Surface Sputtering Research Articles

Analytical criteria for controlling glow-discharge nitriding

A system of analytical characteristics is proposed to estimate the results of glow-discharge nitriding using the energy concepts of this process. The following parallel subprocesses, which form a modified surface layer, are taken into account: the formation of nitride structures, the diffusion of nitrogen deep into a metal, and surface sputtering.

Fluence dependent changes of erosion yields and surface morphology of the iron-tungsten model system: SDTrimSP-2D simulation studies

The effect of different sample structures of an iron-tungsten model system (as a surrogate for reduced activation ferritic martensitic steels like EUROFER) on the development of surface morphologies, tungsten surface enrichment and sputter yields under low-energy monoenergetic perpendicular 200 eV deuterium bombardment has been studied with SDTrimSP-2d simulations. Previous modeling studies considering diffusive effects also could reasonably reproduce and explain the experimental results for a large set of experimental parameters like temperature, flux and sample concentration. However, for settings with negligible Fe-W-interdiffusion the fluence needed for steady-state conditions differed between the experiments and the simulations. Thus, the main focus of the present study is directed towards the elucidation of this fluence mismatch. Comparison of one and two-dimensional simulation results reveal a strong dependency of the tungsten enrichment on the sample homogeneity and a significantly delayed reduction of the erosion yield due to a pronounced formation of surface structures from initially flat sample surfaces.

Analytic method for sputtering yield calculation in nanoislands

A theoretical approach based on the well-known work of Sigmund to explain the sputtering of surfaces covered with nanoclusters is developed. Predictions of this approach are compared with molecular dynamics results of bombardment of a periodical array of Co nanoislands deposited on a Cu(001) substrate with 1-keV argon ions. Sputtering yield is analyzed distinguishing among particles leaving the target across the nanoisland surface and across the flat substrate surface without nanoparticle above, and the sum of both. Results consider the dependence on two factors: the spacing among nanoislands and the nanoisland height.

Electrochemical Impedance Spectroscopy study in micro-grain structured amorphous silicon anodes for lithium-ion batteries

Abstract In this paper, a study of the lithiation mechanism of micro-grain structured silicon anode is presented. Micro-grain amorphous silicon was deposited on special copper foil and it is shown that after several decades of galvanostatic cycles, it preserves its granular nature with minor degradation. In order to shed light on the lithiation mechanisms of the micro-grain silicon, Electrochemical Impedance Spectroscopy (EIS) was conducted on silicon half-cells at various State-of-Charge (SoC) and various discharging current values and the Solid-Electrolyte Interphase (SEI) R SEI and polarization resistance R pol were determined. Results reveal that R pol highly increases for cell voltages lower than 0.2 V and it strongly depends on the discharging C-rate. From X-ray Photoelectron Spectroscopy (XPS) measurements combined with surface sputtering, the existence of a Li x Si y O z interlayer between SEI and silicon is confirmed, which is believed to play an important role to the lithium kinetics. Finally, combining our results, a lithiation mechanism of the micro-grain silicon anode is proposed.

Surface biasing influence on the physical sputtering in fusion devices

A new simplified analytical expression for the electromagnetic field in the Debye sheath in the presence of an oblique magnetic field including surface biasing effect is suggested. It is in good agreement with the numerical solution of the integral equation for the potential distribution in the Debye sheath. The energy and angular impact distributions and corresponding surface sputtering yields were analyzed in the presence of an oblique magnetic field and surface biasing. The analytical expression was used to estimate a) the effective sputtering yield of the W target with a varying negative voltage against plasma in PSI-2 linear device and b) erosion of the JET outer wall Be limiter near the ICRH antenna enhanced during RF emission.

