Ga Focused Ion Beam Research Articles

Detection of a single enzyme molecule based on a solid-state nanopore sensor

The nanopore sensor as a high-throughput and low-cost technology can detect a single molecule in a solution. In the present study, relatively large silicon nitride (Si3N4) nanopores with diameters of ∼28 and ∼88 nm were fabricated successfully using a focused Ga ion beam. We have used solid-state nanopores with various sizes to detect the single horseradish peroxidase (HRP) molecule and for the first time analyzed single HRP molecular translocation events. In addition, a real-time monitored single enzyme molecular biochemical reaction and a translocation of the product of enzyme catalysis substrates were investigated by using a Si3N4 nanopore. Our nanopore system showed a high sensitivity in detecting single enzyme molecules and a real-time monitored single enzyme molecular biochemical reaction. This method could also be significant for studying gene expression or enzyme dynamics at the single-molecule level.

Transport properties of YBa2Cu3Ox /La0.67Sr0.33MnO3 nanostrips and YBa2Cu3Ox/La0.67Sr0.33MnO3/YBa2Cu3Ox nanojunctions

A metallic ferromagnet (F) in proximity with a superconductor (S) can transport supercurrent on a long distance through conversion of opposite-spin singlet Cooper pairs (CP) into equal-spin triplet CP (long range triplet component, LRTC), which are not broken by the exchange energy of F. The optimal conditions for the conversion are yet to be clarified; however, it is accepted that the key point to this process include high interface transparency and magnetic inhomogeneity at the SF interface. The aim of our paper is to study SF nanostrips (length of about 1500 nm and width down to 300 nm) and lateral SFS nanojunctions based on high critical temperature YBa2Cu3Ox (YBCO) and half-metallic La0.67Sr0.33MnO3 (LSMO) thin films. We applied a focused Ga+ ion beam (FIB) for patterning the SF nanostrips, as well as lateral SFS nanojunctions, by creating a slot in the nanostrip after removing the YBCO film in the slot along a length of about 200 nm. The temperature dependences of the samples resistance R(T) show critical temperature TCn ≈ 89 K of the SF nanostrips; however, the SFS nanojunctions at T < TCn show a residual resistance R < 100 Ω corresponding to a dirty LSMO (ρ≈ 10 mΩ cm) in the slot. The LRTC was not observed in our lateral SFS nanojunctions until now.

Single Nanoparticle Translocation Through Chemically Modified Solid Nanopore.

The nanopore sensor as a high-throughput and low-cost technology can detect single nanoparticle in solution. In the present study, the silicon nitride nanopores were fabricated by focused Ga ion beam (FIB), and the surface was functionalized with 3-aminopropyltriethoxysilane to change its surface charge density. The positively charged nanopore surface attracted negatively charged nanoparticles when they were in the vicinity of the nanopore. And, nanoparticle translocation speed was slowed down to obtain a clear and deterministic signal. Compared with previous studied small nanoparticles, the electrophoretic translocation of negatively charged polystyrene (PS) nanoparticles (diameter ~100 nm) was investigated in solution using the Coulter counter principle in which the time-dependent nanopore current was recorded as the nanoparticles were driven across the nanopore. A linear dependence was found between current drop and biased voltage. An exponentially decaying function (td ~ e−v/v0) was found between the duration time and biased voltage. The interaction between the amine-functionalized nanopore wall and PS microspheres was discussed while translating PS microspheres. We explored also translocations of PS microspheres through amine-functionalized solid-state nanopores by varying the solution pH (5.4, 7.0, and 10.0) with 0.02 M potassium chloride (KCl). Surface functionalization showed to provide a useful step to fine-tune the surface property, which can selectively transport molecules or particles. This approach is likely to be applied to gene sequencing.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1255-6) contains supplementary material, which is available to authorized users.

Superconductivity of In/Mo narrow wires fabricated using focused Ga-ion beam

By using a focused-ion-beam (FIB) method with Ga ions, we prepared quasi-one-dimensional (q-1D) In/Mo specimens with widths of ≈200nm and ≈500nm from two dimensional (2D) films deposited on a SiO2/Si substrate. We observed the superconducting transition of q-1D In/Mo, whose transition temperature Tc is higher than Tc≈3.6K of a 2D In/Mo specimen on a glass substrate. For specimens fabricated using the FIB method, the element distributions analyzed by energy dispersive x-ray spectroscopy reveal Ga invasion into the q-1D In/Mo region. The gradually changing resistance of q-1D In/Mo at temperatures below Tc can be well explained by the thermal activation phase-slip model with Tc=5.1K and coherence length ξ(0)≈9.5nm.

