Volume 92, Issue 10, 15 November 2002
Index of content:
- DEVICE PHYSICS (PACS 85)
92(2002); http://dx.doi.org/10.1063/1.1513187View Description Hide Description
We evaluated amorphous siliconthin-film transistors(TFTs) fabricated on polyimide foil under uniaxial compressive or tensile strain. The strain was induced by bending or stretching. The on- current and hence the electron linear mobility μ depend on strain ε as where tensile strain has a positive sign and the strain is parallel to the TFT source-drain current path. Upon the application of compressive or tensile strain the mobility changes “instantly” and under compression then remains constant for up to 40 h. In tension, the TFTs fail mechanically at a strain of about but recover if the strain is released “immediately.”
Correlation between channel mobility and shallow interface traps in SiC metal–oxide–semiconductor field-effect transistors92(2002); http://dx.doi.org/10.1063/1.1513210View Description Hide Description
The shallow interface trap density near the conduction band in siliconcarbide(SiC) metal–oxide–semiconductor (MOS)structure was evaluated by making capacitance–voltage measurements with gate-controlled-diode configuration using the n-channel MOSfield effect transistors(MOSFETs). The close correlation between the channel mobility and the shallow interface trap density was clearly found for the 4H- and 6H-SiC MOSFETs prepared with various gate-oxidation procedures. This result is strong evidence that a significant cause of the poor inversion channel mobility of SiCMOSFETs is the high density of shallow traps between the conduction band edge and the surface Fermi level at the threshold.
Superconducting trapped-field magnets: Temperature and field distributions during pulsed-field activation92(2002); http://dx.doi.org/10.1063/1.1515098View Description Hide Description
We calculate the temperature and magnetic field distributions in a bulk superconductor during the process of pulsed-field magnetic activation. The calculations are based on the heat diffusion equation with account of the heat produced by flux motion, and the critical state model with temperature dependent critical current density. For a given activation time, the total amount of trapped flux is maximum for an optimal value of the maximal applied field. We analyze how and depend on the material parameters and the field ramp rate.
Thermal stability of the exchanged biased CoFe/IrMn electrode for the magnetic tunnel junction as a function of CoFe thickness92(2002); http://dx.doi.org/10.1063/1.1516623View Description Hide Description
Pinned electrodes of the magnetic tunnel junction(MTJ) consisting of where were thermally annealed and analyzed using Auger electron spectroscopy and transmission electron microscopy in order to study the effects of the CoFe thickness on the interdiffusion of elements in the pinned electrode. Increasing CoFe thickness reduced the Mn migration out of the IrMn layer towards the tunnel barrier. An CoFe layer completely blocked the Mn diffusion up to 350 °C with minimal reduction of the tunneling magnetoresistance (TMR) ratio when full junction was fabricated. Although other mechanisms could be responsible for the thermal degradation of the MTJ, the Mn diffusion appears to be related to the reduction of the TMR at 300 °C. Since the presence of Mn in the tunnel barrier as an impurity is detrimental to the junction performance, reduction of Mn migration towards the tunnel barrier by increasing the CoFe electrode should improve the postannealed performance of the junction.