Spectroscopic and microstructural characterization of 18 MeV He+ ions irradiated pure Al

This study reports the spectroscopic and microstructural characterization of helium (He+) ions irradiated pure Aluminum (Al) (99.99%). The specimens of Al were irradiated by 18MeV helium (He+) ions in the fluence range of 1×1013 ions/cm2 − 1×1016 ions/cm2 at 300K under vacuum conditions using Cyclotron accelerator. The Field emission scanning electron microscope (FESEM) analysis reveals the generation and growth of cavities, micro size pits, voids and incoherent structures at various irradiation fluences, due to melting, re-deposition and exfoliational sputtering of the irradiated surface. The X-ray diffractometer (XRD) results depicted significant variations in diffraction peaks intensities, peak shifting and broadening that became more pronounced with an increase of the irradiation fluence, whereas, anomalous behavior in crystallite size and lattice strain is observed after irradiation. These structural changes are related to the accumulation of irradiation induced stresses inside the lattice structure.

Diamond-like carbon and nanocrystalline diamond film surfaces sputtered by argon cluster ion beams

Conventional (monoatomic) ion beam sputtering of solid surfaces is currently used for surface cleaning and concentration depth profiling. Due to ion-surface interactions, however, a modified near-surface layer arises, characterized with the changed composition and chemical bonding. As a consequence, this complicates data interpretation. A lot of efforts have been devoted to eliminate the problem. Now, the most promising method seems to be application of multi atomic or molecular ion beams.In the present contribution we examine the influence of argon cluster ion beam on composition and chemical bonding of diamond-like carbon (DLC) and nanocrystalline diamond (NCD) film surfaces by using high-energy resolution core-level photoelectron spectroscopy (XPS). Particularly, peak widths and hybridization of carbon atoms is evaluated from C 1s lines. The extent of bonding transformation from C sp3 to C sp2 depended on average energy per Ar atom in the clusters. For the energy as low as a few eV per Ar atom the modification is mild. Prime novelty statementThe novelty of the presented research is the examination of the interaction between Argon cluster ion beam with DLC and NCD surfaces via high-energy resolved C 1s photoelectron spectra. Our results show that bonding transformation from C sp3 to C sp2 due to Ar cluster ion beam sputtering was found mild, if the average argon atom energy in clusters is comparable to the bond strength of the surface target atoms.

Temperature and layer thickness dependent in situ investigations on epindolidione organic thin-film transistors

We report on in situ performance evaluations as a function of layer thickness and substrate temperature for bottom-gate, bottom-gold contact epindolidione organic thin-film transistors on various gate dielectrics. Experiments were carried out under ultra-high vacuum conditions, enabling quasi-simultaneous electrical and surface analysis. Auger electron spectroscopy and thermal desorption spectroscopy (TDS) were applied to characterize the quality of the substrate surface and the thermal stability of the organic films. Ex situ atomic force microscopy (AFM) was used to gain additional information on the layer formation and surface morphology of the hydrogen-bonded organic pigment. The examined gate dielectrics included SiO2, in its untreated and sputtered forms, as well as the spin-coated organic capping layers poly(vinyl-cinnamate) (PVCi) and poly((±)endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, diphenylester) (PNDPE, from the class of polynorbornenes). TDS and AFM revealed Volmer-Weber island growth dominated film formation with no evidence of a subjacent wetting layer. This growth mode is responsible for the comparably high coverage required for transistor behavior at 90–95% of a monolayer composed of standing molecules. Surface sputtering and an increased sample temperature during epindolidione deposition augmented the surface diffusion of adsorbing molecules and therefore led to a lower number of better-ordered islands. Consequently, while the onset of charge transport was delayed, higher saturation mobility was obtained. The highest, bottom-contact configuration, mobilities of approximately 2.5×10−3cm2/Vs were found for high coverages (50nm) on sputtered samples. The coverage dependence of the mobility showed very different characteristics for the different gate dielectrics, while the change of the threshold voltage with coverage was approximately the same for all systems. An apparent decrease of the mobility with increasing coverage on the less polar PNDPE was attributed to a change in molecular orientation from upright standing in the thin-film phase to tilted in the bulk phase. From temperature-dependent mobility measurements we calculated activation barriers for the charge transport between 110meV and 160meV, depending on the dielectric configuration.

