Implantation Profiles Research Articles

Implantation and patient profiles for pacemakers and cardioverter-defibrillators in France (2008–2009)

An ageing population and the extension of indications will in all probability result in an increasing number of cardiac device implantations. Patients implanted in 2008 and 2009 were identified by means of the French National Hospital Discharge database to establish the implantation rate and the National Health Insurance (NHI) Information System database for patient profiles (76% of the population). Of the 64,306 pacemaker implantations (1003.7 per million inhabitants [pmi]) in 2009, 21.4% were single chamber, 75.4% double chamber and 3.2% triple chamber (CRT-P). Of the 9028 cardioverter-defibrillator implantations (140.8 pmi) in 2009, 30.1% were single chamber, 27.5% double chamber and 42.5% triple chamber (CRT-D), accounting for 65% of cardiac resynchronization therapy (CRT) implants. Among NHI beneficiaries, 58.6% of cardioverter-defibrillators were implanted for primary prevention. Between 2008 and 2009, CRT-P implantations increased by 8.8% and CRT-D implantations by 29.3%. Regional variations in implantation rates were observed regarding single-chamber pacemakers (15-33%) and CRT-D among CRT (46.2-73.8%). Pacemaker implantations cost €158.4 million overall, 4.5% of which was for CRT-P; cardioverter-defibrillator implantations cost €96 million, 49% of which was for CRT-D. For NHI beneficiaries, 11.9% of CRT-P patients and 6.5% of CRT-D patients already had a device of the same type implanted in the 3 preceding years. The results confirm the increase in cardioverter-defibrillator implantations in France. The implantation rate remains lower than that in the USA but falls within the European average. Reasons behind significant regional variations in implantation rates need further study.

The positron distribution in a layered stack sample studied with the use of positron lifetime spectroscopy

Computer simulation using GEANT4 codes indicates an enhancement of the fraction of implanted positrons stopped in the denser regions of a layered sample. However, positron lifetime measurements performed for layers of pure aluminum, silver and gold foils do not reveal this effect, indicating instead that backscattering plays an important role in determining the positron implantation profile in layered and/or heterogeneous samples.

Methane plasma-based ion implantation of metallic and galvanically oxidized tantalum

Tantalum and oxidized tantalum exhibit distinct differences when treated with plasma-based ion implantation of methane with − 20 kV. The implantation profiles of carbon are similar, but carbides are formed in the case of tantalum, as verified with X-ray diffraction and X-ray photoelectron spectrometry in combination with depth profiling, whereas there is no detectable carbide in the tantalum oxide film. The distributions of the co-implanted hydrogen also vary in that the intensity in depth profiling with secondary ion mass spectrometry does steadily decrease in the oxidized Ta, while in the metallic Ta it shows a short indentation below the surface and then decreases only very slowly.

Phosphorus implanted cadmium telluride solar cells

Polycrystalline cadmium telluride layers were implanted with phosphorus (P) in order to obtain an enhanced p-type doping close to the back contact of CdTe solar cells. The implantation parameters were adjusted based on computer simulations using SRIM. While the implantation profile was kept constant, different CdTe layer thicknesses were investigated. Furthermore, different annealing and activation processes and their influence on the P distribution in the device as well as ion beam induced damage were investigated. The P level was identified by photoluminescence measurements, the effective doping was investigated by means of capacitance–voltage measurements, and the effect on the solar cell properties was analyzed by current voltage characteristics. The results show the P distribution in the CdTe layer to depend strongly on the thermal and chemical post-implantation treatment. The effect of the P-doping on the solar cell properties becomes obvious by an increase of the open-circuit voltage due to the implantation.

SIMS and RBS Investigation of Zn Implanted Si

We present results of secondary ion mass-spectrometry and Rutherford backscattering spectroscopy of the Zn implantation profile in the damaged layer of a n-type Cz-Si(100) substrate, as well as the profile change during annealing. Si wafers were implanted with 64Zn+ ions at energy of 100keV and ion dose of 2×1014cm−2. They were then subsequently annealed at 400°C for 60min and 700°C for 10min. Analysis of experimental data shows that in the as-implanted sample on a silicon surface a damage gauzy amorphous layer with thickness about 80nm was created, located inside the substrate at the ion-implantation depth. After two annealing steps the defects were completely annealed out. From the Zn depth profiles we observe that during annealing the Zn concentration decreases and the Zn peak concentration moves to the wafer surface. The Zn concentration maximum exceeds the solubility limit of Zn in Si, suggesting decomposition of Zn solid solution in Si and Zn precipitation.

