Langmuir analysis on hydrogen gas response of palladium-gate FET

Hydrogen sensors based on Ni/SiO2/Si MOS capacitors

“…For all the concentrations, the recovery is much slower than the response. The response/recovery of our Ni sensors is very similar to that of palladium sensors reported [5,15]. It was also reported that the dissolved hydrogen atoms diffused through the thin oxide layer and trapped at the Si/SiO 2 interface [5,22,23].…”

“…3, it is plausible to use the Langmuir isotherm model to explain the adsorption/desorption mechanism of dissolved hydrogen at the metal/SiO 2 interface in nitrogen ambient, similar to those proposed for palladium devices [15,16]. The Langmuir isotherm model assumes that, on a given interface, there are a fixed and evenly distributed number of active sites for a certain kind of gaseous specie to be adsorbed; and one active site can only adsorb one molecule or atom.…”

A Pt–Ti–O gate Si-metal-insulator-semiconductor field-effect transistor hydrogen gas sensor

“…The excellent sensor characteristics of Pd-gate Si-MOSFETs are demonstrated to detect a wide range of hydrogen concentrations diluted by air from 1 ppm to 1%. 4 The hydrogen concentration dependence of threshold voltage shift is well fitted by Langmuir relationship for the wide concentration range. 4 Several critical issues on reliability, however, remain as unsolved problems such as blister formation by hydrogen exposure, 5 degradation of sensing amplitude under long-term ͑about 1000 h͒ operations, 6 and crack generation under high-humidity ͑95%͒ and high-temperature ͑85°C͒ environments.…”

“…4 The hydrogen concentration dependence of threshold voltage shift is well fitted by Langmuir relationship for the wide concentration range. 4 Several critical issues on reliability, however, remain as unsolved problems such as blister formation by hydrogen exposure, 5 degradation of sensing amplitude under long-term ͑about 1000 h͒ operations, 6 and crack generation under high-humidity ͑95%͒ and high-temperature ͑85°C͒ environments. 7 These issues concerning catalytic palladiumgate films are now understood as intrinsic properties of palladium to absorb and accumulate hydrogen gases and/or water in their films.…”

Hydrogen Detection Using a Single Palladium Nano-Aperture on a Fiber Tip

“…Furthermore, palladium and platinum films also catalyze the dissociation of diatomic hydrogen, leading to a high absorption rate or facilitating diffusion into other materials. For ideal films, this process is limited by surface adsorption described by the Langmuir equation [8], which for diatomic molecules, the fractional coverage of the surface, h, is given by:…”