Ion Beam Diameter Research Articles

A comparison of neon versus helium ion beam induced deposition via Monte Carlo simulations

The ion beam induced nanoscale synthesis of PtCx (where x ∼ 5) using the trimethyl (methylcyclopentadienyl)platinum(IV) (MeCpPtIVMe3) precursor is investigated by performing Monte Carlo simulations of helium and neon ions. The helium beam leads to more lateral growth relative to the neon beam because of its larger interaction volume. The lateral growth of the nanopillars is dominated by molecules deposited via secondary electrons in both the simulations. Notably, the helium pillars are dominated by SE-I electrons whereas the neon pillars are dominated by SE-II electrons. Using a low precursor residence time of 70 μs, resulting in an equilibrium coverage of ∼4%, the neon simulation has a lower deposition efficiency (3.5%) compared to that of the helium simulation (6.5%). At larger residence time (10 ms) and consequently larger equilibrium coverage (85%) the deposition efficiencies of helium and neon increased to 49% and 21%, respectively; which is dominated by increased lateral growth rates leading to broader pillars. The nanoscale growth is further studied by varying the ion beam diameter at 10 ms precursor residence time. The study shows that total SE yield decreases with increasing beam diameters for both the ion types. However, helium has the larger SE yield as compared to that of neon in both the low and high precursor residence time, and thus pillars are wider in all the simulations studied.

Carbon isotope heterogeneity in metamorphic diamond from the Kokchetav UHP dolomite marble, northern Kazakhstan

We analysed isotopic compositions of metamorphic microdiamond secondary ion mass spectrometry. Typical microdiamonds in this dolomite marble show star-shaped morphologies (S-type) consisting of single-crystal cores and polycrystalline rims. Four S-type microdiamonds and two R-type microdiamonds (single crystals with rugged surfaces) were analysed using a 5 μm diameter ion beam. S-type microdiamonds have heterogeneous carbon isotopic compositions even in a single grain. Analysis of a typical S-type microdiamond (no. xx01-1-13) revealed clear difference in δ13C between core and rim. The rim shows lighter isotopic compositions ranging from −17.2‰ to −26.9‰, whereas the core is much heavier, with δ13C ranging from −9.3‰ to −13.0‰. The δ13C values of R-type microdiamonds fall into narrow ranges from −8.3‰ to −14.9‰ for no. xx01-1-10 and from −8.3‰ to −15.3‰ for no. xx01-1-16. These δ13C values are similar to those of the S-type microdiamond cores. The R-type probably formed at the same stage as the core of the S-type, whereas rim growth at a second stage did not occur or occurred very weakly in R-type microdiamonds. These carbon isotopic data support the two-stage growth of microdiamonds in the Kokchetav ultrahigh-pressure host rock. To explain the second stage growth of S-type microdiamonds, we postulate a simple fluid infiltration of light carbon from neighbouring gneisses into the dolomite marble.

Core–shell structure of fly ash particles ‐ SIMS depth profile analysis

Depth profile analysis in secondary ion mass spectrometry (SIMS) is applied for fly ash particles collected from three electrostatic precipitators in coal combustion type Thermoelectric Power Plant in Warsaw, Poland. Prior to analysis, particles of the collected material were size separated in nine stage cascade impactor with rotating substrate plates. Bulk analysis of the chosen size fractions was performed by atomic absorption spectroscopy. For SIMS depth profile analysis, particles were deposited on indium foils of high purity. Sputtering with 5 keV Ar+, 100 µm diameter ion beam was performed over 1.2 × 1.8 mm area of the indium foil in SIMS system (SAJW‐05 model) equipped with Physical Electronics ion gun and QMA‐410 Balzers quadrupole analyzer. SIMS data are quantified based on bulk concentration values of: carbon, sodium, aluminium, silicon, calcium, chromium, manganese, iron and nickel. Core–shell structure, and also cenosphere structure, is found. Depth profile analysis shows that shell layers of particles are enriched in carbon, calcium, chromium and nickel. Inner parts of particles or their cores are enriched in sodium and aluminium. Copyright © 2012 John Wiley & Sons, Ltd.

