Authors: M Senoner A Maaßdorf H Rooch W Österle M Malcher M Schmidt F Kollmer D Paul VD Hodoroaba S Rades W E S Unger
Publish Date: 2015/02/21
Volume: 407, Issue: 11, Pages: 3259-3260
Abstract
Unfortunately one reference number 14 in the new list of references see below was absent in the published list of references The citation of this missing ref14 in the published text page 4 left column is correct Beginning on page 4 second column last paragraph the numbers of all references are wrong and must be corrected by adding one In the following text this correction has been done“Another analytical method able of mapping elemental composition is energy dispersive Xray spectroscopy EDX at a SEM scanning electron microscope In the traditional “reflection” geometry and with bulk samples the spatial resolution is limited by the volume of interaction of the primary electrons with the atoms in the sample This is the volume where the detected Xray photons originate from and is typically in the range of roughly 1 μm3 However recently it has been demonstrated that SEM working in the transmission mode TSEM enables traceable determination of nanoparticle size distribution 23 24 Coupling EDX to TSEM and employing thin electron transparent samples eg FIB lamellae prepared on TEM grids results in a significant improvement of the spatial resolution in EDX element maps from the micrometer range down to well below 100 nm 25 The limiting factor however is the low Xray signal intensity emitted by the tiny amount of material in the lamellae Recently developed largearea EDS detectors however deliver sufficient sensitivity to overcome the problem The spatial resolution attained practically by EDX in combination with highresolution TSEM mode can be determined by using a BAML200 lamella An example of a linescan of the AlKα intensity across the gratings P11 P12 P13 and P14 of the BAML200 pattern acquired with a modern largearea EDS detector 100 mm2 active area in the TSEM mode is shown in Fig 4 Note that the P11 grating period 42 nm is clearly resolved Moreover the presence of the weak Al Kα signal in the EDX linescan across the narrow stripe W11 35 nm width is remarkable Further improvements of the signal to noise ratio by using more sensitive detectors may lead to significantly better results in the near future The EDX line profile presented in Fig 4 represents only a single linescan and was not extracted from the full data set of a hypermap The latter option is available for SEM/EDX too but stability issues are often a critical point at such high magnifications required to resolve features at the low nm scalePossible fine artifacts such as an eccentricity of the profile of the primary electron beam at the low nanometer scale range may occur but control on this problem can be reached readily by rotating BAML200 in a way which is analogues to that displayed for the SIMS case in Fig1Intentionally the BAML200 CRM has been designed as a test sample for instruments which use a beam of primary ions electrons or photons Nevertheless applications in the field of scanning probe microscopy are possible too One example is the imaging of BAML200 by Kelvin probe force microscopy where lateral resolutions of better than 30 nm 26 and 10 nm 27 respectively have been demonstrated”
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