Electron impact decomposition process and electron transport property in organic silicon compound

基于到达时间谱理论，采用双关漂移管实验确定了四甲基硅烷蒸气（TMS, Si(CH_3)_4）和四甲基硅烷/氢（TMS/H_2）混合物的电离系数α/N、平均到达时间电子漂移速度W_m、电子纵向扩散系数与气体密度的乘积ND_L和特征能D_L/μ。这些系数对于等离子体分析和等离子体控制以及电子冲击截面的测定都是非常重要的。TMS蒸汽和TMS/H_2混合物在等离子体增强化学气相沉积和等离子体聚合等领域有着广泛的应用。在本工作中，首次在30-5000Td （1Td=10^<-21>Vm^2）宽E/N范围内确定了系数值，E为电场，N为气体密度。备注如下：TMS中α/N值与单硅烷（SiH_4）中的α/N值相差不大。TMS/H_2混合物的α/N在E/N =400 ~ 1800td范围内达到最大值。TMS/H_2混合物中的W_m基本符合Blanc定律。TMS/H_2混合物的D_L/μ随H_2配比的变化而变化。通过稳态实验验证了漂管实验得到的α/N系数。两个实验得到的α/N值吻合较好，说明本实验与α/N值的现值是有效的。TMS中的电子附着很小，可以忽略不计。用四极杆质谱仪（QMS）研究了电子冲击对TMS的解离作用。在QMS中受电子束冲击的TMS分子被分解成一些基团，其中甲基自由基与TMS分子分离。QMS中电子束获得的质谱与TMS/Ar等离子体产生的质谱不同。在漂移管和稳态实验中，TMS蒸气的分解可以忽略不计。目前，这些结果正在准备以论文的形式发表。少

A double-shutter drift tube experiment based on the arrival-time spectra theory has been performed to determine four coefficients, namely the ionisation coefficient α/N, the mean arrival-time electron drift velocity W_m, the product of the electron longitudinal diffusion coefficient and the gas density ND_L and the characteristic energy D_L/μ in tetramethylsilane vapor (TMS, Si(CH_3)_4) and tetramethylsilane/hydrogen (TMS/H_2) mixture. Such coefficients are very important for plasma analysis and plasma control in the plasma application field as well as for determination of electron impact cross sections. TMS vapor and TMS/H_2 mixture are widely used in the field such as plasma-enhanced chemical vapor deposition and plasma polymerisation. In the present work, values of the coefficients were determined for the first time in a wide E/N range of 30-5000Td (1Td=10^<-21>Vm^2), E being the electric field and N the gas density. Remarks are as follows ;1. Values of the α/N in the TMS almost coi … More ncide with those in monosilane (SiH_4).2. The α/N in the TMS/H_2 mixture takes maximum at certain mixture ratios in a range of E/N =400-1800Td.3. The W_m in the TMS/H_2 mixture almost obeys Blanc's law.4. The D_L/μ in the TMS/H_2 mixture sensitively changes depending on the H_2 mixture ratio.A steady-state experiment has been also conducted to check the coefficient α/N obtained in the drift tube experiment5. The α/N obtained from both experiments are in good agreement, which suggests validity of the present experiments and the present values of the α/N.6. Electron attachment in the TMS is negligible small.Dissociation of the TMS by electron impact was also investigated by using a quadrupole mass spectrometer (QMS).7. The TMS molecule impacted by an electron beam in the QMS is decomposed to some groups with molecules which methyl radical is detached by ones from the TMS.8. The mass spectrum obtained by the electron beam in the QMS differs from that produced by a TMS/Ar plasma9. Decomposition of the TMS vapor in both the drift tube and the steady-state experiments is negligible.Now, publication of these results as papers is in course of preparation. Less