Circuit Editing and Failure Analysis Applications using a Three-Ion-Beam (Ga, He and Ne) System and Gas Injection System (GIS)

The focused ion beam (FIB) is widely used in semiconductor industries for circuit editing (CE), failure analysis (FA) and nanofabrication. Gallium FIB is most developed for CE and FA for feature size >10 nm. In general, after the FIB processing, the structural characterization is performed using SEM. A gas injection system (GIS) is integrated into a FIB or SEM microscope system to mill or deposit the materials in electron or ion induced processing in CE and FA. Ga FIB induced processing cannot fabricate small enough metal or insulator nanostructures to meet the shrinkage of feature size in current semiconductor processing. In the Zeiss NanoFab system, the Ga ion beam is used to perform the fast and large scale milling, and the helium ion beam is used to obtain the high resolution images. In addition, the neon ion beam is used to mill or assist deposition of smaller functional structures. Appropriate precursors for ion induced etching or deposition are introduced via an integrated GIS. In this paper we evaluate applications in CE and FA using a combination of three different focused ion beams.

Influence of Post-Implantation Annealing Parameters on the Focused Ion Beam Directed Nucleation of InAs Quantum Dots

We present the effect of post-implantation annealing conditions on the structural and optical quality of InAs quantum dots (QDs) grown by combination of focused ion beam (FIB) and molecular beam epitaxy (MBE) approach. A FIB of Ga + ion was employed to pattern a homogeneously GaAs buffer layers and then, an in situ annealing step followed by InAs deposition was performed. Three different post-implantation annealing conditions were tested and under well-optimized conditions, a dislocation and defect-free InAs QDs growth on FIB patterned surface was successfully achieved. Furthermore, using photoluminescence (PL) study, we demonstrate that our best sample shows almost similar optical quality as MBE grown QDs on unimplanted GaAs surface. The patterning technique described here can presumably be applied to systems other than InAs / GaAs and highly interesting for site-controlled nucleation of QDs that finds its potential applications in nanooptoelectronic devices.

DNA-functionalized silicon nitride nanopores for sequence-specific recognition of DNA biosensor.

Nanopores have been proven to be novel and versatile single-molecule sensors for individual unlabeled biopolymer detection and characterization. In the present study, a relatively large silicon nitride (Si3N4) nanopore with a diameter of approximately 60 nm was fabricated successfully using a focused Ga ion beam (FIB). We demonstrated a simple ex situ silanization procedure to control the size and functionality of solid-state nanopores. The presented results show that by varying the silanization time, it is possible to adjust the efficiency of probe molecule attachment, thus shrinking the pore to the chosen size, while introducing selective sensing probes. The functionalization of nanopores was verified by analysis of field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and electrical measurements. Based on this study, we envision that the functionalized silicon nitride nanopores with the DNA probe might provide a biosensing platform for the detection and discrimination of a short single-stranded DNA oligomer of unknown sequences in the future.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-0909-0) contains supplementary material, which is available to authorized users.

Annealing recovery of nanoscale silicon surface damage caused by Ga focused ion beam

Abstracts In this paper, molecular dynamics method with the Tersoff–ZBL combined interatomic potential was adopted to study the dynamics of focused ion beam (FIB) milling and subsequent annealing. The Ga FIB induced damage and its recovery mechanism during subsequent annealing process were investigated in nanoscale time and space. To investigate the nanoscale damage during FIB milling with the ion energy of 0.5 keV, 1 keV and 2 keV, radial distribution function, bond length distribution, bond angle distribution, and common neighbour analysis (CNA) were calculated and analyzed under various ion doses. FIB irradiated silicon substrate with ion dose of 2 × 1014 ions/cm2 was annealed at various annealing temperatures from 1400 K to 2400 K. Molecular dynamics simulation illustrated that as a-Si region was surrounded by c-Si after implantation, the recrystallization lead to a c-Si regrowth processes both from bottom towards top surface and from periphery to centre. The damage area profiles by CNA represented a shortest recovery time of 2.0 ns at 2200 K. Both melting on the top surface and recrystallization at crystalline/amorphous interface have existed as annealing at 2400 K, which is near the melting point. Ga migrated together and moved towards the surface with the a-Si/c-Si interface.

