Depth profiling by secondary ion mass spectrometry

Abstract

The principles and applications of depth profiling by secondary ion mass spectrometry (SIMS) are reviewed. Discussed are the basic physical processes and instrumental factors which influence the shape of depth profiles and which have to be understood or controlled for successful experimental measurements. Microroughness caused by sputtering, atomic mixing by primary beam knock‐on, and sample consumption limit the depth resolution which can be achieved while the chemical effect of ion yield enhancement by reactive species, matrix effects, and preferential sputtering can strongly affect the secondary ion signal. Instrumental effects to be controlled include beam uniformity, sample charging, and beam, and residual gas contamination. High depth resolution and sensitivity are the reasons for a wide variety of applications for SIMS depth profiling. Reviewed are measurements of the range distribution of ions implanted into semiconductors and their redistribution by subsequent annealing, studies of thin films and of oxide layers, diffusion measurements in metals, semiconductors, and minerals, measurements of elemental surface enhancements in airborne particles, and lunar glass spherules, and the search for solar wind implanted ions in lunar crystals.

Oxygen diffusion studies. I. A preliminary ion microprobe investigation of oxygen diffusion in some rock-forming minerals

“…However, preliminary analyses of samples using a 6 keV 4~ + primary beam indicate little detectable difference from the 10 keV 4~ analyses, and are within the over-all grain-to-grain reproducibility of results. These findings are in qualitative agreement with other workers in that a primary beam of high mass to charge (4~ produces less knock-on effects than a beam of low mass to charge (160-) of equivalent energy (Zinner et al, 1976). The calculated diffusion coefficient at 600~…”

“…In common with other workers (Giletti et al, 1978;Arita et al, 1979;Zinner, 1980) it was found that for silicates and oxides there is a linear correlation between sputtering time and depth. The extent of sputterinduced microroughness (Wilson, 1973) was checked by interference contrast microscopy.…”

“…Consequently, the accuracy of SIMS data is strongly instrument-dependent, and operational parameters must be borne in mind in interpreting data (Zinner, 1980). Giletti et al (1978) have provided a thorough investigation of many of these effects and provided they are minimized, SIMS should provide the most sensitive method for determining diffusion coefficients in geological materials.…”

“…Oxygen penetration profiles in quartz (llc) for diffusion at temperatures of 600 and 750 ~ were only 0.084 #m and 0.15 #m in length respectively. It is possible that the true isotope distributions in these profiles may have been distorted by atomic mixing caused by the knock-on of specimen atoms by the primary ion beam, the so-called 'knock-on' effect (Ishitani and Shimizu, 1975;Giletti et al, 1978;Zinner, 1980). However, preliminary analyses of samples using a 6 keV 4~ + primary beam indicate little detectable difference from the 10 keV 4~ analyses, and are within the over-all grain-to-grain reproducibility of results.…”

Kinetic processes of mantle minerals

“…The ion microprobe at WHOI (Cameca IMS 3t) was used to determine concentration profiles ofNa, Mg, AI, Si, and Ca by a depth profiling method described in detail elsewhere (e.g., Sneeringer et aI., 1984;Zinner, 1980). Typically, a primary beam current of 100-50 nA with 80-50 !lm beam diameter was achieved.…”