Thin membranes are highly sought-after for nanopore-based single-molecule sensing and fabrication of such membranes becomes challenging in the \lesssim10 nm thickness regime where a plethora of useful molecule information can be acquired by nanopore sensing. In this work, we present a scalable and controllable method to fabricate silicon nitride (SixNy) membranes with effective thickness down to ~1.5 nm using standard silicon processing and chemical etching using hydrofluoric acid (HF). Nanopores were fabricated using the controlled breakdown method with estimated pore diameters down to ~1.8 nm yielding events >500,000 and >1,800,000 from dsDNA and bovine serum albumin (BSA) protein, respectively, demonstrating the high-performance and extended lifetime of the pores fabricated through our membranes. We used two different compositions of SixNy for membrane fabrication (near stoichiometric and silicon-rich SixNy) and compared them against commercial membranes. The final thicknesses of the membranes were measured using ellipsometry and were in good agreement with the values calculated from the bulk etch rates and DNA translocation characteristics. The stoichiometry and the density of the membrane layers were characterized with Rutherford backscattering spectrometry while the nanopores were characterized using pH-conductance, conductivity-conductance and power spectral density (PSD) graphs.
Technical challenges in molecule sensing and chemical detection have created an increasing demand for transformative materials with high sensitivity and specificity. Biohybrid nanopores have attracted growing interest as they can ideally combine the durability of solid-state nanopores with the precise structure of biological nanopores. Particular care must be taken to control how biological nanopores adapt to their surroundings once in contact with the solid-state nanopore. Two major challenges are to precisely control this adaptability under dynamic conditions and provide predesigned function…
We demonstrate the fabrication of individual nanopores in hexagonal boron nitride (hBN) with atomically precise control of the pore size. Previous methods of pore production in other 2D materials create pores of irregular geometry with imprecise diameters. By taking advantage of the preferential growth of boron vacancies in hBN under electron beam irradiation, we are able to observe the pore growth via transmission electron microscopy, and terminate the process when the pore has reached its desired size. Careful control of beam conditions allows us to nucleate and grow individual triangular an…
The atomically-precise controlled synthesis of graphene stripes embedded in hexagonal boron nitride opens up new possibilities for the construction of nanodevices with applications in sensing. Here, we explore properties related to electronic structure and quantum transport of a graphene nanoroad embedded in hexagonal boron nitride, using a combination of density functional theory and the non-equilibrium Green's functions method to calculate the electric conductance. We find that the graphene nanoribbon signature is preserved in the transmission spectra and that the local current is mainly con…
Controlled breakdown has recently emerged as a highly appealing technique to fabricate solid-state nanopores for a wide range of biosensing applications. This technique relies on applying an electric field of approximately 0.6-1 V/nm across the membrane to induce a current, and eventually, breakdown of the dielectric. However, a detailed description of how electrical conduction through the dielectric occurs during controlled breakdown has not yet been reported. Here, we study electrical conduction and nanopore formation in SiN$_x$ membranes during controlled breakdown. We show that depending o…
Angstrom confined solvents in two-dimensional laminates travel through interlayer spacings, gaps between adjacent sheets, and via in plane pores. Among these, experimental access to investigate the mass transport through in plane pores is lacking. Here, we create these nanopores in graphene oxide membranes via ion irradiation with precise control over functional groups, pore size and pore density. Low ion induced pore densities result in mild reduction and increased water permeation for the membranes. Higher pore densities lead to pronounced reduction and complete blockage of pure water howeve…
Large-area nanopore drilling is a major bottleneck in state-of-the-art nanoporous 2D membrane fabrication protocols. In addition, high-quality structural and statistical descriptions of as-fabricated porous membranes are key to predicting the corresponding membrane-wide permeation properties. In this work, we investigate Xe-ion focused ion beam as a tool for scalable, large-area nanopore fabrication on atomically thin, free-standing molybdenum disulphide. The presented irradiation protocol enables designing ultrathin membranes with tunable porosity and pore dimension, along with spatial unifor…
A wide range of approaches have been explored to meet the challenges of graphene nanostructure fabrication, all requiring complex and high-end nanofabrication platform and suffering from surface contaminations, potentially giving electrical noise and increasing the thickness of the atomically thin graphene membrane. Here, with the use of an electrical pulse on a low capacitance graphene-on-glass (GOG) membrane, we fabricated clean graphene nanopores on commercially available glass substrates with exceptionally low electrical noise. In situ liquid AFM studies and electrochemical measurements re…
Controlling the size and shape of nanopores in two-dimensional materials is a key challenge in applications such as DNA sequencing, sieving, and quantum emission in artificial atoms. We here investigate experimentally and theoretically triangular vacancies in (unconventional) Bernal-stacked AB-h-BN formed using a high-energy electron beam. Due to the geometric configuration of AB-h-BN, triangular pores in different layers are aligned, and their sizes are controlled by the duration of the electron irradiation. Interlayer covalent bonding at the vacancy edge is not favored, as opposed to what oc…
