TRANSIENT SCANNING ELECTRON BEAM ANNEALING METHODS USED TO STUDY DIFFUSION AND DEFECTS IN IMPLANTED SILICON.

Rapid thermal annealing of arsenic and boron difluoride implants, such as those used for source/drain regions in CMOS, has been carried out using a scanning electron beam annealer, as part of a study of transient diffusion effects. Three types of e-beam anneal have been performed, with peak temperatures in the range 900 -1200 degree C; the normal isothermal e-beam anneals, together with sub-second fast anneals and 'dual-pulse' anneals, in which the sample undergoes an isothermal pre-anneal followed by rapid heating to the required anneal temperature is less than 0. 5s. The diffusion occuring during these anneal cycles has been modelled using SPS-1D, an implant and diffusion modelling program developed by one of the authors. This has been modified to incorporate simulated temperature vs. time cycles for the anneals. Results are presented applying the usual equilibrium clustering model, a transient point-defect enhancement to the diffusivity proposed recently by Fair and a new dynamic clustering model for arsenic. Good agreement with SIMS measurements is obtained using the dynamic clustering model, without recourse to a transient defect model.

Conduction bottleneck in silicon nanochain single electron transistors operating at room temperature

Single electron transistors are fabricated on single Si nanochains, synthesised by thermal evaporation of SiO solid sources. The nanochains consist of one-dimensional arrays of ~10nm Si nanocrystals, separated by SiO 2 regions. At 300 K, strong Coulomb staircases are seen in the drain-source current-voltage (I ds-V ds) characteristics, and single-electron oscillations are seen in the drain-source current-gate voltage (I ds-V ds) characteristics. From 300-20 K, a large increase in the Coulomb blockade region is observed. The characteristics are explained using singleelectron Monte Carlo simulation, where an inhomogeneous multiple tunnel junction represents a nanochain. Any reduction in capacitance at a nanocrystal well within the nanochain creates a conduction " bottleneck", suppressing current at low voltage and improving the Coulomb staircase. The single-electron charging energy at such an island can be very high, ~20k BT at 300 K. © 2012 The Japan Society of Applied Physics.

Hot electron field emission via individually transistor-ballasted carbon nanotube arrays.

We present electronically controlled field emission characteristics of arrays of individually ballasted carbon nanotubes synthesized by plasma-enhanced chemical vapor deposition on silicon-on-insulator substrates. By adjusting the source-drain potential we have demonstrated the ability to controllable limit the emission current density by more than 1 order of magnitude. Dynamic control over both the turn-on electric field and field enhancement factor have been noted. A hot electron model is presented. The ballasted nanotubes are populated with hot electrons due to the highly crystalline Si channel and the high local electric field at the nanotube base. This positively shifts the Fermi level and results in a broad energy distribution about this mean, compared to the narrow spread, lower energy thermalized electron population in standard metallic emitters. The proposed vertically aligned carbon nanotube field-emitting electron source offers a viable platform for X-ray emitters and displays applications that require accurate and highly stable control over the emission characteristics.

Optimization of thermal material in a flux pump system with high temperature superconductor

Superconductors are known for the ability to trap magnetic field. A thermally actuated magnetization (TAM) flux pump is a system that utilizes the thermal material to generate multiple small magnetic pulses resulting in a high magnetization accumulated in the superconductor. Ferrites are a good thermal material candidate for the future TAM flux pumps because the relative permeability of ferrite changes significantly with temperature, particularly around the Curie temperature. Several soft ferrites have been specially synthesized to reduce the cost and improve the efficiency of the TAM flux pump. Various ferrite compositions have been tested under a temperature variation ranging from 77K to 300K. The experimental results of the synthesized soft ferrites-Cu 0.3 Zn 0.7Ti 0.04Fe 1.96O 4, including the Curie temperature, magnetic relative permeability and the volume magnetization (emu/cm3), are presented in this paper. The results are compared with original thermal material, gadolinium, used in the TAM flux pump system.-Cu 0.3 Zn 0.7Ti 0.04 Fe 1.96O 4 holds superior characteristics and is believed to be a suitable material for next generation TAM flux pump. © 2011 IEEE.

Temperature dependent electron transport in amorphous oxide semiconductor thin film transistors

A temperature-dependent mobility model in amorphous oxide semiconductor (AOS) thin film transistors (TFTs) extracted from measurements of source-drain terminal currents at different gate voltages and temperatures is presented. At low gate voltages, trap-limited conduction prevails for a broad range of temperatures, whereas variable range hopping becomes dominant at lower temperatures. At high gate voltages and for all temperatures, percolation conduction comes into the picture. In all cases, the temperature-dependent mobility model obeys a universal power law as a function of gate voltage. © 2011 IEEE.

Magnetophonon resonance in graphite: High-field Raman measurements and electron-phonon coupling contributions

We perform Raman scattering experiments on natural graphite in magnetic fields up to 45 T, observing a series of peaks due to interband electronic excitations over a much broader magnetic field range than previously reported. We also explore electron-phonon coupling in graphite via magnetophonon resonances. The Raman G peak shifts and splits as a function of magnetic field, due to the magnetically tuned coupling of the E 2g optical phonons with the K- and H-point inter-Landau-level excitations. The analysis of the observed anticrossing behavior allows us to determine the electron-phonon coupling for both K- and H-point carriers. In the highest field range (>35 T) the G peak narrows due to suppression of electron-phonon interaction. © 2012 American Physical Society.