STEM strain analysis at sub-nanometre scale using millisecond frames from a direct electron read-out CCD camera

18th Microscopy of Semiconducting Materials Conference

物理学;材料科学

Müller, K.^1 ; Ryll, H.^2 ; Ordavo, I.^2 ; Schowalter, M.^1 ; Zweck, J.^3 ; Soltau, H.^2 ; Ihle, S.^4 ; Strüder, L.^4 ; Volz, K.^5 ; Potapov, P.^5 ; Rosenauer, A.^1

Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany^1

PNSensor GmbH, Römerstraße 28, 80803 München, Germany^2

Universität Regensburg, Universitätsstraße 31, 93040 Regensburg, Germany^3

Max-Planck-Institut Halbleiterlabor, Otto-Hahn-Ring 6, 81739 München, Germany^4

Philipps Universität Marburg, Hans-Meerwein-Straße, 35032 Marburg, Germany^5

关键词: Compressive strain;    Convergence angle;    Cross correlations;    Equivalent strains;    Growth directions;    Nanobeam electron diffraction;    Spatial resolution;    Strain profiles;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/471/1/012024/pdf
DOI  :  10.1088/1742-6596/471/1/012024

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

We report on strain analysis by nano-beam electron diffraction with a spatial resolution of 0.5nm and a strain precision in the 4-7·10-4range. Series of up to 160000 CBED patterns have been acquired in STEM mode with a semi-convergence angle of the incident probe of 2.6mrad, which enhances the spatial resolution by a factor of 5 compared to nearly parallel illumination. Firstly, we summarise 3 different algorithms to detect CBED disc positions accurately: selective edge detection and circle fitting, radial gradient maximisation and cross-correlation with masks. They yield equivalent strain profiles in growth direction for a stack of 5 InxGa1-xNyAs1-y/GaAs layers with tensile and compressive strain. Secondly, we use a direct electron read-out pnCCD detector with ultrafast readout hardware and a quantum efficiency close to 1 both to show that the same strain profiles are obtained at 200 times higher readout rates of 1kHz and to enhance strain precision to 3.5·10-4by recording the weak 008 disc.