Surface modification and sputtering erosion of reduced activation ferritic martensitic steel F82H exposed to low-energy, high flux deuterium plasma

Targets prepared from Reduced Activation Ferritic Martensitic (RAFM) steel F82H were exposed to low-energy (200eV) deuterium (D) plasma at various temperatures with highfluxes of about 1022 D/m2s to various fluences in the range from 1025 to 2.5×1026 D/m2. Under the plasma exposure, micro-structured layers are formed on the target surfaces, and the surface morphology is dependent on the exposure temperature. The erosion yield of the F82H samples increases by a factor of about two as the exposure temperature rises in the range from 403 to 773K.

Oscillations and huge preferences of PbTe crystal surface sputtering under Secondary Neutral Mass Spectrometry conditions

Sputtering of PbTe crystals by Ar+ plasma with ion energies 50–550eV is investigated. A dependence of sputter yields of the Te and Pb on the sputtering ion energy and sputtering time is measured. New phenomena: aperiodical oscillations of Pb and Te sputtering; a huge preference of Te sputtering reaching more than two orders of magnitude at the beginning of sputtering process; and a significant excess of Te integrated sputter yield over that of Pb for prolonged sputtering by low energy plasma at 50–160eV, are observed. It is substantiated that these phenomena can be caused by the peculiarities of the charge states of the interstitial Pb and Te in PbTe crystal matrix and the processes of re-deposition of sputtered atoms on the sputtered surface.

Influence of surface corrugation on the sputtering of carbon materials under high-fluence ion bombardment

The results of experimental and computer-based studies of the sputtering and erosion of carbonmaterial surfaces under high-fluence irradiation with 30-keV Ar+ ions at various angles of ion incidence are given. The irradiation of highly oriented pyrolytic graphite (HOPG) and polyacrylonitrile fibers of carbon–carbon composites, which are characterized by surface corrugation, is considered. A model is proposed for taking into account the influence of parameters of symmetric corrugation on the characteristics of sputtering of the irradiated materials. Calculation shows that taking experimental values of the corrugation slopes into account allows one to explain the angular dependence of the sputtering yield of HOPG. It is found that the pronounced (about two times) suppression of sputtering within the range of incidence angles of 60°–80° is connected with the rear (relative to the ion beam) faces of the corrugation being obscured. Unlike the case of the normal incidence of ions, the sputtering yield at large incidence angles decreases as the corrugation period increases due to blocking of the sputtering of the rear and neighboring faces of microrelief elements.

An Effective Approach to Improving Cadmium Telluride (111)A Surface by Molecular-Beam-Epitaxy Growth of Tellurium Monolayer.

The surface cleansing treatment of non-natural cleavage planes of semiconductors is usually performed in vacuum using ion sputtering and subsequent annealing. In this Research Article, we report on the evolution of surface atomic structure caused by different ways of surface treatment as monitored by in situ core-level photoemission measurements of Cd-4d and Te-4d atomic levels and reflection high-energy electron diffraction (RHEED). Sputtering of surface increases the density of the dangling bonds by 50%. This feature and the less than ideal ordering can be detrimental to device applications. An effective approach is employed to improve the quality of this surface. One monolayer (ML) of Te grown by the method of molecular beam epitaxy (MBE) on the target surface with heating at 300 °C effectively improves the surface quality as evidenced by the improved sharpness of RHEED pattern and a reduced diffuse background in the spectra measured by high-resolution ultraviolet photoemission spectroscopy (HRUPS). Calculations have been performed for various atomic geometries by employing first-principles geometry optimization. In conjunction with an analysis of the core level component intensities in terms the layer-attenuation model, we propose a "vacancy site" model of the modified 1 ML-Te/CdTe(111)A (2 × 2) surface.

