[en] Measurements of the threshold for secondary electron emission and shifts of the carbon Auger line position have been used to deduce the surface potential of several common phosphors during irradiation by electrons in the 0.5--5.0 keV range. All of the insulating phosphors display similar behavior: the surface potential is within ±1 V of zero at low electron energies. However, above 2--3 kV it becomes increasingly negative, reaching hundreds of volts within 1 keV of the turn-on energy. The electron energy at which this charging begins decreases dramatically after Coulomb aging at 17 microA/cm² for 30--60 min. Measurements using coincident electron beams at low and high electron energies to control the surface potential were made to investigate the dependence of the cathodoluminescence (CL) process on charging. Initially, the CL from the two beams is identical to the sum of the separate beam responses, but after Coulomb aging large deviations from this additivity are observed. These results indicate that charging has important, detrimental effects on CL efficiency after prolonged e-beam irradiation. Measurements of the electron energy dependence of the CL efficiency before and after Coulomb aging will also be presented, and the implications of these data on the physics of the low-voltage CL process will be discussed

[en] We report experimental results suggesting that mobile protons are generated at strained Si-O-Si bonds near the Si/SiO₂ interface during annealing in forming gas. Our data further suggest that the presence of the top Si layer plays a crucial role in the mobile H⁺ generation process. Finally, we show that the diffusion of the reactive species (presumably H₂ or H⁰) towards the H⁺ generation sites occurs laterally along the buried oxide layer, and can be impeded significantly due to the presence of trapping sites in the buried oxide

[en] Defect centers generated in vacuum-ultraviolet irradiated chemical-mechanical polished oxides have been characterized using electron paramagnetic resonance and C-V analysis. Both oxide trap E_γ and interface trap P_b0 centers were detected in unpolished and polished oxides. In addition, another interface defect center known as the P_b1 center was only identified in the polished oxides, suggesting that the polishing process altered the SiO₂/Si interface

[en] Shifts of the surface potential were measured for several commercial phosphors by monitoring secondary and Auger electron spectra during electron beam irradiation at energies between 0.5 and 5 keV. The insulating phosphors charge strongly negative above 2 keV, whereas the conductive ones do not. This charging behavior is exaggerated after prolonged beam exposure. Measurements using two coincident electron beams to control the surface potential demonstrate that aging-enhanced surface charging decreases the phosphor cathodoluminescence. The dependence of the phosphor surface potential on the voltage applied to the metal plate on which they are deposited was also determined. These data suggest the presence of substantial space charge in the phosphors, even at low electron beam energies where no beam-induced shifts of the surface potentials are seen. We suggest that the electric fields due to these near-surface space charge regions are crucial in altering secondary emission and in establishing a steady state charge balance in the case where no currents can flow from the irradiated phosphor surface to the conductive backplane. copyright 1997 American Institute of Physics

[en] We demonstrate that extended e-beam exposure produces a contaminating overlayer on phosphors whose opacity increases roughly linearly with time. Raman scattering data and optical analysis indicate that this layer is graphitic in nature, arising from the electron-beam-stimulated conversion of hydrocarbons adsorbed from the vacuum ambient. The presence of this contamination optically attenuates emitted cathodoluminescence, prevents many low energy electrons from ever reaching the phosphor grains, and exacerbates surface charging which reduces the arrival energy of electrons above 1.5 endash 2 keV. All of these effects are shown to impact cathodoluminescent output in an important way, but an accurate accounting of their total impact will be required to assess the importance of other degradation mechanisms like enhanced nonradiative electron-hole recombination at surfaces, both carbon and noncarbon related. copyright 1997 American Institute of Physics

[en] A low-voltage, radiation-tolerant, nonvolatile field effect transistor (NVFET) memory involving proton motion in SiO₂ is illustrated in both bulk Si and silicon-on-insulator devices. The authors discuss a mechanism by which the protons are created in the oxide layer by a forming gas anneal. At low temperature (T < 250 C), the H+ is largely imprisoned in the buried SiO₂ layer; i.e., the ions are sandwiched between the two encapsulating Si layers. The Si layers can be either c-Si or poly-Si, thus the technology is compatible with standard Si processing. The protons can be reliably and controllably drifted from one interface to another without any noticeable degradation in the signal past 10⁶ cycles. Under an unbiased condition, the net proton density is not significantly affected by radiation up to at least 100 krad (SiO₂). Last, the authors compare many of the properties of the NVFET to commercial flash nonvolatile memories

[en] We find that the reduction of the switchable polarization in BaTiO₃ crystals via repeated polarization reversals (fatigue) is accompanied by the trapping of electronic charge and atomic scale distortions in the perovskite oxygen octahedron. The distortions are proposed to involve oxygen vacancies. copyright 1995 American Institute of Physics

[en] Doped oxide thin films are quite commonplace in the microelectronics community as insulating layers in Si device technologies. Thus, it is somewhat surprising that very little is known about the electronic structure of defects in these thin film dielectrics. The role of dopants in SiO₂ films is of interest to both the commercial and radiation-hardened microelectronics communities when considering issues such as wet clean contamination, plasma processing, x-ray lithography, and source-drain dopant interpenetration into the oxide in sub-micron MOSFET's. An electron paramagnetic resonance, thermally stimulated current, and capacitance-voltage study has been carried out on phosphorus (PSG), boron (BSG), and boron and phosphorus (BPSG) co-doped oxide films on Si. The principal spin-active defects are the phosphorus-oxygen-hole-center (POHC) and the boron-oxygen-hole-center (BOHC), which are unpaired electrons on oxygen atoms with P or B in the near vicinity. The centers are activated by hole capture. The authors find that holes are trapped in the PSG, BSG, and BPSG dielectrics; however, hole trapping is most effective in the PSG and BPSG dielectrics. They find that electrons are trapped to differing extents in the doped films. The BPSG films are the most efficient in trapping electrons; the PSG films are the least efficient. The electrical data can be explained by assuming that the precursor to the BOHC is negatively charged and the precursor to the POHC is electrically neutral. Last, the charge trapping properties of PSG, BSG, and BPSG dielectrics are compared and contrasted with those observed in thermally grown oxides

[en] Scanning cathodoluminescence (SCL) is a technique that has been widely used to categorize local minority carrier lifetime nonuniformities in bulk and thin film semiconductors. In the case of phosphor powders it has been less popular, partly because the collection and scattering of light generated in an array of particles complicates the extraction of quantitative information about light generation efficiency. Here we demonstrate that by coupling SCL with modern digital imaging manipulation techniques, we can extract quantitative information about the beam energy dependence of phosphor cathodoluminescence with high spatial resolution. A number of common phosphors are examined and a wide range of behavior is observed. We find that materials like ZnS:Ag and SrGa₂S₄:Eu display uniformly high nonradiative surface energy losses, while other materials like ZnO:Zn have surface losses which are spatially very nonuniform

[en] We find that two paramagnetic ''trivalent silicon'' centers appear to be responsible for damage resulting from Fowler--Nordheim injection of electrons into thermal oxides on silicon