Correction of topographic artefacts of ToF‐SIMS element distributions

Images of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) element distributions at the sample surface may be distorted when dealing with topographically structured samples and an oblique primary ion beam angle. This distortion becomes problematic if topographic feature heights exceed the primary ion beam diameter. Such topographic features may stem from initial topography, but they can also be introduced through differential sputtering of the sample during depth profiling. Current ToF‐SIMS software cannot take sample topography or differential sputtering into account. Instead, it assumes a flat surface and the same constant sputter rate for the whole sample which results in laterally and vertically distorted element distributions in depth profiles. Both of these negative effects are demonstrated using a thin layer system. We propose an algorithm to correct both kinds of defects for 2D and 3D ToF‐SIMS element distributions by combining them with topographic information. Copyright © 2012 John Wiley & Sons, Ltd.

Characterization of the Ion Beam Focusing in a Mass Spectrometer Using an IonCCD™ Detector

A position sensitive pixel-based detector array, referred to as the IonCCD, has been employed to characterize the ion optics and ion beam focusing in a custom built mass spectrometer designed for soft and reactive landing of mass-selected ions onto surfaces. The IonCCD was placed at several stages along the path of the ion beam to determine the focusing capabilities of the various ion optics, which include an electrodynamic ion funnel, two radiofrequency (rf)-only collision quadrupoles, a mass resolving quadrupole, a quadrupole bender, and two einzel lens assemblies. The focusing capabilities of the rf-only collision quadrupoles and einzel lenses are demonstrated by large decreases in the diameter of the ion beam. In contrast, the mass resolving quadrupole is shown to significantly defocus the mass-selected ion beam resulting in an expansion of the measured ion beam diameter. Combined with SIMION simulations, we demonstrate that the IonCCD can identify minor errors in the alignment of charged-particle optics that result in erratic trajectories and significant deflections of the ion beam. This information may be used to facilitate the design, assembly, and maintenance of custom-built mass spectrometry instrumentation.

Nanopillar growth by focused helium ion-beam-induced deposition

A 25 keV focused helium ion beam has been used to grow PtCnanopillars on a silicon substrate by beam-induced decomposition of a(CH3)3Pt(CPCH3) precursor gas. The ion beam diameter was about 1 nm. The observed relatively high growthrates suggest that electronic excitation is the dominant mechanism in heliumion-beam-induced deposition. Pillars grown at low beam currents are narrow and havesharp tips. For a constant dose, the pillar height decreases with increasing current, pointingto depletion of precursor molecules at the beam impact site. Furthermore, the diameterincreases rapidly and the total pillar volume decreases slowly with increasing current.Monte Carlo simulations have been performed with realistic values for the fundamentaldeposition processes. The simulation results are in good agreement with experimentalobservations. In particular, they reproduce the current dependences of the vertical andlateral growth rates and of the volumetric deposition efficiency. Furthermore, thesimulations reveal that the vertical pillar growth is due to type-1 secondary electrons andprimary ions, while the lateral outgrowth is due to type-2 secondary electrons and scatteredions.

Study of the parameters affecting ion beam emerging from cold conical cathode ion source

The aim of this work is study of the parameters affecting ion beam emerging from cold conical cathode ion source. The input discharge and output ion beam characteristics have been measured at different pressures using nitrogen and argon gases. The optimum distance between the ion exit aperture of the cathode and the movable copper ion collector plate has been determined using nitrogen and argon gases. The ion collector plate has been placed at different distances from the ion exit aperture of the cathode equal to 2, 3, 4, 4.5, 5, 5.5 and 6 cm respectively. It is found that the optimum distance between the ion exit aperture of the cathode and the ion collector plate equals 5 cm for high output ion beam current. At this optimum distance, the efficiency of the ion source reaches 28.3% and 21.3% using nitrogen and argon gases respectively. The divergence angle of the ion beam exit from the cathode aperture has been determined for each distance by measuring the ion beam diameter which obtained on the ion collector plate. It is found that at the optimum distance between the ion exit aperture of the cathode and the ion collector plate, a minimum divergence angle of the ion beam emerging from the ion source equal to 1.14º and 2.29º using nitrogen and argon gases respectively. Also the aspect ratio of the ion source, the ratio between the radius of the ion exit aperture of the cathode to the distance between the ion exit aperture of the cathode and ion collector plate, has been determined.

