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We created a unique sodium ion battery (NIB, SIB) cathode based on selenium in cellulose-derived carbon nanosheets (CCNs), termed Se-CCN. The elastically compliant two-dimensional CCN host incorporates a high mass loading of amorphous Se (53 wt%), which is primarily impregnated into 1 cm3 g−1 nanopores. The results in facile sodiation kinetics due to short solid-state diffusion distances and a large charge transfer area of the nanosheets were established. The architecture also leads to an intrinsic resistance to polyselenide shuttle and to disintegration/coarsening. As a Na half-cell, the Se-CCN cathode delivers a reversible capacity of 613 mA h g−1 with 88% retention over 500 cycles. The exceptional stability is achieved by using a standard electrolyte (1 M NaClO4 EC-DMC) without secondary additives or high salt concentrations. The rate capability is also superb, achieving 300 mA h g−1 at 10C. Compared to recent state-of-the-art literature, the Se-CCN is the most cyclically stable and offers the highest rate performance. As a Se–Na battery, the system achieves 992 W h kg−1 at 68 W kg−1 and 384 W h kg−1 at 10144 W kg−1 (by active mass in a cathode). We are the first to fabricate and test a Se-based full NIB, which is based on Se-CCN coupled to a Na intercalating pseudographitic carbon (PGC) anode. It is demonstrated that the PGC anode increases its structural order in addition to dilating as a result of Na intercalation at voltages below 0.2 V vs. Na/Na+. The {110} Na reflections are distinctly absent from the XRD patterns of PGC sodiated down to 0.001 V, indicating that the Na metal pore filling is not significant for pseudographitic carbons. The battery delivers highly promising Ragone chart characteristics, for example yielding 203 and 50 W h kg−1 at 70 and 14000 W kg−1 (via total material mass in the anode and cathode).

Here we investigate the oxygen reduction reaction electrocatalytic activity and the corrosion stability of several ternary Pt–Au–Co and Pt–Ir–Co alloys, with Pt–Au–Co having never been previously studied for ORR. The addition of Au fine tunes the lattice parameter and the surface electronic structure to enable activity and cycling stability that is unachievable in Pt–25 atom % Co (state-of-the-art binary baseline). The ternary alloys exhibit a volcano-type dependence of catalytic efficacy on the content of Au or Ir. Pt–2.5 atom % Au–25 atom % Co alloy shows a specific activity of 1.41 mA cm–2 at 0.95 V, which is 16% and 404% higher than those of identically synthesized Pt–Co and pure Pt, respectively. This enhancement is promising in comparison to a range of previously published Pt “skeleton” and Pt “skin” alloys and is in fact the most optimum reported for a skeleton-type system. The catalysts exhibit dramatically improved corrosion stability with increasing levels of Au or Ir substitution, with the spec...

A key advancement target for oxygen reduction reaction catalysts is to simultaneously improve both the electrochemical activity and durability. To this end, the efficacy of a new highly conductive support that comprises of a 0.5 nm titanium oxynitride film coated by atomic layer deposition onto an array of carbon nanotubes has been investigated. Support effects for pure platinum and for a platinum (50 at %)/nickel alloy have been considered. Oxynitride induces a downshift in the d-band center for pure platinum and fundamentally changes the platinum particle size and spatial distribution. This results in major enhancements in activity and corrosion stability relative to an identically synthesized catalyst without the interlayer. Conversely, oxynitride has a minimal effect on the electronic structure and microstructure, and therefore, on the catalytic performance of platinum-nickel. Calculations based on density functional theory add insight with regard to compositional segregation that occurs at the alloy catalyst-support interface.

Nearly monodispersed 1.6 nm Ir, 2.3 nm Pd nanoparticles, 2.7 nm Pd(core)–Ir(shell) and 2.2 nm Pd–Ir alloys with mixed surface atoms were synthesised in the presence of polyvinylpyrrolidone (PVP) and studied in the atmospheric ring opening of indan. The nanoparticles and supported catalysts were characterised by UV–vis spectroscopy, TGA, TEM, EDX, TPR, XPS, ISS and XANES. The nanoparticle size and structure control allowed insights into the bimetallic catalyst functioning. As soon as two contiguous surface Ir atoms exist on the nanoparticle surface, they display the same catalytic properties, most likely through the dicarbene ring-opening mechanism. Palladium serves only as a dispersing agent in Pd(core)–Ir(shell) structures providing 100% Ir dispersion, or as an inert surface diluting metal in Pd–Ir formulations with mixed nanoparticle surface. The Pd–Ir core–shell structure allows maximum selective ring-opening yield, which is 19% higher than that for the industrial Pt–Ir catalyst.

