In this article, we present a detailed characterisation of a multicusp-assisted inductively coupled RF plasma source for plasma immersion ion implantation (PIII). Using laser-induced fluorescence (LIF) and RF-compensated Langmuir probe diagnostics, we measured ion temperature T i and drift velocity v z in argon plasmas near an immersed electrode. The multicusp configuration enhances plasma density at low pressure, enabling stable operation down to 0.8 mTorr. Timeaveraged measurements show no detectable perturbation near the pulsed electrode, indicating full plasma recovery between high-voltage pulses. LIF-derived potential profiles match Riemann's presheath theory, and ion velocity distributions reveal acceleration consistent with sheath dynamics. These results support the use of LIF for steady-state characterisation of the bulk and presheath regions in PIII systems.

Plasma fusion devices will require plasma-facing components (PFCs) which can withstand the extreme environment at the edge of a hot fusion plasma. Despite the excellent properties of tungsten(W) as a hard refractory metal, adverse effects such as embrittlement, melting, and morphological evolution have been observed in W when it is bombarded by a high-fluence of low-energy ions including helium. This study investigates the effect of helium ion bombardment on pure tungsten and a tungsten heavy alloy (W-HA) (NAECOMET 1000). Pure tungsten and NAECOMET 1000 samples were implanted with 3 keV helium ions with fluences ranging from 1.15 x 10(21)m(-2) to 2.21 x 1022m(-2), using Plasma Immersion Ion Implantation (PIII). After PIII treatment, samples were analysed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), which revealed differences in surface morphology and topography. Although the melting and cracking of the Ni/Cu binder phase in the NAECOMET 1000 samples was seen under all implantation conditions, the Ni/Cu presence did somewhat slow the formation of W fuzz in comparison to pure tungsten. X-ray diffraction (XRD) studies showed peak shifts increasing with helium ion fluence for both the pure W and NAECOMET 1000 samples, as well as increase in mean crystallite size, confirming the distortion of the lattice. XPS compositional analysis showed a strong oxidation (> 97%) near the metal surface, after helium PIII treatment, for both pure W and NAECOMET 1000 W-HA samples. Some conclusions about the potential suitability of W-HA materials for fusion plasma PFCs are drawn.

Detectors based on an ensemble of nitrogen-vacancy (NV) centres in diamond are the latest addition to the list of magnetometers capable of detecting weak magnetic fields. Here, we report the design, construction, and testing of an NV magnetometer with a wide spatial area excitation and collection capability. The system was developed for the purpose of magnetic field measurement in an Halbach magnet configuration. The designed system performance was comparable to a conventional NV confocal system in the low power excitation region. From the dip profiles observed in the optically detected magnetic resonance (ODMR) spectrum, each NV centre experienced a static magnetic field in the 2.14-6.07 mT range of the Halbach magnet. The sensitivity of the field mapping system using the continuous wave (CM-ODMR approach was estimated and found to be approximately 0.2 mu T/root Hz at 170 MHz. Extensive details of the setup and the experimental procedures are presented, and the system can be easily reproduced by those who are not familiar with NV centre instrumentation. The results obtained pave way for the development of scalable NV sensors using wide area illumination and collection methods, especially for the mapping B-0 and B-1 field in magnetic resonance imaging (MRI) to facilitate non-FFT image reconstruction.

Plasma Immersion Ion Implantation(PIII) is a versatile material processing technique [1] , [2] . In PIII a solid target is immersed in plasma, and negative-polarity high-voltage(NPHV) pulses are applied to the target. During a NPHV pulse electrons are repelled from the near-target region, resulting in a positive ion sheath surrounding the target; ions traversing the sheath are implanted into the target surface. Lieberman et al. [2] developed a PIII sheath model which captures basic aspects of the sheath evolution during PIII pulses. However, some key assumptions used in this model do not hold. In particular, experiments show that the plasma density and electron temperature do not remain constant during the NPHV pulses, due to various effects, including the effect of secondary electrons ejected from the target. The ejected electrons accelerate back through the sheath, depositing their energy in the bulk plasma; this can significantly increase the plasma density and electron temperature above the nominal steady-state values measured before the PIII pulse [3] , [4] , [5] . To further elucidate the effect of secondary electrons, we report on recent PIII experiments with variable pulse lengths(10us-100us) on a range of target materials including silicon, stainless steel, brass, and tungsten alloys with a range of NPHV pulse amplitudes(1-5 kV). We discuss the results of these experiments and the various mechanisms involved.

