Secondary ion mass spectrometry relative sensitivity factor of ⁶⁹Ga in ZnS

Multispectral zinc sulfide (MS-ZnS) is an important broadband optical material used in various imaging and sensing technologies. To address the challenge of withstanding aerodynamic loads during operational use, surface hardening treatments of MS-ZnS using Ga₂S₃ have demonstrated effectiveness while preserving optimal optical properties. Secondary ion mass spectrometry (SIMS) is particularly well-suited for analyzing Ga incorporation in the subsurface of post-treated ZnS windows. Herein, we report the determination of the relative sensitivity factor (RSF) for Ga in a ZnS matrix to calibrate Ga concentration profiles. The RSFs of ⁶⁹Ga in ZnS were obtained from multiple SIMS measurements on three ⁶⁹Ga-implanted ZnS coupons at doses of 0.5 × 10¹⁵, 2.5 × 10¹⁵, and 5.1 × 10¹⁵ (at. cm⁻²). We found that the elemental RSF values are 1.78 × 10²⁰ (±17%), 1.76 × 10²⁰ (±21%), and 1.48 × 10²⁰ (±13%) (at.  cm⁻³), indicating a proportional relationship with the amount of Ga as deduced from standard analysis versus the ratio of ⁶⁹Ga and ⁶⁴Zn count rates. These RSF determinations provide a reliable tool for analytical and process optimization purposes.