Analysis of Correcting Ability of Ion Beam Figuring

In ion beam figuring process, typically, the smaller ion beam diameter has a good ability to “correct” the optical surface error, i.e. the smaller ion beam diameter indicates the higher material removal efficiency ε. The material removal efficiency is defined as the ratio of the volume of desired material removal to that of the real material removal. However the smaller ion beam diameter always results in more processing time, which usually decreases the process reliability. In this paper, the relationship between the material removal efficiency and the ion beam diameter is analyzed. The theoretical result shows that the material removal efficiency is a negative exponential function of the ratio of ion beam diameter to the spatial error wavelength, (i.e. d/λ). And when d/λ= 0.5, the material removal efficiency is 87%, which is acceptable in ion beam figuring process. When d/λ = 1, it rapidly decreases to 58%, which is unacceptable. According to theoretical analysis and simulation results, we recommend that d/λ should be less than 0.5 in order to obtain acceptable material removal efficiency in ion beam figuring process.

FIB-milling of photonic structures and sputtering simulation

Focused ion beam milling is used first to sputter simple geometric structures to investigate sputter depth dependence on parameters like ion fluence, beam diameter, and scanning strategy and second to structure photonic crystal etching masks and Fresnel micro-lenses in various materials. Computer simulation of specific scanning strategies is performed to achieve the highest possible precision with respect to the initial design and to obtain controllable and reproducible milling processes.

Deglacial sea surface temperatures of the western tropical Pacific: A new look at old coral

Using Secondary Ion Mass Spectrometry (SIMS) ion microprobe techniques, we generated annual Sr/Ca cycles with subweekly resolution from chunks of Porites coral retrieved from a Tahiti barrier reef drill core (149°W, 17°S), representing the period 13,650 to 13,100 years B.P. The centers of pristine skeletal septa were selectively targeted with a 10 μm diameter ion beam spot, avoiding adjacent pore spaces occupied by secondary aragonite needles. Applying a Sr/Ca–sea surface temperature (SST) calibration equation derived from modern Tahiti Porites having the same low growth rate as the fossil specimens, we obtained SSTs ∼0.5°–1.5°C cooler during the Bølling‐Allerod relative to the present day, with no significant change in seasonality. On the contrary, we estimate that analysis of bulk samples would yield excessively cool Sr/Ca‐based SST estimates due to the occupation by secondary aragonite crystals of up to 50% of the skeletal pore space in the ancient samples. We find that growth rate effects on coral Sr/Ca further depress the apparent mean annual derived SSTs (by >3°C) and amplify the apparent seasonality by selectively enhancing wintertime cooling. Our microscale analysis of pristine skeleton and application of an appropriate growth‐dependent calibration yield Sr/Ca‐derived SSTs that are in good agreement with those derived from Mg/Ca ratios of calcitic foraminifera which indicate a continuous postglacial warming of the western tropical Pacific, in phase with the warming of the tropical Atlantic.

White electroluminescent nanostructures in silicon fabricated using focused ion implantation

The use of an accelerator fed microbeam as an implanter enables highest flexibility in doping substrates. Dopant, implantation dose, and pattern can be chosen individually and adopted to sequentially implanted structures. On the other hand, high throughput of arbitrarily shaped and identically doped samples, as needed in semiconductor device fabrication, can be achieved in conjunction with the Bochum Ion Projector. This machine is capable of focusing an ion beam down to 300 nm and allows both, prototyping and small series production of devices without the need of a coating mask on the substrate surface. We report on a method for producing nanoscale white light emitting structures by focused ion beam implantation in crystalline silicon. Focused ion beam implantation of acceptor ions into n-type doped Si yields lateral npn-junctions. These junctions emit light from their nanoscale depletion zones if operated in (reverse biased) breakdown mode, depending on voltage polarity on either side of the implanted area. The actual ion beam diameter is not a limiting factor for the submicron width light sources because radiation originates only from depletion zones with lateral sizes in the order of 100 nm. Compatibility with standard silicon processing allows monolithic integration of such light sources in conventional circuit designs. Their emission spectrum covers the whole visible range without showing sharp peaks. However, three distinct maxima can be observed. Their positions and relative heights slightly vary with implantation dose and applied voltage.