Blue energy relies on the chemical potential difference generated between solutions of high and low ionic strength and would provide a sun-and-wind independent energy source at estuaries around the world. Converting this osmotic energy through reverse-electrodialysis relies on ion-selective membranes. A novel generation of these membranes is based on atomically thin MoS$_2$ membranes to decrease the resistance to current flow to increase power output. By modulating the surface charge by light we are able to raise the ion selectivity of the membrane by a factor of 5 while staying at a neutral p…
One of the most promising applications in nanoscience is the design of new materials to improve water permeability and selectivity of nanoporous membranes. Understanding the molecular architecture behind these fascinating structures and how it impacts the water flow is an intricate but necessary task. We studied here, the water flux through multi-layered nanoporous molybdenum disulfide (MLNMoS$_2$) membranes with different nanopore sizes and length. Molecular dynamics simulations show that the permeability do not increase with the inverse of the membrane thickness, violating the classical hydr…
A flow-through sensing platform based on open-ended porous silicon (PSi) microcavity membranes that are compatible with integration in on-chip sensor arrays is demonstrated. Due to the high aspect ratio of PSi nanopores, the performance of closed-ended PSi sensors is limited by infiltration challenges and slow sensor responses when detecting large molecules such as proteins and nucleic acids. In order to improve molecule transport efficiency and reduce sensor response time, open-ended PSi nanopore membranes were used in a flow-through sensing scheme, allowing analyte solutions to pass through …
The Helium Ion Microscope (HIM) has the capability to image small features with a resolution down to 0.35 nm due to its highly focused gas field ionization source and its small beam-sample interaction volume. In this work, the focused helium ion beam of a HIM is utilized to create nanopores with diameters down to 1.3 nm. It will be demonstrated that nanopores can be milled into silicon nitride, carbon nanomembranes (CNMs) and graphene with well-defined aspect ratio. To image and characterize the produced nanopores, helium ion microscopy and high resolution scanning transmission electron micros…
Researchers are currently exploring nanoporous two-dimensional materials, such as hexagonal boron nitride (hBN), as potential desalination membranes. Here, we study the effect of grain boundaries (GBs) and interfacial electrostatic interactions on the desalination performance of bicrystalline nanoporous hBN, using classical molecular dynamics simulations supported by quantum-mechanical density functional theory (DFT) calculations. We investigate three different nanoporous bicrystalline hBN configurations, with symmetric tilt GBs having misorientation angles of 13.2°, 21.8°, and 32.2°. We find …
Nanopores in 2D materials are highly desirable for DNA sequencing, yet achieving single-stranded DNA (ssDNA) transport through them is challenging. Using density functional theory calculations and molecular dynamics simulations we show that ssDNA transport through a pore in monolayer hexagonal boron nitride (hBN) is marked by a basic nanomechanical conflict. It arises from the notably inhomogeneous flexural rigidity of ssDNA and causes high friction $\textit{via}$ transient DNA desorption costs exacerbated by solvation effects. For a similarly sized pore in bilayer hBN, its self-passivated ato…
Transition metal nitrides (TMNs) exhibit fascinating physical properties that hold great potential in future device applications. To stack two-dimensional TMNs with other functional materials that have dissimilar orientations and symmetries requires to separate epitaxial TMNs from the growth substrates. However, the lattice constants of TMNs are not compatible with those of most sacrificial layers, leading to a great challenge to fabricate high-quality single crystalline TMN membranes. In this letter, we report the application of a water-soluble BaO sacrificial layer as a general approach to c…
Diamond heat-spreaders for gallium nitride (GaN) devices currently depend upon a robust wafer bonding process. Bonding-free membrane methods demonstrate potential, however, chemical vapour deposition (CVD) of diamond directly onto a III-nitride (III-N) heterostructure membrane induces significant thermal stresses. In this work, these thermal stresses are investigated using an analytical approach, a numerical model and experimental validation. The thermal stresses are caused by the mismatch in the coefficient of thermal expansion (CTE) between the GaN/III-N stack, silicon (Si) and the diamond f…
Carbon nitride-based nanostructures have attracted special attention (from theory and experiments) due to their remarkable electromechanical properties. In this work we have investigated the mechanical properties of some graphene-like carbon nitride membranes through fully atomistic reactive molecular dynamics simulations. We have analyzed three different structures of these CN families, the so-called graphene-based g-CN, triazine-based g-C3N4 and heptazine-based g-C3N4. The stretching dynamics of these membranes was studied for deformations along their two main axes and at three different tem…
Novel uses for 2-dimensional materials like graphene and hexagonal boron nitride (h-BN) are being frequently discovered especially for membrane and catalysis applications. Still however, a great deal remains to be understood about the interaction of environmentally and industrially elevant molecules such as water with these materials. Taking inspiration from advances in hybridising graphene and h-BN, we explore using density functional theory, the dissociation of water, hydrogen, methane, and methanol on graphene, h-BN, and their isoelectronic doped counterparts: BN doped graphene and C doped …
