Auad Yves, Walls Michael, Blazit Jean-Denis, Stéphan Odile, Tizei Luiz H G, Kociak Mathieu, De la Peña Francisco, Tencé Marcel
Laboratoire des Physique des Solides, Université Paris Saclay, CNRS UMR 8502, Orsay, France.
Laboratoire des Physique des Solides, Université Paris Saclay, CNRS UMR 8502, Orsay, France.
Ultramicroscopy. 2022 Sep;239:113539. doi: 10.1016/j.ultramic.2022.113539. Epub 2022 May 13.
The acquisition of a hyperspectral image is nowadays a standard technique used in the scanning transmission electron microscope. It relates the spatial position of the electron probe to the spectral data associated with it. In the case of electron energy loss spectroscopy (EELS), frame-based hyperspectral acquisition is much slower than the achievable rastering time of the scan unit (SU), which sometimes leads to undesirable effects in the sample, such as electron irradiation damage, that goes unperceived during frame acquisition. In this work, we have developed an event-based hyperspectral EELS by using a Timepix3 application-specific integrated circuit detector with two supplementary time-to-digital (TDC) lines embedded. In such a system, electron events are characterized by their positional and temporal coordinates, but TDC events only by temporal ones. By sending reference signals from the SU to the TDC line, it is possible to reconstruct the entire spectral image with SU-limited scanning pixel dwell time and thus acquire, with no additional cost, a hyperspectral image at the same rate as that of a single channel detector, such as annular dark-field. To exemplify the possibilities behind event-based hyperspectral EELS, we have studied the decomposition of calcite (CaCO) into calcium oxide (CaO) and carbon dioxide (CO) under the electron beam irradiation.
如今，获取高光谱图像是扫描透射电子显微镜中使用的一项标准技术。它将电子探针的空间位置与其相关的光谱数据联系起来。在电子能量损失谱（EELS）的情况下，基于帧的高光谱采集比扫描单元（SU）可实现的光栅化时间要慢得多，这有时会在样品中导致不良影响，例如电子辐照损伤，而在帧采集过程中未被察觉。在这项工作中，我们通过使用带有两条嵌入式辅助时间数字转换器（TDC）线路的Timepix3专用集成电路探测器，开发了一种基于事件的高光谱EELS。在这样的系统中，电子事件由其位置和时间坐标表征，而TDC事件仅由时间坐标表征。通过从SU向TDC线路发送参考信号，有可能以SU限制的扫描像素驻留时间重建整个光谱图像，从而无需额外成本，以与单通道探测器（如环形暗场探测器）相同的速率获取高光谱图像。为了举例说明基于事件的高光谱EELS背后的可能性，我们研究了方解石（CaCO₃）在电子束辐照下分解为氧化钙（CaO）和二氧化碳（CO₂）的过程。
