Conductive Atomic Force Microscopy Tip Research Articles

Tunable topological domain structures in high-density PbTiO3 nanodots array

In this work, we demonstrated that tunable topological domain structures, e.g., center-type domains and skyrmion-like polar bubbles, can be generated at room temperature in high-density epitaxial PbTiO3 nanodots fabricated via the template-assisted tailoring of thin films. These topological domain structures can be manipulated electrically by applying an appropriate bias on the conductive atomic force microscopy tip, allowing for writing, erasing, and rewriting of topological domains into the nanodot. Moreover, ring-shaped conductive channels are observed around the center-type domain states. These findings provide a playground for further exploring their emerging functionalities and application potentials for nanoelectronics.

Atomic Force Microscopy (AFM) Tip based Nanoelectrode with Hydrogel Electrolyte and Application to Single-Nanoparticle Electrochemistry

<p>An unconventional fabrication technique of nanoelectrode was developed using atomic force microscopy (AFM) and hydrogel. Until now, the precise control of electroactive area down to a few nm<sup>2</sup> has always been an obstacle, which limits the wide application of nanoelectrodes. Here, the nanometer-sized contact between the boron-doped diamond (BDD) as conductive AFM tip and the agarose hydrogel as solid electrolyte was well governed by the feedback amplitude of oscillation in the non-contact mode of AFM. Consequently, this low-cost and feasible approach gives rise to new possibilities for the fabrication of nanoelectrodes. The electroactive area controlled by the set point of AFM was investigated by cyclic voltammetry (CV) of the ferrocenmethanol (FcMeOH) combined with quasi-solid agarose hydrogel as an electrolyte. Single copper (Cu) nanoparticle was deposited at the apex of the AFM tip using this platform whose electrocatalytic activity for nitrate reduction was then investigated by CV and Field Emission-Scanning Electron Microscopy (FE-SEM), respectively.</p>

Controlled Sixfold Symmetric Exfoliation of Oriented MoS2 Monolayers by Coulomb Force

AbstractAtoms, molecules, and nanoparticles can be spatially manipulated by an atomic force microscopy (AFM) tip, through van der Waals (vdW) and/or Coulomb forces. These point‐to‐point manipulations are highly accurate at nanoscale, facilitating the construction and modification of nanostructures. Nevertheless, it is difficult to manipulate 2D layers in vdW crystals by an AFM tip, because the tip‐induced attractive force is usually insufficient to outcompete the interlaminar vdW forces. Herein, manipulation of the surface layers on a MoS2 single crystal by a conductive AFM tip is successfully reported. By applying a bias between the tip and MoS2, the Coulomb attractive force allows the topmost MoS2 layers to be picked up. These exfoliated layers are deformed into micron‐sized bubbles with sixfold symmetry, which are composed of high‐quality monolayers and visually reflecting the hexagonal lattice orientation. The underlying mechanisms of the sixfold symmetric exfoliation and the formation of monolayers are discussed by in situ monitoring of the tunneling volt‐ampere characteristics and simulation of the force distribution. The findings open a new route to obtain high‐quality transition metal dichalcogenide (TMD) monolayers and their derived nanostructures on the surface of TMD single crystals for optoelectronic and photonic device applications.

Atomically thin MXene/WSe2 Schottky heterojunction towards enhanced photogenerated charge carrier

Two-dimensional materials garner increasing interest in next-generation electronics and optoelectronic devices due to their atomic-thin nature and distinctive physical properties. Building on these advances, we present the successful synthesis of a heterostructure composed of the semi-metallic Ti3C2-MXene and the semiconducting WSe2, in which the atomic layers are vertically aligned. The wet impregnation method effectively synthesizes an atomically thin Ti3C2-MXene/WSe2 heterostructure characterized by atomic force microscopy, Raman and time-resolved photoluminescence (TRPL) analysis. In addition, the current–voltage characteristics at the heterostructure reveal the Schottky junction probed by the scanning tunnelling microscopy and the conductive atomic force microscopy tip. The Schottky heterojunction also exhibits enhanced photocatalytic properties by improving the photogenerated charge carriers and inhibiting recombination. This work demonstrates the unique 2D–2D Ti3C2-MXene/WSe2 vertical heterojunction possesses superior photon trapping ability and can efficiently transport photogenerated charge carriers to the reaction sites to enhance photocatalysis performance.