Selective ring opening of naphthenic molecules in oil upgrading should result in no loss in molecular weight. Benzocyclopentane (indan) ring opening was studied under hydrogen atmospheric pressure at 609 K over poly-(vinylpyrrolidone)-stabilized Ru, Ir and Pd monometallic and Ru–Ir and Ru–Pd bimetallic nanocatalysts prepared by simultaneous reductions. The particle size (mostly within 2 nm) and their monodispersity were confirmed by transmission electron microscopy, while X-ray photoelectron spectroscopy indicated the bimetallics' alloy structure. Pd catalysts displayed the lowest activity in the ring opening; Ru showed the highest formation of undesired o-xylene and lights. Monometallic Ir displayed the highest activity and selectivity toward 2-ethyltoluene and n-propylbenzene. In bimetallic structures, higher Ir content led to improved catalytic performance. Next to the monometallic Ir catalyst, the newly developed Ru1Ir4/γ-Al2O3 catalyst (with 1 : 4 molar ratio of Ru to Ir) displayed superior single cleavage selectivity as well as lower cracking activity compared to industrial Pt–Ir catalysts at a comparable indan conversion. The study can pave the way in the development of Pt-free Ru-containing catalysts with narrow size distributions for selective ring opening, especially taking into consideration a possibility of their higher S-resistance as compared to the Pt catalysts.

We employed a polypyrrole hydrogel precursor to create a carbon framework that possesses both huge heteroatom content (13 wt% nitrogen and 11 wt% oxygen) and high surface area (945 m 2 g −1 ) that is equally divided between micropores and mesopores. A sodium ion capacitor (NIC, HIC) electrode fabricated from this N and O Functionalized Carbon (NOFC) has tremendous reversible capacity and rate capability, e.g. 437 mA h g −1 at 100 mA g −1 , and 185 mA h g −1 at 1600 mA g −1 . This is among the most favorable reported, and is due to copious nanoporosity that enables fast ion sorption at the many N and O moieties and graphene defects. The NOFC imbues a NIC device with energy–power characteristics that are not only state-of-the-art for Na hybrids, but also rival Li systems: Ragone chart placement is 111 W h kg −1 and 38 W h kg −1 at 67 W kg −1 and 14,550 W kg −1 , respectively, with 90% capacity retention at over 5000 charge/discharge cycles.

The adsorption of xanthate on pyrite has been extensively studied. However, the adsorption mechanisms remain a subject of controversy. Formation of both dixanthogen and metal-xanthate complexes has been suggested. In this study, both room temperature X-ray photoelectron spectroscopy (XPS) (RT-XPS) and liquid nitrogen temperature XPS (Cryo-XPS) were used to study interactions between pyrite and xanthate. While dixanthogen was not detected by RT-XPS, it was successfully identified through C1s and S 2p peaks using Cryo-XPS. The impact of pH and copper activation on adsorption of xanthate on pyrite was also investigated. It was found that at low pH, dixanthogen is the dominant species of xanthate adsorption on pyrite. At high pH, metal-xanthate complexes were found to be prevalent on pyrite surfaces, which are responsible for the surface hydrophobicity. Copper activation showed a significant effect on xanthate adsorption on Cu-activated pyrite, resulting in mostly the formation of Cu-xanthate complexes rather than dixanthogen, mainly in the form of Cu(I)-isopropyl xanthate complex (CuIPX). Copyright © 2012 John Wiley & Sons, Ltd.

Depth profiling of NbxO/W multilayered samples was carried out using O2+, Cs+ or Ar+ beams of different energies (2 keV, 1 keV and 0.5 keV). The obtained depth profiles showed that sputtering with O2+ or Ar+ beams can reveal the distribution of light elements, while sputtering with Cs+ cannot show correctly their distribution if lower energy of 0.5 keV is applied. SRIM simulations show that changes in primary energy of sputter ions have much stronger effect on deposited energy incl. vacancy/ion and sputter yields than for oxygen and argon ion beam etching. It is suggested that O2+ or Ar+ sputter sources should be used when both light and heavy species are present in nano-scale multilayered targets. Copyright © 2012 John Wiley & Sons, Ltd.

We created a unique SnO 2 –Graphene Dual Aerogel (SnO 2 /GDA) nanocomposite with exquisite lithium and sodium ion battery anode performance (LIB, NIB NAB SIB). In parallel we employed electrochemical methods to be the first to analyze the transition from kinetic control to diffusion control for the conversion reaction (SnO 2 +4Li + +4e − ↔Sn+2Li 2 O) vs. for the alloying reaction (Sn+ x Li + + x e − ↔Li x Sn, x ≤4.4). The material displays a high reversible capacity (1299 mA h g −1 for Li at 0.1 A g −1 , 448 mA h g −1 for Na at 0.05 A g −1 ), very good cycling life (148% after 450 cycles for Li, 82% from 20 to 200 cycles for Na), and superb rate capacity retention (450 mA h g −1 for Li at 25 A g −1 , 184 mA h g −1 for Na at 1 Ag −1 ). In fact, these rate capabilities are among the most favorable reported in literature for each system.

