In₂O₃- and SnO₂-Based Thin Film Ozone Sensors: Fundamentals

Table 5

Typical parameters of RT ozone sensors operated using UV photoreduction effect.

Metal oxide	Technology, film parameters	UV source, conditions of photoreduction	Max.	Conditions of measurements	Response time	Recovery time	References
In2O3	Thin film: d~20–110 nm, t~8–25 nm	UV Hg lamp (254 nm), vacuum	~10^5–10^6	RT, ~30–90 ppb	n/a	n/a	[170, 171, 173, 174]
	Thick film (mesoporous): d—n/a, t~30 nm	UV LED, air (100°C)	~130–350	Pretreatment, RT, 0.2–1.2 ppm, dry	Minutes	2.5–5.3 min	[119, 175]
	Thin film: d—n/a, t—n/a	UV LED (375 nm), air (0.1 Pa)	~4	RT, 2.5 ppm	~10 min	n/a	[169]
	Thin film: d~20 nm, t~7 nm	UV LED (375 nm), n/a	~10^5	RT, 10.4 ppm	Minutes	Minutes	[176]
	Thin film: d—n/a, t~7 nm	UV LED (375 nm), air	~5–12	RT, 0.3–1 ppm	Minutes	Minutes	[121, 163, 177]
SnO2	Thin film: d~450 nm, t—n/a	UV LED (370 nm), air	1.3–1.4	RT, 10 ppm, 60%	Minutes	Tens of minutes	[178]
	Thin film: d~6–9 nm, t—n/a	UV LED (385 nm), air	~1.1	RT, 100 ppb, dry	Tens of minutes	Tens of minutes	[179]
	Thick film: d—n/a, t—n/a	UV light (366 nm), air	26	RT, 2.5 ppm	~50 min	~4-5 min	[180]
Pt/SnO2	Thick film: d—n/a, t—n/a	UV light (366 nm), air	885	RT, 2.5 ppm	~6 min	~1.5 min	[180]
ZnO	Thin film: d~150–1000 nm, t~5–11 nm	UV Hg lamp (254 nm), vacuum	~10^3–10^8	RT, n/a	Tens of minutes	Minutes	[38, 181]
	Thin film: d—n/a, t~40–100 nm	UV lamp (366 nm), air; UV lamp, air (580°C)	~1.2; ~10^3	RT, 2.5 ppm	10 min; 1 min	Minutes; 5 s (580°C)	[182]
	Thick film: d—n/a, t~40 nm	UV LED (400 nm), air	~2–2.5	RT, 70 ppb, 50%	5–10 min	Minutes	[183]
ZnO-SnO2	Thick film: d—n/a, t~20/n/a nm	UV light (366 nm), air	39	RT, 2.5 ppm	~2 min	~7 min	[180]
InGaZnO	Thin film: d~65 nm, t—n/a	UV LED (370 nm), air	14	RT, 2 ppm	10 min	>30 min	[184]
TiO2	Thick film: d—n/a, t~17 nm	UV light (366 nm), air	64	RT, 2.5 ppm	~1 min	~2 min	[180]
	Thick film: d—n/a, t~18 nm	LED (460 nm), air	2	RT, 2.5 ppm	~1.5 min	~1 min	[185]
TiO2-SnO2	Thick film: d—n/a, t~17/n/a nm	UV light (366 nm), air	327	RT, 2.5 ppm	~3 min	~15 s	[180]
Pt/(TiO2-SnO2) (1 : 4)	Thick film: d—n/a, t~17/n/a nm	UV light (366 nm), air	10^3	RT, 2.5 ppm	~3 min	~1 min	[180]
WO3	Thick film: d—n/a, t~16–20 nm	LED (460 nm), air	64	RT, 2.5 ppm	~1 min	~1 min	[185]
TiO2-WO3	Thick film: d—n/a, t~18/20 nm	LED (460 nm), air	1400	RT, 2.5 ppm	~3 min	~8 min	[185]
Pt/(TiO2-WO3) (1 : 4)	Thick film: d—n/a, t~18/20 nm	LED (460 nm), air	2700	RT, 2.5 ppm	15 min	1.5 min	[185]

d: film thickness; t: grain size; S: sensor response (/); conditions of measurements: temperature of operation, gas concentration, and air humidity.