Advanced Chemical Analysis
impact microcrater is only possible because of the high take-off angle and signal acquisition from four different directions. T ere is a tradeoff between high take-off angle and solid angle. For a higher take-off angle the distance between sample and detector has to be increased. So using a take-off angle of more than 65° reduces the solid angle from 1.1 sr to less than 0.5 sr ( Figure 1 ).
The signal acquisition, amplification, and processing of the four channels is completely separated. T is increases the count-rate capability by a factor of four compared to the detector area of one segment. T ree-dimensional information can be obtained using the different detector segments separately.
Conclusion T e annular XFlash
Figure 5 : X-ray element map of the O and Au distribution in a Au-decorated TiO 2 nanotube matrix, acquired using the XFlash ® FlatQUAD, superimposed on an SEM image: 5 kV, input count rate 38 kcps, 1024 × 768 pixels, acquisition time 240 s. Sample and data courtesy of Guangxi University, which also provided measurement time at the SEM, and special thanks to Prof. Xuanyong Liu and Prof. Yi Zeng from Shanghai Institute of Ceramics, Chinese Academy of Sciences, for generously providing the sample [ 12 ].
FlatQUAD with its high take-off angle and high X-ray collection angle allows measurement of the distribution, attachment, and size of the Au nanorods on the highly topographic TiO 2 nanotube surface in one experiment. Furthermore, the Au nanorod distribution from the EDS element map could be correlated with data from fluorescence microscopy. This correlation shows which particular sites on this material attract bone mesenchymal stem cells and promote their spreading and which have antibacterial eff ects. T is sample of Au nanorods on a porous TiO 2 -nanotube structure represents a type of TEM-suitable sample investigated here in the SEM; it shows the promise of highly sensitive EDS systems applied to STEM in SEM, so-called T-SEM EDS [ 13 ].
Discussion T e applications presented show that the annular XFlash
FlatQUAD detector can overcome some of the restrictions of conventional detectors. For the uncoated historic Mocs Meterorite, low kV and low beam current were necessary to avoid charging. T is analysis is also possible with conventional detectors, but the large solid angle of the annular detector reduces the acquisition time signifi cantly.
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The same applies to samples where only small amounts of material are available for analysis, such as small particles or thin layers on bulk and electron transparent samples. Furthermore, light element samples produce low X-ray yields, so the annular design with four detectors is beneficial because it increases X-ray collection efficiency. Also, a low accelerating voltage may be used to produce a small interaction volume for high spatial resolution; again a high collection effi ciency is important.
Energy-dispersive X-ray analysis in the cracks of the meteorite, in the porous polymer, and at the bottom of the
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combines a large solid angle (>1.1 sr) with output count rates up to 2.4 million counts per second. T ese properties can be used for effi cient element mapping-applications such as ultra-fast mapping or large-area mapping. The collection efficiency allows elemental analysis of samples at both low accelerating voltages to achieve a small interaction volume and at low beam currents. These operating conditions provide high spatial resolution and high detection sensitivity without the necessity of applying a conductive coating or working at low vacuum. T e high take-off angle annular detector arrangement enables element distribution mapping of highly topographic samples. Furthermore, use of this annular detector allows the analysis of small amounts of material. New analytical approaches in various fi elds become possible, especially in biological science and cultural heritage studies.
® FlatQUAD detector is a device that
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[7] H Soltau et al ., Microsc Microanal 15 ( Suppl.2 ) ( 2009 ) 204 – 05 .
[8] RR Keller and RH Geiss , J Microscopy 245 ( 2012 ) 245 – 51 . [9] A Esfandiari et al ., Journal of Applied Sciences 8 ( 2008 ) 545 – 61 .
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