National Institute for Nanotechnology, National Research Council of Canada, Edmonton, Alberta, Canada.
Ultramicroscopy. 2013 Aug;131:56-60. doi: 10.1016/j.ultramic.2013.03.013. Epub 2013 Apr 11.
A procedure to control W(111) tip shape during etching to a single atom is described. It is demonstrated that the base of a single atom tip (SAT) can be shaped in order to alter the final operating voltage and emission opening angle of single atom tips for use as gas field ion sources or electron cold field emission sources. The operating voltages for single atom tips varied between 5 and 17kV during helium ion beam generation. The emission properties of SATs were evaluated by fitting SAT images and measuring the full width at half maximum (FWHM) of the helium ion images. The FWHM is related to the linear opening angle and was evaluated as a function of SAT operating voltage. The results show that a forward focussing effect is observed such that the spot size decreases faster than is expected solely from an acceleration effect, indicating an affect from the tip shape. These results have consequences in designing gas field ion sources where etching is used to prepare the emitter.
描述了一种在蚀刻过程中控制 W(111)尖端形状的方法。结果表明，可以对单个原子尖端(SAT)的底部进行塑形，从而改变作为气体场离子源或电子冷场发射源使用的单个原子尖端的最终工作电压和发射开口角度。在氦离子束产生过程中，单个原子尖端的工作电压在 5 到 17kV 之间变化。通过拟合 SAT 图像并测量氦离子图像的半峰全宽(FWHM)来评估 SAT 的发射特性。FWHM 与线性开口角度有关，并作为 SAT 工作电压的函数进行评估。结果表明，观察到前向聚焦效应，使得光斑尺寸的减小速度快于仅由于加速效应所预期的速度，表明尖端形状的影响。这些结果对设计气体场离子源具有重要意义，其中蚀刻用于制备发射器。
