论文标题
开发黑田茎的可行数字脉冲读数
Development of a Practicable Digital Pulse Read-out for Dark-field STEM
论文作者
论文摘要
当表征扫描透射电子显微镜（STEM）中的光束敏感材料时，低剂量技术对于可靠地观察样品的真实状态至关重要。最小化总电子剂量和剂量速率的简单途径是减少电子束电流和/或以较高速度的探针射手。在这些设置的极限和当前检测器的限制下，由此产生的图像遭受了不可接受的人工制品的损失，包括：信号传播，检测器 - 屈曲和信噪比差（SNR）。在此手稿中，我们提出了一种替代方法，可以通过脉冲计数单个电子散布到环形深色场（ADF）检测器时捕获暗场茎图像。以这种方式形成的数字图像不受条纹或余辉的模拟文物的影响，并允许在低光束电流下获得清洁的高SNR图像。我们介绍了在300kV下运行的热燃料FEI Titan G2和在200kV上运行的NION Ultrastem200的结果，并将图像与常规模拟录音进行比较。将ADF数据与每种仪器的模拟对应物进行了比较，在泰坦上进行了数字检测器响应扫描，并评估了各种扫描参数的整体栅格效率。
When characterising beam-sensitive materials in the scanning transmission electron microscope (STEM), low-dose techniques are essential for the reliable observation of samples in their true state. A simple route to minimise both the total electron-dose and the dose-rate is to reduce the electron beam-current and/or raster the probe at higher speeds. At the limit of these settings, and with current detectors, the resulting images suffer from unacceptable artefacts including; signal-streaking, detector-afterglow, and poor signal-to-noise ratios (SNR). In this manuscript we present an alternative approach to capture dark-field STEM images by pulse-counting individual electrons as they are scattered to the annular dark-field (ADF) detector. Digital images formed in this way are immune from analogue artefacts of streaking or afterglow and allow clean, high-SNR images to be obtained even at low beam-currents. We present results from both a ThermoFisher FEI Titan G2 operated at 300kV and a Nion UltraSTEM200 operated at 200kV, and compare the images to conventional analogue recordings. ADF data are compared with analogue counterparts for each instrument, a digital detector-response scan is performed on the Titan, and the overall rastering efficiency is evaluated for various scanning parameters.
