New experimental evidence is presented that supports a model that assumes two distinguishable types of positive oxide charge following, x-irradiation. Two new experiments have been performed designed to separate the annealing properties of the two types of trapped positive charge. It is found that one type of trapped positive charge can be permanently removed at room temperature using substrate hot electron injection. The second type of trapped positive charge is found to be stable at temperatures up to 160 degrees C

The effects of alternating bias anneals of MOS transistors following either x-irradiation or Fowler-Nordheim Tunneling have been studied. It is found that some of the generated defects can be repeatedly charged and discharged with a change of applied oxide field. Two models to explain this phenomenon are discussed. One assumes a single defect, the E' center. The other model assumes a two defect model. The results of this work are shown to be more consistent with the two defect model.

Double-crystal and single-crystal spectrometer measurements of line profile and integral reflection coefficient versus diffraction order are presented. These results are compared with theoretical predictions. The ability of the use of an intermediate layer in the theoretical model to explain the results is emphasized.

Multilayer specimens of high-Z/low-Z alternating layer stacking have utility as efficient elements for the diffraction and reflection of x rays and ultraviolet radiation. Bielement multilayers of W/C and W/Si, prepared commercially on ultrasmooth substrates, have been characterized by atomic force microscopy (AFM) and by scanning tunneling microscopy to assess the smoothness and nature of the diffraction surface and by transmission electron microscopy to evaluate the uniformity of layering. The diffraction properties of these multilayers have been evaluated by measurements using crystal spectrometers, and by calculations using coherent Bragg diffraction atomic scattering and classical multilayer reflection theory based on stacking uniformity. We have found that the x-ray diffraction performance of W/Si multilayers to be better than W/C multilayers. In addition, the surface of the W/Si specimens were determined by atomic force microscopy to be smoother than W/C and that agreement exists with a roughness factor determined by analytical diffraction theory. The evaluation of multilayers will enhance our understanding of nanostructures, leading to improved diffraction structures.

AbstractThe evaluation and understanding of the x-ray diffraction properties of multilayer structures is critical in predicting the degree of success in their utilization in x-ray optics applications. A key material parameter affecting the diffracting efficiency of multilayer structures is the roughness of the interfaces between the deposited layers. This paper will use measured roughness to predict the integral reflection coefficient as a function of diffraction order for several multilayer structures.We have made atomic force microscope (AFM) measurements of the detailed displacement distribution for me surface roughness of W/C and W/Si multilayer structures. This information has been introduced into a theoretical model to predict the reduction of the integral reflection coefficient induced by surface roughness. In a fashion analogous to the Debye-Waller factor, this reduction in diffracted intensity is predicted to be strongly dependent on the diffraction order. These predictions have been compared with experimental integral reflection coefficient data. The measured diffraction results indicate a greater reduction in reflection than is predicted by the AFM measurements. A possible explanation for this discrepancy is that the AFM measurements underestimate the roughness. Possible reasons for the differences between these methods will be discussed.

Data are presented on statistical fluctuations in energy deposition across individual gate oxides at 77 K for 13- to 63-MeV protons. A two-component model based on microdosimetry theory has been developed to describe proton-induced dose fluctuations. The model considers random factors in the energy deposition process for (1) direct proton strikes within the volume of interest and (2) secondary ele...

X-ray spectroscopy is an established diagnostic for the Nuclear Test Program. The high diffraction response of multilayer structures can make important contributions as X-ray diffraction analyzers for UG testing. The soft X-ray performance of a number of commercially deposited multilayers was determined in our laboratory and compared with diffraction theory predictions.

The subthreshold technique was used to study irradiated MOS transistors at 80 K. Stretchout of the subthreshold curve demonstrated production of lateral nonuniformities (LNUs) in the hole distribution. The LNUs were analyzed in terms of a parallel transistor model and the statistics of the nonuniform distribution of dose deposition in the SiO/sub 2/. The results confirm the hypothesis that at 80 K...

Defect growth and annealing mechanisms in MOS devices have been studied. Biases were changed during irradiations. Significant radiation-induced annealing of trapped holes was observed. Apparent room temperature annealing of interface states was also observed. A consistent explanation of this apparent annealing is presented, i.e., an effect of LNU's on the results of the subthreshold analysis technique. A possible physical mechanism for the creation of LNU's due to inhomogeneous energy deposition is explored.

