Biasing

About: Biasing is a research topic. Over the lifetime, 29422 publications have been published within this topic receiving 301035 citations.

Fluorocarbon high‐density plasmas. II. Silicon dioxide and silicon etching using CF4 and CHF3

Abstract: We report a study of the application of CF4 and CHF3 electron cyclotron resonance (ECR) discharges to selective etching of SiO2 over Si. Due to significant fluorocarbon film deposition for plasma operation without rf sample bias in the pressure range below 10 mTorr, rf biasing is required for etching of SiO2 and Si. The rf threshold voltage for etching is 55 V for CHF3 and 35 V for CF4 at a pressure of 1 mTorr. At 100 V rf bias, silicon dioxide etch rates were greater than ≂600 nm/min in CF4 and 450 nm/min for 1000 W plasmas at 1 mTorr pressure. A plot of the oxide etch rate vs rf bias exhibits a fluorocarbon film suppression regime at low rf voltages and an oxide sputtering regime at higher rf voltages. In the fluorocarbon suppression regime, the etch rate is primarily determined by fluorocarbon deposition which results in a thin fluorocarbon film being present on the SiO2 surface during steady‐state etching. In the oxide sputtering regime, the oxide etch rate increases linearly with the ion current to t...

Tunnel junction head structure without current shunting

Abstract: A magnetic tunnel junction (MTJ) device for use as a magnetic field sensor or as a memory cell in a magnetic random access (MRAM) array has one pinned ferromagnetic layer and one free ferromagnetic layer formed on opposite sides of an insulating tunnel barrier layer, and a hard biasing layer that is in proximate contact with and magnetostatically coupled to the free ferromagnetic layer. The magnetic tunnel junction in the sensor is formed on a first shield, which also serves as an electrical lead, and is made up of a stack of layers (MTJ stack). The layers in the MTJ stack are an antiferromagnetic layer, a pinned ferromagnetic layer, an insulating tunnel barrier layer, and a free ferromagnetic layer. The MTJ stack is generally rectangularly shaped with parallel side edges. A layer of hard biasing ferromagnetic material is in abutting contact to or overlapping the MTJ stack to longitudinally bias the magnetic moment of the free ferromagnetic layer in a preferred direction. A first layer of electrically insulating material isolates the hard biasing material from the first shield so that sensing current is not shunted to the hard biasing material but is allowed to flow perpendicularly through the layers in the MTJ stack. A second layer of electrically insulating material isolates the hard bias material from the second shield which also acts as an electrical lead for the MTJ stack.

Ab initio analysis of electron-phonon coupling in molecular devices.

Abstract: We report a first principles analysis of electron-phonon coupling in molecular devices under external bias voltage and during current flow. Our theory and computational framework are based on carrying out density functional theory within the Keldysh nonequilibrium Green's function formalism. Using a molecular tunnel junction of a 1,4-benzenedithiolate molecule contacted by two aluminum leads as an example, we analyze which molecular vibrational modes are most relevant to charge transport under nonequilibrium conditions. We find that the low-lying modes are most important. As a function of bias voltage, the electron-phonon coupling strength can change drastically while the vibrational spectrum changes at a few percent level.

Surface charge in dielectric barrier discharge plasma actuators

Abstract: Direct measurements of the dielectric surface potential and its dynamics in asymmetric dielectric barrier discharge (DBD) plasma actuators show that the charge builds up at the dielectric surface and extends far downstream of the plasma. The surface charge persists for a long time (tens of minutes) after the driving voltage has been turned off. For a sinusoidal voltage waveform, the dielectric surface charges positively. With the voltage waveform consisting of nanosecond pulses superimposed on a dc bias, the sign of the dielectric surface charge is the same as the sign (polarity) of the bias voltage. The surface charging significantly affects DBD plasma actuator performance.

Study of the Piezoelectric Power Generation of ZnO Nanowire Arrays Grown by Different Methods

Abstract: The piezoelectric power generation from ZnO nanowire arrays grown on different substrates using different methods is investigated. ZnO nanowires were grown on n-SiC and n-Si substrates using both the high-temperature vapor liquid solid (VLS) and the low-temperature aqueous chemical growth (ACG) methods. A conductive atomic force microscope (AFM) is used in contact mode to defl ect the ZnO nanowire arrays. No substrate effect was observed but the growth method, crystal quality, density, length, and diameter (aspect ratio) of the nanowires are found to affect the piezoelectric behavior. During the AFM scanning in contact mode without biasing voltage, the ZnO nanowire arrays grown by the VLS method produced higher and larger output voltage signal of 35 mV compared to those grown by the ACG method, which produce smaller output voltage signal of only 5 mV. The fi nite element (FE) method was used to investigate the output voltage for different aspect ratio of the ZnO nanowires. From the FE results it was found that the output voltage increases as the aspect ratio increases and starts to decreases above an aspect ratio of 80 for ZnO nanowires.