Development of nanotopography during SIMS characterization of thin films of Ge1-xSnx alloy

作者：Secchi M^*; Demenev E; Colaux J L; Giubertoni D; Dell'Anna R; Iacob E; Gwilliam M; Jeynes C; Bersani M

来源：Applied Surface Science, 2015, 356: 422-428.

DOI：10.1016/j.apsusc.2015.08.083

• SIMS protocol
• Ge1-xSnx
• Nanotopography
• Ripple

This work presents a study of application of secondary ion mass spectrometry (SIMS) to measure tin concentration in Ge1-xSnx alloy with x higher than solid solubility similar to 1%, i.e. well above the diluted regime where SIMS measurements usually provide the most reliable quantitative results. SIMS analysis was performed on Sn+ ion implanted Ge films, epitaxially deposited on Si, and on chemical vapor deposition deposited Ge0.93Si0.07 alloy. Three SIMS conditions were investigated, varying primary beam ion species and secondary ion polarity keeping 1 keV impact energy. Best depth profile accuracy, best agreement with the fluences measured by Rutherford backscattering spectrometry, good detection limit (similar to 1 x 10(17) at/cm(3)) and depth resolution (similar to 2 nm/decade) are achieved in Cs+/SnCs+ configuration. However, applied sputtering conditions (Cs+ 1 keV, 64 degrees incidence vs. normal) induced an early formation of surface topography on the crater bottom resulting in significant variation of sputtering yield. Atomic force microscopy shows a peculiar topography developed on Ge: for oblique incidence, a topography consisting in a sequence of dots and ripples was observed on the crater bottom. This behavior is unusual for grazing incidence and has been observed to increase with the Cs+ fluence. Rotating sample during sputtering prevents this ripple formation and consequently improves the depth accuracy.

• 出版日期2015-11-30