Silicon Nitride Membrane Research Articles

Coupling Capacitively Distinct Mechanical Resonators for Room-Temperature Phonon-Cavity Electromechanics.

Coupled electromechanical resonators that can be independently driven/detected and easily integrated with external circuits are essential for exploring mechanical modes based signal processing and multifunctional integration. One of the main challenges lies in controlling energy transfers between distinct resonators experiencing nanoscale displacements. Here, we present a room temperature electromechanical system that mimics a "phonon-cavity", in analogy with optomechanics. It consists in a silicon nitride membrane capacitively coupled to an aluminum drum-head resonator. We demonstrate electromechanically induced transparency and amplification through manipulating the mechanical displacements of this coupled system, creating interferences in the measured signal. The anti-damping effects, generated by phonon-cavity force, have been observed in both movable objects. We develop an analytical model that captures the analoguous optomechanical features in the classical limit and enables to fit quantitatively the measurements. Our results open up new possibilities for building compact and multifunctional mechanical systems, and exploring phonon-phonon coupling based optomechanics.

Mitigation of the Magnetic Field Susceptibility of Transition-Edge Sensors Using a Superconducting Groundplane

Transition edge sensor (TES) microcalorimeters and bolometers are used for a variety of applications. The sensors are based on the steep temperature-dependent resistance of the normal-to-superconducting transition, and are thus intrinsically sensitive to magnetic fields. Conventionally the detectors are shielded from stray magnetic fields using external magnetic shields. However, in particular for applications with strict limits on the available space and mass of an instrument, external magnetic shields might not be enough to obtain the required shielding factors or field homogeneity. Additionally, these shields are only effective for magnetic fields generated external to the TES array, and are ineffective to mitigate the impact of internally generated magnetic fields. Here we present an alternative shielding method based on a superconducting groundplane deposited directly on the backside of the silicon nitride membrane on which the TESs are located. We demonstrate that this local shielding for external magnetic fields has a shielding factor of at the least ~ 75, and is also effective at reducing internal self-induced magnetic fields, as demonstrated by measurements and simulation of the eddy current losses in our AC biased detectors. Measurements of 5.9 keV X-ray photons show that our shielded detectors have a high resilience to external magnetic fields, showing no degradation of the energy resolution or shifts of the energy scale calibration for fields of several microTesla, values higher than expected in typical real-world applications.

The Modular µSiM: A Mass Produced, Rapidly Assembled, and Reconfigurable Platform for the Study of Barrier Tissue Models In Vitro.

Advanced in vitro tissue chip models can reduce and replace animal experimentation and may eventually support "on-chip" clinical trials. To realize this potential, however, tissue chip platforms must be both mass-produced and reconfigurable to allow for customized design. To address these unmet needs, an extension of the µSiM (microdevice featuring a silicon-nitride membrane) platform is introduced. The modular µSiM (m-µSiM) uses mass-produced components to enable rapid assembly and reconfiguration by laboratories without knowledge of microfabrication. The utility of the m-µSiM is demonstrated by establishing an hiPSC-derived blood-brain barrier (BBB) in bioengineering and nonengineering, brain barriers focused laboratories. In situ and sampling-based assays of small molecule diffusion are developed and validated as a measure of barrier function. BBB properties show excellent interlaboratory agreement and match expectations from literature, validating the m-µSiM as a platform for barrier models and demonstrating successful dissemination of components and protocols. The ability to quickly reconfigure the m-µSiM for coculture and immune cell transmigration studies through addition of accessories and/or quick exchange of components is then demonstrated. Because the development of modified components and accessories is easily achieved, custom designs of the m-µSiM shall be accessible to any laboratory desiring a barrier-style tissue chip platform.

Quantum backaction evading measurements of a silicon nitride membrane resonator

Quantum backaction disturbs the measurement of the position of a mechanical oscillator by introducing additional fluctuations. In a quantum backaction measurement technique, the backaction can be evaded, although at the cost of losing part of the information. In this work, we carry out such a quantum backaction measurement using a large 0.5 mm diameter silicon nitride membrane oscillator with 707 kHz frequency, via a microwave cavity readout. The measurement shows that quantum backaction noise can be evaded in the quadrature measurement of the motion of a large object.

