Hydrogen interaction with platinum and palladium metal–insulator–semiconductor devices

Abstract

Application of polymer-coated metal-insulator-semiconductor sensors for the detection of dissolved hydrogenComparative hydrogen sensing performances of Pd-and Pt-InGaP metal-oxide-semiconductor Schottky diodes Bridging the pressure gap for palladium metal-insulator-semiconductor hydrogen sensors in oxygen containing environments J. Appl. Phys. 84, 44 (1998); 10.1063/1.368000 Hydrogen adsorption states at the Pd/SiO 2 interface and simulation of the response of a Pd metal-oxide-semiconductor hydrogen sensor Hydrogen-sensitive Pd-SiO 2 -Si and Pt-SiO 2 -Si metal-insulator-semiconductor ͑MIS͒ devices have been studied in ultrahigh vacuum in the temperature range of 223-523 K. Adsorption/ absorption of hydrogen occurs at the metal surface, in the metal bulk, and at the metal-insulator interface. The sensor signal, caused by hydrogen adsorption at the interface, shows a logarithmic dependence on the applied hydrogen pressure. The Pt-MIS device, which is fully functional at atmospheric pressures, is sensitive to changes in hydrogen pressure down to the 10 −12 -Torr scale. We propose that the interface adsorption follows a so-called Temkin isotherm with an interface heat of adsorption that varies with hydrogen coverage as ⌬H i0 ͑1−a͒. The initial heat of adsorption ⌬H i0 is determined to 0.78 eV/ hydrogen atom. The adsorption potential at the external Pt surface is found to be 0.45 eV/ hydrogen atom. These values were obtained by modeling the hydrogen interaction with the MIS devices and fitting the model to a number of experimental results. Also studies of Pd-based devices were performed and compared with Pt. The hydrogen adsorption on the metal surface, previously treated as a first-order process on Pd, is shown to follow a second-order process. Qualitatively the results from the Pd-and Pt-MIS devices agree. Quantitatively there are differences. The hydrogen sensitivity of the Pt-MIS device is only approximately one-third compared to that of the Pd-MIS structure. This agrees with the result that the concentration of available hydrogen adsorption sites at the Pt-SiO 2 interface is approximately 7 ϫ 10 17 m −2 whereas the concentrations of sites at the Pd-SiO 2 interface is roughly three times larger ͑2 ϫ 10 18 m −2 ͒. An estimate of the size of the dipole moments ͑0.6-0.7 D͒ implies that the interface hydrogen atoms are strongly polarized. Differences are also observed in the microstructure of the metal films. Atomic force microscopy results show that the Pd surface reconstructs during H 2 -O 2 exposures, while the Pt surface shows no such change at these temperatures.

Palladium/silicon nanowire Schottky barrier-based hydrogen sensors

“…As H 2 is introduced, it dissoci- ates into H + ions which thereafter diffuse into Pd and settle on the Pd/NW interface. These ions induce a dipole layer and cause the workfunction of the metal to effectively decrease [25]. As seen in Fig.…”

The decoration of TiO2/reduced graphene oxide by Pd and Pt nanoparticles for hydrogen gas sensing

“…Due to role of Pd and Pt nanoparticles as catalysts in performing electronic sensitization mechanism, the both metal decorated samples have presented improved responses (Fig. 8bec) [40]. It was obvious that addition of RGO sheets along with metallic nanoparticles could enhance sensing properties of the TiO 2 based sensors considerably.…”

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

“…2, 3,8,23, and 24 in air at 400°C for 2 h. 15 Hereafter, this procedure is referred to as air annealing. The I-V characteristics of the sensor FETs before and after air annealing did not change significantly but V th did change.…”

“…3 Dissociated hydrogen atoms on the Pd surface migrate and produce a dipole layer at the metal-oxide interface and then the dipole layer causes threshold voltage shift in sensor FETs. 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%.…”