Presentation of the DSIP method for study of recrystallization process in subsurface zone induced by sandblasting

In the paper we demonstrate the application of the positron annihilation experimental technique based on the scan of the positron implantation profile for observation of the recrystallization process in the subsurface zone (SZ). The SZ was created in the copper sample whose surface was exposed to a sandblasting treatment and then annealed at different temperatures. Application of 68Ge/68Ga positron source allows us to scan the depth of c.a. 150 μm. It was found that recrystallization goes faster close to the surface than in deeper regions. The complete rebuilding of the microstructure takes place at temperature of 600 °C. Some changes in the defect structure begin at temperature of 300 °C.

Investigation of silver and iodine transport through silicon carbide layers prepared for nuclear fuel element cladding

Transport of silver and iodine through polycrystalline SiC layers produced by PBMR (Pty) Ltd. for cladding of TRISO fuel kernels was investigated using Rutherford backscattering analysis and electron microscopy. Fluences of 2 × 10 16 Ag + cm −2 and 1 × 10 16 I + cm −2 were implanted at room temperature, 350 °C and 600 °C with an energy of 360 keV, producing an atomic density of approximately 1.5% at the projected ranges of about 100 nm. The broadening of the implantation profiles and the loss of diffusors through the front surface during vacuum annealing at temperatures up to 1400 °C was determined. The results for room temperature implantations point to completely different transport mechanisms for silver and iodine in highly disordered silicon carbide. However, similar results are obtained for high temperature implantations, although iodine transport is much stronger influenced by lattice defects than is the case for silver. For both diffusors transport in well annealed samples can be described by Fickian grain boundary diffusion with no abnormal loss through the surface as would be expected from the presence of nano-pores and/or micro-cracks. At 1100 °C diffusion coefficients for silver and iodine are below our detection limit of 10 −21 m 2 s −1, while they increase into the 10 −20 m 2 s −1 range at 1300 °C.

Embryonic amygdalar transplants in adult rats with motor cortex lesions: a molecular and electrophysiological analysis

Transplants of embryonic nervous tissue ameliorate motor deficits induced by motor cortex lesions in adult animals. Restoration of lost brain functions has been recently shown in grafts of homotopic cortical origin, to be associated with a functional integration of the transplant after development of reciprocal host–graft connections. Nevertheless little is known about physiological properties or gene expression profiles of cortical implants with functional restorative capacity but no cortical origin. In this study, we show molecular and electrophysiological evidence supporting the functional development and integration of heterotopic transplants of embryonic amygdalar tissue placed into pre-lesioned motor cortex of adult rats. Grafts were analyzed 3 months post-transplantation. Using reverse transcriptase quantitative polymerase chain reaction, we found that key glutamatergic, GABAergic, and muscarinic receptors transcripts were expressed at different quantitative levels both in grafted and host tissues, but were all continuously present in the graft. Parallel sharp electrode recordings of grafted neurons in brain slices showed a regular firing pattern of transplanted neurons similar to host amygdalar pyramidal neurons. Synaptic connections from the adjacent host cortex on grafted neurons were electrophysiologically investigated and confirmed our molecular results. Taken together, our findings indicate that grafted neurons from a non-cortical, non-motor-related, but ontogenetical similar source, not only received functionally effective contacts from the adjacent motor cortex, but also developed electrophysiological and gene expression patterns comparable to host pyramidal neurons; suggesting an interesting tool for the field of neural repair and donor tissue in adults.

Parameter Extraction Procedure for Ion Implantation Profiles to Establish Robust Database based on Tail Function

We proposed a tail function parameter extraction procedure for the establishment of a robust ion implantation database. We showed that, for the expression of ion implantation profiles, there are many local minimum values set for the third and fourth moment parameters of r and β for the Pearson function that comprises the standard dual Pearson and tail functions. We proposed the use of a joined tail function as a mediate function to extract r and β, and demonstrated that this enables us to extract the parameters uniquely. Other parameters associated with channeling phenomena can also be simply and uniquely extracted by our procedure.