High temperature oxidation behavior of laser cladding MCrAlY coatings on austenitic stainless steel

The development of coatings has become technologically significant in many industries. A common approach in high temperature applications is the production of new thermal barrier coatings (TBCs). Laser cladding (LC) can be an alternative method to thermal spraying in the production of high quality bond coats in TBCs. In this work, dense coatings that formed adequate metallurgical bonds with the substrate were obtained by overlapping coaxial laser cladding. The oxidation behavior of the coating specimens was assessed by air furnace oxidation tests at 1100°C for up to 200h. The coatings' microstructures are composed of a γ matrix phase and a β interdendritic phase, confirmed by X-ray diffraction (XRD). At high temperatures, the growth and formation of oxide layers protect the underlying coating and substrate from oxidation at elevated temperatures. The possible formation and morphology of oxides on the oxidized surface were evaluated using scanning electron microscopy (SEM), XRD and atom force microscopy (AFM). The evaluation of the thickness and phases present in thermally grown oxide scales was evaluated using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy microanalysis (EDS), with a previous cut using the Focused Ion Beam Ga Column (FIB) method.

Investigation of mixing effects of silicon isotopes under shave‐off condition using atom probe tomography

Shave‐off depth profiling uses a Ga focused ion beam micro‐machining process to provide highly precise depth profiles with nanometer‐scale resolution. This method is a very unique process for acquiring a depth profile using the shave‐off scan mode, in which the primary ion beam perpendicular to the direction of depth irradiates the sample. In our previous study, we confirmed by molecular dynamics simulation that the shave‐off scan mode has a low mixing effect compared with the conventional scan mode, which uses the normal incident angle. However, the current understanding of measurement using the shave‐off scan mode is insufficient. In this study, in order to estimate the sample damage in the shave‐off scan mode, we investigated the degree of mixing effects after the primary ion bombardment under shave‐off conditions using atom probe tomography. To evaluate the mixing effects, the intermixing of silicon isotope multilayers induced by ion beam irradiation was investigated. The depth of the damage from the sample surface caused by Ga focused ion beams was analyzed for both the shave‐off scan mode and the conventional scan mode using the normal incident angle. Results showed that the shave‐off scan mode has a significantly smaller mixing effect than the conventional scan mode. In addition, results showed that the attenuations of the damage and the Ga concentration exhibited almost the same tendency. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Toward site-specific dopant contrast in scanning electron microscopy.

Since semiconductor devices are being scaled down to dimensions of several nanometers there is a growing need for techniques capable of quantitative analysis of dopant concentrations at the nanometer scale in all three dimensions. Imaging dopant contrast by scanning electron microscopy (SEM) is a very promising method, but many unresolved issues hinder its routine application for device analysis, especially in cases of buried layers where site-specific sample preparation is challenging. Here, we report on optimization of site-specific sample preparation by the focused Ga ion beam (FIB) technique that provides improved dopant contrast in SEM. Similar to FIB lamella preparation for transmission electron microscopy, a polishing sequence with decreasing ion energy is necessary to minimize the thickness of the electronically dead layer. We have achieved contrast values comparable to the cleaved sample, being able to detect dopant concentrations down to 1×10(16) cm-3. A theoretical model shows that the electronically dead layer corresponds to an amorphized Si layer formed during ion beam polishing. Our results also demonstrate that contamination issues are significantly suppressed for FIB-treated samples compared with cleaved ones.

Fabrication of nanopore on pyramid

There have been tremendous interests about the fabrication of metallic nanopore due to the ultrafast genome sequencing biosensor capability. In this report, the fabrication of the nanopore on the Au coated SiO2 pyramid has been examined using various high energy electron beam irradiation and focused ion beam (FIB) milling techniques. The microfabricated Au nano-apertures on pyramid were irradiated with various high energy electron beam and FIB techniques. The formation of the nanopore dependent on the probe current was also examined using electron probe micro-analysis (EPMA). The nanopore on the Au coated SiO2 pyramid is found to be an AuSi mixture. The Au nanopore on the crater type hole was also fabricated using FIB Ga ion beam scanning. The shrinking rate was found to be the fastest compared with those fabricated with the other electron beam techniques.