Design and Simulation of Terahertz Apodized Bragg Grating Using Coplanar Stripline Transmission Line a 1 µm-thin Membrane

A guided-wave THz System-on-Chip THz System-on-Chip (TSoC) is emerging as an attractive alternative to the routine free-space THz systems to reduce physical bulk, propagation loss, pulse dispersion and cost of free-space THz systems. Recently, our research group succeeded in demonstrating a novel waveguided TSoC based on the coplanar stripline Coplanar Stripline (CPS) transmission lines on a 1 µm-thin Silicon Nitride membrane. The novelty of this membrane-based platform was bonding the transmitter and receiver directly on the transmission line to eliminate the radiation loss by the routine THz optics. Besides, the delicate thin-membrane dramatically reduces the dielectric loss of the platform which results in low-loss and low-dispersion THz-bandwidth pulses.In this paper, we introduce the design, theoretical model and the simulation results of a novel THz Apodized Bragg Grating (TABG) based on a periodic reflection of consecutive different impedance sections of CPS transmission lines on the membrane platform. This structure was introduced based on theoretical modelling and the simulation results. The CPS-TABG consists of 20 λ/2-length cascaded sections. The central frequency of the bandstop filter was selected around 0.8 THz to avoid signal distortion of the received terahertz pulse.

Influence of the Electron Beam and the Choice of Heating Membrane on the Evolution of Si Nanowires' Morphology in In Situ TEM.

We used in situ transmission electron microscopy (TEM) to observe the dynamic changes of Si nanowires under electron beam irradiation. We found evidence of structural evolutions under TEM observation due to a combination of electron beam and thermal effects. Two types of heating holders were used: a carbon membrane, and a silicon nitride membrane. Different evolution of Si nanowires on these membranes was observed. Regarding the heating of Si nanowires on a C membrane at 800 °C and above, a serious degradation dependent on the diameter of the Si nanowire was observed under the electron beam, with the formation of Si carbide. When the membrane was changed to Si nitride, a reversible sectioning and welding of the Si nanowire was observed.

Mechanical Mode Engineering with Orthotropic Metamaterial Membranes

AbstractMetamaterials are structures engineered at a small scale with respect to the wavelength of the excitations they interact with. These structures behave as artificial materials whose properties can be chosen by design, mocking and even outperforming natural materials, and making them the quintessential tool for manipulation of wave systems. In this paper it is shown how the acoustic properties of a silicon nitride membrane can be affected by nanopatterning. The degree of asymmetry in the pattern geometry induces an artificial anisotropic elasticity, resulting in the splitting of otherwise degenerate mechanical modes. The artificial material introduced has a maximum Ledbetter–Migliori anisotropy of 1.568, favorably comparing to most bulk natural crystals. With an additional freedom in defining arbitrary asymmetry axes by pattern rotation, the described approach can be useful for fundamental investigation of material properties as well as for devising improved sensors of light, mass, or acceleration based on micromechanical resonators.

Coaxial Micro Ring Arrays Fabricated on Self‐Assembled Microtube Cavities for Resonant Light Modulation

AbstractComposite optical microcavities, as a versatile platform for light manipulation, have been theoretically revealed that the configuration of concentrically coupled resonant trajectories can significantly enhance the coupling strength, which is however challenging in experimental preparation. Here coaxial whispering gallery resonator chains were designed and fabricated with optically coupled modes split apart by more than the free spectral range (FSR) of the cavity itself. Because such three dimensional (3D) coupled optical systems are extremely difficult to obtain with traditional processing techniques an approach is developed to release and roll‐up pre‐strained, nanostructured silicon nitride membranes into microtubular optical cavities. Parallel nano‐ridges modified on the patterned membranes form into coaxial micro ring arrays after the membrane rolls up into a microtubular structure. Energetic degeneracy, as a consequence of mode splitting exceeding the FSR, leads to interference between bonding and antibonding modes with different mode identities (mode number), resulting in novel light modulation in the form of hybrid super wave modes, which display a distinct hopping behavior resembling linear stretch modes of an oscillator chain.