Synthesis of porous silicon with silver nanoparticles by low-energy ion implantation

In this paper, a new technique is proposed for synthesis of porous silicon (PSi) layers with silver nanoparticles based on the method of low-energy high-dose metal ion implantation into Si. In order to demonstrate this technique, the implantation at room temperature of a polished Si wafer by Ag+ ions with the ion energy of 30 keV, ion dose of 1.5 × 1017 ion/cm2, and ion current density of 8 µA/cm2 is carried out. Using methods of high resolution scanning electron and atomic-force microscopy, electron probe microanalysis, and Raman scattering, it is shown that ion implantation results in the formation, on the surface of irradiated Si, of a thin amorphous layer of PSi with the average pore size of 150–180 nm, a pore depth of about 100 nm, and wall thickness between pores of about 30–60 nm. Moreover, the PSi structure contains Ag nanoparticles 5–15 nm in size. It is established that, during the ion implantation, the sputtering of the Si surface by Ag+ ions takes place, which was not observed previously. Based on the data obtained, it is concluded that, in contrast to chemical techniques, the proposed physical technique for PSi formation can be integrated into the modern advanced process of fabricating and improving electronic circuits based on industrial ion implantation.

Nanopore formation in TiN membranes by the focused electron beam of a transmission electron microscope

The authors fabricated 2-nm nanopores in metallic TiN membranes with and without a SiNx layer using the highly focused electron beam (e-beam) of a transmission electron microscope. Nanopore evolution in TiN membranes was observed as a function of e-beam exposure time at e-beam energies of 200 and 300 kV. To investigate the mechanism of nanopore drilling in TiN membranes, plots of nanopore diameter against exposure time were converted to characteristic contrast curves of normalized drilling volume versus electron dose. The curves indicated that nanopore drilling in TiN metallic membranes using a high-energy focused e-beam is governed by direct atomic displacement or surface sputtering by elastic scattering between electrons and stationary atoms. The sputtering energy of TiN is about 9 eV.

비정질 및 단결정 실리콘에서 10~50 keV 에너지로 주입된 안티몬 이온의 분포와 열적인 거동에 따른 연구

For the formation of N + doping, the antimony ions are mainly used for the fabrication of a BJT (bipolar junction transistor), CMOS (complementary metal oxide semiconductor), FET (field effect transistor) and BiCMOS (bipolar and complementary metal oxide semiconductor) process integration. Antimony is a heavy element and has relatively a low diffusion coefficient in silicon. Therefore, antimony is preferred as a candidate of ultra shallow junction for n type doping instead of arsenic implantation. Three-dimensional (3D) profiles of antimony are also compared one another from different tilt angles and incident energies under same dimensional conditions. The diffusion effect of antimony showed ORD (oxygen retarded diffusion) after thermal oxidation process. The interfacial effect of a SiO2/Si is influenced antimony diffusion and showed segregation effects during the oxidation process. The surface sputtering effect of antimony must be considered due to its heavy mass in the case of low energy and high dose conditions. The range of antimony implanted in amorphous and crystalline silicon are compared each other and its data and profiles also showed and explained after thermal annealing under inert N2 gas and dry oxidation.

Reconsideration of metal surface sputtering due to bombardment of high-energy argon ion particles: a molecular dynamics study

Some interesting aspects of metal surface sputtering phenomenon are numerically investigated in this work using the molecular dynamics approach. Along with that, we have carried out a critical analysis of the interaction potentials typically used for modeling. Two metallic surfaces, viz., copper, Cu(100), and nickel, Ni(100), are chosen for study that are bombarded by argon ions at various energies and angles of projection. The sputtering yield is calculated by performing molecular dynamics simulations, and the same is compared with experiments and theoretical predictions wherever possible. Furthermore, other interesting parameters like the kinetic energy, velocity, and scattering angle distribution for sputtered and incident atoms are presented and discussed. Through different case studies, the present work emphasizes on the importance of interaction model used for metal surface modeling for a realistic numerical reproduction of the complex metal surface sputtering process.

Application of Analytical Model of the Electric Potential Distribution for Calculation of Charged Particle Dynamics in a Near-Wall Layer and Sputtering of the Plasma Facing Surfaces

Simple analytical formulas are derived for calculation of the electric field potential distribution in the magnetic pre-layer and the Debye layer near the plasma facing surfaces. It is shown that the calculated potential profiles are in good agreement with the dependences of the potential distribution on the magnetic field inclination obtained by solving the magnetic hydrodynamic (MHD) equations and modeling using the PIC code SPICE2. Dependences of the angular distribution of ions incident on the surface of plasma facing elements on the magnetic field inclination are obtained. Results of calculations demonstrate that the surface areas, on which the magnetic field is incident at sliding angles, are critical from the viewpoint of the increase of sputtering.