We employed a glucose mediated hydrothermal self-assembly method to create a SnO2–carbon nanocomposite with promising electrochemical performance as both a sodium and a lithium ion battery anode (NIBs NABs SIBs, LIBs), being among the best in terms of cyclability and rate capability when tested against Na. In parallel we provide a systematic side-by-side comparison of the sodiation vs. lithiation phase transformations in nano SnO2. The high surface area (338 m2 g−1) electrode is named C–SnO2, and consists of a continuous Li and Na active carbon frame with internally imbedded sub-5 nm SnO2 crystallites of high mass loading (60 wt%). The frame imparts excellent electrical conductivity to the electrode, allows for rapid diffusion of Na and Li ions, and carries the sodiation/lithiation stresses while preventing cycling-induced agglomeration of the individual crystals. C–SnO2 employed as a NIB anode displays a reversible capacity of 531 mA h g−1 (at 0.08 A g−1) with 81% capacity retention after 200 cycles, while capacities of 240, 188 and 133 mA h g−1 are achieved at the much higher rates of 1.3, 2.6 and 5 A g−1. As a LIB anode C–SnO2 maintains a capacity of 1367 mA h g−1 (at 0.5 A g−1) after 400 cycles, and 420 mA h g−1 at 10 A g−1. Combined TEM, XRD and XPS prove that the much lower capacity of SnO2 as a NIB anode is due to the kinetic difficulty of the Na–Sn alloying reaction to reach the terminal Na15Sn4 intermetallic, whereas for Li–Sn the Li22Sn5 intermetallic is readily formed at 0.01 V. Rather, with applied voltage a significant portion of the material effectively shuffles between SnO2 and β-Sn + NaO2. The conversion reaction proceeds differently in the two systems: LiO2 is reduced directly to SnO2 and Li, whereas the NaO2 to SnO2 reaction proceeds through an intermediate SnO phase.

Ion reflection based on a two-target-atom model is considered. In this approximation simple estimates of the angular distribution for small sliding angles are obtained (with or without thermal vibrations of atoms). The energy spectra in this case are also discussed. [Russian Text Ignored].

This work is devoted to the secondary ion mass spectroscopic application in the studies of ink layering on paper. Optical methods are often unreliable in the identification of ink layering on substrates. We demonstrated the power of time-of-flight secondary ion mass spectroscopy (ToF-SIMS) by measuring the secondary ion mass spectra of handwriting on paper and assessing the characteristic ions for each colored ink. These ions were then used to collect images from overlapping handwritings. It was shown that the method could reliably determine which color was applied to the paper first. This work has potential applications in forensic studies.

Irradiation by ion beams, used alone or combined with electron beams/X-rays, is in the basis of most vacuum techniques for surface analysis of materials. The ion bombardment effects in solids are however still hard to predict and consequently the ion beam techniques are less quantitative than others. Lack of proper description of some mechanisms and the large number of processes that take place concurrently during the ion beam irradiation lead to difficulties in the interpretation of the experimental data that are collected in the measurements. Computer simulations are considered a promising approach to understand the main physical and chemical phenomena, and a valuable tool in processing and interpreting the analytical data. In this review we summarize the fundamentals and the numerical approximations in modelling the characterization of solid surfaces by ion beams. The approach and the limitations of two major groups of existing codes, known as Monte Carlo and molecular dynamics techniques, are described in more detail. Special attention is paid to recent achievements in the description of phenomena that were not included in earlier stages of computer modelling, such as electron–phonon inelastic losses, bombardment enhanced diffusion and segregation, selective sputtering among others. Examples of the simulation approach to ion scattering and sputtering are given, including sputtering of oxides and multielemental targets, the sputter yield amplification effect, dynamic target modification, reactive sputtering, and shallow depth profiles.

Thin metallic layers of Cu, Cr, or Ag were deposited on Si substrates and then sputtered as in a standard depth profiling mode. The etching was completed by using 1-5 keV Ar + beam, scanned over the surface. The composition of the exposed etched surface was monitored by X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES). When the metal-silicon interface was approached, the etching was stopped and the sample surface was analyzed by scanning electron microscopy (SEM) and scanning Auger microscopy (SAM). We observed clusters of metal on the Si substrate. Their characteristic sizes were 30-60 nm for Cu, 60-90 nm for Cr, and 100-200 nm for Ag. The patterns were sensitive to the ion energy - at 1 keV the Cu network was well defined, whereas at 3-5 keV energy the patterns become fuzzy without clear boundaries. The clustering of thin films near the interface can affect the depth profiles in surface analytical techniques, and can be used as a tool to create clusters in nanotechnology.

