High efficient negative ion production by electron temperature control

用栅格法研究了纯氢射频等离子体中负氢离子的形成。采用栅格法在真空室的分离区产生高、低温等离子体，即等离子体产生区产生高温等离子体，被栅格隔开的下游区域产生低温等离子体。通过对栅极施加负电位来降低电子温度。负氢离子的产生速率取决于等离子体产生区和下游区域的电子温度。在8mtorr的情况下，即使在低温等离子体中也没有检测到明显的负离子。在这种情况下，生产区域的电子温度相对较低。然而，在2 mTorr的情况下，产生区电子温度升高，当电子温度被栅格降低时，我们观察到下游区域有一个有效的负离子形成。在这种情况下，负离子与正离子的密度比达到95%左右。结果表明，存在振动激发的阈值电子温度，并且低电子温度的产生对于解离附着物是重要的。我们制定了一个程序，用网格法为这个新的射频等离子体反应堆申请专利。在该等离子体反应器中，可以控制化学反应，以建立有效的等离子体处理，如负氢离子的产生。

The formation of negative hydrogen ions is investigated in a pure hydrogen RF plasma using a grid method for the electron temperature control. Using the grid method we produce both high and low electron temperature plasmas in the separated regions in the vacuum chamber, i.e., a high electron temperature plasma in the plasma production region and a low electron temperature plasma in the downstream region which is separated by the grid. The electron temperature is decreased by applying negative potential to the grid.The production rate of negative hydrogen ions depends on both the electron temperature in the plasma production region and that in the downstream region. In case of 8 mTorr we did not detect marked negative ions even in the low electron temperature plasma. In this case, the electron temperature in the production region is relatively low. However, in case 2 mTorr, the electron temperature in the production region is increased, then we observe an efficient negative ion formation in the downstream region when the electron temperature is decreased by the grid. The density ratio of negative to positive ions attains to about 95% in this case.The results show the presence of threshold electron temprature for vibrational excitations, and also the production of low electron temperature is important for dissociative attachments.We made a procedure to get a patent for this new RF plasma reactor using a grid method. In this plasma reactor it is possible to control the chemical reaction for establishing efficient plasma processing such as the negative hydrogen ion production.