Competing processes on Formation of Negative Ion and Ozone in Recombining Oxygen Plasma

本文用螺旋波激发产生了10 ^cm~2量级的高密度氧等离子体。<12><-3>等离子体由RF功率的开-关调制，并且分别在RF的开和关阶段产生电离和复合等离子体。本工作的目的是研究负氧离子和臭氧的形成过程，这些负氧离子和臭氧将在余辉（复合等离子体相）中有效地产生。首先，我们通过飞行时间质谱研究了正离子和负离子的行为。在余辉中有效地产生负离子。主要产生O ^-离子，并伴有少量O_2 ^-离子。我们还开发了双光子激光诱导荧光方法来测定在臭氧形成中起重要作用的O原子的绝对密度。发现在氧为50毫托时，氧的离解度约为1%。余辉中O原子的衰变可能主要是由于腔室表面的过程。对于臭氧，我们试图通过观察臭氧离子和250 nm附近的激光吸收来检测它。但是目前还没有成功地实现这一点，因此有必要提高臭氧的检测效率。综上所述，本研究发展了两种对反应等离子体基本过程研究有用的诊断技术，并成功地用于研究氧等离子体中离子和自由基的行为。

In this Work, high density oxygen plasma of the order of 10^<12>cm^<-3> has been produced by exciting helicon waves. The plasma was modulated by ON-OFF of RF power, and ionizing and recombining plasmas were produced at the ON and OFF phases of RF, respectively. The aim of the work is to inevestigate comepeting processes on the formation of negative oxygen ion and ozone which would be effectively produced in the afterglow (recombining plasma phase). First, we have investigated behaviors of positive and negative ions by means of time-of-flight mass spectrometry. Negative ions were effectively produced in the afterglow. The O^- ions were mainly produced with a little O_2^- ions. We have also developed two-photon laser-induced fluorescence method to determine absolute density of O-atoms which play an important role in the formation of ozone. It has been found that the degree of oxygen dissociation was about 1% at oxygen of 50mTorr. The decay of O-atoms in the afterglow may be mainly due to processes on the chamber surfases. For ozone, we have tryed to detect it by observing ions of ozone and by laser absorption around 250nm. However we do not yet succeed to do it. It is necessary to improve the detection efficiency for ozone. As a summary, two kinds of diagnostic techniques which are useful to study of basic processes in reactive plasmas could be developed in this research and successfully used for investigating behaviors of ions and radicals in oxygen plasma.