Fabrication Of Tips Research Articles

Fabrication of controllable porous tungsten tips for indium FEEP by dynamic reciprocating electrochemical etching combined with ultrasonic cleaning method

The porous tungsten emitter is a core component of field emission electric propulsion (FEEP). It combines the advantages of sharp tip and internal propellant transport. The emission performance of a FEEP thruster is highly depended on the emitter's tip apex radius. Traditional processing methods for solid tungsten tips are unsuitable for porous tungsten due to its unique structure and electrochemical properties. This paper introduces a novel approach combining dynamic reciprocating electrochemical etching with ultrasonic cleaning to fabricate cone-shaped porous tungsten tips with controlled apex radii. By alternating between 5 cycles of etching and an ultrasonic cleaning, a 1.9 μm apex radius is achieved after 90 repetitions. The etching current waveform reveals the material dissolution mechanism. The electrochemical characteristics of porous tungsten are investigated, with an optimal processing voltage of 2 V identified. To refine the apex radius and prevent tip collapse, a 1.9 V etching voltage is used in the final stages, maintaining the apex within 2 μm. The effectiveness of the fabricated tip is confirmed through wetting in indium and ignition tests.

Fabrication of tips for scanning probe magnetometry by diamond growth

The use of quantum sensors is promising detailed insights into physical phenomena such as magnetism or superconductivity. One example of such quantum sensors is a microscopic diamond tip containing nitrogen vacancy (NV) centers, which is capable of producing correlated measurements of vectorial magnetic fields and the sample topography on the nanoscale. In this study, we present a chemical vapor deposition (CVD) process to produce diamond tips with NV centers by overgrowing microstructured diamond substrates. The resulting diamond tips exhibit a radius of curvature of approximately 10 nm, suitable for use as a probe in an atomic force microscope. The magnetic sensitivity of the CVD-grown diamond tips is characterized with pulsed measurements of the optically detected magnetic resonance, which yield a minimum magnetic sensitivity of 60 µT Hz−1 . The growth of the diamond microstructures is observed to differ from the commonly used geometric model predicting CVD growth of bulk diamond crystals. We identify an empirical model for the growth behavior of the microstructures by taking into account processes described in the step flow growth model for crystals. Additionally, we demonstrate the applicability of the developed CVD growth process to membrane substrates required for the preparation of magnetometry-capable diamond tips.

Fabrication and characterization of optical nanofiber tips

Fabrication and characterization of optical nanofiber tips

Abstract No. 65 Development of Soft Robotic Microcatheters for Use in Interventional Radiology: Multi-lumen Microfluidic Tubing and Unidirectional Catheter Tip Fabrication

Abstract No. 65 Development of Soft Robotic Microcatheters for Use in Interventional Radiology: Multi-lumen Microfluidic Tubing and Unidirectional Catheter Tip Fabrication

Design, fabrication, and characterization of kinetic-inductive force sensors for scanning probe applications.

We describe a transducer for low-temperature atomic force microscopy based on electromechanical coupling due to a strain-dependent kinetic inductance of a superconducting nanowire. The force sensor is a bending triangular plate (cantilever) whose deflection is measured via a shift in the resonant frequency of a high-Q superconducting microwave resonator at 4.5 GHz. We present design simulations including mechanical finite-element modeling of surface strain and electromagnetic simulations of meandering nanowires with large kinetic inductance. We discuss a lumped-element model of the force sensor and describe the role of an additional shunt inductance for tuning the coupling to the transmission line used to measure the microwave resonance. A detailed description of our fabrication is presented, including information about the process parameters used for each layer. We also discuss the fabrication of sharp tips on the cantilever using focused electron beam-induced deposition of platinum. Finally, we present measurements that characterize the spread of mechanical resonant frequency, the temperature dependence of the microwave resonance, and the sensor's operation as an electromechanical transducer of force.