Negative‐Index Acoustic Metamaterial Operating above 100 kHz in Water Using Microstructured Silicon Chips as Unit Cells

AbstractA major challenge for negative‐index acoustic metamaterials is increasing their operational frequency to the MHz range in water for applications such as biomedical ultrasound. Herein, a novel technology to realize acoustic metamaterials in water using microstructured silicon chips as unit cells that incorporate silicon nitride membranes and Helmholtz resonators with dimensions below 100 μm fabricated using clean‐room microfabrication technology is presented. The silicon chip unit‐cells are then assembled to form periodic structures that result in a negative‐index metamaterial. Finite‐element method (FEM) simulations of the metamaterial show a negative‐index branch in the dispersion relation in the 0.25–0.35 MHz range. The metamaterial is characterized experimentally using laser‐doppler vibrometry, showing opposite phase and group velocities, a signature of negative‐index materials, and is in close agreement with FEM simulations. The experimental measurements also show that the magnitude of phase and group velocities increase as the frequency increases within the negative‐index band, confirming the negative‐index behavior of the material. Acoustic indices from –1 to –5 are reached with respect to water in the 0.25–0.35 MHz range. The use of silicon technology microfabrication to produce acoustic metamaterials for operation in water opens a new road to reach frequencies relevant for biomedical ultrasound applications.

Nanoscale chemical mapping of exometabolites at fungal-mineral interfaces.

Mineral‐associated organic matter is an integral part of soil carbon pool. Biological processes contribute to the formation of such organo‐mineral complexes when soil microbes, and in particular soil fungi, deposit a suite of extracellular metabolic compounds and their necromass on the mineral surfaces. While studied in bulk, micro‐ to nanoscale fungal–mineral interactions remain elusive. Of particular interest are the mutual effects at the interface between the fungal exometabolites and proximal mineral particles. In this work, we have grown saprotrophic and symbiotic fungi in contact with two soil minerals with contrasting properties: quartz and goethite, on top of X‐ray transparent silicon nitride membrane windows and analyzed fungal hyphae by synchrotron‐based scanning transmission X‐ray microscopy in combination with near edge X‐ray fine structure spectroscopy at C(K) and Fe(L) absorption edges. In the resultant chemical maps, we were able to visualize and differentiate organic compounds constituting the fungal cells, their extracellular metabolites, and the exometabolites adsorbing on the minerals. We found that the composition of the exometabolites differed between the fungal functional guilds, particularly, in their sugar to protein ratio and potassium concentration. In samples with quartz and goethite, we observed adsorption of the exometabolic compounds on the mineral surfaces with variations in their chemical composition around the particles. Although we did not observe clear alteration in the exometabolite chemistry upon mineral encounters, we show that fungal–mineral interaction result in reduction of Fe(III) in goethite. This process has been demonstrated for bulk systems, but, to our knowledge, this is the first observation on a single hypha scale offering insight into its underlying biological mechanisms. This demonstrates the link between processes initiated at the single‐cell level to macroscale phenomena. Thus, spatially resolved chemical characterization of the microbial–mineral interfaces is crucial for an increased understanding of overall carbon cycling in soil.

An ultra-thin silicon nitride membrane for label-free CTCs isolation from whole blood with low WBC residue

Microfiltration is the most straightforward and effective method to enrich circulating tumor cells (CTCs) from large numbers of background blood cells in the peripheral blood. It is still very challenging to achieve both high recovery of CTCs and low residue of white blood cells (WBCs) through one-time whole blood filtration. In this study, through a simulation, we revealed that reducing the thickness of the filter significantly reduces the WBC residue. A filter device was created using a 400-nm-thick Si3N4 membrane. The recovery rates of A549 and MCF-7 tumor cell lines were 82.04 ± 1.19% and 86.53 ± 3.27%, respectively, while the residual number of WBCs was largely reduced from 6.84 × 106 cells/mL cells to 604 ± 33.74 cells/mL. In addition, the assembled device could process whole blood without pretreatment at a high throughput of 1 mL/min. Utilizing as small volume of peripheral blood as 1 mL, CTCs were enriched by our device in four of six lung cancer patients and four of five breast cancer patients. The lower WBC residue is advantageous in CTC enumeration and subsequent proteomic or genomic characterization. Therefore, this technology enables label-free CTC isolation with a low WBC residue from whole blood, paving the way for a CTC analysis in clinical applications.

