Real-time atomic oxygen detection using transition metal oxide coated hydrogen-terminated diamond surface

Atomic oxygen (AO) is a major cause for the deterioration of spacecraft materials, such as polymers, composites and optical coatings, in low Earth orbit (LEO). AO exposure can degrade thermal, mechanical, or optical system performance, potentially leading to premature mission failure. Future missions, especially for remote sensing, are designed for very low Earth orbit (VLEO) where the variations of thermospheric density and AO flux are more significant than in higher orbits. Therefore, accurate real-time assessment of the AO fluence impinging upon spacecraft surfaces becomes a crucial issue for mission success, as well as for improving current thermospheric density models. We present a compact, solid-state sensor with high sensitivity and fast response to AO. The sensor is based on two semiconductor components that exhibit unique electrical properties when assembled together: hydrogenated diamond substrate and transition-metal oxide (TMO) coating. The Diamond:H-Transitional Metal Oxide AO sensor (DiMO) was characterized using RF plasma-based and laser detonation AO facilities. Tungsten oxide, WO₃, with thickness ranging from 6 nm to 30 nm was used as TMO coating of choice. The results showed a linear increase in electrical resistance as a function of AO fluence of up to 2 × 10²⁰ O-atoms∙cm^-2, as tested in a laser detonation AO beam facility. The sensitivity of the sensor was found to be tunable, ranging from 10^–14 to 10^–15 Ω∙O-atoms^-1∙cm², and inversely dependent on the coating thickness. This work demonstrates the potential usage of diamond-based devices for real-time AO flux monitoring. Furthermore, compact dimensions and minimal power consumption of the DiMO sensor make it an ideal low-cost solution for the emerging "new-space" era, including nanosatellites applications.