, hence avoiding the formation of crystalline ice, that is detrimental for TEM imaging. To demonstrate the potential of this technology, we tested those devices in imaging experiments verifying their applicability for cryo-TEM applications and proved that vitreous water could be prepared through conventional plunge freezing of the chips.
关键词： nanofabrication,TEM,environmental chamber,microfluidic cell,electron beam lithography,cryo-TEM
更新于2025-09-23 15:23:52
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Resonance reflection of light by ordered silicon nanopillar arrays with the vertical p-n junction
摘要： Silicon nanopillar (Si NP) arrays with the axial p-n junction were formed and investigated. A method to fabricate Si NP ordered arrays by means of electron beam lithography using the negative electron resist and reactive ion etching is presented. The effect of strong resonance light scattering – change of the color of separate Si NPs - was demonstrated. One or several minima were registered in the measured reflection spectra. Thereat, the position of reflection minimum was changed with a change in Si NP diameter. A shift of the minimum position towards the longer wavelength spectral region with an increase in Si NP diameter was observed. A shift of the position of minima to the shorter wavelength spectral region with a decrease in Si NP pitch in microarrays with the same Si NP diameter was observed. The quantitative divergence in the position of reflection minima in Si NPs with calculated dependencies for Mie resonances was found. High photosensitivity of Si NP arrays with axial p-n junction to visible and near IR light was discovered. So, these structures may be used for selective photonic sensors.
关键词： reflectance spectra,silicon nanopillars,electrophysical properties,reactive ion etching,electron beam lithography
更新于2025-09-23 15:23:52
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The Monte Carlo Simulation of Secondary Electrons Excitation in the Resist PMMA
摘要： The Monte Carlo method was used to simulate the process of secondary electrons excitation in resist PMMA with Mott cross section and dielectric function model. By analyzing the characteristics of secondary electrons excitation in the resist PMMA, and the simulation of secondary electrons energy range, we hold the opinion that the secondary electrons can not be ignored in the electron beam lithography.
关键词： Monte Carlo simulation,electron beam lithography (EBL),dielectric function,secondary electrons
更新于2025-09-23 15:23:52
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Strong Quantum Confinement Effects in Nanometer Devices with Graphene Directly Grown on Insulator by Catalyst-free Chemical Vapor Deposition
摘要： Background: The understanding of electrical properties of defective graphene in nanometer regime has lagged behind. Objective: This report intends to characterize defective but practically useful graphene as nanometer devices. Method: A-few-layer-thick graphene was directly grown on SiO2 substrate by alcohol-chemical vapor deposition (alcohol-CVD) using ethanol as carbon source and without the use of any catalytic metal. The graphene film was delineated into nanometer structures by electron beam lithography to make the nanoscale devices. Results: The Raman spectra of the graphene sheet on SiO2 shows relatively large D peak, which means the graphene is defective and consists of nanograins with an estimated size of 17 nm. Modulation of the graphene resistance by the gate voltage Vg was studied at room temperature. The film shows only p-type conduction, with a sheet resistance of 3.7 kΩ/□ and field-effect mobility calculated to be 44 cm2/Vs. From the temperature dependence of the graphene sheet, it is found that the resistance increases only by 7% from room temperature to 10 K, indicating low potential barrier between the domains, even though the graphene film is as thin as 1.6 nm and defective. From the conductance (Id/Vd) contour plot measured at 10 K of these nanodevices, aperiodic Coulomb-blockade feature and transport with a large gap were observed. Conclusion: Correlation among narrowest constriction widths, the variation of the addition energies and transport gaps in disordered graphene nanostructures is evident. These graphene nanodevices may have promising application in various nanodevices like single-electron (or single-hole) transistor, single-molecule transistor, van-der-Waals stacked nanodevices, etc.
关键词： graphene nanometer devices,Graphene nanostructures,sheet resistance,Raman spectra,Coulomb blockade,alcohol chemical vapor deposition,electron beam lithography
更新于2025-09-23 15:21:01
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Effect of deposition angle on fabrication of plasmonic gold nanocones and nanodiscs
摘要： Metal nanocones can exhibit several strong plasmonic resonances, which are associated with intense and accessible electromagnetic hot spots. They can thus be used to enhance light–matter interactions or to facilitate location-specific sensing while enabling separation of some non-specific contributions towards the sensing signal. Nanocones and similar 3D structures are often fabricated with the use of the so-called self-shading effect, which occurs during the evaporation of a metal film into circular nanowells. Unfortunately, a full description of a successful deposition process with all the essential details is currently missing in literature. Here we present a detailed view of the fabrication of ordered arrays of conical gold nanostructures using electron beam lithography and gold electron beam evaporation. We show that the symmetry of the fabricated nanostructures is influenced by the lateral position of the substrate on the sample holder during the deposition. Off-axis deposition or tilt of the sample leads to asymmetric nanostructures. When the deposited film is thick enough, or the nanowells narrow enough, the entrance aperture is clogged, and nanocones with sharp tips are formed. In contrast, flat-top truncated cones are produced for thinner films or wider nanowells. All these findings help to identify inherent limits for the production of wafer-scale arrays of such non-planar nanostructures. On the other hand, they also suggest new fabrication possibilities for more complicated structures such as mutually connected nanocones for electrically addressable chips.