A Study of Structural Damage & Recovery of Si, Ge and Ga FIB implants in Silicon

ABSTRACTThe focused ion beam (FIB) has the necessary precision, spatial resolution and control over ion delivery for potential nano-scale doping of nanostructures such as semiconductor quantum dots (QDs). The ion current density in a FIB is 0.1-10 A/cm2, which is at least three orders of magnitude higher than that in a commercial broad beam ion implanter. Therefore an understanding of FIB implantation damage and recovery is of substantial interest. In this work we employ Raman probes of wavelengths 514 nm and 405 nm for quantifying ion implantation damage—both before and after annealing—in 30 kV Si2+, Ge2+ and Ga+ implants (fluences: 1x1012-5x1015 ions/cm2) into Si(100), for the purpose of understanding the effect of ion species on damage recovery.

Visualization of deuterium flux and grain boundary diffusion in duplex stainless steel and Fe–30 % Ni alloy, using secondary ion mass spectrometry equipped with a Ga focused ion beam

Time of flight secondary ion mass spectrometry (TOF-SIMS) equipped with a high spatial resolution Ga focused ion beam (Ga-FIB) was applied to understand hydrogen diffusion and desorption behavior in duplex stainless steel and Fe–30 % Ni alloys. Deuterium was used as a tracer of hydrogen. Results showed that the secondary ion intensity from body-centered cubic (bcc) and face-centered cubic (fcc) Fe represents the flux of deuterium from the surface and the concentration of deuterium, respectively. The deuterium-depleted zone can be visualized from the interface between bcc and fcc phase to fcc Fe on the surface. Furthermore, direct visualization of the grain boundary diffusion of deuterium is also possible in fcc Fe–30 % Ni alloys, using Ga-FIB-TOF-SIMS.

Fabrication of p-type silicon nanowires for 3D FETs using focused ion beam

A Ga+ focused ion beam (GaFIB) from a FIB/scanning electron microscopy (SEM) dual beam system was used for Si milling and p-type local doping of p+-type silicon nanowires (p+-SiNWs). The resulting p+-SiNWs were then used to create pMOS junctionless nanowire transistor (JNT) prototypes for silicon-on-insulator wafer substrates. The electron beam from the FIB/SEM dual beam system was used to deposit SiO2 gate dielectric and Pt source/drain electrodes for JNT transistors. Width, length, and height dimensions of p+-SiNWs were approximately 35 nm, 6 μm, and 15 nm, respectively, and the JNT gate length was 1 μm. Finally, photolithography, Al sputtering deposition, and lift-off processing were conducted to define the Al gate electrode and contacts on Pt source/drain electrodes. Energy dispersive x-ray spectroscopy measurements were taken to confirm the surface composition of p+-SiNWs and Ga doping. Drain–source current (IDS) versus drain–source voltage (VDS) measurements of JNT transistors indicated that the device is working like a JNT device (gated resistor). The authors noted high resistance on Al/Pt source and drain electrodes, which leads to distortions on IDS versus VDS curves as non-ohmic electrical contact for low VDS signal. However, these distortions can be reduced with a longer contact sintering process or by increased p+-SiNW doping. Our conclusions indicate that utilizing a GaFIB/SEM dual beam system for Si milling, Ga doping, and SiO2 and Pt depositions can be a favorable alternative for fabricating junctionless devices based on p+-SiNWs.

Micro/nanofabrication of poly(L-lactic acid) using focused ion beam direct etching

Micro/nanofabrication of biocompatible and biodegradable poly(L-lactic acid) (PLLA) using focused Ga ion beam direct etching was evaluated for future bio-device applications. The fabrication performance was determined with different ion fluences and fluxes (beam currents), and it was found that the etching speed and fabrication accuracy were affected by irradiation-induced heat. Focused ion beam (FIB)-irradiated surfaces were analyzed using micro-area X-ray photoelectron spectroscopy. Owing to reactions such as the physical sputtering of atoms and radiation-induced decomposition, PLLA was gradually carbonized with increasing C=C bonds. Controlled micro/nanostructures of PLLA were fabricated with C=C bond-rich surfaces expected to have good cell attachment properties.

