TIME RESOLVED REFLECTIVITY MEASUREMENTS APPLIED TO RAPID ISOTHERMAL ANNEALING OF ION IMPLANTED SILICON.

The annealing of ion implantation damage in silicon by rapid isothermal heating has been monitored by the time resolved reflectivity (TRR) method. This technique was applied simultaneously at a wavelength of 632. 8nm and also at 1152nm, where the optical absorption coefficient of silicon is less. The two wavelength method simplifies the interpretation of TRR results, extends the measurement depth and allows good resolution of the position of the interface between amorphous and crystalline silicon. The regrowth of amorphous layers in silicon, created by self implantation and implanted with electrically active impurities, was observed. Regrowth in rapid isothermal annealing occurs during the heating up stage of typical thermal cycles. Impurities such as B, P, and As increase the regrowth rate in a manner consistent with a vacancy model for regrowth. The maximum regrowth rate in boron implanted silicon is limited by the solid solubility.

COMPARISON OF MILLISECOND ANNEALING OF B IMPLANTS AND ISOTHERMAL ANNEALING FOR TIMES OF A FEW SECONDS.

The annealing behaviour of B implants in the millisecond time regime using a combination of swept line beam and background heating is compared with isothermal annealing with heating cycles of a few seconds. Carrier concentration profiles show that under annealing conditions which restrict diffusion, millisecond processing gives higher activation of B implants than isothermal heating. Transmission electron microscopy shows that millisecond annealing also results in a lower defect density.

Loss comparison between an SPWM and harmonic elimination excited small, (<1kW) induction motor drive using Pspice simulation and calorimetry

Adopting square wave excitation to drive induction motors (IMs) can substantially reduce inverter switching losses. However, the low-order time harmonics inherent in the output voltage generates parasitic torques that degrade motor performance and reduce efficiency. In this paper, a novel harmonic elimination modulation technique with full voltage control is studied as an interesting and alternative means of operating small (<1kW) IM drives efficiently. A fully verified harmonic elimination scheme, which removes the 5th, 7th, 11th, 13th and 17 th time harmonics, was implemented and applied to an IGBT driven IM. The power losses incurred in the inverter and the IM as a result of the switching scheme have been determined. © 2008 Crown copyright.

Metastable crystalline AuGe catalysts formed during isothermal germanium nanowire growth

We observe the formation of metastable AuGe phases without quenching, during strictly isothermal nucleation and growth of Ge nanowires, using video-rate lattice-resolved environmental transmission electron microscopy. We explain the unexpected formation of these phases through a novel pathway involving changes in composition rather than temperature. The metastable catalyst has important implications for nanowire growth, and more broadly, the isothermal process provides both a new approach to growing and studying metastable phases, and a new perspective on their formation. © 2012 American Physical Society.

Computation of transient and steady turbulent isothermal flows with an impinging rectangular jet

The computation of both transient and steady turbulent incompressible isothermal flows is studied. The flow is very complex, having streamline curvature, large vortex structures and stagnation resulting from an impinging rectangular jet. For transient computations, the standard k-ε model is adopted. For steady flows, the k-ε, high and low Reynolds number k-l and mixing length models are tried. Zonal approaches combining the above turbulence models are also investigated. None of the models are found to give satisfactory agreement with velocity measurements.