Retracted: Fabrication of Hollow Needle Tips with Nanoholes by Plasma Maskless Processing and Calculation and Detection of Complex Surface Edges

Retracted: Fabrication of Hollow Needle Tips with Nanoholes by Plasma Maskless Processing and Calculation and Detection of Complex Surface Edges

Fabrication of pyramid-shaped gold tip for adiabatic nanofocusing of surface plasmon polaritons

Scattering-type scanning near-field optical microscopy based on adiabatic nanofocusing of surface plasmon polaritons (SPPs) is a powerful technique that can achieve free-background nanoscale optical resolution of material. However, the performance of the propagated confined modes strongly depends on the characteristic structure of the probe. Although the metallic pyramid structure provides excellent tightly confined modes, however, it is challenging to realize the required pyramid geometry. Here, we propose a simple method for fabricating a reproducible and controllable gold pyramid-shaped tip. The produced pyramid-shaped tips were made by electrochemical etching and by applying a pulse wave to the system. From a systematic study, we found that the key factor of fabrication of desired tip geometry is based on the platinum (Pt) wire shapes. Traditional circular-shaped platinum ring electrodes are used for gold tip fabrication in an electrochemical etching. In our method, we bent the Pt wire into a triangular shape as the electrode for the etching process. The influence of the geometrical ring shapes on the fabrication of the Au tip structure is investigated. The gold tip structure was optimized by controlling the Pt ring shape, and the desired pyramid-shaped gold tip was achieved with a yield of 70%. The obtained etched pyramid-shaped tips were then mounted along the side of one of the arms of a quartz tuning fork force sensor to test their performance for shear-force topographical image and for guiding SPPs along the pyramid wedge based on adiabatic nanofocusing microscopy. The result shows topographical images of indium tin oxide with a spatial resolution smaller than 20 nm. Furthermore, we experimentally demonstrate the generation of the SPPs that propagated adiabatically along the wedge of an appropriate fabricated pyramid-shaped tip toward a nanometer-size spot at the tip apex. The demonstration of this method strongly suggests that the obtained pyramid-shaped tip will enable new experiments probing the dynamics of optical excitations of individual metallic, semiconducting, and magnetic nanostructures.

Estimating initiation conditions for extrusion buckling of driven open-ended piles

The potential for pile tip damage and extrusion buckling has become an increasing concern for the offshore wind industry following the trend toward the use of large-diameter thin-walled pile foundations, either as monopiles or as part of a jacket structure. Extrusion buckling may be triggered by an initial pile tip fabrication imperfection or pile damage during transport and handling. It may also be triggered during driving through strong heterogeneous sediments. Numerical analysis of the problem requires advanced and computationally expensive techniques because of the three-dimensional, dynamic and large-deformation nature of the pile and soil deformations. The problem is addressed here by combining coupled Eulerian–Lagrangian simulations with geotechnical centrifuge model test data in dry dense sand. Both approaches consider pre-dented piles with the objective of estimating the soil strength, characterised by the cone resistance, at which minor initial damage will start to propagate. Simplified analysis of structural dent propagation and radial stresses generated in the soil during advance of a deformed pile led to a simple calculation procedure to assess the potential for extrusion buckling. Reasonably good agreement was achieved between the proposed calculation method, numerical simulations and centrifuge tests data, rendering the approach a valuable screening tool for practical application.

Fabrication of Ultra-Sharp Tips by Dynamic Chemical Etching Process for Scanning Near-Field Microwave Microscopy.

This work details an effective dynamic chemical etching technique to fabricate ultra-sharp tips for Scanning Near-Field Microwave Microscopy (SNMM). The protruded cylindrical part of the inner conductor in a commercial SMA (Sub Miniature A) coaxial connector is tapered by a dynamic chemical etching process using ferric chloride. The technique is optimized to fabricate ultra-sharp probe tips with controllable shapes and tapered down to have a radius of tip apex around ∼1 μm. The detailed optimization facilitated the fabrication of reproducible high-quality probes suitable for non-contact SNMM operation. A simple analytical model is also presented to better describe the dynamics of the tip formation. The near-field characteristics of the tips are evaluated by finite element method (FEM) based electromagnetic simulations and the performance of the probes has been validated experimentally by means of imaging a metal-dielectric sample using the in-house scanning near-field microwave microscopy system.

Effects of Mask Material on Lateral Undercut of Silicon Dry Etching.

