Adsorption of toxic gases on silicene/Ag(111).

Silicene is a two-dimensional nanomaterial, composed of Si atoms arranged into a buckled honeycomb network. It has become of great interest in recent years due to its remarkable properties such as its natural compatibility with current silicon-based technology. Due to its extreme thinness on the nanoscale, and large lateral dimensions, it has potential applications in gas sensing, gas storage and components in modern electronic devices. In this work, density functional theory calculations and ab initio molecular dynamics simulations are used to examine the reaction of SO2, NO2 and H2S on the Si/Ag(111) surface. It was shown that each gas will adsorb on the surface in different orientations and adsorption sites. SO2 and NO2 were found to chemisorb on the surface, whereas H2S was found to physisorb. SO2 and H2S adsorb associatively, whereas NO2 readily dissociates, producing adsorbed oxygen, and gaseous NO. At elevated temperatures, the SO2 and NO2 remain strongly bound to the surface, resulting in poisoning of the silicene, while H2S readily desorbs. Ab initio molecular dynamics also show that NO2 will selectively bind before SO2 when both gases are present in the same environment. This work shows that Si/Ag(111) may provide useful properties for gas sensing and storage applications.

Ultrathin silicon oxynitride layer on GaN for dangling-bond-free GaN/insulator interface.

Despite the scientific and technological importance of removing interface dangling bonds, even an ideal model of a dangling-bond-free interface between GaN and an insulator has not been known. The formation of an atomically thin ordered buffer layer between crystalline GaN and amorphous SiO2 would be a key to synthesize a dangling-bond-free GaN/SiO2 interface. Here, we predict that a silicon oxynitride (Si4O5N3) layer can epitaxially grow on a GaN(0001) surface without creating dangling bonds at the interface. Our ab initio calculations show that the GaN/Si4O5N3 structure is more stable than silicon-oxide-terminated GaN(0001) surfaces. The electronic properties of the GaN/Si4O5N3 structure can be tuned by modifying the chemical components near the interface. We also propose a possible approach to experimentally synthesize the GaN/Si4O5N3 structure.