Radiofrequency sputter source for laser-induced fluorescence studies of transition metal atoms and dimers

We have developed a radiofrequency sputter source using a 13.56 MHz transmitter and operating in the pressure range 2-100 mTorr. Absorption, emission, and laser-induced fluorescence spectroscopies have been used to characterize the number densities and temperatures of metal atoms and molecules in the discharge. With an iron target, at a pressure of 100 mTorr, the ground-state iron atom density is 2 × 1012 cm-3, with a translational temperature below 800 K. We estimate a number density of copper dimers of 1010-1011 cm-3 when sputtering a copper target at this pressure, and find a rotational temperature of about 500 K. As an example of the source's utility, a rotationally resolved spectrum of the Cu2 C↔X transition is analyzed to yield the excited-state symmetry and rotational constants. © 1990.