We report on the demonstration of a low emittance, high brightness ion source based on magneto-optically trapped neutral atoms. Our source has ion optical properties comparable to or better than those of the commonly used liquid metal ion source. In addition, it has several advantages that offer new possibilities, including high resolution ion microscopy with ion species tailored for specific applications, contamination-free ion milling, and nanoscale implantation of a variety of elements, either in large quantities, or one at a time, deterministically. Using laser-cooled Cr atoms, we create an ion beam with a normalized rms (root-mean-square) emittance of 6.0 x 10 (-7) mm mrad M e V and approximately 0.25 pA of current, yielding a brightness as high as 2.25 A cm (-2) sr (-1) eV (-1). These values of emittance and brightness show that, with suitable ion optics, an ion beam with a useful amount of current can be produced and focused to spot sizes of less than 1 nm.
Articles you may be interested inTemperature measurement of cold atoms using single-atom transits and Monte Carlo simulation in a strongly coupled atom-cavity system Appl. Phys. Lett.Magnetic anisotropy, interlayer coupling, and magneto-optical effects in single-crystalline Fe/Cr/Fe/MgO/Fe magnetotunnel structures grown on GaAs (001) substrates We have realized a method for producing single Cr atoms on demand by suppressing the stochastic nature of the loading and loss processes of a magneto-optic trap. We observe single-atom trap occupation probabilities as high as (98.7Ϯ0.1)% and demonstrate ejection with greater than 90% efficiency at rates up to 10 Hz. Monte Carlo simulations agree well with extraction measurements and are used to predict ultimate performance. Such a deterministic atom source has potential applications in nanotechnology, quantum information processing, and fundamental quantum investigations.
We discuss analyses of trace levels of surface contamination using X-ray photoelectron spectroscopy (XPS). The problem of quantifying common sources of statistical and systematic uncertainties for these measurements is formulated in terms of the needs of extreme ultraviolet lithography, but the results and conclusions are applicable to a broad range of XPS applications.We quantify the systematic uncertainties introduced by particular cases of overlapping peaks on different substrate structures by simulating measured spectra with the National Institute of Standards and Technology Database for the Simulation of Electron Spectra for Surface Analysis (SESSA). One example demonstrates that the relative atomic concentrations of trace elements such as S, P, and halogens on a Ru surface could be dramatically overestimated if the fitting of the overlapping Ru 3d and C 1s peaks excludes the contribution from carbon. We also show how spectra generated by SESSA can be compared with measured spectra to determine absolute amounts of surface impurities on layered samples of the type used for extreme ultraviolet lithography. We provide estimates of the total uncertainty for such measurements by considering the systematic limitations of SESSA and the statistical uncertainties of the measurements. The same procedure can be employed for other multilayered materials. Finally, we describe two approaches for converting XPS detection limits for an elemental impurity in an elemental matrix to the corresponding detection limits for the impurity as a thin film on the surface of the matrix material.KEYWORDS detection limits, quantitative analysis, surface contamination, systematic uncertainties, x-ray photoelectron spectroscopy 1 | INTRODUCTION Detection and quantification of trace levels of surface contamination is a challenge for many modern analytical techniques. X-ray photoelectron spectroscopy (XPS) is widely used to obtain quantitative information about surface composition and the chemical states of elements in the near-surface region from which the signals originate.Industrial laboratories use XPS to evaluate the type and amount of surface contamination in applications for which the X-ray flux does not cause significant modification of the sample surface during analysis. Our work was motivated by one such industrial application that, until recently, was used to qualify resists for use in extreme ultraviolet (EUV) lithography scanners. 1 High fluxes of energetic EUV photons (13.5 nm) combined with the outgassing from photoresists can damage EUV optics. 2 As a result, every newly formulated EUV photoresist was assessed by exposing a witness sample to its outgas products. X-ray photoelectron spectroscopy was used in the final step of these tests to detect and quantify trace levels of metals, nonmetals, and halogens. This information could be used to estimate potentially irreversible reflection losses of EUV optics associated with the given resist. 3In Part 1 of this work, 4 we described the statistical uncertainties associated with mea...
We report the photodeposition of a carbonaceous layer grown on a TiO 2 thin film by extreme ultraviolet (EUV)induced chemistry of adsorbed n-tetradecane and the subsequent photo-oxidation of this film. Chemical analysis of the carbonaceous layer indicates that irradiation by 92 eV photons converts a fraction of the 14-carbon-atom alkane into two polycyclic aromatic hydrocarbon (PAH) molecules, anthracene and phenanthrene, both also containing 14 carbon atoms. Under continuing irradiation, EUV-induced dehydrogenation and cross-linking of PAHs and precursor alkane fragments form a complex network of carbon bonds with the inferred structure of an sp 2 -carbon rich film. Exposure of the carbonaceous film to five oxygencontaining molecules has little or no effect in the dark at 300 K. However, in the presence of EUV photons, the ability of the molecules to etch the carbonaceous film increases significantly. Their relative photo-oxidation activity follows the trend HThe rate of the photo-oxidation reaction increases with the partial pressure of the oxidizer. Raising the substrate temperature has little effect on the photo-oxidation reaction rate, which is in contrast to the rate of EUV-induced carbonaceous film growth that exhibits a strong temperature dependence. The difference between mechanisms of EUV-induced hydrocarbon decomposition and photo-oxidation of the carbonaceous film is discussed.
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