Chemical fixation creates nanoscale clusters on the cell surface by aggregating membrane proteins

Chemical fixations have been thought to preserve the structures of the cells or tissues. However, given that the fixatives create crosslinks or aggregate proteins, there is a possibility that these fixatives create nanoscale artefacts by aggregation of membrane proteins which move around freely to some extent on the cell surface. Despite this, little research has been conducted about this problem, probably because there has been no method for observing cell surface structures at the nanoscale. In this study, we have developed a method to observe cell surfaces stably and with high resolution using atomic force microscopy and a microporous silicon nitride membrane. We demonstrate that the size of the protrusions on the cell surface is increased after treatment with three commonly used fixatives and show that these protrusions were created by the aggregation of membrane proteins by fixatives. These results call attention when observing fixed cell surfaces at the nanoscale.

Mechanical investigations of free-standing SiN membranes patterned with one-dimensional photonic crystal structures

A detailed investigation of the structural and vibrational properties of various prestressed silicon nitride membranes patterned with one-dimensional photonic crystal structures is presented. The tensile stress related deformation of the structure in the vicinity of the patterned area is determined by atomic force microscopy scans, while the resonance frequencies and quality factors of the out-of-plane membrane vibrations are measured using optical interferometry. We show that these noninvasive measurements, combined with the results of finite element simulations, provide accurate information on the tensile stress, the elasticity modulus, and the density of these nanostructured thin films. The obtained results are interesting in two ways: first, they show that such highly reflective thin membranes already exploited in various photonics applications possess high-mechanical quality, which also makes them attractive for optomechanics and sensing applications. Second, they represent a nondestructive method to determine key material parameters, which can be applicable to a broad range of fragile nanostructured thin films.

Atmospheric Pressure Electron Detection Method for MEMS Electron Microscope

The article presents the results of a new method for electron detection at atmospheric pressure (APED). This method is developed for a MEMS (Micro-Electro-Mechanical System) electron microscope to obtain images of a sample placed on a silicon nitride membrane in air. The electron beam is transmitted through the membrane and, under specific conditions, can reach the detector despite the presence of air molecules. The experiments were carried out on a miniature electron optical microcolumn model consisting of an octupole deflector, an anode with a Si₃N₄ membrane, and an electron collector. The anode, glass spacer, and electron collector formed a microchamber that was filled with air. Measurements were made using an electron beam from JEOL Scanning Electron Microscope (SEM). The first images obtained using the APED method and a quantitative description of the operation principle are presented.

Hybridized Frequency Combs in Multimode Cavity Electromechanical System.

The cavity electromechanical devices with radiation-pressure interaction induced Kerr-like nonlinearity are promising candidates to generate microwave frequency combs. We construct a silicon-nitride membrane based superconducting cavity electromechanical device and study two mechanical modes synergistic frequency combs. Around the threshold of intracavity field instability, we first show independent frequency combs with tooth spacing equal to each mechanical mode frequency. At the overlap boundaries of these two individual mechanical mode mediated instability thresholds, we observe hybridization of frequency combs based on the cavity field mediated indirect coupling between these two mechanical modes. The spectrum lines turn out to be unequally spaced, but can be recognized in combinations of the coexisting frequency combs. Beyond the boundary, the comb reverts to the single mode case, and which mechanical mode frequency will the tooth spacing be depends on the mode competition. Our work demonstrates mechanical mode competition enabled switchability of frequency comb tooth spacing and can be extended to other devices with multiple nonlinearities.

Effect of amorphous carbon coating on the performance of liquid phase transmission electron microscopy (LP-TEM) and the dynamics of enclosed Pt nano-colloids.

