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An overview of the recent operations and the main results of cesium injection in the Source for the Production of Ions of Deuterium Extracted from Rf plasma (SPIDER) negative ion source are described in this contribution. In experiments without cesium injection, all SPIDER plants were tested to verify the basic expectations on the operational parameters (e.g., electron cooling effectiveness of magnetic filter field) and to determine its operational region. For beam properties, it was shown that the current density varies across the beam in the vertical direction. In preliminary cesium experiments, the expected increase of negative ion current and simultaneous decrease of co-extracted electrons were found, along with the influence of the control parameters (polarization of the plasma electrodes, magnetic filter field) on the SPIDER beam uniformity in the horizontal and vertical directions. It was shown that non-Gaussian tails can be identified in the angular distribution on the plane perpendicular to the beam propagation direction. Stray particles, nonhomogeneous beam and large divergence might result in unexpected heat and particle loads over ITER neutral beam injector (NBI) accelerator grids; it is the goal of SPIDER to assess and possibly to identify suitable methods for controlling these beam features. A major shutdown, planned for late 2021, to solve the issues identified during the operation and to carry out scheduled modifications, is outlined. Such improvements are expected to allow SPIDER to pursue the ITER requirements in terms of negative ion current, electron-to-ion ratio, and beam duration.

ITER envisages the use of two heating neutral beam injectors plus an optional one as part of the auxiliary heating and current drive system, to reach the desired performances during its various phases of operation. The 16.5 MW expected neutral beam power per injector is several notches higher than worldwide existing facilities.In order to enable such development, a Neutral Beam Test Facility (NBTF) was established at Consorzio RFX, exploiting the synergy of two test beds, called SPIDER and MITICA. SPIDER is dedicated developing and char-acterizing large efficient negative ion sources at relevant parameters in ITER-like conditions: source and accel-erator located in the same vacuum where the beam propagates, immunity to electromagnetic interferences of multiple radio-frequency (RF) antennas, avoidance of RF-induced discharges on the outside of the source. Three years of experiments on SPIDER have addressed to the necessary design modifications to enable full perfor-mances. The source is presently under a long shut-down phase to incorporate learnings from the experimental campaign, in particular events/issues occurred during operation, which led to the identification of improvement opportunities/necessities (e.g. RF discharges, local burns, water leaks, other damages, configuration/design upgrades to maximize chances/margin to quest target parameters).Parallelly, developments on MITICA, the full-scale prototype of the ITER Neutral Beam Injector (NBI) featuring a 1 MV accelerator and ion neutralization, are underway including manufacturing of the beam source, accel-erator and the beam line components, while power supplies and auxiliary plants, already installed, are under final testing and commissioning.Integration, commissioning and tests of the 1 MV power supplies are essential for this first-of-kind system, unparalleled both in research and industry field. 1.2 MV dc insulating tests of high voltage components were successfully completed. The integrated test to confirm 1 MV output by combining invertor systems, DC gener-ators and transmission lines extracted errors/accidents in some components. To realize a concrete system for ITER, said events have been addressed and solutions for the repair and the improvement of the system were developed.Hence, NBTF is emerging as a necessary facility, due to the large gap with existing injectors, effectively dedicated to identify issues and find solutions to enable successful ITER NBI operations in a time bound fashion. The lessons learned during the implementation on NBTF and future perspectives are here discussed.