Experimental and simulated energy distributions of Ga+ and In+ secondary ions produced by 4 keV Ne+, Ar+ and Kr+ bombardment of the AIIIBV semiconductors (GaP, GaAs, GaSb, InP, InAs and InSb) are reported. The measurements were carried out for a wide range of initial energy (up to 1000 eV) in a small solid angle along the surface normal, without applying electric field to extract the ions into the mass-energy analyser. It is shown that the energy spectra are complex, with evident high-energy hump, whose relative intensity increases with the mass of the second component (P, As, Sb) of the compound. The Sigmund–Thompson distribution cannot fit reliably these data, and a satisfactory approximation of the measured spectra was obtained with a sum of two decaying exponential functions to describe the contribution of both, the isotropic linear collision cascades and the outward knock-on atoms. The experimental results are compared with simulations based on the MARLOWE computer code.

The ejection of energetic particles during steady-state ion surface bombardment has been investigated by means of a dynamic computer simulation as well as in a secondary ion mass spectrometry (SIMS)/low-energy ion scattering from surfaces (LEIS) experiment. The emphasis of this comparative study is on the mass dependence of high-energy tails in sputtering and backscattering for the bombardment of galena (PbS) and pyrite (FeS2) with keV energy ion beam of cesium and oxygen. In the experiment, kinetic energy distributions of sputtered secondary ions ( S + , Fe + , Pb + , S − ), as well as backscattered or re-sputtered primary ions ( Cs + , O + , O − ), have been measured on a modified Cameca IMS-3f magnetic sector mass spectrometer for keV cesium (Cs+) and oxygen ( O 2 + , O − ) bombardment of galena and pyrite. Ejection of high-energy particles, with emission energies of up to ∼40% or up to ∼60% of the bombarding energy for sputtering of the lighter component (S±) with cesium or oxygen, respectively, and of up to ∼40% (Cs+) and ∼80% (O±) for backscattering, has been observed for PbS. The computer simulations were based on the well-known MARLOWE code. In order to model the change of the stoichiometry of the binary compounds, dynamic modification of the target composition in the near-surface region was introduced. Cs incorporation was included, and a relative enrichment of the metallic component (Pb, Fe) in the top few layers due to preferential sputtering of sulfur was allowed. The computer simulations provide information on the formation of altered layer under sputter equilibrium as well as on the energy and angular emission distributions of sputtered and backscattered particles in steady-state conditions. Multiple scattering of Cs projectiles and dynamic re-sputtering of cesium that was previously incorporated in the altered near-surface region can be distinguished in the simulation, and matched with the experimental observations. In addition, information on the inverse velocity dependence of ion formation can be obtained from the comparison of the SIMS/LEIS experiment and the computer simulation.

This is the first report of a hybrid sodium ion capacitor (NIC) with the active materials in both the anode and the cathode being derived entirely from a single precursor: peanut shells, which are a green and highly economical waste globally generated at over 6 million tons per year. The electrodes push the envelope of performance, delivering among the most promising sodiation capacity–rate capability–cycling retention combinations reported in the literature for each materials class. Hence the resultant NIC also offers a state-of-the-art cyclically stable combination of energy and power, not only in respect to previously but also as compared to Li ion capacitors (LICs). The ion adsorption cathode based on Peanut Shell Nanosheet Carbon (PSNC) displays a hierarchically porous architecture, a sheet-like morphology down to 15 nm in thickness, a surface area on par with graphene materials (up to 2396 m2 g−1) and high levels of oxygen doping (up to 13.51 wt%). Scanned from 1.5–4.2 V vs. Na/Na+ PSNC delivers a specific capacity of 161 mA h g−1 at 0.1 A g−1 and 73 mA h g−1 at 25.6 A g−1. A low surface area Peanut Shell Ordered Carbon (PSOC) is employed as an ion intercalation anode. PSOC delivers a total capacity of 315 mA h g−1 with a flat plateau of 181 mA h g−1 occurring below 0.1 V (tested at 0.1 A g−1), and is stable at 10 000 cycles (tested at 3.2 A g−1). The assembled NIC operates within a wide temperature range (0–65 °C), yielding at room temperature (by active mass) 201, 76 and 50 W h kg−1 at 285, 8500 and 16 500 W kg−1, respectively. At 1.5–3.5 V, the hybrid device achieved 72% capacity retention after 10 000 cycles tested at 6.4 A g−1, and 88% after 100 000 cycles at 51.2 A g−1.