The origin and nature of perturbations induced by a high-voltage pulse on plasma parameters and their relationship to operating conditions (power and pressure) in an argon inductively coupled radio frequency plasma device is explored. The plasma parameters are measured with two radio frequency compensated Langmuir probes positioned either vertically above the pulsing target or horizontally along the diameter of the chamber, in the same axial plane as the target and same distance from the RF antenna. Fluctuations are observed in electron density ne, temperature Te, and plasma potential Vpl following negative polarity high voltage pulses and propagate deep in the plasma and well after the end of the pulse. Time-resolved data results indicate that the perturbations are significantly dampened at higher power as well as when closer to the plasma RF coil. The perturbation amplitudes depart significantly from steady state values when the pulse amplitude exceeds 2.0 kV and increase with the increasing pulse amplitude. Perturbation amplitudes are also higher for target materials having larger secondary electron yield. Our experimental results suggest that the underlying mechanism of this perturbation could be plasma heating driven by damping of a beam-plasma instability as a result of a beam of secondary electrons emitted by the target streaming into the plasma.

Plasma Immersion Ion Implantation (PIII) is a versatile material processing technique [1] , [2] with many applications in semiconductor doping and micro- and nano- fabrication [3] , as well as the surface modification of metals for improved resistance against wear and corrosion. In PIII a solid target is immersed in plasma, and negative polarity high voltage (typically 1-20 kV) pulses are applied to the target. During a negative-polarity PIII pulse electrons are repelled from the region near the target, resulting in a positive ion sheath surrounding the target; ions traversing the sheath are implanted into the solid target surface. PIII can provide uniform ion implantation with high ion fluences across broad area targets. The targets need not be planar as the plasma is conformal to the immersed target. For precision PIII processing it is important to accurately predict the implanted ion concentrations. To this end, the P2I code was developed by Bradley, Steenkamp, and Risch [4] , [5] to accurately predict PIII sheath dynamics, ion implantation currents, and total delivered ion fluences. The P2I code is an efficient implementation of the numerical solution of Lieberman's dynamic sheath model [2] with assumptions of quasi-static ion motion and sheath position, collision less ion flow, inertia less electrons and an infinite plasma ion reservoir.

Plasma Immersion Ion Implantation (PIII) is an ion implantation technology in which the target to be implanted (i.e. a semiconductor wafer) is immersed in a plasma, and implanted with positive ions by the application of a high-voltage negative-bias pulse to the target. Because of the high plasma density achievable in modern plasma sources, large fluences can be implanted across large wafer areas, without beam scanning. PIII is well suited for a variety of nanofabrication applications. Because of its compatibility with ordinary silicon CMOS device processing, high fluence PIII is a versatile method for in situ fabrication of nanocrystals for integrated circuit applications. This talk will review the physics of energetic ions implanted into solid materials, and illustrate how post-implant thermal treatment can be used to form nanocrystals in the ion-implanted region. A number of potential applications of PIII as a materials synthesis technique will be discussed.

We report observations of the Raman spectra of 10 keV hydrogen ion-implanted crystalline quartz, lithium niobate and tellurium dioxide over a wide range of ion fluences (10(14)-10(18) protons/cm(2)). We observe the emergence and growth of a new fluorescence feature in the Raman spectra (peaked at 1535 cm(-1)) as a function of fluence in all three materials. When measured, the position and shape of this feature is nearly identical in each material. However, the appearance of this feature in tellurium dioxide has a slightly varied behaviour. Based on our observations, we suggest that this signal is due to the 557.7nm photoluminescence of interstitial atomic O formed radiolytically. While interstitial molecular O-2 has previously been observed in irradiated quartz, the presence of this atomic oxygen signature in proton-irradiated lithium niobate and tellurium dioxide has not been previously reported. Our results are important for the use of these materials, and other crystalline oxides, in charged particle (proton) radiation rich environments, such as those encountered by spaceborne instrumentation.

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Tungsten-Copper-Nickle (W-Cu-Ni) and Tungsten-Tantalum (W-ta) are considered as Plasma facing components (PFCs) as several adverse effects such as embrittlement, melting, and morphological evolution has been observed in W when it is bombarded by low-energy and high-fluence Helium(He) and Deuterium(D) Plasma. (W-Ta) alloys showed better resistance as compared to pure tungsten under simulated fusion plasma conditions. W-Ni-Cu alloys are machinable grades referred to as heat sink material and selected due to their high fracture toughness and tensile strength compared to pure tungsten.