© 2022 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ In this article, a method for phosphorous (n-type) doping of germanium based on spin-on dopant sources and Pulsed Laser Melting (PLM) throughout an amorphous silicon carbide (a-SixC1-x:H) layer, which provides both surface passivation and electrical isolation, has been demonstrated, paving the way towards the development of Ge-based interdigitated back contact thermophotovoltaic devices. This method offers simultaneous opening of the a-SixC1-x:H layer and creation of a heavily doped region underneath without using photolithographic steps, eventually enabling a low-cost and scalable manufacturing process. This article focuses on the optimization of the n+/p junction formation by studying the effect of different laser energy fluences and number of pulses on the diffusion profiles measured by secondary ion mass spectrometry, and on the electrical performance characterized by Van der Pauw-Hall technique. Additionally, the crystalline quality after PLM has been analyzed by Rutherford backscattering measurements in channeling conditions, high-resolution X-Ray diffraction and transmission electron microscopy. High level of donor activation (up to 1·1019 cm- 3 ), low sheet resistance (˜50 O/¿), and high mobility (275–700 cm2 /V·s) have been obtained, with a weaker dependency of these parameters on the explored laser energy fluence range. A prototype diode has been developed demonstrating a rectifying behavior but with high saturation current densities. Point-like contact formation will be implemented in future works to reduce the laser irradiated area, and thus, improve the surface passivation and device characteristics. A. Jiménez acknowledges ‘Programa de Ayudas a la Investigación en Energía y Medio Ambiente 2019-2020 y 2020-2021’ from Fundación Iberdrola, ‘Programa Propio I+D+i para contratos predoctorales’ from Universidad Politécnica de Madrid and ‘Programa de Ayudas para el fomento de la formación y la internalización de doctorandos’ from Consejo Social Universidad Politécnica de Madrid. A. Jiménez and A. Datas acknowledges the Spanish Minister for Science and the Agencia Estatal de Investigación for the funding provided in the Project TERMOCELL (ENE2017-86683-R - MINECO/AEI/FEDER, UE) with the support of FEDER funds and the Universidad Politécnica de Madrid, the Regional Government of Madrid for the project ANDREA funded in the "programa de apoyo a la realización de Proyectos de I+D para jóvenes investigadores 2019” and the funding under project GEPTV (PID2020-115719RB-C22) funded by MCIN/ AEI /10.13039/501100011033. This work has been partially funded from the University of Padova through the grant UNIPD-ISR 2017 ‘SENSITISE’. Luca Bacci and Nicola Argiolas (University of Padova) are acknowledged for their precious technical assistance. Chiara Carraro (University of Padova) is acknowledged for helping discussions and technical assistance in the lab. Isidro Martín and Gema López acknowledge the funding under project GETPV (PID2020-115719RB-C21) funded by MCIN/ AEI /10.13039/501100011033. I.García acknowledges AEI’s funding through project RTI2018-094291-B-I00 Y. K. Ryu and J. Martinez would like to acknowledge ICTS Micronanofabs.

A systematic study of the indiffusion of oxygen in germanium induced by pulsed laser melting (PLM) is reported. In order to evidence the impact of the experimental parameters, different processing conditions have been compared, i.e. with or without pre-PLM etching of the Ge native oxide by H2O or HF dip, Air or N2-rich atmosphere, and single or multi-pulse PLM. Oxygen indiffusion is always observed with surface concentration above 1 × 1019 cm−3 for all the processing conditions. Pre-PLM surface chemical treatments seem to have no significant influence in terms of the oxygen penetration, although HF allows lower surface roughening. On the contrary, a processing atmosphere with reduced oxygen concentration is more efficient in reducing the overall O indiffusion. The present experimental results are crucial in view of the implementation of the PLM technique for highly doped Ge as well as to design studies where contamination issue might be crucial.

To reach fusion conditions and control the plasma configuration in ITER, the next step in tokamak fusion research, two neutral beam injectors (NBIs) will supply 16.5 MW each, by neutralizing accelerated negative hydrogen or deuterium ions. The requirements of ITER NBIs (40A/1 MeV D- ions for ≤1 h, 46A/870 keV H- ions for ≤1000 s) have never been simultaneously attained. So in the Neutral Beam Test Facility (NBTF, Consorzio RFX, Italy) the operation of the full-scale ITER NBI prototype (MITICA) will be tested and optimised up to full performances, focussing on accelerator (including voltage holding), beam optics, neutralisation, residual ion removal. The NBTF includes also the full-scale prototype of the ITER NBI source with 100 keV particle energy (SPIDER), for early investigation of: negative ion production and extraction, source uniformity, negative ion current density and beam optics. This paper will describe the main results of the first two years of SPIDER operation, devoted to characterizing plasma and beam parameters, including investigation of RF-plasma coupling efficiency and magnetic filter field effectiveness in reducing co-extracted electrons. SPIDER is progressing towards the first caesium injection, which aims at increasing the negative ion density. A major shutdown, planned for 2021, to solve the issues identified during the operation and to carry out programmed modifications, will be outlined. The installation of each MITICA power supply and auxiliary system is completed; in-vessel mechanical components are under procurement by Fusion for Energy (F4E). Integration, commissioning and test of the power supplies, procured by F4E and QST, as the Japanese Domestic Agency (JADA), will be presented. In particular, 1.0MV insulating tests were carried out step-by-step and successfully completed. In 2020 integrated tests of the power supplies on the accelerator dummy load started, including the assessment of their resilience to accelerator grid breakdowns using a short-circuit device located in vacuum. The aggressive programme, to validate the NBI design at NBTF and to meet ITER schedule (requiring NBIs in operation in 2032), will be outlined. Unfortunately, in 2020 the coronavirus disease infection affected the NBTF activities. A solution to proceed with integrated power tests despite the coronavirus is presented.

