Volume 92, Issue 5, 01 September 2002
Index of content:
- DEVICE PHYSICS (PACS 85)
92(2002); http://dx.doi.org/10.1063/1.1496123View Description Hide Description
Electrical pull-in instability of microscale structures is an important failure mechanism in microelectromechanical systems(MEMS), in which there is no equilibrium state for the MEMSstructures. Using the elastic membrane theory, the electromechanical interaction of a suspended MEMSstructure in an electric field is presented. The statically mechanical deformation of the microscale membrane under electrostatic loading is examined. The critical value of electric voltage needed to pull the membrane into the contact with the substrate is determined analytically. The critical pull-in electric voltage is proportional to the square root of the residual tensile force and inversely proportional to the length of the membrane if the residual line tensile force is much larger than the line force due to the stretch of the membrane, while it is inversely proportional to the square of the membrane length if the membrane is initially stress free. The contact problem after the occurrence of the pull-in collapse phenomenon is studied. It turns out that the contact length between the membrane and the substrate increases with the increase of the membrane length and the electric voltage, and decreases with the tensile force in the membrane. A closed-form solution on the release–electric voltage is obtained, which depends on the membrane length and the tensile force.
92(2002); http://dx.doi.org/10.1063/1.1499201View Description Hide Description
We present a systematic analysis of the current transients accompanying the formation of the electrode–electrolyte double layers in organic light-emitting electrochemical cells. By using various room-temperature molten salts,conducting polymers, and electrodes, we show that the current I always decreases as a power law of time, The current transients are formed of various time domains, each one being characterized by a power-law exponent Impedance measurements conducted from 5 Hz to 5 MHz demonstrate that these transients represent the time response of a simple combination of constant phase angle (CPA) impedances, and of the electrolyteionic conductivity. The physical origin of the CPA impedance is attributed to the roughness of the interface between the electrodes and the electrolyte, and to the phase separation within the salt–polymer blend.
92(2002); http://dx.doi.org/10.1063/1.1500417View Description Hide Description
Defects in the emitter region of heterojunctionbipolar transistors (HBTs) were investigated by means of deep-level transient spectroscopy. Both annealed (635 °C, 5 min) and as grownmetalorganic chemical vapor depositionepitaxial wafers were investigated in this study, with an electron trap observed in the HBT emitter space-charge region from both wafers. The deep-level activation energy was determined to be below the conduction band, the capture cross section and the defect density of the order of This defect was also found to be localized at the emitter–base interface.
Hafnium oxide gate stack prepared by in situ rapid thermal chemical vapor deposition process for advanced gate dielectrics92(2002); http://dx.doi.org/10.1063/1.1500420View Description Hide Description
A high-quality gate stack with equivalent oxide thickness (EOT) of 7.8 Å and a leakage current of @ has been achieved by an in situ rapid thermal chemical vapor deposition process. It is found that both -based interface layer and postdeposition annealing are very effective in reducing EOT and leakage, and at the same time, improving film qualities. These gate stacks show negligible frequency dependence, small hysteresis in capacitance–voltage and weak temperature dependence of the leakage current. They also show negligible charge trapping at high voltage stress.
Fabrication of niobium superconductor–insulator–superconductor junctions with a magnetic tunneling barrier for millimeter and submillimeter mixer applications92(2002); http://dx.doi.org/10.1063/1.1500415View Description Hide Description
A thin-film superconductor-insulator-superconductor junction with a magnetic barrier, and superconductingelectrode,Nb, was fabricated. It is shown that the Josephson current was strongly suppressed without external magnetic field. The tunneling barrier was formed by plasma oxidation and or thermal oxidation. The junction with thermal oxidation showed low specific resistance and current–voltage characteristics with a clear energy gap structure. It is shown that this junction has the potential for quasiparticle mixer working at higher submillimeter wave frequency region above ∼700 GHz, especially suited for making an imaging array.