B.L. Doyle

Technique for profiling 1H with 2.5‐MeV Van de Graaff accelerators

We describe an elastic recoil detection (ERD) analysis technique for profiling 1H in the near‐surface regions of solids using a 2.5‐MeV Van de Graaff accelerator commonly used for ion‐backscattering analysis. Energy analysis of 1H forward scattered by 2.4‐MeV 4He incident on the target tilted at an angle of ∼75° yields a depth resolution of ≲700 A and a sensitivity of better than 0.1 at.% for 1H to depths of ≲0.6 μm in solids.

Metastable SiGeC formation by solid phase epitaxy

We report the synthesis and detailed structural characterization of SiGeC metastable alloys formed by solid phase epitaxial regrowth. Epitaxial layers with 0.7 and 1.4 at. % C are formed by 700 °C regrowth of multiple energy carbon implants into preamorphized Si0.86Ge0.14 layers on Si substrates. Transmission electron microscopy and Rutherford backscattering spectrometry show heteroepitaxial regrowth of Si1−x−yGexCy layers into the metastable diamond cubic phase. Fourier transform infrared spectroscopy verifies that the carbon occupies substitutional lattice sites. Double crystal x‐ray diffraction measurements of Si1−x−yGexCy and Si1−yCy reference layers quantify the C‐induced tensile strain component. This strain compensates for the compressive strain in the SiGe layers, and indicates a change in lattice constant per atomic fraction C in agreement with Vegard’s law.

Impact of passivation layers on enhanced low-dose-rate sensitivity and pre-irradiation elevated-temperature stress effects in bipolar linear ICs

Final chip passivation layers are shown to have a major impact on the total dose hardness of bipolar linear technologies. It is found that devices fabricated without passivation layers do not exhibit enhanced low-dose-rate sensitivity (ELDRS) or pre-irradiation elevated-temperature stress (PETS) sensitivity, whereas devices from the same production lot fabricated with either oxide/nitride or doped-glass passivation layers are ELDRS and PETS sensitive. In addition, removing the passivation layers after fabrication can mitigate ELDRS and PETS effects. ELDRS and PETS effects do not appear to be inherently related to circuit design or layout, but are related to mechanical stress effects, hydrogen in the device, or a combination of the two. These results suggest that proper engineering of the final chip passivation layer might eliminate ELDRS and PETS effects in bipolar integrated circuits.

Deposition of carbon, deuterium, and metals on the wall and limiters of the Tokamak Fusion Test Reactor

Following a two‐year operational period the Tokamak Fusion Test Reactor (TFTR) graphite fixed bumper limiter has been examined by a variety of methods. The areal density of metals was mapped in situ by beta backscattering. Several tiles were examined in detail by nuclear‐reaction analysis, Rutherford backscattering, and proton‐induced x‐ray emission to measure areal densities of deuterium and impurities. Some areas of the limiter were found to be covered by deposited material several microns thick. Other areas where the incident plasma flux is higher were much cleaner. Long‐term collection coupons were also examined to characterize deposition on the wall. From these results the total amount of deuterium on the limiter and wall in TFTR is estimated to be ∼1.3×1024 atoms. The implications of this for wall‐pumping effects and future tritium inventory are discussed.

The analysis of elastic recoil detection data

Abstract The physical concepts involved in elastic recoil detection (ERD) are reviewed in order to facilitate more quantitative use of this powerful ion beam analysis technique. Analytical expressions analogous to those developed for Rutherford backscattering are provided and recommendations are given for the optimization of depth resolution. Examples involving the concentration depth profiling of light elements are used to illustrate the analysis.

Charge collection in SOI capacitors and circuits and its effect on SEU hardness

Focused ion microbeam and broadbeam heavy-ion experiments on capacitors and SRAMs are used to investigate increased saturation upset cross sections recently observed in some silicon-on-insulator (SOI) integrated circuits (ICs). Experiments performed on capacitors show a very strong bias and oxide thickness dependence for charge collection. In combination with three-dimensional (3-D) simulations, these data suggest that the mechanism for charge collection in capacitors is due to perturbation of the substrate electric fields by charge deposition in the substrate. For substrates biased in depletion, these perturbations induce displacement currents through the oxide. Charge collection by displacement currents can be substantially reduced or mitigated by using heavily doped substrates. Experiments performed on SRAMs also show enhanced charge collection from displacement currents. However, experimental data and 3-D simulations show that for SRAMs, a second mechanism also contributes to charge collection. The 3-D simulations suggest that the charge collection results from drain and body-tie heavy-ion strikes within a few tenths of a micron of the body-to-drain junctions. These charge collection mechanisms can substantially reduce the SEU hardness and soft-error reliability of commercial SOI ICs.

Steady state hydrogen transport in solids

Abstract The analytical formalism for evaluating the steady state hydrogen (tritium) inventory, recycle and permeation rate and recycle time for surfaces exposed to the plasma of an operating magnetic confinement fusion reactor is reviewed and new material relevant to the application of this theory is presented. The formalism includes hydrogen trapping, diffusion, and effects of thermal gradients (e.g., Ludwig-Soret effect), and is applicable for all orders of release kinetics at the inner and outer surfaces. The problem is formulated in terms of a unitless transport parameter, W=(Rφ/D)(k1/φ)l/r, where r is the order of the release kinetics, R is the range of the implant, φ is the penetrating part of the incident flux, kl is the recombination coefficient and D is the diffusion coefficient. The steady state analytical theory is applied to several materials of interest to controlled fusion.

Fast lithium-ion conducting thin-film electrolytes integrated directly on flexible substrates for high-power solid-state batteries.

By utilizing an equilibrium processing strategy that enables co-firing of oxides and base metals, a means to integrate the lithium-stable fast lithium-ion conductor lanthanum lithium tantalate directly with a thin copper foil current collector appropriate for a solid-state battery is presented. This resulting thin-film electrolyte possesses a room temperature lithium-ion conductivity of 1.5 × 10(-5) S cm(-1) , which has the potential to increase the power of a solid-state battery over current state of the art.

Bonding and hardness in nonhydrogenated carbon films with moderate sp3 content

Amorphous carbon films with an sp3 content up to 25% and a negligible amount of hydrogen have been grown by evaporation of graphite with concurrent Ar+ ion bombardment. The sp3 content is maximized for Ar+ energies between 200 and 300 eV following a subplantation mechanism. Higher ion energies deteriorate the film due to sputtering and heating processes. The hardness of the films increases in the optimal assisting range from 8 to 18 GPa, and is explained by crosslinking of graphitic planes through sp3 connecting sites.

A new approach to nuclear microscopy: the ion–electron emission microscope

Abstract A new multidimensional high lateral resolution ion beam analysis technique, ion–electron emission microscopy (IEEM) is described. Using MeV energy ions, IEEM is shown to be capable of ion beam induced charge collection (IBICC) measurements in semiconductors. IEEM should also be capable of microscopically and multidimensionally mapping the surface and bulk composition of solids. As such, IEEM has nearly identical capabilities as traditional nuclear microprobe analysis, with the advantage that the ion beam does not have to be focused. The technique is based on determining the position where an individual ion enters the surface of the sample by projection secondary electron emission microscopy. The x – y origination point of a secondary electron, and hence the impact coordinates of the corresponding incident ion, is recorded with a position sensitive detector connected to a standard photoemission electron microscope (PEEM). These signals are then used to establish coincidence with IBICC, atomic, or nuclear reaction induced ion beam analysis signals simultaneously caused by the incident ion.