Effect of boron on formation of interstitial‐related luminescence centres in ion implanted silicon

AbstractThe presence of boron in silicon has been shown to have a deleterious effect on the luminescence of interstitial‐related centres, particularly the W‐centre which is often observed after ion implantation and a low temperature anneal. Competition between silicon‐interstitial and boron‐interstitial centre formation is considered to be a possible mechanism underlying this dramatic reduction. Previous work on silicon implantation of boron‐doped substrates is extended to examine the effect of B implantation itself on W‐centre formation. W centres formed via the implantation of B and a low temperature anneal and via a Si implant over an activated B‐implant profile followed by low temperature anneal are compared. These studies contrast the effects of boron and silicon implantation and examine the effect of overlapping implantation profiles. Studying the effect of boron on optical centre formation provides insight into defect interactions in silicon and new data for theoretical modelling.

Evidence of formation of tetravacancies in uniformly oxygen irradiated n-type silicon

High purity n-type silicon single crystal with resistivity in the order of 4000 Ω cm has been irradiated with high-energy oxygen ions at room temperature up to a fluence of 5E15 ions/cm 2. The energy of the beam was varied from 3 to 140 MeV using a rotating degrader to achieve a depthwise near-uniform implantation profile. Radiation induced defects and their dynamics have been studied using positron annihilation spectroscopy along with isochronal annealing up to 700 °C in steps of 50 °C for 30 min. After annealing the sample at 200 °C for 30 min, formation of silicon tetravacancies has been noticed. The formation of the tetravacancies was found to be due to agglomeration of divacancies present in the irradiated sample. An experimentally obtained positron lifetime value of 338±10 ps has been reported for silicon tetravacancies, which has a very close agreement with the value obtained from recent theoretical calculations. The tetravacancies were found to dissociate into trivacancy clusters upon further annealing. The trivacancies thus obtained were observed to agglomerate beyond 400 °C to form larger defect clusters. Finally, all the defects were found to anneal out after annealing the sample at 650 °C.

Delayed emission of cold positronium from mesoporous materials

It is well known that ortho-positronium (ortho-Ps) atoms are emitted with high efficiency from various porous materials following the implantation of positrons. Since the ortho-Ps lifetime in a mesoporous material may be a substantial fraction of the ortho-Ps vacuum lifetime ($142$ ns), the time dependence of Ps emission may have to be considered when conducting certain types of experiments, such as time of flight measurements or pulsed ortho-Ps-laser interactions, when using this kind of target as a positronium source. By taking into account the positron implantation profile and subsequent Ps diffusion and decay in a mesoporous film we calculate the time dependent ortho-Ps emission rate $\ensuremath{\Gamma}$($t$), which in turn allows us to establish the total annihilation rate, arising from the decay of ortho-Ps both inside and outside the sample. Using time-delayed laser spectroscopy and single-shot lifetime measurements we have directly probed the rate at which Ps is emitted into vacuum from a target with $~$3-nm diameter pores and have observed delayed ortho-Ps emission that is consistent with our model. From the ortho-Ps decay spectrum we find that, whereas a simple two-component lifetime fit gives a short lifetime of $25.3$$\ifmmode\pm\else\textpm\fi{}$$0.3$ ns, an analysis that properly takes into account the emission rate yields an ortho-Ps lifetime inside the porous material of $32.3$$\ifmmode\pm\else\textpm\fi{}$$1.2$ ns, demonstrating that the ortho-Ps escape rate into vacuum can significantly modify the apparent lifetime of ortho-Ps inside a mesoporous material. Our measurements yield a Ps diffusion coefficient $D$ $=$ $0.07$ $\ifmmode\pm\else\textpm\fi{}$ $0.01$ cm${}^{2}$ ${\mathrm{s}}^{\ensuremath{-}1}$, which is consistent with a tunneling limited diffusion process.

An Interlocking Ligamentous Spinal Disk Arthroplasty with Neural Network Infrastructure