Ion microprobe U–Pb dating of hydrothermal xenotime from an episyenite: evidence for rift-related reactivation

Hydrothermally intergrown xenotime–monazite from an episyenite in the Bohus granite, southwest Sweden, has been analyzed in situ by ion microprobe. Although the analysed xenotime crystals are extremely small, sometimes less than the ion beam diameter (∼17 μm), they retain relatively undisturbed U–Pb systems, which yielded a 206Pb/ 238U age of 252±8 Ma. The evolution of this episyenite involved an initial stage of quartz dissolution accompanied by albitization, followed by a second stage of vug-infilling and replacement of igneous Fe–Ti phases. The obtained age shows that the second alteration stage, during which xenotime was precipitated, was coeval with the thermal anomaly associated with Permo-Carboniferous crustal thinning and the development of the nearby Oslo Rift. Moreover, the development of the permeable episyenite structure must be ascribed to a preceding high-temperature event, most likely the post-magmatic cooling of the host granite at 920 Ma. This study shows that U–Pb dating of young xenotimes may address geochronological problems, though further work is required to characterize possible matrix effects which presently limit the accuracy of the method.

Simple cylindrical ion mirror with three elements

A new cylindrical ion mirror has been designed to create an electric field that is non-linear or curved along the flight path axis for general-purpose time-of-flight mass spectrometers. The inclusion of one or two grids is found to improve the radial field homogeneity especially around the aperture. Only three cylindrical electrodes are used in the design. Changing the electrode dimensions and voltages affects the electric field distribution. Once the electrode dimensions are fixed, there are only two adjustable parameters for achieving optimum nonlinear electric field shape. Resolving powers of 7000 and 16 100 have been achieved with kinetic energy variations of 34 and 10.5%, respectively. Simulations show that the electric field homogeneity in the radial direction enables the use of ion beam diameters up to 15 mm with only modest loss of resolving power. Increasing the mirror diameter could further increase the practical ion beam diameter. This article details the electric field distribution within the cylindrical mirror in both axial and radial directions. The voltages of the middle and rear electrodes affect the resolving power and the kinetic energy range over which focus can be achieved. The predicted arrival time spread for a single m/z value is narrower than that caused by the turn-around time of ions in a gas-phase ion source. In this case, the broad energy range over which good focus is achieved enables the use of higher extraction fields for turn-around time reduction.

Field emitter array fabricated using focused ion and electron beam induced reaction

A dual beam system consisting of focused ion and electron beams was used for manufacturing of Nb-gated silicon field emitter arrays. Gate opening was produced either by reactive focused ion beam etching of both the niobium and the silicon dioxide layer or by physical sputtering of the niobium layer by focused ion beam and subsequent wet etching of the underlying silicon dioxide layer. Platinum tips were deposited into the gate opening using an electron beam induced chemical reaction. Prototype devices, which exhibit field emission, were produced successfully. Several process parameters such as ion dose, beam diameter, and etch duration were systematically varied to identify the optimum condition for the fabrication of field emitter arrays.

A source of broad homogeneous beams of low-energy (∼0.5 keV) gas ions

A source of gas ions (argon, oxygen, nitrogen, etc.), the operating principle of which is based on the use of a glow discharge in an electrode system of a wide-aperture hollow cathode and anode in a magnetic field, is described. The exit aperture diameter of the hollow cathode, increased up to a size close to the ion beam diameter (10 cm), ensures the uniform ion emission of the plasma generated in the discharge region near the anode. A decreased angular divergence or increased ultimate ion-beam current density is achieved by a change in the potential drop in the space charge sheath between the plasma and the ion optics. The source generates broad (50 cm2) slightly diverging (ω/2∼3°–5°) ion beams with energies of 300–1000 eV at a beam current density of ∼0.5 mA/cm2.

