The nuclear matter and charge radii of the helium isotopes (A=4,6,8) are calculated by quantitati... more The nuclear matter and charge radii of the helium isotopes (A=4,6,8) are calculated by quantitative geometrical thermodynamics (QGT) taking as input the symmetry of the alpha‐particle, the very weak binding (and hence halo nature) of the heavier helium isotopes, and a characteristic length scale given by the proton size. The results follow by considering each isotope in its ground state, with QGT representing each system as a maximum entropy configuration that conforms to the Holographic Principle. This allows key geometric parameters to be determined from the number of degrees of freedom available. QGT treats 6He as a 4He core plus a concentric neutron shell comprising a holomorphic pair of neutrons, and the 8He neutron halo is treated as a holomorphic pair of holomorphic pairs. Considering that the information content of each system allows a correlation angle of 2π/3 between the holomorphic entities to be inferred, then the charge radii of the three isotopes can be calculated from...
Double-spiral galaxies are common in the Universe. It is known that the logarithmic double spiral... more Double-spiral galaxies are common in the Universe. It is known that the logarithmic double spiral is a Maximum Entropy geometry in hyperbolic (flat) spacetime that well represents an idealised spiral galaxy, with its central supermassive black hole (SMBH) entropy accounting for key galactic structural features including the stability and the double-armed geometry. Over time the central black hole must accrete mass, with the overall galactic entropy increasing: the galaxy is not at equilibrium. From the associated entropic Euler–Lagrange Equation (enabling the application of Noether’s theorem) we develop analytic expressions for the galactic entropy production of an idealised spiral galaxy showing that it is a conserved quantity, and we also derive an appropriate expression for its relativistic entropic Hamiltonian. We generalise Onsager’s celebrated expression for entropy production and demonstrate that galactic entropy production (entropy production corresponds to the intrinsic dis...
Influence of dynamic annealing on the depth distribution of germanium implanted in (100) silicon at elevated temperatures
MRS Proceedings, 1997
(100) silicon wafers were implanted at elevated temperatures up to 600°C with l×lO15-5×1015 Ge+/c... more (100) silicon wafers were implanted at elevated temperatures up to 600°C with l×lO15-5×1015 Ge+/cm2 using 120 keV. The wafers were tilted by 5–7° and rotated by 5–15°. The implanted germanium profile was monitored as a function of implant temperature using RBS-channelling. Considerable profile broadening was seen together with apparent mass germanium migration away from the surface in samples implanted at 300°C and above. Control implants into hot and cold samples simultaneously rule out excess loss of germanium from the heated wafers. Channelling data indicate that while room temperature implants lead to amorphisation, with hot implants good quality layers are obtained in which the germanium atoms occupy substitutional sites. Hot implants into a sample previously implanted with germanium at room temperature does not lead to any redistribution in the original germanium profile. This result indicates that the apparent enhanced indiffusion of germanium is not a radiation assisted phenomenon and could be explained by a considerable channelling of the implanted germaniumatoms along the <100> direction.
Understanding the effect of radiation damage and noble gas accommodation in potential ceramic hos... more Understanding the effect of radiation damage and noble gas accommodation in potential ceramic hosts for plutonium disposition is necessary to evaluate the long-term behaviour during geological disposal. Polycrystalline samples of Nd-doped zirconolite and Nd-doped perovskite were irradiated ex-situ with 2 MeV Kr + at a dose of 5x10 15 ions.cm -2 to simulate plutonium nuclei recoil during alpha decay. The feasibility of thin section preparation of both pristine and irradiated samples by Focussed Ion Beam sectioning was demonstrated. After irradiation, the Nd-doped zirconolite revealed a well defined amorphous region separated from the pristine material by a thin (40-60 nm) damaged interface. The Nd-doped perovskite contained a defined irradiated region composed of an amorphous region surrounded by damaged regions. In both samples, as revealed by electron diffraction, the damaged regions and interface have a structure in which the fluorite sublattice is present while the pristine lattice is absent. In addition in Nddoped perovskite, the amorphisation dose depended on crystallographic orientation and possibly sample configuration (thin section and bulk). In Nd-doped perovskite, Electron Energy Loss Spectroscopy study revealed a change in Ti coordination associated with the crystal to amorphous transition.
Rutherford backscattering is used to obtain absolute compositional data from InGaAs thin Ðlms wit... more Rutherford backscattering is used to obtain absolute compositional data from InGaAs thin Ðlms without any reference standards. Carbon-doped thin Ðlms with compositions varying between 0.02 AE x AE 0.4 have In x Ga 1~x As been analysed and values of x obtained with an estimated accuracy of ¿1% in most cases. The observed variation in two measurements of a set of nine samples with a range of values of x has a mean of 1.000 and a standard deviation of 2.2% . This observed error is not inconsistent (at the 5% signiÐcance level) with the estimated error. The analytical method described is valid for many compound thin Ðlms.