Imaging of Polycyclic Aromatic Hydrocarbons by Means of Sputtered Neutrals Mass Spectrometry Using a Diode-pumped Solid-State Laser

Laser post-ionization of sputtered molecules by pulsed Ga focused ion-beam (Ga-FIB) bombardment was examined for the detection and imaging of polycyclic aromatic hydrocarbons (PAHs) on particles. As model samples, pyrene and pelyrene adsorbed on TiO2, blended regents of pyrene and n-heneicosan were used. The TiO2 particle size was selected to be several micro-meters. Laser light and Ga-FIB were synchronized with each other. The repetition rate synchronized with Ga-FIB was 1 kHz for pyrene analysis and 2 kHz for perylene, respectively. The laser wavelength was set to 266 nm. The wavelength was a generated fourth harmonic of a Nd:YAG DPSS (diode-pumped solid-state) micro-chip laser (UV microchip laser). By using a UV microchip laser, laser-SNMS (laser post-ionized sputtered neutral mass spectrometry) analysis and imaging were performed. The imaging of pyrene (m/z = 202, C16H10) and perylene (m/z = 252, C20H12) has been successful. Both the scanning ion microscopy image of TiO2 and the PAHs image in laser-SNMS analysis were well-fitted with each other.

Carbon nanotube’s modification by focused ion beam irradiation and its healing strategies

Single-walled carbon nanotube (SWNT) clusters’ properties and performance have been studied after irradiated by focused ion beam (FIB) Ga ions and post annealing recovery methods. The SWNT was irradiated by FIB with different energy and different doses ranging from 1013 to 1017ions/cm2. Raman spectroscopy results showed that FIB with larger energy or larger ion dose would cause distinct SWNT structure defects. It was also found that scanning electron microscope (SEM) observations would slightly affect the SWNT’s Raman results by electron beam induced carbon deposition. Resulting from the unique reconstruction ability of carbon nanotube’s (CNT’s) network structures, the SWNT’s ion-induced defects can be effectively healed by the post heat annealing from 300°C to 600°C for the ion dose less than 1016ions/cm2. And laser irradiation annealing method also studied to heal the defects in SWNT with 25mW laser power. Research results would be beneficial for the optimization of the carbon nanotube devices’ functionalizations using FIB Ga ions irradiation.

Fabrication of large area nanogap electrodes for sensing applications

ABSTRACTA large area nanogap electrode fabrication method combinig conventional lithography patterning with the of focused ion beam (FIB) is presented. Lithography and a lift-off process were used to pattern 50 nm thick platinum pads having an area of 300μm × 300μm. A range of 30-300 nm wide nanogaps (length from 300μm to 10 mm ) were then etched using an FIB of Ga+at an acceleration voltage of 30 kV at various beam currents. An investigation of Ga+beam current ranging between 1-50 pA was undertaken to optimise the process for the current fabrication method. In this study, we used Monte Carlo simulation to calculate the damage depth in various materials by the Ga+. Calculation of the recoil cascades of the substrate atoms are also presented. The nanogap electrodes fabricated in this study were found to have empty gap resistances exceeding several hundred MΩ. A comparison of the gap length versus electrical resistance on glass substrates is presented. The results thus outline some important issues in low-conductance measurements. The proposed nanogap fabrication method can be extended to various sensor applications, such as chemical sensing, that employ the nanogap platform. This method may be used as a prototype technique for large-scale fabrication due to its simple, fast and reliable features.

Focused ion beam induced synthesis of antimony nanowires for gas sensor applications

In this paper the formation of antimony (Sb) nanowires (NWs) by a focused Ga ion beam approach and their gas sensing capability is reported. The NWs with uniform diameters of only 25 nm and lengths up to several microns are synthesized at predefined positions at room temperature in an ion beam induced self-assembling process. Then individual Sb-NWs are deposited on insulating substrates and provided with gold electrodes. Subsequently sensing characteristics of individual Sb-NWs are investigated at room temperature for H2O, CO, H2, He, O2 and ethanol over a wide concentration range. The Sb-NWs exhibit selective sensing properties for ethanol and H2O with exceptional sensitivities of more than 17 000 and 60 000, respectively.