Detection of sputtered metals with cavity ring-down spectroscopy

Abstract

We report on use of cavity ring-down spectroscopy (CRDS) as a means to detect and quantify ion sputtering of refractory metal species. CRDS measurements are made with a neodymium:YAG-pumped optical parametric oscillator laser system in the 375-400 nm region. CRDS sputtering measurements are presented for argon ions incident on iron, aluminum, molybdenum, and titanium. The measurements are based on absorption from fine-structure levels of the electronic ground-state multiplets. For each species, characteristic spectra are provided, the dependence of sputtered particle number density on the beam current is examined, measured densities are compared with a sputter model, and detection limits are determined. For iron, aluminum, and titanium we probe multiple fine-structure levels within the ground-state multiplet and obtain information on their relative populations.

Total and Differential Sputter Yields of Boron Nitride Measured by Quartz Crystal Microbalance and Weight Loss (Preprint)

“…In these devices, sputter erosion of grids and other components places a fundamental limitation on lifetimes. Additionally, sputtered particles from within the * 8 , collector plates [9][10] , mass spectrometry 11 , quartz crystal microbalance [2][3][4][5][6][12][13][14] , Rutherford backscattering [15][16] , radioactive tracers 17 , and cavity ring-down spectroscopy 18 . In this contribution we present sputter measurements of BN obtained by both weight loss and the quartz crystal microbalance (QCM).…”

Measurement of Aluminum Erosion Rate by Cavity Ring-Down Spectroscopy

“…We ignore the upper state population of aluminum atoms, since Azer et al 16) showed that the population follows a Boltzmann distribution and its Boltzmann temperature is in the range of 300-2000 K. That is, we estimate the aluminum number density as the sum of two ground state populations ( …”

Species-Specific Sputtering Measurements with Cavity Ring-Down Spectroscopy (Preprint)

“…As reported in our earlier work, for the species and conditions of interest, the measured lower state population can be converted to overall species population through the energy level distributions 25 . We use equation (3) to determine the path-integrated concentration along a chord.…”

“…Detailed reviews of the technique may be found in references 28 and 29. Our previous development of CRDS for sputter diagnostics has been previously described [24][25][26][27] . As shown in Fig.1, the absorbing sample is contained within a high-finesse optical cavity typically formed from two (or three) highreflectivity (R) mirrors with R ~0.9999.…”

“…The work presented here builds upon our previous development of cavity ring-down spectroscopy (CRDS) for sputtering measurements [24][25][26][27] . CRDS is a highly sensitive laser-based absorption method allowing species-specific measurement of concentrations of trace species.…”