An elastomeric spinal disk prosthesis design (BioFI™) with vertebral interlocking anchors has been modified using an embedded TiNi wire array. Bioinert styrenic block copolymer (Kraton®) and polycarbonate urethane (Bionate®) thermoplastic elastomer (TPE) matrices were utilized. Fatigue resistant NiTi wire was pretreated to induce superelastic martensitic microstructure. Stent-like helical structures were produced for incorporation within homogenous TPE matrix. Composite prototypes were fabricated in a vacuum hot press using transfer moulding techniques. Implant prototypes were subject to axial compression using a BOSE ® ELF3400. The NiTi reinforced implants exhibited reduction in axial strain, compliance, and creep compared to TPE controls. The axial properties of the NiTi reinforced Bionate® BioFI™ implant best approximated those of a spinal disk followed by Kraton®-NiTi, Bionate® and Kraton® prototypes. An ovine lumbar segment biomechanical model was used to characterize the disk prosthesis prototypes. Specimens were subject to 7.5Nm pure moments in axial rotation, flexion-extension and lateral bending with a custom jig mounted on an Instron® 8874. The motion preserving ligamentous nature of this arthroplasty prototype was not inhibited by NiTi reinforcement. Joint stiffness for all prototypes was significantly less than the intact and discectomy controls. This was due to lack of vertebral anchor rigidity rather than BioFI™ motion segment matrix type or reinforcement. Implant stress profiles for axial compression and axial torsion conditions were obtained using finite element methods. The biomechanical testing and finite element modelling both support existing BioFI™ design specifications for higher modulus vertebral anchors, endplates and motion segment periphery with gradation to a low modulus core within the motion segment. This closer approximation of the native spinal disk form translates to improvements in prosthesis biomechanical fidelity and longevity. Axial compressive strain induced within a TiNi reinforced Kraton® BioFI™ was found to be linearly proportional to the NiTi helical coil electrical resistance. This neural network capability delivers opportunities to monitor and telemeterize in situ multiaxis joint structural performance and in vivo spine biomechanics.

Etching Effects of Nanotechnology Fabrication on CMOS Transistor Gate Wafer Manufacturing Process Integration

As wafer nanotechnology gate is scaling down, the fabrication technology of gate spacer for transistor becomes more critical in manufacturing processes. Because wafer fabrication technologies, sidewall spacers play an important role in the control of short channel effects by offsetting ion implantation profiles from the edge of the gate. The present study is to overcome the fabrication processes limitations and proposed modified feasible etching processes integration on the formation processing for complementary metal oxide semiconductor nanofabrication process of gate spacer technology and electrical characteristics.

Perceptual threshold and neuronal excitability as long‐term safety evaluation in retinal implants

Abstract Purpose Despite the recent progress of retinal implants the effects of continuing stimulation still remains an open issue. Sofar the established safety limits are based on laboratory findings and clinical observations.This study examined the changes of perceptual threshold over time and its relation to longterm stimulation. The goal of the study was to establish stimulus induced depression of neuronal excitability (SIDNE) measurements as a method to gain further insight on the safety profile of epiretinal implants. Methods As part of a clinical trial a prototype of an epiretinal implant ( IMI Intelligent medical implant) with 61 active platinum electrodes was implanted in a retinitis pigmentosa (RP) patient. The threshold was defined as the level of stimulation intensity at which the patient had a visual perception in a defined probability of 50% using the Best‐PEST method. SIDNE is measured by comparing the thresholds of two electrodes obtained at the beginning and at the end of a stimulation session. One electrode is actively used during the stimulation, the other remains passive. The stimulation is regarded as safe when the threshold raise of active electrodes is not significantly higher than of the inactive electrode. Results The threshold remained stable over the observation period. The threshold raise of the active electrodes never exceeded that of the inactive electrode. Conclusion SIDNE measurement is feasible in epiretinal implants. After prolonged stimulation the thresholds may increase by more than 16 % due to the patients fading concentration, however the stimulation was performed within the safety limits.

Feasible approach for processes integration of CMOS transistor gate/side-wall spacer patterning fabrication

As the gate length is scaling down, the spacer design for CMOS transistor becomes increasingly critical manufacturing process. In recent CMOS technologies, side-wall spacers play an important role in the control of short channel effects by offsetting ion implantation profiles from the edge of the gate. The present approach to overcome these fabrication limitations. The spacer patterning technology yields critical dimension variations of minimum-sized features which are much smaller than achieved by optical integrated lithography and etching processes. Generally relates to semiconductor manufacturing, and more particularly to nanotechnology fabrication feasibility for CMOS wafer process on gate spacer technology manufacture feasibility. A modified side-wall spacer patterning method was implemented for using conventional lithography and etching processing technology. Based on the systematical investigation of the effects of the various etch conditions on etching profile and their impacts on the sidewall transistor gate structure, a novel integrated process for well controlled side-wall spacer formation was developed for fabrication.

