Preparation of Super-Hard Nitride Thin Films for Next Generation by High Density Plasma PVD

β-C_3N_4薄膜是下一代极具吸引力的超硬氮化材料之一，1997 - 1999年对其形成进行了研究。第一个目标是通过开发一种在低压下工作的高密度螺旋波激发等离子体溅射源来获得具有化学计量成分的薄膜，在该源中容易获得高激发的自由基和离子。3年项目取得的成果总结如下：1)利用简单的螺旋线圈天线，在0.1 ~ 1 Pa的氩气中，在外磁场中获得了密度达到10^<13> cm^<-3>的高密度等离子体，射频输入功率为100w。即使在氮气环境下，等离子体密度也很容易达到10^2 cm^<-3>。2)研制了基于该等离子体的溅射机，制备了CN_x薄膜，发现增加氮通量使薄膜中N含量增加，通过适当控制C和N通量，成功获得了化学计量膜成分。薄膜由sp^2相和sp^3相的混合物组成，随N含量的增加而增加。3)薄膜的显微硬度不高，在接近化学计量组成的离子轰击条件下，薄膜的显微硬度约为25 GPa。认为薄膜的软化是由石墨相和杂质原子（如O和/或H）的存在引起的，形成了类似聚合物的化合物。

Research on the formation of β-C_3N_4 thin films as one of the most attractive super-hard nitride materials in the next generation has been conducted between 1997 and 1999. The first goal was settled to obtain films with stoichiometric composition for the first by developing a high density helicon-wave excited plasma sputtering source operated at low pressures, in which highly excited radicals and ions could easily be obtained. Results obtained within 3 years project are summarized as follows.1) Using a simple helical coil antenna of several turns a high density plasma with a density reaching to 10^<13> cm^<-3> was obtained in Ar gas of 0.1 - 1 Pa in an external magnetic field with an RF power input of Several 100 W.Even in N_2 gas environment a plasma density of 10^2 cm^<-3> was also obtained easily.2) Developing a sputtering machine based on this plasma, preparation of CN_x films were performed and it was found that increasing nitrogen flux brought an increase of N content in the films and succeeded in obtaining stoichiometric film composition by controlling C and N flux appropriately. Films were composed of mixture of sp^2 and sp^3 phases that increased with N content.3) Micro-hardness of the films was not so high with a value of about 25 GPa in the condition of ion bombardment at a nearly stoichiometric composition. It was considered that softening of films was induced by the existence of graphite phase and impurity atoms such as O and/or H in the films causing polymer-like compound formation.