Analysis of desorption species from MOS structure surfaces induced by gate voltages

Hot carriers, which have energies over the Fermi level, are able to activate surface reaction. A MOS structure is able to generate tunable hot carriers under gate bias-voltages, would be suitable for the hot-carrier injection to surface from the metal side, but not vacuum side. In this research, I desire to make a proposition of catalytic devices using MOS structures. Desorption is one of the important paths in catalytic reaction, and would be observed when the bais-voltage is applied. We found desorption on N$_2$O exposed MOS (Fe/SiO$_2$/$p$-Si) structure, detected by a mass spectrometer. The desorption were observed only when the metal surface was in negative polarity, the hole injection. The desorption of CH$_4$ molecules was confirmed by mass analysis with cracking corrections. Since non-polar molecules (e.g., CH$_4$) are hard to adsorb, the origin of CH$_4$ is not adsorbed one as the molecule, but the catalytic reaction. At the same time, NH$_3$ and H$_2$O background intensities decreased. We consider the following scenario. The CH$_4$ is generated from CO and adsorbed H over Fe$_x$N$_y$/SiO$_2$ surface with hot-carrier activation. The CH$_4$ formation inhibit H$_2$O and NH$_3$ suitable generation via decrease adsorbed H concentration. Most of desorption species can be expl