关键词： Plasmonics,Optical antenna,Nanodisc,Nanocone,Electron beam evaporation,Electron beam lithography
更新于2025-09-23 15:19:57
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Tunable plasmonic HfN nanoparticles and arrays
摘要： We present the fabrication of tunable plasmonic hafnium nitride (HfN) nanoparticles. HfN is a metallic refractory material with the potential of supporting plasmon resonances in the visible range, similar to silver and gold, but with the additional benefits of high melting point, chemical stability, and mechanical hardness. However, the preparation of HfN nanoparticles and the experimental demonstration of their plasmonic potential are still in their infancy. Here, high quality HfN thin films were fabricated, for which ellipsometry shows their plasmonic potential. From these thin films, nanorods and nanotriangles were milled using a focused ion beam and the plasmon resonances were identified using cathodoluminescence mapping. As an alternative fabrication strategy, an optimized electron-beam lithography procedure was used to prepare arrays of HfN nanoparticles, which also exhibited clear surface plasmon resonances. These results pave the way to further explore HfN nanoparticles in plasmonically-powered applications where materials robustness is essential.
关键词： electron-beam lithography,plasmonic,cathodoluminescence,nanoparticles,hafnium nitride
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Deterministic Integration of Quantum Dots into On-Chip Multi-Mode Interference Couplers Via in-Situ Electron Beam Lithography
摘要： On-chip quantum optical circuits offer superior performance and scalability compared to bulky optical setups. Additionally, the up-scaling of quantum systems will foster the realization of photonic quantum computers to outperform their classical counterparts. In this context, the deterministic integration of quantum emitters into on-chip photonic elements is crucial for the implementation of scalable on-chip quantum circuits. Recent activities in this field include hybrid QD-waveguides for enhanced photon in-coupling [1] and first, rather tedious steps towards the controlled integration of QDs using multistep-lithography [2] as well as AFM tip transfer [3]. Here we report on the deterministic integration of single quantum dots (QD) into on-chip beam splitters using in-situ electron beam lithography (EBL) [4]. In this single-step technique, photonic building blocks are patterned by means of EBL on top of chosen QDs immediately after spatially and spectrally pre-characterizing QDs by means of cathodoluminescence mapping at cryogenic temperatures (~10 K) [5]. The used in-situ EBL technology platform allows for the realization of complex on-chip quantum circuits with high process yield (see Fig. 1(a-d)). To underline the high potential of this method we realize 50/50 coupling elements connected to waveguide sections with deterministically integrated QDs (see Fig. 1(e)). The couplers act as central building blocks of on-chip quantum circuits and we chose a robust design based on tapered multimode interference (MMI) splitters which feature relaxed fabrication tolerances and a constant 50/50 splitting ratio. We demonstrate the functionality of the deterministic QD-waveguide structures by high-resolution μPL spectroscopy and by studying the photon cross-correlation between the two MMI output ports (Port 1 and Port 2 in Fig. 1(e)). The latter confirms single-photon emission and on-chip splitting associated with g(2)(0) < 0.5. Present work focusses on the deterministic realization of heterogeneous integrated quantum photonic devices and multi-QD quantum circuits allowing for on-chip Hong-Ou-Mandel experiments.
关键词： on-chip quantum circuits,quantum dots,photonic quantum computers,electron beam lithography,quantum emitters
更新于2025-09-11 14:15:04
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Pancharatnam–Berry Optical Elements for Spin and Orbital Angular Momentum Division Demultiplexing
摘要： A Pancharatnam–Berry optical element is designed, fabricated, and optically characterized for the demultiplexing of beams with different polarization and orbital angular momentum states at the telecom wavelength of 1310 nm. The geometric phase control is achieved by fabricating properly-oriented subwavelength gratings on a silicon substrate, inducing a spatially-variant form birefringence. The digital grating pattern is transferred to the silicon substrate with a two-step nanofabrication protocol, using inductively coupled plasma reactive ion etching to transfer the resist pattern generated with high-resolution electron beam lithography. The optical characterization of the sample confirms the expected capability to sort circularly polarized optical beams with different handedness and orbital angular momentum. Encompassing optical element design and silicon photonics, the designed silicon metasurface paves the way to innovative devices for total angular momentum mode division multiplexing with unprecedented levels of integration.
关键词： subwavelength gratings,electron beam lithography,metasurfaces,silicon,orbital angular momentum,reactive ion etching,mode division multiplexing,polarization division multiplexing,Pancharatnam–Berry optical elements
更新于2025-09-10 09:29:36