The silicon etching process is a core component of production in the semiconductor industry. Undercut is a nonideal effect in silicon dry etching. A reduced undercut is desired when preparing structures that demand a good sidewall morphology, while an enlarged undercut is conducive to the fabrication of microstructure tips. Undercut is related to not only the production parameters but also the mask materials. In this study, five mask materials-Cr, Al, ITO, SiNx, and SiO2-are chosen to compare the undercut effect caused by the isotropic etching process and the Bosch process. In the Bosch process, the SiNx mask causes the largest undercut, and the SiO2 mask causes the smallest undercut. In the isotropic process, the results are reversed. The effect of charges in the mask layer is found to produce this result, and the effect of electrons accumulating during the process is found to be negligible. The undercut effect can be enhanced or suppressed by selecting appropriate mask materials, which is helpful in the MEMS process. Finally, using an Al mask, a tapered silicon tip with a top diameter of 119.3 nm is fabricated using the isotropic etching process.

Fabrication of Spindt-Type Nanometer-Sized Chromium Tips for Application as Field-Electron Emitters by Releasing the Stress of the Deposited Thin Film

Metal cone-shaped nanotip field-electron emitters which are fabricated by directional thin-film deposition (so-called Spindt-type tips) have shown promising potential for application in modern vacuum micro-/nanoelectronics. Although the fabrication processes of Spindt-type tips have been well established, the in situ release of the initial stress in the deposited metal thin film is still an open issue. Herein, an in situ stress-release process was developed to fabricate chromium (Cr) tip arrays. Patterned photoresist microcavities with surrounding trenches were designed. The microcavities were used as templates for forming the metal tips. Trenches were employed for the in situ internal stress release of the Cr film on the top of the resist. The trenches not only separated the deposited Cr film into small-sized slices (square film on the photoresist) for decreasing the deformation but also provided sufficient space for possible deformation. High-aspect-ratio (∼2) tips were achieved by plasma etching the Si substrate using the Cr tip as the mask, forming a Cr tip on a Si pillar. The Cr tips maintaining a good tip shape demonstrated that the Cr nanotips possessed good etch resistance to the SF6/O2 plasma. The gated Cr-tip array was fabricated following a self-aligned microfabrication procedure. The fabrication process was compatible with the semiconductor manufacturing technology. The gated devices showed an emission current of 33 μA at a gate voltage of 137 V. This work provides a well-developed in situ stress-releasing fabrication process to obtain Spindt-type Cr-tip field-electron emitters, which has potential for application in ionization vacuum gauges and neutralizers for propulsion.

Close-packed silicon field emitter arrays with integrated anode fabricated by electron-beam lithography

Design, fabrication, and characterization of close-packed field emitter tips enclosed in an Si trench and stand-alone arrays are presented. The two types of field emitter arrays (FEAs) are fabricated using a combination of high-throughput electron-beam lithography, plasma etching, and anode bonding integration technology. The field emitter array inside the trench shows a higher turn-on voltage compared to the stand-alone array. Without any tip sharpening, a current of 7.5 μA was observed at 300 V from FEAs inside the trench, while a higher current of 12.5 μA was observed at the same voltage for the stand-alone array.

Length-Controllable Gold-Coated Silver Nanowire Probes for High AFM-TERS Scattering Activity.

Tip-enhanced Raman scattering (TERS) microscopy is an advanced technique for investigation at the nanoscale that provides topographic and chemical information simultaneously. The TERS probe plays a crucial role in the microscopic performance. In the recent past, the development of silver nanowire (AgNW) based TERS probes solved the main tip fabrication issues, such as low mechanical strength and reproducibility. However, this fabrication method still suffers from low control of the protruded length of the AgNW. In this work, a simple water-air interface electrocutting method is proposed to achieve wide controllability of the length. This water cutting method was combined with a succedent Au coating on the AgNW surface, and the probe achieved an up to 100× higher enhancement factor (EF) and a 2× smaller spatial resolution compared to pristine AgNW. Thanks to this excellent EF, the water-cut Au-coated AgNW probes were found to possess high TERS activity even in the nongap mode, enabling broad applications.