Partially ordered but not graphitized carbons are widely employed for sodium and lithium ion battery (NIB and LIB) anodes, either in their pure form or as a secondary supporting phase for oxides, sulfides and insertion electrodes. These “pseudographitic” materials ubiquitously display a poor initial coulombic efficiency (CE), which has been historically attributed to solid electrolyte interface (SEI) formation on their large surface areas (up to ∼2500 m2 g−1). Here we identify the other sources CE loss by examining a pseudographitic carbon with a state-of-the-art capacity (>350 mA h g−1 for NIB, >800 mA h g−1 for LIB), but with a purposely designed low surface area (14.5 m2 g−1) that disqualifies SEI from having a substantial role. During the initial several (

Clusters of independently tailored areal density and size distribution were grown on semiconductor surfaces by molecular beam epitaxy and were used subsequently as masks for selective ion beam modification. Field emission scanning electron microscopy shows sharp interfaces between the amorphous area exposed to ion beams and areas of crystalline silicon covered by clusters. Partial etching of the substrate leads to narrow trenches around the initial cluster site, suggesting significantly enhanced etching near the amorphous-crystalline interface. The results are explained on the basis of a slight density variation in the substrate near the cluster periphery due to a break in symmetry of the recoil atom incorporation. Computer simulations were carried out to further characterize these results, using a program based on the well-established TRIM code to model atomic collision cascades in a matrix. The resulting density distributions correlate well with the experimentally observed wet etching patterns, strongly suggesting a relation between cluster-masking related density variations in the amorphized silicon and the etching rate.

Aluminium nitride thin films were deposited by reactive d.c. magnetron sputtering on various substrates. The analytical tools used to characterise the aluminium nitride thin films were electron beam diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray analysis and polarised infrared reflection. From these techniques the structure, microstructure, chemical state, percentage content of the elements and IR properties of the films were observed and the formation of the AlN compound was confirmed.

Thin films of AlN were deposited at a total gas pressure of 7×10−4 mbar and a nitrogen partial presure of 9×10−5 mbar by reactive d.c. magnetron sputtering. Low-carbon steel 08KP, Si (100) wafers and monocrystal KCl were used as substrates. Electron microprobe analysis (EMA), X-ray photoelectron spectroscopy (XPS), polarised infra-red reflection and infra-red (PIRR) transmission measurements were carried out to characterise these films. The EMA analysis confirms the microcrystalline structure of our films. From an XPS spectrum of the deposited AlN films, we have demonstrated that AlN was formed at these values of total and partial pressures. The PIRR measurements indicate the presence of a phonon at about 680 cm−1, typical for AlN. The deposited films have a high transmittance (about 80%) in the wavelength region between 2.5 and 12 μm.

Low-power pulsed-laser annealing was applied to Zn+-implanted InP samples. In order to avoid surface oxidation during the treatment, the laser irradiation was carried out in inert ambient of nitrogen at different pressures. The analytical techniques used include Rutherford backscattering spectroscopy, reflection high energy electron diffraction, and electrical measurements. The highest carrier activation, about 80%, was achieved at the same laser power density (6.5 MW/cm2) at which the best crystal recovery was obtained.

A two-dimensional classical dynamics model for calculating the reflection coefficient of keV-ion beams backscattered from a crystal surface at glancing incidence is presented. The target is considered as consisting of one or two layers of atomic strings. A string potential of cylindrical symmetry was constructed by using the well-known iuniversali pair potential or the Molire interatomic potential. The critical transverse energy needed for a 100% reflection of light ions from the surface is assessed for the most open (11 _ 0) direction of Cu(111), Ni(111), and Al(111) crystal surfaces. The distribution of the backscattered ions on the azimuthal scattering angle exhibits the multimode structure related to the zig-zag trajectories in surface semichannels. The energy spectra are compared to the experimental data. The simulations show that the reflection coefficient is substantially dependent on the interatomic potential used but is not much affected by the model adopted for description of the inelastic losses. The inelastic-interaction model affects mostly the energy peak position, so that an estimate based on OennRobinson empirical formulae compares better with the experimental data than the original Firsov model. Resume : Nous prOsentons un modle de dynamique classique en 2-D pour calculer le

The structure of (100) silicon implanted with Zn+ ions at an energy of 50 keV was studied. The ion doses were varied from 1×1015 to 1×1017 cm−2 and the beam current density was 10 μA cm−2. The analytical techniques employed for sample characterization included cross‐sectional transmission electron microscopy and x‐ray energy dispersion analysis. The energy deposition of the ion beam was calculated by using computer simulation codes. For the two lower doses of 1×1015 and 1×1016 a crystalline‐to‐amorphous transformation was observed in the implanted layer and this was correlated with the thermal history of the implants and the attendant changes in morphology. In contrast, an amorphous‐to‐crystalline transition was found to occur at higher doses, namely 5×1016 and 1×1017, where the formation of a complex, structured layer consisting of an amorphous phase mixed with crystalline grains of Zn and partly recrystallized Si was identified together with other specific structural features. Detailed characterization ...