Transistor behavior in the subthreshold region is used to compare the production of oxide trapped charge and interface states produced by x-ray and Co-60 radiation. For the oxides used in this study, the subthreshold data indicates the presence of two types of interface states. One of these interface states appears to differ from the more commonly observed amphoteric defect. The characteristics of these states suggest that they are donor defects. These states further complicate testing protocols because they anneal at room temperature. A modification to the subthreshold measurement technique of McWhorter and Winokur is proposed for oxides in which these donor states occur. Using this revised subthreshold technique, less interface dose enhancement occurs during x-ray exposures than was observed previously with thick-oxide-capacitor measurements.

X-ray spectral analysis plays a major role as a diagnostic for hot, dense plasmas. Various diffraction media are utilized as flat or convex-curved surfaces for collecting soft x-ray spectral data in the 200 eV - 2 keV energy range. Calibration of the diffracting surface provides means for absolute line emission measurements from plasma generating sources i.e., pulsed-discharge gas puff and focused laser-target interaction experiments. The purpose of this work is the evaluation and absolute intensity calibration of diffraction surfaces consisting of grown crystals (acid phthalate), naturally occurring crystals (beryl) and surfaces formed by vacuum deposition (multilayered structures). The sources and experimental equipment used for the calibration work were: 1) a conventional sealed x-ray tube, x-ray fluorescer, and a single-crystal spectrometer, 2) a soft x-ray facilities incorporating a Henke tube with demountable anodes and double-crystal spectrometer.

Kodak Direct Exposure film (DEF) has replaced Kodak No-Screen film for use in x-ray diffraction analysis and in autoradiography. DEF is a double-emulsion film which has been found to have improved radiographic characteristics over No-Screen. A set of H-D curves has been generated for DEF at five photon energies: 0.930, 1.49, 1.74, 4.51/4.93, and 6.93 keV. The KMSF x-ray calibration facility was utilized to study the absolute sensitivity of this film over its full dynamic range. Physical examination of the film was followed by theoretical modeling, which adequately reproduced the measured curves.

X-Ray optics can be broadly classified as being either reflective or transmissive, with either broad or narrow band pass, configured to be either non-focusing or focusing. Multilayers which reflect (diffract) soft x-rays with intermediate resolution, which can be elastically bent into either convex, non-focusing or concave, focusing geometries, are of interest in this work. Preparation and characteristics of the multilayers are described with the experimental details of the concave and convex geometries following in the succeeding two sections.

X-ray spectral analysis plays a major role as a diagnostic for hot, dense plasmas. One means for collecting spectra is the use of convex-curved diffraction crystals. Synthetic multilayer structures offer high reflectivity for soft x-rays. Convex diffraction surfaces can be formed by sputtering onto smooth surfaces and by dipping into solutions such as lead myristate. Convex-curved multilayer structures have been evaluated by analytical diffraction models and experimentally by collecting aluminum spectra from plasmas generated by exploded wires sources and by focused laser beams.

Hole trapping, interface-state production and annealing were studied in NMOS transistors irradiated with x-rays and Co-60. Hole trapping showed a photon energy dependence that can be explained by existing models. However, interface-state generation showed an energy dependence that cannot be explained using previously available models. The results given here suggest that hole production and trapping in the oxide may involve different mechanisms than the generation of interface states. In addition, annealing of hole trapping observed in what is called "super recovery" or "rebound" was found to be reversible.

Accurate wavelengths for highly-ionized L-shell spectra were measured in the 10–16Å region. The purpose being to determine lines in coincidence with L-shell transitions from the elements oxygen, fluorine, and neon. L-shell transitions have been proposed for resonant photopumping of K-shell electrons in these elements to, generate lasing between upper levels in the 40–150 eV region. The current effort improves on and expands the earlier spectroscopic work performed at KMS Fusion, Inc., where possible line coincidences were identified for photoionizing in the 1–3 and 1–4 levels in fluorine. New experimental techniques have led to a wavelength accuracy now believed to be ± 2 mÅ for cases in which adequate calibration lines are available. Exact spectral line matches were found for Mn with the F H,-line at 12.643Å and for both Mn and Cr with the F He line at 14.458Å. The Mn line at 12.643Å has been identified, using ab initio atomic structure calculations, as the 1D2 − 1F3 transition in Be-like Mn XXII. The Mn line emissivity was determined to be 30 MW into 2 steradians for a conversion efficiency of 0.04%. Photopumping with Mn coated gasfilled targets is presently being tried in gain measurement experiments at LLNL.