Domain wall nature of sketched LaAlO3/SrTiO3 nanowires

The rich electron correlations and highly coherent transport in reconfigurable devices sketched by a conductive atomic force microscope tip at the $\mathrm{LaAl}{\mathrm{O}}_{3}/\mathrm{SrTi}{\mathrm{O}}_{3}$ interface have enabled the oxide platform an ideal playground for studying correlated electrons and quantum technological applications. Why these one-dimensional devices possess enhanced properties over the two-dimensional interface, however, has remained elusive. Here, we provide evidence that one-dimensional $\mathrm{LaAl}{\mathrm{O}}_{3}/\mathrm{SrTi}{\mathrm{O}}_{3}$ nanowires are intrinsically ferroelastic domain walls by nature through thermodynamic study. We have observed spreading resistance anomalies under thermostimulus and temperature cycles with characteristic temperatures matching domain-wall polarity. This information is crucial in understanding the novel phenomena including superconductivity and high mobility quantum transport.

Conductive filament nanostructures and their magnetization reversal in NiO resistive switching memory cells

We demonstrate that conductive filament (CF) nanostructures in NiO thin film resistive switching memory (RRAM) cells present unique magnetic properties. The CF nanostructures of nanodots and nanorods formed using a conductive atomic force microscopy tip were fabricated through the forming process of CFs for the NiO RRAM cells. In the current–voltage curve, unipolar resistive switching behavior was observed. The ferromagnetic domain and magnetization switching of CF nanostructures were characterized using magnetic force microscopy. In principle, nanoscale-sized magnetic nanostructures possess superparamagnetism due to their thermal fluctuations. In this study, however, CF nanorods with a length of 30 nm exhibited ferromagnetism because the exchange bias effect occurred at the interface between the antiferromagnetic NiO and the CF nanorod. Therefore, the ferromagnetism of the CF nanostructures is the origin of the magnetization switching and can be favorable in magnetic storage device applications by overcoming the superparamagnetic limits with the exchange bias effect.

Fabrication of Polyaniline (PANI) through Parallel Nanopores: Charge Transport Properties of PANI@SiO2 Nanopore Molecular Junctions

Aniline is electropolymerized through mesoporous silica nanopores (100 nm-long, 3 nm in diameter) orthogonally oriented on indium-tin oxide (ITO). Only a few polyaniline (PANI) wires are accommodated in the nanochannels and their growth is electrochemically controlled. The electronic transport properties of PANI@SiO2 are studied by Conductive Atomic Force Microscopy (C-AFM), using a Pt-coated C-AFM tip. Three different behaviors are observed. First, linear I/V curves are obtained when PANI is deposited in the nanopores with material spilling over the silica membrane; electron transport occurs through many PANI@SiO2 channels and the overall conductance is high. Second, flat I/V curves are recorded, indicating “insulator” behavior when the SiO2 nanopores are not fully filled by PANI wires. Thirdly, non-linear I/V curves, which are quantitatively highly reproducible and independent of the point probed, are obtained. These are attributed to the formation of molecular junctions where the C-AFM tip in contact with the nanopores acts as the top electrode and vertical PANI wires just fill the SiO2 channels. The size of the top electrode and the reproducilility of the I/V suggest that the C-AFM is seeing about 5 nanopores each filled with one or two PANI wires.

Nanoscale thermal imaging of VO2 via Poole–Frenkel conduction

We present a method for nanoscale thermal imaging of insulating thin films using atomic force microscopy (AFM), and we demonstrate its utility on VO2. We sweep the applied voltage V to a conducting AFM tip in contact mode and measure the local current I through the film. By fitting the IV curves to a Poole–Frenkel conduction model at low V, we calculate the local temperature with spatial resolution better than 50 nm using only fundamental constants and known film properties. Our thermometry technique enables local temperature measurement of any insulating film dominated by the Poole–Frenkel conduction mechanism and can be extended to insulators that display other conduction mechanisms.

