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Extremely low count detection for EELS spectrum imaging by reducing CCD read-out noise

2019; Elsevier BV; Volume: 207; Linguagem: Inglês

10.1016/j.ultramic.2019.112827

1879-2723

Mitsutaka Haruta, Yoshifumi Fujiyoshi, Takashi Nemoto, Akimitsu Ishizuka, Kazuo Ishizuka, Hiroki Kurata,

Integrated Circuits and Semiconductor Failure Analysis

Extremely low count detection for EELS spectrum imaging is required to overcome problems with electron irradiation and widen the range of available applications. We have made a systematic statistical study of the reduction of CCD noise for EELS. We propose a calculation method to estimate the properties of noise and a procedure to reduce it. Since the dominant noise is a practically random component, it can be reduced by subtracting the population mean of the dark reference and a summation over an appropriate number of spectra, depending on the standard deviation of the noise. A gain-averaging method can further improve the signal-to-noise (SN) ratio. It is thereby demonstrated that a high-SN spectrum can be obtained even for a single-count core-loss signal. The present method would be useful for measuring low signal spectrum such as monochromated spectra and for radiation sensitive materials.