The composition and structure of an InP{100} surface in both the (1 × 1) and the reconstructed (4 × 2) phases, prepared by ion bombardment and annealing, have been examined by time-of-flight scattering and recoiling spectrometry (TOF-SARS) and low-energy electron diffraction (LEED) . Time-of-flight spectra of scattered and recoiled neutrals plus ions were collected as a function of crystal azimuthal rotation angle δ and primary beam incident angle α. Compositional analyses of the surfaces were obtained from 4 keV Ar+ scattering and recoiling spectra. Structural analyses of the phases were obtained from the azimuthal anisotropy of the δ-scans and the features of the polar incident α-scans using 4 keV Ne+ scattering from In atoms and 4 keV Kr+ for recoiling of P atoms. These azimuthal δ-scans and incident a-scans were simulated by means of a shadow cone focusing model and a modified version of the MARLOWE code, respectively. The totality of this data leads indubitably to a model in which every fourth In 〈011〉 row is missing, the In atoms are trimerized along the 〈011〉 azimuth, and the 2nd-layer P atoms exposed in the 〈011〉 troughs are dimerized. This In missing-row-trimer P dimer model (MRTD) is consistent with all of the data, is autocompensated, and has In intratrimer spacings of 3.65 ± 0.20 A and P intradimer spacings of 2.95 ± 0.20 A. The results of the simulations suggest that the two end In atoms of the trimers are relaxed downward by a minimum of 0.15 A. Two other models were considered: (1) An In missing-row (MR) model without trimers or dimers in which every fourth In 〈011〉 row is missing. (2) An In missing-row-dimer (MRD) model, similar to that proposed for the GaAs (4 × 2) structure, in which every fourth In 〈011〉 row is missing and In dimers form along 〈011〉. These MR and MRD models are inconsistent with large portions of the experimental data and the simulations.

The surface and subsurface compositional changes of Cu-Ni alloys with different stoichiometries were studied in situ using 5 keV Ar ion sputtering and X-ray photoelectron spectroscopy. The altered layer formed at room temperature exhibits enrichment of Cu-atoms at the surface due to segregation phenomena and diffusion. The size of the effect depends on the initial composition of the alloy. Additional information on the elemental depth distribution was obtained by varying the photoelectron take-off angle. Modeling of the preferential sputtering of Cu-atoms and of the depth distributions was also carried out. The simulations allowed to distinguish between the temperature and ballistic effects during the ion beam bombardment.

The azimuthal anisotropy of 3 keV Ar + ions scattered from a Ni(111) single crystal surface at relatively large angle (θ = 40°) is investigated. Shadowing mode (incidence angle, α = 5° measured from the surface) was used. Correlation between the azimuthal anisotropy and the energy distribution of the scattered ions is observed both experimentally and by computer simulations using a MARLOWE-based computer code. A noticeable dependence of the primary ion azimuthal angular distribution on the energy of the scattered particles is observed.

Time was introduced in the well-known TRIM code without changing the “event-driven” logic of the program. This modified TRIM code was used to simulate the slowing-down process of fast Cu ions in amorphous Cu targets. Distributions of the radial range and slowing-down time of the ions together with other time-dependent characteristics of the process were obtained at different projectile energies. A comparison was made with the results obtained by Robinson using the time-dependent MAR-LOWE computer code [Phys. Rev. B 40 (1989) 10717].

Wafers of (100) GaAs have been implanted with 140 keV Zn+ ions at off-channeling direction up to a fluence of 1×1014 cm−2. The target temperature was kept at 110±10°C. The defect clusters and the damage depth distributions were investigated by planar and cross-sectional high-resolution transmission electron microscopy (HRTEM and XHRTEM) and were modelled by a MAR-LOWE-based computer code. The experimental mean depth of the damage profile located at about 85 nm exceeds the calculated deposited energy and vacancy distributions by more than 50%. The correlation between the deposited energy density within the cascade and the inner structure of the observed defect clusters is discussed.