Characteristics of NdBa2Cu3O7-δ Josephson Junctions Fabricated by Deca-Nanoscale Focused Ion Beam

Grain boundary Josephson junctions were fabricated on microgrooves formed by a focused ion beam (FIB) system with a nominal ion beam diameter of 10 nm. Among the 40 junctions fabricated under the constant condition, 29 working junctions exhibit resistively-shunted-junction-type current–voltage characteristics and follow empirical scale rule of linear relation between IcRn and Ic1/2. For Rn, the distribution is Gaussian-type and 1σ is estimated to be 40%. On the other hand, Ic is distributed with three peaks and 1σ is estimated to be 60%. The peak separation in the Ic distribution indicates the existence of different types of grain boundaries, corresponding to three kinds of tilting angles with lattice matches.

The Tomographic Atom Probe: A New Dimension In Material Analysis

Abstract Today material science requires the use of increasingly powerful tools in material analysis. The last twenty years have witnessed the development of a number of analytical techniques. However, among these techniques, only a few allow observation and analysis of materials at the nanometer level ; one can mention scanning transmission electron microscopy coupled with electron energy loss spectrometry (STEM-EELS), SIMS and atom-probe techniques. In the STEM combined with electron energy loss spectrometry the spatial resolution can be better than one nanometer on a wide scanning area. However the in-depth spatial resolution is limited by the specimen thickness and therefore strongly depends on samples preparation. On the contrary, In SIMS techniques the in-depth spatial resolution can be as good as one nanometer but the lateral resolution is set by the ion beam diameter.

Focused Ion Beam Milling for Site Specific Scanning and Transmission Electron Microscopy Specimen Preparation

It has been shown that a focused ion beam (FIB) instrument may be used to prepare site specific cross-sectioned specimens to within < 0.1 μm for both scanning and transmission electron microscopy (SEM and TEM, respectively). FIB specimen preparation has been used almost exclusively in the microelectronics industry. Recently, FIB specimen preparation has been utilized for other materials systems and applications.A cross-sectioned SEM specimen is produced by sputtering away a trench of material from near the region of interest. Large amounts of material are sputtered using large ion beam diameters (e.g., l00’s nm) and high beam current (e.g., l000’s pA), while the final sputtering operations are achieved using smaller beam diameters (e.g., < 10 nm) and lower beam current (e.g., 10’s of pA). The SEM specimen may then be etched to reveal particular microstructural features of interest. A low magnification SEM image of a multi-layered device prepared for cross-section analysis by the FIB method is shown in FIG. 1.

Design and Fabrication of DC Ion Beam for Heating of Plasma

DC type ion beam is produced by using different percentages of argon gas content. In this manner, about 90% of argon gas was ionized, and the ion beam diameter is controllable by the extractor in 10−3torr. The density of charged particles was measured by Faraday cup. In this paper, some recent findings are presented dealing with the analysis of the production of ion beam with different energy levels. Result of measurements compare with that of other sources.

A broad beam cold cathode Penning ionization gauge ion source for ion-beam-assisted deposition

A broad beam cold cathode Penning ionization gauge ion source is developed for ion-beam-assisted deposition. The ion source is composed of several modules and it is 88 mm in diameter and 80 mm in height without any cooling system. The discharge voltage is 500 V. The multiaperture extracted ion beam diameter at the exit is 35 mm. It can be operated dc in oxygen, argon, nitrogen, and other gases. The ion energy can be adjusted from 50 to 1500 eV and the maximum extraction current density is above 200 μA/cm2. The extracted ion beam is matched to the arched rack in different vacuum coaters. Due to the small volume of the ion source, single or multiple sources can be installed according to the volume of the coaters.