聚焦离子束的束径测量

报道了聚焦离子束装置的束径测量方法和典型测量结果。偏转离子束使其扫过金属栅网的边缘 ,由法拉第筒接收到的离子流强度变化所形成的S形电流曲线可确定束径大小。在数据处理中 ,采用了快速傅立叶变换滤波的办法来消除微小电流测量结果中的噪声 ,从而可以对S形电流曲线进行微分 ,得到束流密度空间分布。在改变透镜光阑口径而维持靶室离子流强度不变的测量模式中 ,证实了离子间库仑相互作用增大束径的效应

Beam Diameter Measurement in Focused Ion Beam System

The diameter of beams in the focussed ion beam was measured by evaluating the S shaped current distribution resulting from the variations in beam intensity in the Faraday cup when the ion beams is scanned over the grid edge.After fast Fourier transformation,the noisy current can be differentiated and be used to determine its density distribution.When the target current is kept constant and the aperture size is varied,we verified that Coulomb interaction of the ions markedly enlarges the beam diameter in the case of a strong beam intensity and a small aperture diameter.