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Shiv Nadar University

(SoNS) School of Natural Sciences

This paper presents results on the direct synthesis of the β-FeSi2 phase by ion beam mixing of Fe/Si bilayers with Xe ions. The influence of the substrate temperature, ion fluence and energy on the growth of this phase was investigated using Rutherford backscattering (RBS), X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS). Complete growth of single-phase β-FeSi2 was achieved by 205 keV Xe ion irradiation to a fluence of 2 × 1016 ions/cm2 at 600°C. We propose a two-step reaction mechanism involving thermal and ion beam energy deposition. © 2001 Elsevier Science B.V.

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Physics

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Synthesizing single-phase β-FeSi2 via ion beam irradiations of Fe/Si bilayers

On the lattice fermions paired and then composed with precise phases are the lattice bosons. We construct rules for deforming the underlying algebra that keep unchanged the boson interpretation. These deformations alter the phases of the fermion pairs. The solutions of the deformed algebra are the pair-phase excitations of the lattice bosons. We find these eigenstates of the Dirac Hamiltonian of fermions with mass. The gauge interactions are shown to excite the k-deformed modes. © 2001 Published by Elsevier Science B.V.

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Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

Algebraic bosonisation: The case of the Dirac fermion

The effect of pure electronic excitations (by ∼ 835 MeV Kr irradiation) on a stable icosahedral quasicrystal is compared with the effect of electronic excitations combined with the nuclear collisions (by 100 MeV Ni irradiation) occurring in a similar quasicrystal. The critical stopping power was kept at 1300 eV/Å for both the experiments. Under the pure electronic excitations, the R(Φ))/R(0) [ratio of resistance at fluence Φ and the resistance on the same piece with zero fluence) of quasicrystal goes through oscillatory changes, until at ∼ 1 × 1012 ions/cm2 where this ratio drops considerably. The ex-situ XRD on the irradiated sample does show the evidence of degradation of the structure. In contrast, the Ni-irradiated sample shows an increase in resistivity after a critical fluence of 2.5 × 1013 ions/cm2, which remains constant for higher fluences. Corresponding defect annihilation effects are observed in the XRD of Ni-irradiated samples.

Materials Research Society Symposium - Proceedings

The effect of swift heavy ion irradiation on quasicrystals

We construct an isospectrum system in terms of a real and a complex potential to show that the underlying PT-symmetric complex Hamiltonian possesses a real spectrum which is shared by its real partner.

Journal of Physics A: Mathematical and General

A new PT-symmetric complex Hamiltonian with a real spectrum

The family of complex PT-symmetric sextic potentials is studied to show that for various cases the system is essentially quasi-solvable and possesses real, discrete energy eigenvalues. For a particular choice of parameters, we find that under supersymmetric transformations the underlying potential picks up a reflectionless part. (C) 2000 Elsevier Science B.V.

Physics Letters, Section A: General, Atomic and Solid State Physics

PT-symmetric sextic potentials

Modern Physics Letters A

Erratum: Higher derivative supersymmetry, a modified crum-darboux transformation and coherent state (Modern Physics Letters A (1999) 14.1 (27-34))

A new model of supersymmetry between bosons and fermions is proposed. Its representation space is spanned by states with PT symmetry and real energies but the inter-related partner Hamiltonians themselves remain complex and non-Hermitian. The formalism admits vanishing Witten index. (C) 2000 Elsevier Science B.V.

Supersymmetry without hermiticity within PT symmetric quantum mechanics

Thin Ta layers deposited on Si (100) substrates were irradiated with 475 keV Xe+ ions to fluences of (0.5-2) x 1016 ions/cm2 at temperatures between room temperature and 400 °C. By means of Rutherford Backscattering Spectrometry, the interface mixing and tantalum silicide formation were monitored as function of the ion fluence. TaSi2 phase formation was verified using X-ray diffraction. The interface broadening variance was found to depend linearly on the ion fluence and was explained with the help of a compound formation model involving global thermal spikes.

Physica Status Solidi (B) Basic Research

Mixing and silicide formation during Xe-Ion beam irradiations of Ta/Si bilayers

Nitrides, carbides and oxides are important ceramic materials for wide range of applications in coating, nuclear reactor and semiconductor technology. The study of their bonding properties to metals and semiconductors, for instance via ion irradiation, is of great importance. In this work, we report on the effects induced by 100 and 450 keV Xe+ ions in 70-100 nm Ni3N layers deposited on Si substrates. Low-energy irradiation at 80 K was found to cause a preferential nitrogen loss in the near-surface regions and an increase in surface roughness of the Ni3N film. After the 450 keV Xe+ ion irradiation, strong mixing and the formation of Ni2Si and Si3N4 phases were detected at the Ni3N/Si interface. These findings demonstrate the dissociation of Ni3N under ion bombardment and the competition of chemical driving forces and collision cascade mixing at the interface.

Ion-beam irradiation effects on Ni3N/Si bilayers

We report on the room-temperature synthesis of the low-resistivity TaSi2 phase using ion-beam mixing of Ta/Si bilayers with Ar ions. The formation of the silicide phase is observed for different damage energies deposited at the Ta/Si interface. The variance Δσ2 of the reacted (TaSi2) layer thickness varies linearly with the ion fluence Φ and the reaction rate Δσ2/Φ is proportional to the deposited damage energy density FD. The measured mixing/reaction efficiency, Δσ2/ΦFD = 10 ± 1 nm5/keV, is in agreement with the value calculated by the model of compound formation under local thermal spikes.