Fabrication of tungsten tips with controllable shape by a two-step rapid reciprocating electrochemical etching method.

Traditional electrochemical etching methods for the needle of a liquid metal ion source (LMIS) easily produce an exponential profile with an uncontrollable tip length and apex radius. Meanwhile, a ledge forms between the needle tip and the needle rod under the etching of the meniscus, which becomes an obstacle for the flow and replenishment of the liquid metal. This paper proposed a two-step rapid reciprocating etching method, which aims to fabricate LMIS tungsten needles with controllable tip length and apex radius, and also with a smooth transition region between the needle tip and the needle rod. In the first step of rough machining, the needle rapidly reciprocates up and down in the electrolyte and rotates to produce a uniform conical profile. However, an ellipsoidal residual portion is generated concomitantly at the needle tip. In the second step of finish machining, the needle shifts down for a given distance and continues to reciprocate until the sharp tip is formed. The tip length fabricated varied from 0.59 to 5.53mm at different reciprocating strokes. The apex radius ranged from 0.3 to 0.7 µm, and can also be increased to 2 µm by extra reciprocate etching in the electrolyte to meet the LMIS working requirement. A variable named transitivity was defined to quantitatively describe the smoothness of the region between the tip and rod during the etching process. The experimental results showed that a rotation speed of 600 rpm combined with a reciprocating speed of 0.5 mm/s can significantly improve the transitivity of the needle. Those fabricated needle tips have been tested for the indium LMIS and the maximum emission current of the needle tip reached 12 µA.

Fabrication of high aspect ratio atomic force microscope probes using focused ion beam milled etch mask

The shape and dimension of atomic force microscope (AFM) probes are essential considerations to acquire high resolution images at the nanoscale. In the cases of nanostructures with high aspect ratio (HAR) features, including dot and line arrays, commercially available standard silicon AFM probes fail to provide satisfactory results. This is due to the low aspect ratio pyramidal tip profile which cannot adequately follow the sample surface. Here a simple method is introduced to convert commercially available pyramidal probes to HAR probes by combining focused ion beam (FIB) and plasma etching techniques. A bilayer metal is deposited on standard AFM probes using e-beam evaporation, followed by a quick FIB milling process to pattern the very thin top metal layer. The FIB milled metal layer is used as the hard mask to transfer the pattern to the underlying metal layer and an HAR pillar on top of the tip apex was achieved via plasma etching. Compared to the traditional HAR tip fabrication, where the tips are individually manufactured at high cost and in a time-consuming fashion, our method significantly reduces the usage of FIB milling. Additionally, this method is suitable for batch fabrication via plasma etching once the simple FIB milling step is performed.

Fabrication of Hollow Needle Tips with Nanoholes by Plasma Maskless Processing and Calculation and Detection of Complex Surface Edges

The plasma maskless processing method combines the advantages of plasma etching and scanning probe processing, such as high etching efficiency, wide range of applicable materials, and high resolution. This method is based on the probe driving and detection of piezoelectric thin films, which enables all probes in the array to be processed completely independently, greatly improving the overall processing efficiency, and can effectively etch specific nano-scale regions of various materials. And it provides an effective solution for efficiently processing small batches of multi-variety micro-nano devices. In this study, a hollow needle tip with nanoholes was fabricated by plasma maskless processing, and use edge computing to calculate the complex surface shape of the needle tip. By establishing a plasma reactor, using the calculation method of the complex surface edge of the needle tip, and testing the stability of the processed nanotip by means of filling air pressure and power excitation in the experiment. The results show that when the breakdown voltage SF6 discharges, with the increase of air pressure, the breakdown voltage of the arrester first decreases and then increases gradually, and it is the smallest at 5 kPa and reaches the optimal 490 V, (PD) m = 0.5 Pa·m. And the Ar reaction ionization potential (15.76 eV) and excitation potential (11.53 eV, 11.72 eV) are lower than the splitting potential (≥16 eV) of SF6. As time goes on, high-energy particles are neutralized with the vessel wall, so the ion concentration is gradually smaller, sparse between 200 and 250, and increases from 100 to 300, which is close to the peak value, according to the gradual increase of the discharge voltage. The data obtained from the experimental test proves the reliability of the nanotips prepared in this study, and the properties remain stable under different breakdown voltages. Therefore, the nanohole hollow tip processed by maskless scanning plasma in this study has reached the standard of process use and has important application significance.

