我国萤石资源现状及展望

Brief Communications STM Studies on the Threshold Phenomenon in Nanoscale Fabrication Process *

萤石由于其独特的物理、化学性质，主要用于钢铁、化工、建材三大行业。近年来，化工行业已成为萤石的最大用户。尤其在氟化工方面，用以制造氢氟酸及其衍生物，特别是氟碳化合物，更广泛地应用于各工业部门。不同行业对萤石的质量要求不同，有各自的标准。作为我国外贸的创汇产品，对萤石资源的进一步开发工作仍需重视，制酸级萤石在氟化工生产方面尚具发展潜力。

It is observed that the characteristics of nanometer scale features generated on graphite surfaces using STM displays a significant correlation with static junction resistance.The field emission of electrons and electrical breakdown of the tunnel junction are considered responsible for producing craters and mounds,respectively.In addition,it is pointed out that the characteristic geometry of the craters could be closely related to the local electron transport properties.