Corrections to the article

N. D. Morgulis, CATHODE SPUTTERING

(Uspekhi Fizicheskikh Nauk, vol. 28, nos. 2–3, p. 202, 1946.)

1. In Fig. 9 (p. 215), the numbers of curves 2 and 3 should be interchanged.

2. On p. 219, in the interval between the phrases on the 22nd line from the top, the following should be inserted:

In fact, the application of equilibrium formulas to estimate the permissible value, in our case of cathode sputtering, is possible only if the following criterion is satisfied:

\[ n\frac{\lambda_a}{\omega}\frac{dT}{dt} \ll T, \quad \text{or} \quad n\frac{\lambda_a}{\omega} \ll \tau_a \simeq 10^{-13}\ \text{sec}, \]

where \(\lambda_a\) is the “mean free path” of sound quanta, \(\omega\) is the speed of sound, \(n\) is a quantity of the order of several units, and \(\tau_a\) is a relaxation time of the order of the period of vibration of the lattice atoms; in the typical case of Au, the quantity

\[ n\frac{\lambda_a}{\omega} \simeq 10^{-11}\ \text{sec}, \]

i.e., this criterion is not satisfied here.

1. On p. 221, before the last paragraph from the bottom (“It should be noted…”), the following should be inserted:

At very high ion-current densities \(I_p = eN_p\), which occur, for example, in the pulsed mode of operation of gas-discharge devices (see, for example, P. Drewell, Zschr. f. techn. Phys. 17, 252, 1936), the occurrence of “cumulative” sputtering of surface atoms by two successive impacts of incident ions with energy \(v < v_0\), i.e., less than the critical value, but within the limits

\[ \frac{1}{2}v_0 < v < v_0, \]

is possible, provided only that these impacts occur one after the other within a time not exceeding the relaxation time \(\tau_a = 10^{-13}\ \text{sec}\). If by \(n' = \tau_a G\) we denote the surface concentration of “excited” atoms after the first impact, and by \(G = aN_p\) the rate of their excitation \((a \leq 1)\), then the coefficient of their cumulative sputtering is

\[ N'\frac{n'}{n_a}G = a^2\frac{\tau_a}{n_a}N_p\ \text{cm}^{-2}\ \text{sec}^{-1}, \]

where \(n_a \simeq 10^{14}\ \text{cm}^{-2}\) is the total concentration of surface atoms.

Let us set, for example, \(N' \simeq 10^9\), at which, in the absence of reactivation, approximately 5% of the complete tungsten filament can be sputtered in several hours by evaporation, which will lead to a decrease in the emission of the latter at \(1900^\circ\) K by approximately a factor of 3.3. In that case, for this, assuming \(a \simeq 0.1\), one requires

\[ I_p \simeq 1\frac{A}{\text{cm}^2}, \]

which is already almost reaching the limits attainable in modern high-power gas-discharge devices in pulsed operation.

1. The bibliography should be supplemented with the following articles:

2. A. Güntherschulze, Zschr. f. Phys., 118, 145 (1941); 119, 79, 685 (1942).

3. R. Seeliger, Zschr. f. Phys., 119, 482 (1942).
4. H. Fetz, Zschr. f. Phys., 119, 590 (1942).
5. L. Jacob, Nature, 157, 586 (1946).