Controllable fabrication of silver nanofilament for using as tip in tip-enhanced Raman spectroscopy

Tip-enhanced Raman spectroscopy (TERS) is a technique offering chemical information at a single molecule level as well as chemical fingerprints with nanoscale spatial resolution. Currently, TERS tip fabrication in terms of size, shape, and stability has still been challenged due to its low reproducibility. In this work, electron beam irradiation and chemical bath deposition (CBD) were used to create a silver nanofilament (AgNF) on an atomic force microscope (AFM) tip, and it was further used as a TERS tip. Conditions, i.e., accelerated voltage and irradiation time, in the electron beam irradiation with different Ag thin film thicknesses in the production of the AgNF tip were investigated. The highest density of AgNF of the TERS probe was achieved with 52.5×109 NF/cm2 by using an accelerated voltage of 20 kV and an irradiation time of 20 minutes. This study will pave the way for the use of the AgNF tip as the TERS tip.

A Simple Method for Fabrication of Self‐sharpened Silicon Tips for Atomic Force Microscopy Applications (Crystal Research and Technology 6/2022)

Crystal Research and TechnologyVolume 57, Issue 6 2270011 Cover PictureFree Access A Simple Method for Fabrication of Self-sharpened Silicon Tips for Atomic Force Microscopy Applications (Crystal Research and Technology 6/2022) First published: 09 June 2022 https://doi.org/10.1002/crat.202270011AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract In article number 2100217, Savitha Purakkat, Basavaraju Yeriyur Basavaiah, and co-workers present a simple and high yield method to bulk produce self-sharpened silicon tips using cost-effective chemicals. The generated silicon tips are successfully adopted to fabricate atomic force microscopy probes. After installing in a commercial atomic force microscope, the developed probes produce the images of quality and accuracy of those obtained with commercially available probes. Volume57, Issue6June 20222270011 RelatedInformation

Fabrication of probe tips via the FIB method for nanodiagnostics of the surface of solids by atomic force microscopy

In this work, we carried out an investigation of commercial atomic force microscope (AFM) probes for contact and semi-contact modes, which were modified by focused ion beam (FIB). This method was used to modify the original tip shape of silicon AFM probes, by ion-etching and ion-enhance gas deposition. we show a better performance of the FIB-modified probes in contrast with the non-modified commercial probes. These results were obtained after using both probes in semi-contact mode in a calibration grating sample.

Optimizing the near‐field and far‐field properties of tips in tip‐enhanced Raman scattering

AbstractThe process of tip‐enhanced Raman scattering (TERS) depends critically on the morphology near the apex of the tip used in the experiment. Many tip designs have focused on optimization of electromagnetic enhancement in the near‐field, which is controlled to a large extent by subtle details at the nanoscale that remain difficult to reproduce in the tip fabrication process. The use of focused ion beams (FIB) permit modification of larger features on the tip in a reproducible manner, yet this approach cannot produce sub‐20‐nm structures important for optimum near‐field enhancement. Nonetheless, FIB milling offers excellent opportunities for improving the far‐field radiation properties of the tip‐antenna, a feature that has received relatively little attention in the TERS research community. In this work, we use finite‐difference time‐domain (FDTD) simulations to study both the near‐field and far‐field radiation efficiency of several tip‐antenna systems that can be constructed with FIB techniques in a feasible manner. Starting from blunt etched tips, we find that excellent overall enhancement of the TERS signal can be obtained with pillar‐type tips. Furthermore, by applying vertical grooves on the tip's shaft, the overall efficiency can be improved even more, producing TERS signals that are up to 10‐fold stronger than signals obtained from an ideal (unmodified) sharp tip of 10‐nm radius. The proposed designs constitute a feasible route toward a tip fabrication process that not only yields more reproducible tips but also promises much stronger TERS signals.