The structure factors and normal-incidence reflectances of the alkali-metal-doped fulleride crystals M(6)C(60) (where M = K, Rb, or Cs) were calculated, and the peak reflectances are in the 2-20% range for incident wavelengths of 9-17 Å, which indicates that C(60) may be a promising transmissive (spacer) material for normal-incidence mirrors that have relatively high normal-incidence reflectance in the x-ray region.

Capillary optics appear to permit the fabrication of practical collimator systems for laser-driven x-ray point sources. With such collimators, the illumination of wafers can meet the tight requirements for lithographic patterning of sub-micron device structures. However, the use of x-radiation with photon energies between 800–1200 eV makes capillaries of conventional silica-based glass capillaries marginal due to their low reflectivity. The reflectivity of various materials were examined with the goal of finding alternate glasses, elements for doping glasses or surface coatings that may enhance these collimators for lithographic applications. Coating capillary surfaces with more reflective materials may be the most viable method for improving the radiation transport properties for capillary optics to be used in x-ray lithography.

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.

The use of artificial multilayer structures (MLS) as wavelength dispersive elements has proven of great importance in soft x-ray (2 to 15 nm) spectroscopy. Much of the early work in this field has concentrated on structures consisting of alternating layers of a pair of materials, one of high atomic number (most commonly tungsten) and one of low atomic number (most commonly carbon). Although the ideal performance of multilayer pairs can be calculated,1 the performance of a MLS can be substantially degraded by imperfections introduced in their manufacture. In particular, it has become clear that optimum performance of MLS is strongly dependent upon the quality of the interfaces (roughness, interdiffusion, etc.) between the two materials. These interface properties are dependent upon the chemical-metallurgical properties of the materials chosen. Since such properties are typically not amenable to theoretical prediction, the choice of good layer pairs is typically an Edisonian process. The purpose of this paper is to explore the soft x-ray diffracting properties of the material pair Mo-B4C. We will concentrate on the ways in which the measured diffraction behavior deviates from ideality and, especially, possible reasons for this non-ideality.

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.

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 response of MOS capacitors with TaSi/Al and Al electrodes to medium- and low-energy x-irradiation is investigated. Experimentally measured dose-enhancement effects are compared with computer simulations for these structures.

Consider a particle performing a random walk to nearest neighbors on a simple cubic lattice in any number of dimensions D. The lattice contains a fraction q of randomly located ’’trapping’’ sites which absorb the walker when stepped on. We calculate the mean time to trapping. This involves the expected number V(t) of distinct sites that a walker would visit in t steps in absence of traps, a quantity known only asymptotically for large t; however, an exact calculation possible in one dimension suggests that the results are unexpectedly precise. The trapping time is proportional to q−1 for D=3 or greater, and more complicated for D=1,2.

As a model for the growth of silver aggregates on the surface of silver halide crystallites, we have studied the following problem: Independent ions perform random walks on a closed two-dimensional lattice containing, initially, one trap; when a walker reaches a site adjacent to a trap, that site itself becomes a trap. Several simplifications are necessary and justifiable to enable us to use standard random-walk theory: they include replacing the actual crystallite surface by a toroidal one, averaging over all starting points at an early stage, and replacing the irregularly growing cluster by a simply shaped one. Upper and lower limits on the rate of cluster growth are obtained, and results are fitted to experimental observations.

A solution to the heat equation is given which describes a cylindrical body uniformly heated along its axis. The application considered is the determination of bulk and surface absorption coefficients of the sample material from temperature-vs-time measurements when the heat source is a weakly absorbed narrow light beam. Under certain conditions, the full solution can be greatly simplified and the inference of absorption coefficients thus facilitated; these conditions are discussed and specified quantitatively. Equivalent results for rectangular samples are also given. The utility of the analysis is illustrated by several experimental examples.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text E. D. Palik, N. Ginsburg, Herbert B. Rosenstock, and R. T. Holm, "Transmittance and reflectance of a thin absorbing film on a thick substrate," Appl. Opt. 17, 3345-3347 (1978) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article