Atomic-scale boron redistribution during reactive diffusion in Ni–Si

The redistribution of boron during the formation of the Ni silicides was investigated using atom probe tomography and transmission electron microscopy. A 7 nm amorphous intermixed region was found after deposition of a 30 nm thick Ni film at room temperature. The formation of this Ni–Si layer was found to have almost no influence on the boron implantation profile. After heating at 290 °C for 1 h, three types of silicides (Ni2Si, NiSi, and NiSi2) were identified below a thin remaining film of Ni (8 nm). The unexpected presence of the silicon-rich NiSi2 phase at this temperature may be caused by the presence of a thin silicon oxide (SiO2) observed at the Ni/Ni2Si interface that may act as a diffusion barrier. The average boron profile in NiSi2 and NiSi silicides is similar to the profile in the silicon substrate before reaction. A segregation of boron at several interfaces was detected. Small boron clusters (1.5 at. %) were found in NiSi, NiSi2, and Si phases but not in Ni2Si. After a 1 min heat treatment at 450 °C, the NiSi phase is the only silicide present. Boron clusters with a platelet shape and a concentration of 3 to 5 at. % of boron were found in both NiSi and Si. The presence of boron in the Ni silicide and its precipitation in the form of tiny clusters is likely to affect the electrical properties of the contacts.

Study of iodine diffusion in silicon carbide

Diffusion of iodine in 6H-SiC and polycrystalline CVD-SiC was investigated using Rutherford backscattering spectroscopy and electron microscopy. A fluence of 1 × 10 16 cm −2 of 127I + was implanted with an energy of 360 keV at room temperature, producing an amorphous surface layer of approximately 220 nm thickness. The implantation profile reached an atomic density of approximately 1.3% at the projected range of about 95 nm. Broadening of the implantation profile and iodine loss through the front surface during isochronal and isothermal vacuum annealing was determined. At a temperature of 1100 °C no iodine loss was observed after 120 h and a diffusion coefficient of less than 10 −21 m 2 s −1 was extracted from the analysis of profile widths. Relatively strong broadening occurred after 60 h annealing at 1200 °C with the iodine profile extending beyond 300 nm into the bulk, accompanied by a surprisingly modest iodine loss through the surface. Electron microscopic studies reveal a drastic restructuring of the surface region at this temperature, indicating possible chemical reactions between iodine and silicon carbide.

A new high-temperature plasma immersion ion implantation system with electron heating

Abstract The temperature of the substrate has strong influence on the diffusion coefficient of nitrogen ions during plasma immersion ion implantation (PIII) performed in metallic surfaces, which affect the ion implantation profiles and can lead to the formation of thick implanted layers. In order to heat conveniently a large spectrum of metals and metallic alloys in vacuum and in the presence of plasma, as mandatory for efficient PIII, it is necessary to count on a stable heat source, able to provide steady temperatures in the range of 200 °C to more than 1000 °C. This has been accomplished in the current experiment by means of a thermionic cathode composed of a rolled tantalum foil covered with (Ba,Sr,Ca)O. Work-function of this electron source is around 2.1 eV, which is much lower than 4.5 eV of typically used tungsten filament. Metallic samples studied, in this case, are the anode of the discharge itself, being polarized during the heating cycle by positive DC voltages in the 100–800 V range. They are implanted with negative pulses up to 10 kV/300 Hz/40 µs.

Ion beam characterization of Fe-implanted GaN

Abstract Fe ion implantation in GaN has been investigated by means of ion beam analysis techniques. Implantations at an energy of 150 keV and fluences ranging from 2 × 10 15 to 1 × 10 16 cm −2 were done, both at room temperature and at 623 K. Secondary Ions Mass Spectrometry was used to determine the Fe implantation profiles, whereas Rutherford Backscattering in channeling conditions with a 2.2 MeV 4 He + beam allowed us to follow the damage evolution. Particle Induced X-ray Emission in channeling conditions with a 2 MeV H + beam was employed to study the lattice location of Fe atoms after implantation. The results show that a high fraction of Fe-implanted atoms are located in high symmetry sites in low fluence implanted samples, where the damage level is lower, whereas the fraction of randomly located Fe atoms increases by increasing the fluence and the resulting damage. Moreover, dynamical annealing present in high temperature implantation has been shown to favor the incorporation of Fe atoms in high symmetry sites.