Space charge

About: Space charge is a research topic. Over the lifetime, 18000 publications have been published within this topic receiving 272648 citations.

Conduction mechanisms responsible for leakage currents in RF sputtered HfO2 high-κ gate-oxide thin film MOS capacitors

Abstract: MOS capacitors with HfO2 thin films as a high-κ gate-oxide layer were fabricated by RF sputtering for varied film thicknesses. These films were amorphous with thicknesses ranged from 35.9 to 87.9 nm. XPS confirmed the presence of SiOx interfacial layer. The HfO2 film of physical thickness 49.3 nm had shown a dielectric constant of 26.9 and an effective oxide thickness of 7.1 nm. However, the lowest leakage current was measured as 4.6 × 10−7 A/cm2 at −1 V in the MOS capacitor with a 35.9 nm thick HfO2 gate-oxide layer. The leakage currents were majorly due to the conduction, which is space charge limited and was effective almost in the entire considered region of biasing (0 to −15 V). Additionally, the emissions at different voltage regions are explained based on Poole-Frenkel (from 0 to −3 V), Schottky effect (−3 to −9 V), trap-assisted, and Fowler-Nordheim tunnelling (−9 to −15 V). Complete leakage current mechanisms are discussed.

II. The Space Charge Distribution in the Pre-Oscillation Magnetron

Abstract: A description is given of a molecular beam apparatus which has been used to study the space charge distribution in a smooth anode cylindrical magnetron operating below cut-off. Relative values of the density have been measured as a function of both the radius and the anode voltage in magnetrons with anode to cathode radius ratios of 2·0 and 2·5. The results show that the density falls off gradually from the cathode, smoothly at first, and then in a series of small steps beyond the cloud radius predicted by the stream theories. The space charge has no definite edge. Increasing the anode voltage increases the radius of the cloud and the density at each point in the space charge. None of the quantitative theories predicts a distribution of this form and the implications of this are discussed in a companion paper.

Space Charge Experiments and Simulation in the Fermilab Booster

Abstract: We have studied space charge effects in the Fermilab Booster. Our studies include investigation of coherent and incoherent tune shifts and halo formation. We compare experimental results with simulations using the 3-D space charge package Synergia.

Space Charge Studies with High Intensity Single Bunch Beams in the CERN SPS

Abstract: In order to reach the target beam parameters of the LHC injectors upgrade (LIU) project the beam degradation due to losses and emittance growth on the long injection plateau of the SPS needs to be minimized. A detailed study of the dependence of losses, transverse emittance blow-up and transverse beam tail creation as function of the working point is presented here for a high brightness single bunch beam with a vertical space charge tune spread of about 0.2 on the 26 GeV injection plateau. The beam behavior close to important betatron resonances is characterized and a region in the tune diagram with minimal beam degradation is identified. Implications about the performance for LIU beams are discussed.

Role of Near Substrate and Bulk Polymer Morphology on Out-of-Plane Space-Charge Limited Hole Mobility

Abstract: Charge transport is a central issue in all types of organic electronic devices. In organic films, charge transport is crucially limited by film microstructure and the nature of the substrate/organic interface interactions. In this report, we discuss the influence of active layer thickness on space-charge limited hole transport in pristine polymer and polymer/fullerene bulk heterojunction thin films (∼15–300 nm) in a diode structure. According to the results, the out-of-plane hole mobility in pristine polymers is sensitive to the degree of polymer chain aggregation. Blending the polymers with a fullerene molecule does not change the trend of hole mobility if the polymer tends to make an amorphous structure. However, employing an aggregating polymer in a bulk heterojunction blend gives rise to a marked difference in charge carrier transport behavior compared to the pristine polymer and this difference is sensitive to active layer thickness. In aggregating polymer films, the thickness-dependent interchain in...