Obtaining short-wavelength-infrared (SWIR; 1.4 mu m-3.0 mu m) room-temperature photodetection in a low-cost, group IV semiconductor is desirable for numerous applications. We demonstrate a non-equilibrium method for hyperdoping germanium with selenium or tellurium for dopant-mediated SWIR photodetection. By ion-implanting Se or Te into Ge wafers and restoring crystallinity with pulsed laser melting induced rapid solidification, we obtain single crystalline materials with peak Se and Te concentrations of 10(20) cm(-3) (10(4) times the solubility limits). These hyperdoped materials exhibit sub-bandgap absorption of light up to wavelengths of at least 3.0 mu m, with their sub-bandgap optical absorption coefficients comparable to those of commercial SWIR photodetection materials. Although previous studies of Ge-based photodetectors have reported a sub-bandgap optoelectronic response only at low temperature, we report room-temperature sub-bandgap SWIR photodetection at wavelengths as long as 3.0 mu m from rudimentary hyperdoped Ge:Se and Ge:Te photodetectors.

The fabrication of highly doped and high quality Ge layers is a challenging and hot topic for advancements in nanoelectronics, photonics and radiation detectors. In this article, we report on a simple method for junction formation consisting in sputter depositing or evaporating a thin pure Sb layer on Ge followed by cycles of Pulsed Laser Melting (PLM). We show that PLM promotes an efficient diffusion of high Sb concentrations into the melted Ge subsurface layer, followed by a fast epitaxial regrowth. The resulting layer is perfectly pseudomorphic to the Ge substrate, preserving the high strain level induced by the Sb, having covalent radius higher than Ge. In addition, it shows extremely high active concentrations up to 3 × 1020 cm−3 and a record low resistivity of 1.4 × 10-4 Ohm cm. The carrier mobility is also in line with the extrapolation of literature data with no signs of mobility degradation. Furthermore, infrared reflectivity confirms the good optical quality of the doped layers and demonstrates, for the first time, plasma wavelengths in Ge below 3 µm. These results are highly relevant for nanolectronic and plasmonic applications.

The integration in Si technology of highly doped of Ge layers with a controlled amount of strain is crucial for nanoelectronic and photonic applications. N-type doping of Ge layers epitaxially grown on Si by P ion-implantation and pulsed laser melting is reported. In particular, samples with or without a post-growth annealing cycle in order to reduce the amount of threading dislocations (TDs) have been studied, in comparison with bulk Ge. Samples have been characterized by Secondary Ion Mass Spectrometry, Van der Paw-Hall and High-Resolution X-ray Diffraction. A very low out-diffusion, 1 × 1020 cm−3 carrier concentration with 100% P activation, as well as an increase of the tensile strain together with an improvement of the crystalline quality is reported, regardless of the as-grown TD density.

We first found that ScCo(CN)6 of Prussian blue analogues has a large isotropic negative thermal expansion which occurs in a wide temperature range from 25K to 600K. More intriguingly, the present material of ScCo(CN)6 exhibits the merits of the facile fabrication via chemical coprecipitation and the good environment stability of water-free, which are very important for the applications. The transverse vibration of C and N atoms is critical for the occurrence of negative thermal expansion, which is confirmed by the atomic mean square relative displacements. The present new material of ScCo(CN)6 will be promising for the applications.

The investigation of innovative dynamical processes for the fabrication of highly doped andhigh quality Ge layers is currently a hot topic in many applicative fields such as nanoelectronics,photonics and radiation detectors. [...]

