用高分辨力热场发射显微镜观察Zr原子在W尖上的吸附

The Observation of Zr Atoms Adsorbed on W Tip with a HRTFEM

从理论与实际方面研究了获得高分辨力场发射电镜（ＦＥＭ）的条件，认为在适当的场强及温度下０．２ｎｍ的分辨力是可以达到的，这与当前认为的ＦＥＭ分辨力只能在２ｎｍ上下高一个数量级．我们称这种显微镜为高分辨力热场发射显微镜（ＨＲＴＦＥＭ）．利用这种显微镜，我们研究了Ｗ尖端上Ｚｒ原子吸附情况．这种吸附Ｚｒ的Ｗ尖端是用于Ｓｃｈｏｔｋｙ发射阴极的尖端，是由Ｗ（１００），Ｗ（１１０）及Ｗ（１１１）单晶经化学腐蚀为０．５μｍ曲率半径的尖端后再涂上Ｚｒ而制成的．从ＨＲＴＦＥＭ的结果表明，吸附在Ｗ尖端上的Ｚｒ原子表现为一些亮点，Ｗ（１１１）方向上的Ｚｒ原子有规则的排列成等腰三角形，但在Ｗ（１００）及Ｗ（１１０）方向上则没有明显吸附，因此我们认为，作为Ｓｃｈｏｔｌｋｙ阴极，Ｗ（１１１）单晶应是首选材料．

:A High resolution thermal field emission microscope (HRTFEM) have been studied theoretically and practically and a resolution of 0.2nm can be approached under proper condition of field strength and temperature.This is superior to 2nm which is believed newadays.By use of this HRTFEM the state of adsorption of Zr atoms on W tip have been studied.The Zr adsorbed tungsten tip is prepared for the emitter of Schottky electron emission cathode and is made of different oriented W(100),and W(111) single crystal wire of 0.12nm diameter and then etched electrochemically to about 0.5μm of radius of curvature.The experiment results show in HRTFEM that each Zr atom is a very bright apot.On W(111) face the Zr atoms range regularly in a trianglal figure.But on W(100) and W(110) face no such bright spots appeared.We conclude that on tungsten tip the (111) face is the stable adsorption face for Zr atoms and is the main face which electron emitted from in Sccottky emission cathode.