Ultra-thin silicon nitride (SiN) membranes are critical in microfabrication-based liquid cells (LCs) for transmission electron microscopy (TEM). This study used a homemade LC with a 50-nm SiN membrane to study the dynamics of 2.58-nm platinum (Pt) nanoparticles (NPs) in approximately 200-nm-deep water. When a strong beam with electron flux ranging from 2.5 × 103 to 1.4 × 106 e-/(nm2 s) was applied to resolve the NPs, the beam caused NP aggregation and even drilled a hole on the top membrane. The hole drilling was prevented by coating a 1-4-nm-thick amorphous carbon layer on both sides of the membrane. The NP aggregation rate also decreased with increasing carbon thickness. After overcoming the aforementioned issues, lattice fringes of the Pt NPs were visible when the NPs were attached to the membrane of the 4-nm-carbon-coated LC containing a thin liquid layer. The effects of the electron beam and carbon on the LC and Pt NPs were investigated and discussed. This work provides a reference for LC-TEM research using strong electron beams.

β-silicon nitride membrane with robust inorganic-organic hybrid hydrophobic surface for water-in-oil emulsion separation

Robust hydrophobic membranes are promising for effective separation of water-in-oil emulsion, which is becoming extremely critical challenge in many sectors, including oil refinery and petrochemical industries. In this paper, robust hydrophobic ceramic membrane was fabricated and successfully applied for the water-in-oil emulsion separation process. First, porous β-silicon nitride (Si3N4) membranes with unique rod-like grains and three-dimensional network structure were fabricated. The preparation procedure was optimized considering the morphological properties, porosity, permeability and mechanical characteristics. Then, the optimized membrane was converted to a hydrophobic structure with water contact angle of 136.1°. The hydrophobic modification was achieved using organosilane pyrolysis coating method, which resulted in the formation of a robust inorganic-organic hybrid hydrophobic coating layer on the membrane structure. The hydrophobic membrane was employed for the separation of water-in-oil emulsion. At a feed pressure of 1 bar, a permeate flow of 80 L/m2 h with a water rejection of 94.3% was obtained. The presented hydrophobic silicon nitride membrane in this study is promising for a range of water-in-oil emulsion separation applications, particularly in harsh conditions.

Strong Parametric Coupling between Two Ultracoherent Membrane Modes.

We demonstrate parametric coupling between two modes of a silicon nitride membrane. We achieve the coupling by applying an oscillating voltage to a sharp metal tip that approaches the membrane surface to within a few 100nm. When the voltage oscillation frequency is equal to the mode frequency difference, the modes exchange energy periodically and faster than their free energy decay rate. This flexible method can potentially be useful for rapid state control and transfer between modes, and is an important step toward parametric spin sensing experiments with membrane resonators.

Monte Carlo simulation of the secondary electron yield of silicon rich silicon nitride

The effect of doping in Si3N4 membranes on the secondary electron yield is investigated using Monte Carlo simulations of the electron-matter interactions. The effect of the concentration and the distribution of the doping in silicon rich silicon nitride membranes is studied by using the energy loss function as obtained from ab initio density functional theory calculations in the electron scattering models of the Monte Carlo simulations. An increasing doping concentration leads to a decreasing maximum secondary electron yield. The distribution of the doped silicon atoms can be optimised in order to minimize the decrease in yield.

Inhibition of vacuum sublimation artefacts for (Scanning) Transmission Electron Microscopy ((S)TEM) of sulphur samples via encapsulation.

Lithium-sulfur battery is one of promising candidates for next-generation energy storage device due to the sulfur cathode material with low cost and nontoxicity, and super high theoretical energy density (nearly 2600Wh kg -1) and specific energy (2567Wh kg -1). Sulphur, however, poses a few interesting challenges before it can gain widespread utilisation. The biggest issue is known as the polysulphide shuttling effect which contributes to rapid capacity loss after cycling. Accurate characterisation of sulphur cathodic materials becomes critical to our understanding polysulphide shuttling effect in the quest of finding mitigating solutions. Electron microscopy is playing a crucial role in battery research in determining structure-property-function relations. However, sulphur undergoes sublimation at a point above the typical pressures found in the column of a transmission electron microscope (TEM) at room temperature. This makes the imaging and characterisation of any sort of nanostructured sulphur samples challenging, as the material will be modified or even disappear rapidly as soon as it is inserted into the TEM vacuum. As a result, materials characterised by such methods are prone to deviation from normal conditions to a great extent. To prevent this, a novel method of encapsulating sulphur particles between silicon nitride (SiN x) membranes is demonstrated in this work.