Fundamentals of Ion-Solid Interaction: A Compact Introduction

Abstrac

Physical Sputtering of Metallic Systems by Charged-Particle Impact

The present paper provides a brief overview of our current understanding of physical sputtering by charged-particle impact, with the emphasis on sputtering of metals and alloys under bombardment with particles that produce knock-on collisions. Fundamental aspects of ion-solid interactions, and recent developments in the study of sputtering of elemental targets and preferential sputtering in multicomponent materials are reviewed. We concentrate only on a few specific topics of sputter emission, including the various properties of the sputtered flux and depth of origin, and on connections between sputtering and other radiation-induced and -enhanced phenomena that modify the near-surface composition of the target. The synergistic effects of these diverse processes in changing the composition of the integrated sputtered-atom flux is described in simple physical terms, using selected examples of recent important progress

NMOS DEVICE OPTIMIZATION AND FABRICATION USING ATHENA & ATLAS SIMULATION SOFTWARE

Experiment has proven that NMOS performs better than PMOS due to higher drive current, higher mobility, easier to implement scaling technology and low power consumption. However, there is still room for further optimization as the technology trend for the miniaturization ofNMOS and integrated devices continue to grow. In this project, several objectives have been outlined to be completed within 2 semester period. These include detailed understanding of fabrication aspect and NMOS properties, optimizing NMOS by reducing threshold voltage, minimizing off-stage leakage, reducing gate length, increasing switching speed and designing a mixed mode circuit. However, the cost required to perform experimental analysis and optimization of semiconductor devices using fabrication process can be very expensive especially when involving purchase of expensive electrical testing equipment. Thus, it is recommended to perform optimization and analysis using simulation. One ofthe best device process and simulation tool is Silvaco ATHENA & ATLAS simulation software. It provides user with various capability in process and electrical testing. After manipulating and improving process parameters, the optimized device has recorded significant improvement over the predecessor. Optimizations include better threshold voltage extraction (0.2v), drain current rise beyond pinch off, better drain current extraction, higher switching speed at 2Ghz, better device structure after ion implantation due to tilted implantation, lower off-stage leakage current (1.2589 x 10' A/um) and minimization ofjunction breakdown effect

Historical review of computer simulation of radiation effects in materials

In this Article, I review the development of computer simulation techniques for studying radiation effects in materials from 1946 until 2018. These developments were often closely intertwined with associated experimental developments, which are also briefly discussed in conjunction with the simulations. The focus is on methods that either deal directly with the primary radiation damage generation event, or with such defects or phase changes that typically occur due to radiation. The methods discussed at some length are, in order of historical appearance: Reaction rate theory or rate equations (RE), Monte Carlo neutronics calculations (MCN), Metropolis Monte Carlo (MMC), Molecular Dynamics (MD), Binary Collision Approximation (BCA), Kinetic Monte Carlo (KMC), Discrete Dislocation Dynamics (DDD), Time-Dependent Density Functional Theory (TDDFT), and Finite Element Modelling (FEM). For each method, I present the origins of the methods, some key developments after this, as well as give some opinions on possible future development paths. (C) 2019 The Author. Published by Elsevier B.V.Peer reviewe

Optoelectronic applications of heavily doped GaAs and MoSe₂/FePS₃ heterostructures