The discovery of unusual negative thermal expansion (NTE) provides the opportunity to control the common but much desired property of thermal expansion, which is valuable not only in scientific interests but also in practical applications. However, most of the available NTE materials are limited to a narrow temperature range, and the NTE effect is generally weakened by means of various modifications. Here, we report an enhanced NTE effect that occurs over a wide temperature range (\alpha V = -5.24 * 10-5 {\deg}C^-1, 25-575 {\deg} C), and this NTE effect is accompanied by an abnormal enhanced tetragonality, a large spontaneous polarization, and a G-type antiferromagnetic ordering in the present perovskite-type ferroelectric of (1-x)PbTiO3-xBiCoO3. Specifically, for the composition of 0.5PbTiO3-0.5BiCoO3, an extensive volumetric contraction of ~4.8 % has been observed near the Curie temperature of 700 {\deg}C, which represents the highest level in PbTiO3-based ferroelectrics. According to our experimental and theoretical results, the giant NTE originates from a synergistic effect of the ferroelectrostriction and spin-crossover of cobalt on the crystal lattice. The actual NTE mechanism is contrasted with previous functional NTE materials, in which the NTE is simply coupled with one ordering such as electronic, magnetic, or ferroelectric ordering. The present study sheds light on the understanding of NTE mechanisms and it attests that NTE could be simultaneouslycoupled with different orderings, which will pave a new way toward the design of large NTE materials., Comment: 30 pages

The diffusion of oxygen and its interactions with dopants during laser thermal annealing (LTA) in the melting regime is investigated. O is shown to penetrate from the surface and to diffuse during LTA both into germanium un- and also implanted with arsenic or boron. In the latter cases, the diffusion is unaffected by As, whereas it is significantly reduced by B. Accordingly, the electrical activation of As and B are respectively un-and anti-correlated with O. Therefore, it is concluded that O does not interact with As nor in the melt, nor in the solid phase during the cooling transient. On the other hand, the B–O clustering reported in literature to explain the B deactivation during LTA [Impellizzeri et al., J. Appl. Phys. 113(2013) 113505] occurs already in the liquid phase during the regrowth. Thence, the present data provide noteworthy results for the LTA implementation in future complementary metal-oxide devices.

Germanium recently attracted a renewed interest for its potential applications in several fields such as nanoelectronics, photonics, plasmonics, etc., but well-known issues about doping at high concentration and controlling impurity profiles prevent its integration in technology. To this purpose, p-type doping aluminum ion implantation followed by pulsed laser annealing in the melting regime has been investigated for the first time. In particular, two different regimes have been studied, in order to explore the limit of incorporation for such a method: 6.4 × 1014 Al/cm2 and 4.2 × 1015 Al/cm2, both at 25 keV, corresponding to concentrations below and above the solid solubility, respectively. We found that in the former case, oxygen contamination precludes full activation (

Laser Thermal Annealing (LTA) at various energy densities was used to recrystallize and activate amorphized germanium doped with phosphorous by ion implantation. The structural modifications induced during the recrystallization and the related dopant diffusion were first investigated. After LTA at low energy densities, the P electrical activation was poor while the dopant distribution was mainly localized in the polycrystalline Ge resulting from the anneal. Conversely, full dopant activation (up to 1 x 10(20) cm(-3)) in a perfectly recrystallized material was observed after annealing at higher energy densities. Measurements of lattice parameters performed on the fully activated structures show that P doping results in a lattice expansion, with a perpendicular lattice strain per atom beta(Ps) = +0.7 +/- 0.1 angstrom(3). This clearly indicates that, despite the small atomic radius of P compared to Ge, the "electronic contribution" to the lattice parameter modification (due to the increased hydrostatic deformation potential in the conduction band of P doped Ge) is larger than the "size mismatch contribution" associated with the atomic radii. Such behavior, predicted by theory, is observed experimentally for the first time, thanks to the high sensitivity of the measurement techniques used in this work. (c) 2018 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license.