The reaction of ion-beam mixed titanium layers on silicon induced by electron beam heating
Semiconductor Science and Technology, 1989
... F Mahmood?, VK Ramant:, RA McMahon?, H Ahmedt, C Jeynesg and D Sarkarll t Microelectronics Re... more ... F Mahmood?, VK Ramant:, RA McMahon?, H Ahmedt, C Jeynesg and D Sarkarll t Microelectronics Research Laboratory, Physics Department ... different time and temperature conditions and the properties of the reacted layers were explored by sheet resistance measurements ...
Systematic Monte Carlo simulation studies have been carried out to search for a possible optimal ... more Systematic Monte Carlo simulation studies have been carried out to search for a possible optimal experimental condition on the irradiation damage profile production with a given mask structure. The results suggest that minimum ion scattering broadening tails could be achieved with projectile ranges in Nb mask about half of the mask thickness. Provided the projectile range to mask thickness is maintained, similar irradiation damage profiles could be created by different ions, including ions as heavy as Cu þ .
RBS/simulated annealing analysis of silicide formation in Fe/Si systems
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998
... Poor vacuum conditions induced further oxidation of Fe during post-implantation annealing. Th... more ... Poor vacuum conditions induced further oxidation of Fe during post-implantation annealing. The annealing seems to have induced a more rapid Fe oxidation than an FeSi reaction, ie, the FeSi reaction was retarded due to rapid Fe oxidation. ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
Perturbation of proton beam damage pro®le due to sidewall interactions in very high aspect ratio ... more Perturbation of proton beam damage pro®le due to sidewall interactions in very high aspect ratio implant masks has been studied using Monte Carlo simulations. The model structure is composed of amorphous Nb metal mask, crystalline high temperature superconducting YBa 2 Cu 3 O 7Àd (YBCO) thin ®lm, and amorphous LaAlO 3 substrate. The simulation results reveal the existence of enhanced proton beam penetration in target materials due to sidewall interactions.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2001
Monte Carlo simulations of irradiation damage pro®les in high aspect ratio Nb masked YBa 2 Cu 3 O... more Monte Carlo simulations of irradiation damage pro®les in high aspect ratio Nb masked YBa 2 Cu 3 O 7Àd thin ®lm reveal an improved damage pro®le when O beams are used instead of proton beams. The overall damage pro®le is insensitive to either beam divergence or beam misalignment but the damage accumulation levels are signi®cantly aected by these eects.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002
Recent experimental progress in high T c Josephson junction fabrication using masked ion beam irr... more Recent experimental progress in high T c Josephson junction fabrication using masked ion beam irradiation damage technique demands a further study on the irradiation damage defect accumulation and distribution inside YBCO thin films under different Au mask structures. Both primary energy depositions and irradiation produced vacancy concentrations have been estimated using Monte Carlo simulation codes CRYSTAL and TRIM-CASCADE, respectively. The properties of the irradiation damaged barrier layer are very closely associated with the effective production and distribution of lattice vacancies on different sublattice sites. With a 50 keV proton beam irradiation, a uniform and effective production of vacancies is expected with 100 nm YBCO thin film on LaAlO 3 substrate covered with 150 nm Au mask. A similar vacancy distribution is expected with a thinner Au mask and a lower energy proton beam irradiation.
A 2 MV heavy ion Van de Graaff implanter for research and development
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1993
A high energy heavy ion implantation system is described which is based upon a 2 MV High Voltage ... more A high energy heavy ion implantation system is described which is based upon a 2 MV High Voltage Engineering Europa Van de Graaff accelerator, which incorporates an ion source rapid exchange mechanism. The design and performance are described with particular reference to the system mass resolution, beam transport and performance of a sputter ion source. The system is used to provide a wide ranging implantation service and also supports material science studies, some of which are described briefly.
Patterned ion beam implantation of Co ions into a SiO 2 thin film via ordered nanoporous alumina masks
Nanotechnology, 2012
Spatially patterned ion beam implantation of 190 keV Co(+) ions into a SiO(2) thin film on a Si s... more Spatially patterned ion beam implantation of 190 keV Co(+) ions into a SiO(2) thin film on a Si substrate has been achieved by using nanoporous anodic aluminum oxide with a pore diameter of 125 nm as a mask. The successful synthesis of periodic embedded Co regions using pattern transfer is demonstrated for the first time using cross-sectional (scanning) transmission electron microscopy (TEM) in combination with analytical TEM. Implanted Co regions are found at the correct relative lateral periodicity given by the mask and at a depth of about 120 nm.
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Papers by Chris Jeynes