(Invited) Nanoscale Probing of Field-Driven Ion Migration in TaOx for Neuromorphic Memristor Applications

In semiconducting metal oxides, application of electric fields often causes migration of the constituent ions (oxygen ions, metal cations, and ionic vacancies) via ionic conduction and diffusion. The field-driven ion migration has been considered a key phenomenon in the recent development of oxide-based resistive random access memory (ReRAM) and memristive neuromorphic devices because their operations are generally made through the migration and resultant changes in the valence/resistance states of the oxide layers. Semiconducting amorphous TaOx is known as a practical material of switching layers in ReRAMs, and moreover, has recently been considered of critical importance in the development of neuromorphic hardware because of its variety of neuromorphic resistive switching functions. Many important functions, including multilevel (or analog) resistive switching, stochastic switching, and spike-rate/spike-timing dependent plasticity, have been demonstrated in junctions with a structure of metal/TaOx/metal, and the origin of the neuromorphic functionality has been ascribed to the high ionic conductivities (both for O2− and Ta5+) and degree of structural freedom of amorphous TaOx.Regarding the mechanisms of the neuromorphic switching, however, limited understanding has been achieved in the previous works. The mechanisms have so far been inferred from the switching behaviors in electrical measurements or numerical modeling because of the experimental difficulty in observing nanoscale ion migration during the neuromorphic resistive switching. To directly design of the neuromorphic functions and establish oxide-based neuromorphic computing, therefore, experimental probing of the ion migration processes is now importantly required for neuromorphic resistive switching of TaOx.In this study, we fabricated ultra-flat thin films of amorphous TaOx (3.0–10 nm thick) with a root-mean-square roughness of <0.2 nm by the pulsed laser deposition method, which will offer suitable conditions for ion migration analysis by probe microscopy. In the conductive tip atomic force microscopy investigations, we observed a stable resistive switching phenomenon at arbitrary positions on the TaOx surface by voltage applications from a probe. The positional independence of the switching characteristics ensures the experimental advantages of the ultra-flat films in the investigations. Additionally, this indicates that "easy spots" for resistive switching, of which the formation has been suggested in other metal oxides, are not present in the thin films of amorphous TaOx, and initial clustering of oxygen vacancies is not importantly involved in the switching. When multiple voltage stresses of >3.0 V were applied from a probe, we observed a multilevel switching phenomenon in the TaOx thin films. In the measurements, we observed that the multilevel switching appears with very small amount of structural changes of TaOx (<1.0 nm in the out-of-plane direction), and relatively large-scale structural deformations (2.0 nm in the out-of-plane direction and 150 nm in the in-plane direction) started to be observed only after breakdown-like behaviors in the resistance with formation of a 10 nm-sized conductive spot. This indicates that the intrinsic ion migration distance involved in the multilevel switching of TaOx is in a range of <1.0 nm in out-of-plane direction, which is smaller than previous predictions. From these results, the spatial extents of neuromorphic resistive switching of TaOx were revealed in this study, which will offer important insights into the process development for TaOx-based neuromorphic memristor.

Dynamic Nanofriction of Graphene Oxide Induced by a Positively Biased Conductive AFM Tip

Graphene oxide (GO) with properties of large-scale preparation and application is an attractive solid lubricant. Understanding the tribological properties of GO under an electric field is crucial for the application of GO as a lubricant in electromechanical devices. Here, nanofriction properties of GO was measured in real-time using atomic force microscopy (AFM) with a positively biased conductive tip. The nanofriction force between the AFM tip and GO decreased sharply in the initial few tens of scan cycles. Then, a gradual decrease in nanofriction force was observed. The nanofriction force leveled off as the scan cycles further increased. The significant decrease in nanofriction force resulted from the reduction of oxygen-containing functional groups during the scan of the positively biased tip, which also led to the drop of height in the scanned area. Also, biased voltages, relative humidity, scan velocities, and normal loads affected the reduction and thus the nanofriction force. The exhibited low nanofriction force of GO after reduction makes it become an economically viable coating with the potential to extend the lifetime of electromechanical systems.

