O₂⁺ probe‐sample conditions for ultra low energy SIMS depth profiling of nanometre scale Si_0.4Ge_0.6/Ge quantum wells

Abstract

The O 2 + probe-sample conditions and subsequent data analysis required to obtain high depth resolution SIMS depth profiles from Si 1Àx Ge x /Ge quantum well structures (0.6 ≤ x ≤ 1) are presented. For primary beam energies E p >500 eV and x approaching 1, a significant decrease in the Ge + ionisation probability resulted in unrepresentative and unquantifiable depth profiles. For E p ≤ 500 eV, a monotonic increase in the Ge + signal with x was observed resulting in profiles representative of the sample structure and enabling x to be found. A depth scale was also established using a point-by-point approach taking into account the local erosion rate, which is a function of x. Both the composition and the thickness of the Si 1Àx Ge x and Ge layers were found to be in excellent agreement with those obtained using X-ray and transmission electron microscopy.

Atomic spectrometry update. Review of advances in the analysis of metals, chemicals and functional materials

“…For example, an O 2 + probe has been used to obtain high resolution depth proles from a Si-Ge type quantum well structure. 159 It was shown that when primary ion beam energies above 500 eV were used, depth proles became unrepresentative. However below this threshold, quantication could be achieved, and it was reported that good agreement was obtained with data derived from TEM and X-ray techniques.…”