Stabilized amorphous selenium (a-Se) photoconductive layers are currently used in the majority of modern digital x-ray flat panel imaging detectors in mammography. We examine the effects of pre-exposure of a-Se to high-dose x-ray irradiation on both hole and electron lifetimes, τe and τh, respectively, without any field applied to the device. The x-ray irradiation was from an Al-filtered tungsten target x-ray tube. We show that reduction in τh and τe depends only on the total or accumulated dose, D, absorbed in a-Se, and not on the rate of dose delivery, dD/dt, over the range of 0.15 Gy/s–2.5 Gy/s or on the x-ray energy over 50–90 kVp, corresponding to a mean photon energy over 31.9 keV–44.7 keV. The x-ray induced effects on charge transport are independent of the x-ray intensity and x-ray photon energy but dependent on the total energy absorbed in a-Se. The latter finding allows x-ray induced drop in the carrier lifetimes to be simply and conveniently modeled by τo/τ = 1 + AD, where τo is the lifetime before x-ray exposure (equilibrium lifetime), τ is the lifetime after exposure, D is the absorbed total dose, and A is a constant, which is 0.203 (±0.021) Gy−1 for the hole lifetime and 0.0620 (±0.0090) Gy−1 for the electron lifetime, a factor of three smaller than that for holes. X-ray irradiation had no effect on hole and electron drift mobilities. Reduction in carrier lifetimes with the total dose was examined at 10 °C, 23.5 °C, and 35.5 °C, close to the glass transition temperature, where x-ray induced effects are stronger. A is independent of hole and electron lifetimes but has a strong temperature dependence, increasing sharply with temperature. After the cessation of x-ray irradiation, carrier lifetimes relax (increase) to their pre-exposed equilibrium values over time scales that depend on temperature. Recovery has been interpreted and analyzed in terms of considering the kinetics of the rate at which x-ray induced capture centers are removed, as the structure restores the equilibrium concentration of deep traps. The annealing process of excess hole traps has a fast and a slow decay component, with time constants τr1 and τr2, respectively. The recovery processes associated with τr1 and τr2 exhibit activation energies larger than those typically involved in electronic transitions and are comparable to bond breaking energies in Se–Se and Se–As. Near 35.5 °C, close to the glass transition temperature, τr2-recovery has a large activation energy, pointing to structural relaxation phenomena. Fast annealing (∼6 min) of excess hole traps at 35.5 °C is, in a general sense, in agreement with the disappearance of irreversible photoinduced effects and suppression of crystallization (strain relief) at the a-Se/substrate interface, as observed previously. In the case of recovery of the electron lifetime, single exponential decay in excess electron traps and clear activation energy of 1.91 eV/atom point to a probable Se–Se bond breaking involved in returning excess electron traps to equilibrium concentration. Interpretations based on x-ray induced excess valence alternation pair (VAP) and intimate VAP type defects are also considered, including conversion from neutral defects to charged VAP defects. The implications of the present findings on x-ray sensitivity of a-Se detectors through the charge collection efficiency (CCE) are also examined and discussed. An effective carrier lifetime concept is used to describe the effect of x-ray irradiation on carrier lifetimes, which is then used to find CCE in a pre-exposed a-Se detector. The results indicate that x-ray induced effects are negligible for nearly all practical applications of a-Se mammographic detectors in use provided that the detector is operated at a sufficiently high field and a-Se has sufficiently long initial lifetimes, i.e., it is a high quality electronic grade material.

•The effect of step-wise surface nitrogen doping in PCDs deposited at low pressure has been investigated.•NCDs with a large quantity of sp2/a-C (amorphous carbon) phases were formed on the surface of the PCDs at low nitrogen flow rates.•Increasing the nitrogen flow rate reduced the formation of nano-grains resulting in a decrease in the sp2/a-C contents in the grains and grain boundaries.•The decrease in the sp2/a-C content at a high surface nitrogen flow rate (10 sccm) enhanced the formation of NV− centres.•The low surface roughness of highly doped films will optimize the performance of magnetometers that uses these diamond films as NV detectors.