Defect Distribution in Doped Silicon Nanostructures Characterized By Means of Scanning Spreading Resistance Microscopy

Scanning Spreading Resistance Microscopy (SSRM) is a well-known technique for electrical characterization of dopant distributions in semiconductors. The resistance between a conductive atomic force microscope (AFM) tip and a large area contact on a semiconductor sample gives direct hint of sample resistivity underneath the tip. The sample surface has to be polished to achieve a smooth surface which is crucial for a low ohmic electrical contact between tip and sample. In theory, the formula of spreading resistance Rspr = ρ/4a with tip radius a connects SSRM raw data to resistivity data which can be transformed to concentration data of corresponding dopants. In experiment, additional series resistances and electrical defects have an impact on the SSRM analysis so that the formula does not hold any more. A SSRM scan on a calibration sample with regions of different well-known dopant concentrations enables an empirical relationship between R and ρ. This relationship is only valid for the specific defect distribution and tip-sample contact of the calibration sample. Both the defect distribution and the tip sample contact, respectively, depend strongly on sample preparation. Reliable calibration of unknown dopant distributions in semiconductor samples is only possible in the case of a perfectly reproducible sample preparation which is however hard to attain. Therefore, an accurate quantification of SSRM data remains difficult.One first step towards SSRM quantification requires an improved understanding and control of electrical defects on the sample surface which affect the SSRM measurement. In this work, we apply SSRM on well characterized n- and p-type dopant profiles in silicon bulk- and nanostructures. The deviation of the experimental SSRM data from simulated spreading resistance profiles provides direct information on type, quantity and origin of electrical defects in the sample.Our analysis of bulk samples reveals two type of preparation induced defects: n-type surface defects and hydrogen traps which deactivate boron atoms. The number of surface defects is proportional to the surface roughness. An improved sample preparation with additional polishing steps reduces the impact of this defect on the SSRM analysis. Hydrogen traps are driven into the sample during water based chemical mechanical polishing steps. An annealing of the sample at 250°C for 20 minutes reactivates most of the boron atoms.A third type of defect was noticed in nanostructured samples. Silicon nano pillars with diameters between 500 and 600 nm are manufactured in a top-down approach out of a silicon wafer with a 600 nm deep boron diffusion profile. Figure 1 shows the SSRM data of the bulk sample (a), the cross-sectional prepared nano pillar (b), and the depth profiles of SSRM analysis (c). The SSRM signal at the top of the pillar is dominated by the boron profile (b). The side walls are covered with gold as second contact for SSRM analysis. Obviously, the SSRM depth profile at the shell region (#2, circles) of the pillar is deeper than at the core (#3, triangles) and in the bulk sample (#1, squares) (c). The dopant distribution itself cannot vary across the pillar as the nanofabrication is done by dry-etching at cryogenic temperatures. We explain the variance in SSRM signal by acceptor defect states at the pillar shell which increase the number of p-type charge carriers in the shell region.COMSOL simulations of the SSRM analysis, including the impact of defects on the resistance profile, is used to quantify the defect distributions. The calculated resistance profiles accurately describe the experimental data (black dotted lines in (c)) and support our assumption on the distribution of electrical defects in silicon nanostructures. Figure 1

Automated pick-and-place of single nanoparticle using electrically controlled low-surface energy nanotweezer

In this work, we developed electrically controlled nanotweezers, which are capable of picking, moving, and placing a single sub-50 nm particle precisely and repeatably in ambient air. The nanotweezers are made of a fluoride polymer coated conductive atomic force microscope tip. By applying voltages on such a low surface energy tip, one can tune the binding energy between the tip and the nanoparticle up and down and consequently pick and place a nanoparticle with a high success rate (&amp;gt;90%). Moreover, we automated the whole pick-and-place procedure with the help of the computer vision technique, and it allows us to pattern nanoparticles into arbitrary patterns without any manual operation.

Origin of leakage current in vertical GaN devices with nonplanar regrown p-GaN

This work demonstrates large-area vertical GaN-on-GaN Schottky barrier diodes (SBDs) with different p-GaN terminations fabricated by the p-GaN regrowth on planar and nonplanar n-GaN structures and studies the leakage current in these regrown p-GaN terminations. The SBDs with planar p-GaN terminations demonstrate a higher breakdown voltage than the non-terminated SBDs. In contrast, the SBDs with nonplanar regrown terminations exhibit a significantly higher leakage current, which agrees with the tunneling behavior. The microscopic current mapping and local current–voltage (I–V) spectra are acquired using conductive atomic force microscopy (C-AFM) in the nonplanar regrown junction region. The local leakage currents and conduction types are derived from the I–V characteristics of the Schottky barrier between the metalized C-AFM tip and GaN. The dominant leakage path is revealed to be the tunneling across the Schottky barrier to the regrowth sidewall assisted by high-concentration interfacial impurities, followed by current flow along the regrowth sidewall. An ∼0.7 μm-wide n-type compensation layer is found next to the non-polar regrowth sidewall, which does not directly induce a major leakage path but moves the p-GaN away from the regrowth interface, thus weakening the p-GaN depletion of the sidewall interfacial impurities as well as facilitating the formation of a crowded electric field and tunneling at the Schottky contact to the regrowth region.