Optoelectronics is quickly becoming a fast emerging technology field. It refers to detect or emit electromagnetic radiation, and convert it into a form that can be read by an integrated measuring device. These devices can be a part of many applications like photodiodes, solar cells, light emitting diode (LED), telecommunications, medical equipment, and more. Due to their different applications, the semiconductor optoelectronic devices can be divided by their operating wavelength and working mechanisms. In this work, I have focused on semiconductor plasmonic systems operating in the mid-infrared and on the optical detectors made of 2D materials operating in the UV-visible spectral range. Mid-infrared plasmonic devices are very attractive for chemical sensing. Our results show that ultra-doped n-type GaAs is ideal for mid-infrared plasmonics, where the plasmon wavelength is controlled by electron concentration and can be as short as 4 μm. Ultra-doped n-type GaAs is achieved using ion implantation of chalcogenides like S and Te followed by nonequillibrium thermal annealing, namely ns-range pulsed laser melting or ms-range flash lamp annealing. I have shown that the maximum electron concentration in our GaAs layer can be as high as 7×10¹⁹ cm⁻³, which is a few times higher than that obtained by alternative techniques. In addition to plasmonic applications, the ultra-doped n-type GaAs shows negative magnetoresistance, making GaAs potential material for quantum devices and spintronic applications. UV-visible optical detectors are made of 2D materials based on van der Waals heterostructures, i.e. transition metal dichalcogenides (TMDCs) e.g. MoSe₂ and transition metal chalcogenophosphates (TMCPs) with a general formula MPX₃ where M=Fe, Ni, Mn and X=S, Se, Te. The external quantum efficiency of a self-driven broadband photodetector made of a few layers of MoSe₂/FePS₃ van der Waals heterojunctions is as high as 12 % at 532 nm. Moreover, it is shown that multilayer MoSe₂ on FePS₃ forms a type-II band alignment, while monolayer MoSe₂ on FePS₃ forms a type-I heterojunction. Due to the type-I band alignment, the PL emission from the monolayer MoSe₂ is strongly enhanced

Application of ion beams for fabricating and manipulating III-Mn-V dilute ferromagnetic semiconductors

Manganese (Mn) doped III-V dilute ferromagnetic semiconductors (DFSs) are a candidate materials for semiconductor spintronics due to their intrinsic ferromagnetism mediated by holes. In this thesis, Mn doped III-V dilute ferromagnetic semiconductors (DFSs), including (Ga,Mn)As, (In,Mn)As, (Ga,Mn)P, and (In,Ga,Mn)As have been successfully prepared by ion implantation and pulsed laser melting. All (In,Ga,Mn)As films are confirmed to be well recrystallized and ferromagnetic while their Curie temperatures depend on the Ga concentration. (Ga,Mn)As and (Ga,Mn)P have an inplane easy axis, while an out-of-plane easy axis for (In,Mn)As is observed. However, all of them do not present strong in-plane uniaxial anisotropy between [110] and [110] directions, which always occurs in low temperature molecular beam epitaxy (LT-MBE) grown (Ga,Mn)As samples. The reason is ascribed to the fact that the ultra-fastrecrystallization induced by pulsed laser melting weakens the formation of Mn-Mn dimers along the [100] direction which occurs in LT-MBE grown (Ga,Mn)As. Then selected samples were co-doped with Zn or irradiated with He ions. The Zn co-doping leads to the increase of conductivity of (Ga,Mn)P, however both the Curie temperature and magnetization decrease, which is probably due to the suppression of active Mn substitution by Zn co-doping. By using Rutherford Backscattering Spectroscopy and Particle-Induced X-ray Emission, the substitutional Mn atoms in (Ga,Mn)As are observed to shift to interstitial sites, while more Zn atoms occupy Ga sites. This is consistent with first-principles calculations, showing that the formation energy of substitutional Zn and interstitial Mn is 0.7 eV lower than that of interstitial Zn and substitutional Mn. For ion irradiated (Ga,Mn)As, (In,Mn)As and (Ga,Mn)P, both Curie temperature and magnetization decrease due to the hole compensation. However, the compensation effect is the strongest in (In,Mn)As and the least in (Ga,Mn)P. This is due to the different energy level of the produced defect relative to the band edges in different semiconductors. The results in the thesis point to an important issue: the difference in the band alignment and the hole binding energy of Mn dopants in different III-Mn-V dilute ferromagnetic semiconductors have strong influence on their magnetic properties and should be taken into account in the material design

Antenna near-field wave studies in magnetized plasmas as part of the optimization of auxiliary heating in fusion devicesAntenna near-field wave studies in magnetized plasmas as part of the optimization of auxiliary heating in fusion devices

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Characterization of ion implanted antimony

Ion implanted antimony (121Sb) is characterized as an n-type dopant in single crystal (100) oriented silicon. The required implantation equipment and critical parameters are discussed. The experimental procedures used in this study are presented along with the resulting data on dopant distribution and crystal damage annealing. The tradeoffs between antimony and arsenic, the more commonly used heavy n-type dopant, are examined from both a process end a device perspective. The context of this comparison is in applications that require a heavily doped layer beneath a thin deposit of epitaxial silicon. Results of a specific buried layer process characterization are included