The understanding of the negative thermal expansion (NTE) mechanism is vital not only for the development of new NTE compounds but also for effectively controlling thermal expansion. Here, we report an interesting isotropic NTE property in cubic GaFe(CN)6 Prussian blue analogues (α l = -3.95 × 10-6 K-1, 100-475 K), which is a new example to understand the complex NTE mechanism. A combined study of synchrotron X-ray diffraction, X-ray total scattering, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations shows that the NTE of GaFe(CN)6 originates from the low-frequency phonons (< ∼100 cm-1), which are directly related to the transverse vibrations of the atomic -Ga-N≡C-Fe- chains. Both the Ga-N and Fe-C chemical bonds are much softer to bend than to stretch. The direct evidence that transverse vibrational contribution to the NTE of GaFe(CN)6 is dominated by N, instead of C atoms, is illustrated. It is interesting to find that the polyhedra of GaFe(CN)6 are not rigid, which is a starting assumption in some models describing the NTE properties of other systems. The NTE mechanism can be vividly described by the "guitar-string" effect, which would be the common feature for the NTE property of many open-framework functional materials, such as Prussian blue analogues, oxides, cyanides, metal-organic frameworks, and zeolites.

The achievement of controlling thermal expansion is important for open-framework structures. The present work proposes a feasible way to adjust the coefficient of thermal expansion continuously from negative to positive via inserting guest Na+ ions or H2O molecules into a GaFe(CN)6 framework. The guest ions or molecules have an intense dampening effect on the transverse vibrations of CN atoms in the −Ga–N≡C–Fe– linkage, especially for the N atoms. This study demonstrates that electrochemical or redox intercalation of guest ions will be an effective way to tune thermal expansion in those negative thermal expansion open-framework materials induced by low-frequency phonons.

A new method for the formation of hole-barrier contacts in high purity germanium (HPGe) is described, which consists in the sputter deposition of a Sb film on HPGe, followed by Sb diffusion produced through laser annealing of the Ge surface in the melting regime. This process gives rise to a very thin ( $ \le 100$ nm) n-doped layer, as determined by SIMS measurement, while preserving the defect-free morphology of HPGe surface. A small prototype of gamma ray detector with a Sb laser-diffused contact was produced and characterized, showing low leakage currents and good spectroscopy data with different gamma ray sources.

International audience; Laser annealing of semiconductor materials is a processing technique offering interesting application features when intense, transient and localized heat sources are needed for electronic device manufacturing or other nano-technological applications. The space-time localization of the induced thermal field (in the nanoseconds/ nanometers scale) promotes interesting non-equilibrium phenomena in the processed material which only recently have been systematically investigated and modelled. In this review paper we discuss the current knowledge on anomalous kinetics occurring in implanted silicon and germanium (i.e. thin layers of disorder diluted alloys of Si and Ge, with variable initial disorder status according to the implantation conditions) during the pulsed laser irradiation. In particular, we focus our attention on the anomalous impurity redistribution in the transient melting stage and on the formation of non conventional and metastable extended defects.

The control of thermal expansion of solid compounds is intriguing but remains challenge. In this study, we investigate the effect of guests on the thermal expansion of open-framework structures. It is interesting to observe that the presence of guest ions (K+) and molecules (H2O) can largely switch thermal expansion of YFe(CN)6 from negative (αv = -33.67*10-6 K-1) to positive (αv = +42.72*10-6 K-1), a range which covers the thermal expansion of most inorganic compounds. The mechanism of such giant switching of thermal expansion is revealed via joint studies of synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting the negative thermal expansion. The present study demonstrates an effective method to control the thermal expansion in open-framework materials by adjusting the presence of guests.

Ge-on-Si has been demonstrated as a platform for Si foundry compatible plasmonics. We use laser thermal annealing to demonstrate activated doping levels >1020 cm−3 which allows most of the 3 to 20 μm mid-infrared sensing window to be covered with enhancements comparable to gold plasmonics.

The goal of this paper is to introduce, and make a preliminary discussion of the mathematical properties of the Boltzmann Collisional Operator which describes the electron flow in a semiconductor device. The collision operator of the Boltzmann equation models the scattering processes between electrons and phonons which are assumed in thermal equilibrium. Due to the particular nature of the scattering mechanisms in the semiconductor case, the collision operator assumes a distinct aspect

High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8 x 10(19) cm(-3) has been achieved starting from an incorporated phosphorous concentration of 1.1 x 10(20) cm(-3). Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved.