Current timer switch in a GaAs-based nanowire coupled with polyoxometalate nanoparticle and conductive AFM tip

We demonstrate a current timer switch function in a GaAs-based nanowire electrostatically coupled with a polyoxometalate nanoparticle (POM NP) and a conductive atomic force microscopy (AFM) tip. The nanowire current associated with the charge state of the POM NP on the nanowire surface abruptly changed after several ten seconds from biasing the conductive tip. The current switch timing changed depending on the tip voltage. The timer switch function appeared when the tip approached the POM NP where the AFM phase image showed phase lag at high atmospheric humidity condition. We discuss the timer mechanism in terms of the configuration of the electromechanical potential of the cantilever and dynamic potential modulation by mobile ions and polarized molecules in the water-absorbed POM NP surface.

Deformation-induced charge redistribution in ceria thin film at room temperature

Tuning electronic properties through strain engineering of metal oxides is an important step toward understanding electrochemical and catalytic reactions in energy storage and conversion devices. Traditionally, strain engineering studies focused on movement of oxygen ions at high temperatures (500 °C and above), complicating electrical properties by introducing mixed electronic and ionic conductivity. In this study, we demonstrate formation of oxygen vacancies and room temperature charge redistribution in a CeO2 thin film as a result of phase transformation in a localized region by mechanical deformation. Mechanical indentation of the CeO2 thin film at room temperature results in irreversible deformation. Conductive-tip atomic force microscopy (C-AFM) analysis shows increased current passing through the locally deformed area of the CeO2 thin film. Electron energy loss spectroscopy (EELS) analysis equipped with transmission electron microscopy (TEM) suggests that the increase in current contrast in the deformed region arises from an increased concentration of Ce3+ ions. We herein discuss the fundamental reason behind the increased amount of Ce3+ ions in the deformed area, based on the atomic scale computational works performed by molecular dynamics (MD) simulations and first-principles density functional theory (DFT) calculations, and scanning transmission electron microscopy (STEM) analyses. Mechanical deformation not only facilitates the formation of oxygen vacancies in a localized region, but also induces a phase transformation of cubic fluorite CeO2 into a newly formed T-CeO2 structure. These are considered as the critical factors for the enhanced current in the deformed CeO2 thin film at room temperature.

Diffusive Memristive Switching on the Nanoscale, from Individual Nanoparticles towards Scalable Nanocomposite Devices

Nanoscale memristive phenomena are of great interest not only to miniaturize devices and improve their performance but also to understand the details of the underlying mechanism. Herein, we utilize conductive atomic force microscopy (C-AFM) as a non-invasive method to examine the nanoscale memristive properties of individual noble metal alloy nanoparticles that are sparsely encapsulated in a thin SiO2 dielectric matrix. The measurement of current-voltage hysteresis loops at the level of individual nanoparticles, enabled by the nanoscopic contact area of the C-AFM tip, indicates reliable memristive switching for several hours of continuous operations. Alongside the electrical characterization on the nanoscale, the method of C-AFM offers the potential for in situ monitoring of long term operation induced morphological alterations and device failure, which is demonstrated at the example of nanoparticle-based devices with additional Cr wetting layer. The application of alloy nanoparticles as reservoir for mobile silver species effectively limits the formation of stable metallic filaments and results in reproducible diffusive switching characteristics. Notably, similar behaviour is encountered on macroscopic nanocomposite devices, which incorporate multiple stacks of nanoparticles and offer a high design versatility to tune switching properties and engineer scalable memristive devices with diffusive switching characteristics. No additional forming step is required for the operation of the presented alloy nanoparticle based memristive devices, which renders them very attractive for applications.

