Etch yield Si/Cl+

The Si etch yield for saturated surfaces was taken to be Y_Si = 3, independent of the incident angle of ions striking the surface. On the other hand, the SiO2 sputter yield was assumed to be dependent on the incident ion angle, based on the data obtained from the Cl2+/Cl+ ion beam experiments: <- YSiの値は、この後に R = eVs/kTi = 100 (e.g., eVs = 50 eV and kTi = 0.5 eV)と書いてあるので 50eV の場合である。しかし、reference が引いてないので根拠の無い仮定か？[Tuda, Effects of etch products and surface oxidation.. 1996]

The etch yield was taken to be YSi(0) = 0.4 from the experimental data at Ei = 50 eV for normal ion incident (Φ=0)[22], where Φ is the incident ion angle from the surface normal. [Tuda, 1997] -> これを元に、Eth = 10 eV としてCを計算すると C = 0.102 となる。しかし、[22] では Eth の値が１０より大きく、従って傾き C の値も大きい（はず）
[22]→ M. Balooch, M. Moalem, Wei-E. Wang, and A. V. Hamza, J. Vac. Sci. Technol. A 14, 229 (1996).

(For Y = C(√E - √Eth)f(θ))
The proportionality constant C affects only the relative rate of notch formation and is not significant for the simulation, as long as it is not excessively large or small. To speed up the calculation, this parameter can be selected so that the most energetic ions of a given IEDF will etch with probability one on normal incidence. For improved importance sampling of the IEDF, all of the results presented here were obtained with C = 0.1, corresponding to a reaction probability of one for ions with incident energy of 177 eV. Negative values of Y signify no reaction. [Hwang, Giapis 1997]