International audience; Heavy doping of Ge is crucial for several advanced micro-and optoelectronic applications, but, at the same time, it still remains extremely challenging. Ge heavily n-type doped at a concentration of 1 X 10(20) cm(-3) by As ion implantation and melting laser thermal annealing (LTA) is shown here to be highly metastable. Upon post-LTA conventional thermal annealing As electrically deactivates already at 350 degrees C reaching an active concentration of similar to 4 x 10(19) cm(-3). No significant As diffusion is detected up to 450 degrees C, where the As activation decreases further to similar to 3 x 10(19) cm(-3). The reason for the observed detrimental deactivation was investigated by Atom Probe Tomography and in situ High Resolution X-Ray Diffraction measurements. In general, the thermal stability of heavily doped Ge layers needs to be carefully evaluated because, as shown here, deactivation might occur at very low temperatures, close to those required for low resistivity Ohmic contacting of n-type Ge.

The electrical activation of B+ implanted at 20 keV with a fluence of 1 × 1015 cm−2 in crystalline Ge, following a laser annealing (λ = 308 nm) with multipulses (1, 3, or 10), was studied. Incomplete activation was observed for all the irradiated samples. The inactivation of B was correlated to the presence of oxygen, coming from the native germanium oxide. The formation of B–O complexes occurs during the solidification of the Ge, hampering the substitutionality and the electrical activation of the dopant. We estimated the diffusivity of oxygen in liquid Ge, ∼3 × 10−5 cm2 s−1, by fitting the experimental O concentration profiles. These studies clarify the key role played by oxygen on the electrical activation of B in Ge by laser annealing, and have to be considered for the fabrication of junctions in advanced scaled Ge-based devices.

High purity germanium (HPGe) is the key material for gamma ray detectors production. Its high purity level (≤2 10−4 ppb of doping impurity) has to be preserved in the bulk during the processes needed to form the detector junctions. With the goal of improving the device performance and expanding the application fields, in this paper many alternative doping processes are evaluated, in order to verify their effect on the purity of the material. In more detail, we investigated the electrical activation of contaminating doping defects or impurities inside the bulk HPGe, induced by both conventional and non-conventional surface doping processes, such as boron ion implantation, phosphorus and gallium diffusion from spin-on doping sources, antimony equilibrium diffusion from a remote sputtered source and laser thermal annealing (LTA) of sputtered antimony. Doping defects, thermally-activated during high temperature annealing, were characterized through electrical measurements. A phenomenological model describing the contamination process was developed and used to analyze the diffusion parameters and possible process thermal windows. It resulted that out-of-equilibrium doping processes confined to the HPGe surface have higher possibilities to be successfully employed for the formation of thin contacts, maintaining the pristine purity of the bulk material. Among them, LTA turned out to be the most promising.

International audience; The microscopic mechanisms involving dopants, contaminants, and defects in Ge during pulsed melting laser thermal annealing (LTA) are investigated in detail. Samples both un-implanted and implanted with As or B are processed by LTA as well as characterized in terms of chemical (1D and 3D), electrical, and strain profiling. The clustering of As is directly measured by 3D chemical profiling and correlated with its partial electrical activation along with a reduction of the lattice strain induced by As atoms. A semi-quantitative microscopic model involving the interaction with mobile As-vacancy (AsV) complexes is proposed to describe the clustering mechanism. Boron is shown to follow different clustering behavior that changes with depth and marked by completely different strain levels. Oxygen penetrates from the surface into all the samples as a result of LTA and, only in un-implanted Ge, it occupies an interstitial position inducing also positive strain in the lattice. On the contrary, data suggest that the presence of As or B forces O to assume different configurations with negligible strain, through O-V or O-B interactions for the two dopant species, respectively. These data suggest that LTA does not inject a significant amount of vacancies in Ge, at variance with Si, unless As atoms or possibly other n-type dopants are present. These results have to be carefully considered for modeling the LTA process in Ge and its implementation in technology. (C) 2016 AIP Publishing LLC.