Photodetection Characteristics of Gold Coated AFM Tips and n-Silicon Substrate nano-Schottky Interfaces

Silicon (Si)-based photodetectors are appealing candidates due to their low cost and compatibility with the complementary metal oxide semiconductor (CMOS) technology. The nanoscale devices based on Si can contribute efficiently in the field of photodetectors. In this report, we investigate the photodetection capability of nano-Schottky junctions using gold (Au) coated conductive atomic force microscope (C-AFM) tips, and highly cleaned n-Si substrate interface. The Au nanotip/n-Si interface forms the proposed structure of a nano Schottky diode based photodetector. The electrical characteristics measured at the nanoscale junction with different Au nanotip radii show that the tunneling current increases with decreasing the tip radius. Moreover, the tunneling process and photodetection effects are discussed in terms of barrier width/height decrease at the tip-semiconductor interface due to the applied electric field as well as the generation of plasmon-induced hot-electron at the nanoparticle (i.e. C-AFM tip)/n-Si interface. Furthermore, the photodetection sensitivity is investigated and it is found to be higher for C-AFM tips with smaller radii. Moreover, this research will open a new path for the miniaturization of photodetectors with high sensitivity based on nano-Schottky interfaces.

Layer-Dependent Interfacial Transport and Optoelectrical Properties of MoS2 on Ultraflat Metals.

Layered materials based on transition-metal dichalcogenides (TMDs) are promising for a wide range of electronic and optoelectronic devices. Realizing such practical applications often requires metal-TMD connections or contacts. Hence, a complete understanding of electronic band alignments and potential barrier heights governing the transport through metal-TMD junctions is critical. However, it is presently unclear how the energy bands of a TMD align while in contact with a metal as a function of the number of layers. In pursuit of removing this knowledge gap, we have performed conductive atomic force microscopy (CAFM) of few-layered (1 to 5 layers) MoS2 immobilized on ultraflat conducting Au surfaces [root-mean-square (rms) surface roughness < 0.2 nm] and indium-tin oxide (ITO) substrates (rms surface roughness < 0.7 nm) forming a vertical metal (CAFM tip)-semiconductor-metal device. We have observed that the current increases with the number of layers up to five layers. By applying Fowler-Nordheim tunneling theory, we have determined the barrier heights for different layers and observed how this barrier decreases as the number of layers increases. Using density functional theory calculations, we successfully demonstrated that the barrier height decreases as the layer number increases. By illuminating TMDs on a transparent ultraflat conducting ITO substrate, we observed a reduction in current when compared to the current measured in the dark, hence demonstrating negative photoconductivity. Our study provides a fundamental understanding of the local electronic and optoelectronic behaviors of the TMD-metal junction, which depends on the numbers of TMD layers and may pave an avenue toward developing nanoscale electronic devices with tailored layer-dependent transport properties.

Formation and characterization of charge coupled structure of polyoxometalate particles and a GaAs-based nanowire for readout of molecular charge states

To investigate the molecular charge dynamics of polyoxometalate (POM) molecules, we formed and characterized a charge coupled structure with POM molecular particles and a GaAs-based nanowire. In our system, the charge sensitivity was locally increased by capacitive coupling between a metal tip and the POM particle. Surface dispersion of POM particles on the GaAs nanowire was carried out in a controlled manner by choosing an appropriate solvent and POM concentration. We found that, after POM surface dispersion, the current in the GaAs nanowire remarkably increased by charging the POM particles using a conductive atomic force microscopy tip. The current change strongly depended on humidity of the measurement environment. The nanowire current under capacitive coupling between the conductive tip and the POM particle on the nanowire surface showed steps with a height of approximately 70 nA, suggesting that multiple hole charging and discharging occurred in the particle in a synchronized manner.

Nanopore Formation via Tip‐Controlled Local Breakdown Using an Atomic Force Microscope

AbstractThe dielectric breakdown approach for forming nanopores has greatly accelerated the pace of research in solid‐state nanopore sensing, enabling inexpensive formation of nanopores via a bench top setup. Here the potential of tip‐controlled local breakdown (TCLB) to fabricate pores 100× faster, with high scalability and nanometer positioning precision using an atomic force microscope (AFM) is demonstrated. A conductive AFM tip is brought into contact with a silicon nitride membrane positioned above an electrolyte reservoir. Application of a voltage pulse at the tip leads to the formation of a single nanoscale pore. Pores are formed precisely at the tip position with a complete suppression of multiple pore formation. In addition, the approach greatly accelerates the electric breakdown process, leading to an average pore fabrication time on the order of 10 ms, at least two orders of magnitude shorter than achieved by classic dielectric breakdown approaches. With this fast pore writing speed over 300 pores can be fabricated in half an hour on the same membrane.