Modeling of sputtering of the ice surfaces under impact of H+ ions: Redistribution of the h and o isotopes applied to the satellites of Jupiter

Using computer modeling, the current models for sputtering coefficient calculation of the ice surfaces under the impact of H+ ions are statistically analyzed and the sputtering coefficients and their confidence intervals are calculated over a wide range of ion energies. It was established that the approximation model (Fama et al., 2008) with a calculated confidence interval of ±20% is less sensitive to the variable parameters. The sputtering coefficients of water ice p = 0.94, T = 80 K) are calculated under the impact of H+ ions for energies from several eV to 10 keV and the results are verified with experimental data. The maximum sputtering coefficient is 0.9 H2O/ion at the energy of the incident H+ ions of 200 eV. The modeling of the sputtering coefficients dependence of H2O molecules from the ice surface temperature showed that they weakly vary in the temperature range of 40–100 K and increase with an increase in the surface temperature. At maximum of distribution under T = 40–100 K, the sputtering coefficient Y(E = 200 eV) is 0.9 H2O/ion at T = 200 K — 1.1 H2O/ion. The distribution by kinetic energy of the dispersed H2O molecules and H and O atoms are modeled for the energy of 1–100 keV of the incident H+ ions. These results may be applied for modeling of variable isotopic compositions of the exosphere of the Jupiter’s satellites in the course of sputtering. The calculated ratios of the sputtering coefficients of H, D, 18O, and 16O from the surface for the Jupiter’s satellites (Europe, Ganymede, Callisto) under the impact of H+ ions for energy from several eV to 10 keV are (1.7 ± 0.3) × 10−5 and 0.18 ± 0.03, respectively. These ratios are distinct from the initial isotope ratios on the surface of the Jupiter’s satellites. This significant difference may lead to the redistribution of isotopes on the surface of the Jupiter’s satellites. The variation in the D/H ratio on the surface of the Jupiter’s satellites depends on the flux density of the radiated ions.

Nanostructured fuzz growth on tungsten under low-energy and high-flux He irradiation.

We report the formation of wave-like structures and nanostructured fuzzes in the polycrystalline tungsten (W) irradiated with high-flux and low-energy helium (He) ions. From conductive atomic force microscope measurements, we have simultaneously obtained the surface topography and current emission images of the irradiated W materials. Our measurements show that He-enriched and nanostructured strips are formed in W crystal grains when they are exposed to low-energy and high-flux He ions at a temperature of 1400 K. The experimental measurements are confirmed by theoretical calculations, where He atoms in W crystal grains are found to cluster in a close-packed arrangement between {101} planes and form He-enriched strips. The formations of wave-like structures and nanostructured fuzzes on the W surface can be attributed to the surface sputtering and swelling of He-enriched strips, respectively.

Self‐consistent multifluid MHD simulations of Europa's exospheric interaction with Jupiter's magnetosphere

AbstractThe Jovian moon, Europa, hosts a thin neutral gas atmosphere, which is tightly coupled to Jupiter's magnetosphere. Magnetospheric ions impacting the surface sputter off neutral atoms, which, upon ionization, carry currents that modify the magnetic field around the moon. The magnetic field in the plasma is also affected by Europa's induced magnetic field. In this paper we investigate the environment of Europa using our multifluid MHD model and focus on the effects introduced by both the magnetospheric and the pickup ion populations. The model self‐consistently derives the electron temperature that governs the electron impact ionization process, which is the major source of ionization in this environment. The resulting magnetic field is compared to measurements performed by the Galileo magnetometer, the bulk properties of the modeled thermal plasma population is compared to the Galileo Plasma Subsystem observations, and the modeled surface precipitation fluxes are compared to Galileo Ultraviolet Spectrometer observations. The model shows good agreement with the measured magnetic field and reproduces the basic features of the plasma interaction observed at the moon for both the E4 and the E26 flybys of the Galileo spacecraft. The simulation also produces perturbations asymmetric about the flow direction that account for observed asymmetries.