Effects of detector dead-time on quantitative analyses involving boron and multi-hit detection events in atom probe tomography.
In atom probe tomography (APT), some elements tend to field evaporate preferentially in multi-hit detection events. Boron (B) is one such element. It is thought that a large fraction of the B signal may be lost during data acquisition and is not reported in the mass spectrum or in the 3-D APT reconstruction. Understanding the relationship between the field evaporation behavior of B and the limitations for detecting multi-hit events can provide insight into the signal loss mechanism for B and may suggest ways to improve B detection accuracy. The present work reports data for nominally pure B and for B-implanted silicon (Si) (NIST-SRM2137) at dose levels two-orders of magnitude lower than previously studied by Da Costa, et al. in 2012. Boron concentration profiles collected from SRM2137 specimens qualitatively confirmed a signal loss mechanism is at work in laser pulsed atom probe measurements of B in Si. Ion correlation analysis was used to graphically demonstrate that the detector dead-time results in few same isotope, same charge-state (SISCS) ion pairs being properly recorded in the multi-hit data, explaining why B is consistently under-represented in quantitative analyses. Given the important role of detector dead-time as a signal loss mechanism, the results from three different methods of estimating the detector dead-time are presented. The findings of this study apply to all quantitative analyses that involve multi-hit data, but the dead-time will have the greatest effect on the elements that have a significant quantity of ions detected in multi-hit events.
Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. Electronic address: frederick.meisenkothen@nist.gov.
Frederick
F
Meisenkothen
Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Eric B
EB
Steel
CAMECA Instruments, Inc., 5500 Nobel Drive, Madison, WI 53711, USA.
Ty J
TJ
Prosa
Intel Corporation, Hillsboro, OR, 97124, USA.
Karen T
KT
Henry
Department of Materials Science and Engineering, 2144 Chemical and Nuclear Engineering, Building #090, University of Maryland, College Park, MD 20742, USA.
R
R
Prakash Kolli
Atom probe; Boron; Dead-time; Dopant; Field evaporation; Multi-hit