Highly n-type Ge attained by shallow As implantation and excimer laser annealing was studied with positron annihilation spectroscopy and theoretical calculations. We conclude that a high concentration of vacancy-arsenic complexes was introduced by the doping method, while no sign of vacancies was seen in the un-implanted laser-annealed samples. The arsenic bound to the complexes contributes substantially to the passivation of the dopants. Published by AIP Publishing.

Obtaining high level active n+ carrier concentrations in germanium (Ge) has been a significant challenge for further development of Ge devices. By ion implanting phosphorus (P) and fluorine (F) into Ge and restoring crystallinity using Nd:YAG nanosecond pulsed laser melting (PLM), we demonstrate 1020 cm−3 n+ carrier concentration in tensile-strained epitaxial germanium-on-silicon. Scanning electron microscopy shows that after laser treatment, samples implanted with P have an ablated surface, whereas P + F co-implanted samples have good crystallinity and a smooth surface topography. We characterize P and F concentration depth profiles using secondary ion mass spectrometry and spreading resistance profiling. The peak carrier concentration, 1020 cm−3 at 80 nm below the surface, coincides with the peak F concentration, illustrating the key role of F in increasing donor activation. Cross-sectional transmission electron microscopy of the co-implanted sample shows that the Ge epilayer region damaged during implantation is a single crystal after PLM. High-resolution X-ray diffraction and Raman spectroscopy measurements both indicate that the as-grown epitaxial layer strain is preserved after PLM. These results demonstrate that co-implantation and PLM can achieve the combination of n+ carrier concentration and strain in Ge epilayers necessary for next-generation, high-performance Ge-on-Si devices.

The diffusion and activation of arsenic implanted into germanium at 40 keV with maximum concentrations below and above the solid solubility (8 x 10(19) cm(-3)) have been studied, both experimentally and theoretically, after excimer laser annealing (lambda = 308 nm) in the melting regime with different laser energy densities and single or multiple pulses. Arsenic is observed to diffuse similarly for different fluences with no out-diffusion and no formation of pile-up at the maximum melt depth. The diffusion profiles have been satisfactorily simulated by assuming two diffusivity states of As in the molten Ge and a non-equilibrium segregation at the maximum melt depth. The electrical activation is partial and decreases with increasing the chemical concentration with a saturation of the active concentration at 1 x 10(20) cm(-3), which represents a new record for the As-doped Ge system. (C) 2014 AIP Publishing LLC.

An experimental and theoretical study of the effect of excimer laser annealing (ELA) on B redistribution and electrical activation in Ge is reported. We performed detailed structural, chemical, and electrical characterizations of Ge samples implanted with B (20 keV, 1 x 10 15, or 1 x 10(16) B/cm(2)) and processed by ELA (lambda = 308 nm) with multiple pulses (1, 3, or 10). We also developed a diffusion model, in order to simulate the B redistribution induced by the ELA process. We found an anomalous impurity redistribution in the molten phase, which causes a dopant incorporation during the melt-growth at the maximum melt depth. The investigated samples showed a partial electrical activation of the B dopant. The inactivation of B in the samples implanted with 1 x 10(15) B/cm(2) was correlated to an oxygen contamination, while the poor electrical activation of B in the samples implanted with 1 x 10(16) B/cm(2) was related to the precipitation of the dopant, in good agreement with the experimental and theoretical results.

The negative-ion based neutral beam injector for heating and current drive of the ITER plasma (ITER HNB) is under development, at present focusing on the optimization of the full-scale plasma source in the SPIDER test stand. The production of H− or D− ions in the ion source is based on the low work function surfaces obtained by caesium evaporation. This paper describes the caesium conditioning procedure and the corresponding beam performances during the first operation of SPIDER with caesium. Technical solutions to overcome present limitations of the test stand are described. The influence of source parameters on the caesium effectiveness was investigated in short beam pulse operation; with total radio-frequency (RF) power of 400 kW and filling pressure below 0.4 Pa, and a limited number of extraction apertures, a negative ion current density of about 200 A m−2 was extracted in hydrogen, with beam energy lower than 60 keV. Beam optics and beam uniformity were assessed thanks to the acceleration of isolated ion beamlets. A possible procedure to accelerate a uniform beam was demonstrated at low RF power. The results obtained in this first investigation provided key indications on the operation of one of the largest existing sources of accelerated negative hydrogen-like ions.