This page contains a Flash digital edition of a book.
Acceptance Angle Control


shift to center a sample feature on the optic axis can lead to complex image contrast that can change in unexpected ways because the optic axis moves with respect to the STEM detector. Depending on the amount of applied beam shift, effects similar to the ones observed in Figure 8 can be obtained, albeit unexpectedly. For example, although the user may have carefully chosen a set of apertures to obtain Z-contrast, using the beam shift skews the acceptance angle, and contrast other than that due to incoherent Rutherford scattering may be present in the image. To avoid this potential complication, the sample stage should be used to center features of interest.


Conclusion


A modular detection system and new sample holder for transmission-SEM imaging have been described. By combining different masks/apertures and using the sample positioning stage to adjust the camera length, comprehensive detector acceptance angle control is possible. The acceptance angle control enabled here is unavailable in commercial SEM detectors: thin annular detection schemes are feasible, separating diffraction contrast from Z-contrast is feasible, and BF-DF transition region signals can be used to obtain unusual image contrast. Although the system has not been fully explored, several examples show that it is a promising approach to extending the imaging capabilities of almost any SEM.


Disclaimers T is contribution is by NIST, an agency of the US government, and is not subject to copyright in the United States. Commercial instruments, equipment, or materials are identifi ed only in order to adequately specify certain procedures. In no case does such identifi cation imply recommendation or endorsement by NIST, nor does it imply that the products identifi ed are the best available for the purpose.


References [1] T Klein et al ., Adv Imag Elect Phys 171 ( 2012 ) 297 – 356 . [2] RJ Woolf et al ., J Phys E: Sci Instrum 5 ( 1972 ) 230 – 33 . [3] U Valdre et al ., Ultramicroscopy 15 ( 1984 ) 109 – 18 . [4] E Oho et al ., J Elec Microsc Tech 5 ( 1987 ) 51 – 58 . [5] M Haider et al ., Ultramicroscopy 54 ( 1994 ) 41 – 59 . [6] A Khursheed et al ., Rev Sci Instr 74 ( 2003 ) 134 – 40 . [7] E Buhr et al ., Meas. Sci Tech 20 ( 2009 ) 084025 . [8] B Jacobson et al ., Proc of SPIE 9376 ( 2015 ) 93760K . [9] K Varoon et al ., Science 334 ( 2011 ) 72 – 75 . [10] J Holm and R Keller , Ultramicroscopy 167 ( 2016 ) 43 – 56 . [11] S Findlay et al ., Ultramicroscopy 110 ( 2010 ) 902 – 23 . [12] J Cowley , J Elec Microsc 50 ( 2001 ) 147 – 55 . [13] J Cowley et al ., Ultramicroscopy 58 ( 1996 ) 18 – 24 . [14] OL Krivanek et al ., Nature 464 ( 2010 ) 571 – 74 . [15] DE Jesson and SJ Pennycook , Proc R Soc Lond A 449 ( 1995 ) 273 – 93 .


18


www.microscopy-today.com • 2017 March


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76