3D x-ray fluorescence microscopy with 1.7 μm resolution using lithographically fabricated micro-channel arrays

We report the fabrication and characterization of lithographically-fabricated arrays of micron-scale collimating channels, arranged like spokes around a single source position, for use in 3D, or confocal x-ray uorescence microscopy. A nearly energy-independent depth resolution of 1.7±0.1μm has been achieved from 4.5-10 keV, degrading to 3⊥0.5μm at 1.7 keV. This represents an order-of-magnitude improvement over prior results obtained using state-of-the-art, commercial polycapillaries as the collection optic. Due to their limited solid angle, the total collection efficiency of these optics is approximately 10× less than that obtained with polycapillaries. Three designs have been tested, with 1, 2, and 5-μm-wide channels ranging from 30-50 μm in depth and 2 mm in length. In addition to characterizing the devices in confocal geometry, the transmission behavior of individual channels was characterized using a small, highly collimated incident beam. These measurements reveal that, despite taking no particular steps to create smooth channel walls, they exhibit close to 100% reectivity up to the critical angle for total external reflection. Most of this reflected power is spread into a diffuse angular region around the specular reflection condition. These results significantly impact future designs of such collimating channels, since transmission through the channels via side-wall reflection limits their collimating power, and hence device resolution. Ray-tracing simulations, designed specifically for modeling the behavior of channel arrays, successfully account for the transmission behavior of the optics, and provide a useful tool for future optic design.

[1]  Kazuo Sato,et al.  Improvement of high aspect ratio Si etching by optimized oxygen plasma irradiation inserted DRIE , 2009 .

[2]  G. Falkenberg,et al.  Confocal MXRF in environmental applications , 2011, Analytical and bioanalytical chemistry.

[3]  Bart Vekemans,et al.  Three-dimensional trace element analysis by confocal X-ray microfluorescence imaging. , 2004, Analytical chemistry.

[4]  David M. Paganin,et al.  X-ray interactions with matter , 2006 .

[5]  F. Brenker,et al.  Fundamental parameter based quantification algorithm for confocal nano-X-ray fluorescence analysis , 2012 .

[6]  R. Van Grieken,et al.  X-ray spectrometry : recent technological advances , 2004 .

[7]  B. Kanngießer,et al.  Reconstruction procedure for 3D micro X-ray absorption fine structure. , 2012, Analytical chemistry.

[8]  N. Grlj,et al.  Three-dimensional imaging of aerosol particles with scanning proton microprobe in a confocal arrangement , 2008 .

[9]  Mark L. Schattenburg,et al.  Plasma etch fabrication of 60:1 aspect ratio silicon nanogratings with 200 nm pitch , 2010 .

[10]  Birgit Kanngießer,et al.  A new 3D micro X-ray fluorescence analysis set-up - First archaeometric applications , 2003 .

[11]  Jörg Maser,et al.  Focusing of hard x-rays to 16 nanometers with a multilayer Laue lens , 2008 .

[12]  Colin R. Janssen,et al.  Waterborne versus dietary zinc accumulation and toxicity in Daphnia magna: a synchrotron radiation based X-ray fluorescence imaging approach. , 2012, Environmental science & technology.

[13]  C. Pérez,et al.  Latest developments and opportunities for 3D analysis of biological samples by confocal μ-XRF , 2010 .

[14]  M. Chukalina,et al.  Quantitative comparison of X-ray fluorescence microtomography setups: Standard and confocal collimator apparatus☆ , 2007 .

[15]  Muradin A. Kumakhov,et al.  Capillary optics and their use in x‐ray analysis† , 2000 .

[16]  Colin R. Janssen,et al.  Element-to-tissue correlation in biological samples determined by three-dimensional X-ray imaging methods , 2010 .

[17]  F. Brenker,et al.  In situ identification of a CAI candidate in 81P/Wild 2 cometary dust by confocal high resolution synchrotron X-ray fluorescence , 2009 .

[18]  K. Nakano,et al.  Application of confocal 3D micro-XRF for solid/liquid interface analysis. , 2008, Analytical sciences : the international journal of the Japan Society for Analytical Chemistry.

[19]  D. Burr,et al.  Increased strontium uptake in trabecular bone of ovariectomized calcium-deficient rats treated with strontium ranelate or strontium chloride. , 2011, Journal of synchrotron radiation.

[20]  P. Walter,et al.  Confocal micro-X-ray fluorescence analysis as a new tool for the non-destructive study of the elemental distributions in pharmaceutical tablets. , 2011, Talanta.

[21]  Noelle Ocon,et al.  The Unique History of The Armorer’s Shop: AN APPLICATION OF CONFOCAL X-RAY FLUORESCENCE MICROSCOPY , 2008 .

[22]  F. Brenker,et al.  Three-dimensional Fe speciation of an inclusion cloud within an ultradeep diamond by confocal μ-X-ray absorption near edge structure: evidence for late stage overprint. , 2011, Analytical chemistry.

[23]  N. Grlj,et al.  Construction of a confocal PIXE set-up at the Jožef Stefan Institute and first results , 2011 .

[24]  B. Patterson,et al.  Three-dimensional density measurements of ultra low density materials by X-ray scatter using confocal micro X-ray fluorescence spectroscopy , 2012 .

[25]  T. Ishikawa,et al.  Breaking the 10 nm barrier in hard-X-ray focusing , 2010 .

[26]  D. Sokaras,et al.  A deep view in cultural heritage—confocal micro X-ray spectroscopy for depth resolved elemental analysis , 2012 .

[27]  K. Nakano,et al.  Depth elemental imaging of forensic samples by confocal micro-XRF method. , 2011, Analytical chemistry.

[28]  R Tucoulou,et al.  ID22: a multitechnique hard X-ray microprobe beamline at the European Synchrotron Radiation Facility. , 2005, Journal of synchrotron radiation.