Practical stability and boundedness criteria of impulsive differential system with initial time difference

In this paper, an impulsive differential system is investigated for the first time for practical stability and boundedness criteria with respect to initial time difference. The investigations are carried out by perturbing Lyapunov functions and by using comparison results. A generalized Lyapunov function has been used for the investigation. The present results indicate that the stability criteria significantly depend on the moment of impulses.Publisher's Versio

Inquietud: Año IV Número 41 - (18/11/52)

Several experimental techniques are available to investigate materials but microscopic techniques based on hyperfine interaction form a subclass that can characterize materials at the smallest possible atomic scale. The interaction of the nuclear electromagnetic moments with the hyperfine fields arising from the extranuclear electronic charges and spin distributions forms the basis of hyperfine methods. In this review article, one of the hyperfine methods, known as perturbed angular correlation (PAC), has been described as it provides local-scale fingerprints about the formation, identification, and lattice environment of defects and/or defect complexes in semiconductors at the PAC probe site. In particular, the potential of the PAC technique has been demonstrated in terms of measured electric field gradient, its orientation, and the symmetry at the probe site for a variety of defects in semiconductors such as Si, InP, GaAs, InAs, ZnO, GaP, and InN

Characterization of radiation damage annealing of recoil-implanted GaP

The recovery of crystallinity as a function of annealing temperature in GaP recoil-implanted with111In has been monitored on an atomic scale using the perturbed angular correlation (PAC) technique. This technique is based on hyperfine interaction of the electric quadrupole moment of probe nuclei with the electric field gradient (EFG) of the host lattice. The111In/Cd probe nuclei were recoil-implanted at room temperature with an energy of up to 8 MeV following heavy-ion nuclear fusion evaporation reactions. Measurements were performed at room temperature for as-implanted and furnace annealed samples. Isochronal annealing in ambient nitrogen up to 950 °C showed a progressive reduction of disorder around the probe nuclei as indicated by a continual decrease in the width of the EFG distribution. These measurements suggest that recoil implantation did not result in drastic damage to the sample, and that annealing at 800 °C for 30 min is sufficient to produce an optimum recovery of crystallinity. Also, complementary double crystal X-ray diffraction measurements were in qualitative agreement with the results derived from PAC

Impact of initial time difference on stability criteria of impulsive differential equations

In this paper, an impulsive differential system is investigated for the first time for several stability criteria relative to initial time difference. The investigations are carried out by perturbing Lyapunov functions and by using comparison results. A generalized Lyapunov function has been used for the investigation.The results that are obtained to investigate the stability significantly depend on the moment of impulses. An example is given to illustrate the derived result.Publisher's Versio

Room temperature relaxation of irradiated InP, GaAs and InAs characterized with the perturbed angular correlation technique

The structural relaxation of irradiated III-V compound semiconductors InP, GaAs and InAs arising from room temperature annealing has been studied using perturbed angular correlation spectroscopy. Amorphous zones were produced by MeV Ge ion implantation in single crystal substrates at liquid nitrogen temperature. These amorphous zones were found to relax continuously to a disordered state of lower energy with characteristic relaxation times of a few hours to a few days which are described by a double exponential decay function. We attribute this transformation or relaxation of amorphous to disordered material to a process akin to solid-phase-epitaxial-growth

Probing the Indium Nitride Lattice Locally with the Radioisotope Probe 111In/Cd

The lattice structure of both InN grains with submicron dimensions and a MBE-grown InN film have been studied with the radioisotope probe 111in/Cd and Perturbed Angular Correlation spectroscopy. The quadrupole interaction frequency of the probe in this material has been measured to be of the order of 28 MHz, consistent with results for ALN and GaN. Strong damping of the signal indicates that InN has a highly defective lattice with diverse defect structures, which are not cured by annealing in the accessible temperature range

Variation of ion-irradiation induced strain as a function of ion fluence in Si

Strain in Si induced by ion irradiation at temperatures of 200-400 °C has been measured at room temperature. Quantitative analysis of the strain distribution produced by 750-keV Si ion implantation in Si substrates was characterized by double-crystal X-

Pd-Vacancy Complex in Si Identified with the Perturbed Angular Correlation Technique

A Pd-vacancy (Pd-V-) complex in Si has been identified with the perturbed angular correlation technique using the radioactive Pd100 probe produced by recoil implantation. The fraction of Pd probes in the complex has been determined as a function of dopant type (B, P, As, and Sb), dopant concentration (1015-6×1019cm-3) and annealing temperature (21-500°C). The Pd-V- complex, with a unique interaction frequency of 13.1(2)MHz, was observed only in n+-Si with a maximum relative fraction of ∼52% achieved between 200-300°C while a broad distribution of interaction frequencies was apparent in n-, p-, and p+-Si. Annealing beyond 300°C yielded a reduction in the Pd-V- fraction with a dissociation energy of 2.5(7)eV. Density functional theory calculations of the electric field gradient for the given defect configuration were consistent with a measured value of 3.58×1021V m2