This work is part of a series of investigations started a few years ago to study high fluence ion beam effects. Experimental and computer techniques are applied here to the implantation of 40 keV As + in (111) Si samples at doses ranging from 1 × 10 16 to 2 × 10 17 cm −2 . The experimental evolution of the profile was analyzed by 2 MeV RBS spectroscopy. A special procedure was used to deconvolute the RBS data for highly nonhomogeneous layers. The atomic collision cascades were also simulated by a dynamic computer code, based on sputtering yield values and impurity depth distributions resulting from the well-known static code TRIM.SP. The distributions were used as input data to a procedure which takes into account the modification of the stopping power, the surface erosion by sputtering and the lattice relaxation.

A dynamic Monte Carlo program developed for the simulation of high-fluence effects in ion bombardment of multicomponent targets is described. The program includes a code for modelling the chemically guided motion of the slowed down primaries and recoils. Examples of the application of the simulation program to Ar + sputtering of CdHgTe and SiO 2 , O + implantation into Si and Ar + sputtering of Al/Si with concurrent adsorption of O 2 are presented and compared with experimental results.

Mesa structures and thin membranes are obtained by means of wet anisotropic etching using the etch-stop effect of nitrogen-implanted silicon. Dynamic Monte Carlo simulation is applied to calculate the implanted nitrogen profile. The use in sensor technology of nitrogen ion implantation in silicon with doses as low as 5×10 16 cm −2 is described.

Depth profiling of 200 A Al thin films on Si substrates is performed experimentally using oxygen in the ion beam source or in the analysis chamber. These depth profiles are also obtained by dynamic Monte Carlo simulation. In addition to the simulation of the ballistic cascade development, the computer code also includes additional chemically guided atomic relocation mechanisms. The comparison between experiment and simulation on the one hand, and between the two profiling methods on the other yields information about the target modification induced by the use of reactive species.

Depth distributions of displaced atoms for boron and arsenic implanted (111) silicon have been studied both by RBS channeling measurements and by a Monte Carlo simulation technique. The experiments and calculations are compared for ion energies of 80 and 160 keV and different doses. The computer code based on TRIM depth distributions takes into account the accumulation, diffusion and migration of the implantation-induced defects.

GaAs 〈100〉 wafers were implanted and later annealed by using three different techniques: furnace thermal annealing (FTA), flash lamp (RTA) and low-power laser annealing (LPLA). The resulting modifications of the structure were studied by RHEED. The RHEED pattern analysis indicates that: (a) A well annealed structure is observed after thermal treatment in furnace at 850 °C for 30 min; (b) the particular RTA employed leads to some texturing, but is not sufficient to provide good structural effects; (c) best annealing under our conditions is obtained by the LPLA technique, especially for low ion doses (less than 1013 cm−2); (d) variable-glancing-angle RHEED is an effective and convenient method to investigate the ion induced disorder in crystals at small depths.

Low‐power annealing by a pulsed laser is used to recover the structure of low‐dose implanted (100) GaAs crystals. Reflection high‐energy electron diffraction with variable glancing incidence is employed to detect the structural changes at different depths in the specimens. The depth dependence of the damage is studied in more detail by Rutherford backscattering analysis. The annealing results depend on the irradiation conditions. A laser energy window below the melting threshold is found within which the structure can be restored to about as high degree of crystallinity as the virgin one, without any visible surface damage. A simple theoretical estimate shows that the temperature rise of the material is far below the melting threshold. This rise is too short in time to cause substantial dopant diffusion; however, it can enhance well the point‐defect mobility.

Semi-insulating Cr-doped (100) GaAs was implanted with Bi+ with energy 40 keV at room temperature in a 7 ° off-axis direction. The implanted dose was varied between 2 × 1015 cm−2 and 1 × 1016 cm−2. The profile evolution was studied experimentally by RBS measurements and theoretically by a new dynamic computer code. It is based on sputtering yield values and impurity depth distributions, obtained by using the static simulation program TRIM.SP.

The effect of 12 MeV electron irradiation of p-type Si-SiO2 structures is studied by Deep Level Transient Spectroscopy (DLTS) measurements. The DLTS spectra of non-irradiated samples exhibit one peak only corresponding to a deep level located in the forbidden gap at 0.56 eV above the valence band edge of the Si matrix. Four additional, shallower levels are found in the spectra after bombardment with high-energy electrons, whereas the peak intensity is dependent on the irradiation dose. The corresponding activation energy of the created defects, as well as the density of the traps and the electron-capture cross sections are evaluated.

structures implanted with 50-keV boron ions is studied by deep-level transient spectroscopy (DLTS) measurements. The DLTS spectra of ion-implanted samples exhibit one peak which corresponds to a deep level located in the forbidden gap of the silicon matrix at Ec-0.40 eV below the conducting band edge. New additional shallower levels are found in the spectra following bombardment by high-energy electrons, the peak intensity being dependent on the irradiation dose. The corresponding activation energy of the created defects, the density of the traps, and the electron-capture cross sections are evaluated.