We report on the measurement of the transmittance and reflectance of unpolarized light (425-700 nm) in three birefringent, acousto-optic materials, including quartz, lithium niobate, and tellurium dioxide, after exposure to varying fluences of proton radiation ($ {10^{14}} {-} {10^{18}}\;{\rm protons}/{{\rm cm}^2} $1014-1018protons/cm2) delivered by a 10 keV hydrogen ion beamline. We observe a general monotonic decrease in transmittance with increasing fluence for all three materials, but with varying rates of change and critical points of change. Reflectance measurements also exhibit a general monotonic trend with fluence, but increases in quartz are observed versus decreases in both lithium niobate and tellurium dioxide. These observations are used to assess the suitability of the materials for acousto-optic applications in the space environment where charged particles from the solar wind are dominant and pose a threat to device operation. Our measurements agree with previously reported work concluding that tellurium dioxide is suitable for space applications at low fluences (below $ {{10}^{16}}\;{\rm ions}/{{\rm cm}^2} $1016ions/cm2), but our findings also raise previously unreported concerns for higher accumulated fluences observed for longer mission lifetimes of greater than five to 10 years in space in an unshielded configuration.

Nitrogen-vacancy (NV) centres in diamonds are emerging quantum materials having applications in quantum computing and magnetic field sensing. The ability to synthesize polycrystalline diamond films from chemical vapour deposition technique offers a possibility to grow cheap diamonds with NV centres over large areas. Till date, extensive studies have not been carried out to understand the influence of nitrogen flow rate on the formation of NV centres in polycrystalline diamonds. In this study, we investigate the effect of nitrogen flow rate on the morphology, optical, and electrical properties of polycrystalline diamonds deposited at low pressure. Several samples were prepared in different nitrogen flow regimes using the microwave plasma chemical vapour deposition (MPCVD) technique. The films were characterized using Raman spectroscopy and scanning electron microscopy (SEM). The I–V characteristics of the samples were measured using a point contact method at room temperature. Results obtained showed the formation of both neutral and negatively charged NV centres at an optimum nitrogen flow rate of 10 sccm. An increase in nitrogen flow rate led to a decrease in the electrical resistivity of the films. Furthermore, nitrogen flow rates greater than 20 sccm results to a decrease in the reflectance spectra of samples and a depreciation in the crystalline quality of films. This study is important in benchmarking an optimal parameter space for the growth of nitrogen doped polycrystalline diamonds suitable for sensing applications.

Introduction The purpose of this study was to compare pre-operative acetabular cup parameters using this novel dynamic imaging sequence to the Lewinnek safe zone Methods We retrospectively reviewed...

Protein-energy malnutrition (PEM) pre-existing at stroke onset is believed to worsen functional outcome, yet the underlying mechanisms are not fully understood. Since brain inflammation is an important modulator of neurological recovery after stroke, we explored the impact of PEM on neuroinflammation in the acute period in relation to stroke-initiated sensori-motor abnormalities. Adult rats were fed a low-protein (LP) or normal protein (NP) diet for 28 days before inducing photothrombotic stroke (St) in the forelimb region of the motor cortex or sham surgery; the diets continued for 3 days after the stroke. Protein-energy status was assessed by a combination of body weight, food intake, serum acute phase proteins and corticosterone, and liver lipid content. Deficits in motor function were evaluated in the horizontal ladder walking and cylinder tasks at 3 days after stroke. The glial response and brain elemental signature were investigated by immunohistochemistry and micro-X-ray fluorescence imaging, respectively. The LP-fed rats reduced food intake, resulting in PEM. Pre-existing PEM augmented stroke-induced abnormalities in forelimb placement accuracy on the ladder; LP-St rats made more errors (29 ± 8%) than the NP-St rats (15 ± 3%; P < 0.05). This was accompanied by attenuated astrogliosis in the peri-infarct area by 18% and reduced microglia activation by up to 41 and 21% in the peri-infarct area and the infarct rim, respectively (P < 0.05). The LP diet altered the cortical Zn, Ca, and Cl signatures (P < 0.05). Our data suggest that proactive treatment of pre-existing PEM could be essential for optimal post-stroke recovery.

Summary form only given. Plasma density enhancement is frequently observed during plasma ion implantation processes 1 . It can most clearly be measured using an optically isolated Faraday cup with secondary electron suppression. It manifests itself a significantly increased current density to the target, which persists after the transient high current pulse to the target has decayed. The enhanced plasma density presents issues for accurate dosimetry in plasma ion implantation processes. While it can be modeled using an empirically determined density enhancement factor 2 , a first-principles approach would be preferable. This paper discusses the mechanisms leading to plasma density enhancement, their modeling in the context of plasma ion implantation processes, and their implications for accurate dosimetry in plasma ion implantation applied to semiconductor processing and other applications.