A method based on a thermocouple detector measuring simultaneously the total flux of energetic particles and the portion of the charged particles is proposed and studied. These data allow the neutral fraction of the ion beam to be easily calculated and the fraction is determined for different values of the working gas pressure in Ar and SF 6 . The results obtained are in good agreement with the theoretical model, for an ion beam accelerating bias of 500 V.

(1 0 0)-oriented silicon substrates were implanted with 50 keV Te + or Pb + ions at room temperature with doses varied in the range 1×10 15 to 1×10 18 cm −2 . Formation of ion beam-assisted Te and Pb nanocrystals in the layer amorphised by the implantation has been established. The accumulation of impurities, sputtering and formation of high-dose implantation profile was modelled by a dynamic computer simulation code. The calculated concentration profiles at various ion fluences were compared with the measured RBS profiles and the depth distribution of ion beam-induced nanoclusters obtained by cross-sectional transmission electron microscopy (XTEM), in an attempt to clarify the role of these effects in the formation of precipitates at high-dose irradiation conditions.

Thin films containing iron silicides are prepared by two methods. The first one consists in depositing a-Si:H:Fe thin films by magnetron co-sputtering followed by rapid thermal annealing (RTA). The second one is ion implantation of Fe in a-Si:H thin films and RTA treatment. The samples are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Rutherford back-scattering (RBS). FTIR spectra show absorption bands typical for β-FeSi2 at 263, 293, 308, 345 and 425 cm−1. It is shown that the optimal concentration of Fe in the co-sputtered films to obtain β-FeSi2 is 35–40% and the optimal RTA temperature is 900°C. XPS spectra show that β-FeSi2 is formed in as-deposited and annealed co-sputtered a-Si:H:Fe and implanted a-Si:H thin films.

It has been shown [Todorov and Fossum, J Vac Sci Technol , B6 , 466 (1988)] that ultra-thin ( d ≈ 50 A) oxide films can be grown on silicon surfaces at reduced substrate temperatures using oxygen-containing low energy ion beams ( E

The effects of the ambient atmosphere in the annealing chamber on the electrical and structural characteristics of Zn-implanted III-V compound semiconductors, processed by low-power pulsed-laser annealing are presented. The samples were analyzed using several complementary experimental techniques: Reflection high-energy electron diffraction, Rutherford backscattering spectroscopy, Raman spectroscopy, secondary ion mass spectroscopy, and electrical measurements. During the laser beam irradiation in the presence of gas inlet into the annealing chamber the ambient gas atoms diffused well into the target changing the stoichiometry and the electrical parameters. Redistribution of the implanted impurity was also observed. By varying the type of gas used and its pressure, it was possible to achieve electrical activation of up to 80%. It seems all structure and electrical parameters achieve their best values at the same ambient atmosphere and density of the deposited laser power P, e.g., 1.5 atm of ${\mathrm{N}}_{2}$ and $P=6.5 {\mathrm{M}\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}$ for InP.

Data on the effects of 140 keV Zn+ implanation of (100)GaAs and the consequent low-power pulsed laser annealing (LPPLA) on the composition of the surface layers are presented. The implantation does was 1014 cm −2 and the sample temperature was kept at 110 ± 10°C. THE LPPLA was carried out by 10–30 pulses of a Q-switched ruby laser (λ = 694.3 nm, τ = 25 ns and P0 = 4–6 MW cm−2) equipped with a spatial homogenizer. The crystal surface was studied by XPS analysis combined with depth profiling with the use of 1 keV Ar+. The results presented include the depth redistribution of oxygen and the As/Ga ratio as well as the oxide thickness for (a) virgin, (b) as-implanted and (c) implanted and then annealed samples.

〈100〉GaAs crystals were implanted with 140 keV Zn ions at random incidence and a dose of 1014 cm−2. Annealing by a low-power pulsed laser was used to recover the radiation damage. The samples were analysed by RHEED and RBS techniques. The effect of the annealing on the recovery of structure defects in GaAs is reported.

Computer simulation of the reflection of a keV ion beam from a single crystal is carried out for different target temperatures. Ar ions bombarding obliquely a Cu lattice with 2 keV, and a Ni crystal with 30 keV energy are considered. The potentials used are of Born-Mayer ( A e −r/b ) and Firsov ( Br −2 ) type respectively. Uncorrelated thermal vibrations of atoms with Gaussian distribution of their displacements are taken into account. The spatial and energy distribution of the reflected ions obtained for different temperatures are discussed. The energy spectra are compared with the experimental data for the same conditions.