Thermal Decomposition of C2N2 on Si(100)-2x1 and Si(111)-7x7

ADSORPTION AND DECOMPOSITION OF ClCN ON Si (100)-(2×1) SURFACE: A DENSITY FUNCTIONAL THEORY STUDY

The adsorption and decomposition of ClCN on Si (100)-(2×1) surface is studied by using density functional theory and the cluster model method. The Si 9 H 12 dimer cluster is used to simulate the surface. The present calculations show that ClCN may be adsorbed molecularly without a barrier onto the surface with both linear (L1) and parallel (S1) modes. L1 can isomerize to S1 with a small barrier of 5.6 kcal/mol. Both ClCN and ClNC end-on adsorbates were found to dissociate readily to produce Cl and CN species, which was in excellent agreement with the experiment.

Cycloaddition reactions of cyanogen (C2N2) on the Si(100)-2×1 surface

Multireference as well as density functional theories in combination with the surface integrated molecular orbital molecular mechanics were adopted to study the surface reactions of cyanogens on Si(100)-2x1 surface. Three different products were identified as minima in the initial surface reaction. Among these, the [2+2] product is both kinetically easily accessible and thermodynamically the most stable. Therefore, it can be considered as the experimentally found strongly bound surface species. Unlike other conjugated systems, the [4+2] product is less stable than the [2+2] product. Subsequent surface isomerization studies revealed that kinetically favorable channels exist between the initially formed low-temperature species and the high-temperature species, indicating that surface morphology changes gradually as a function of surface temperature. Theses two channels eventually lead to the same final surface products, which is consistent with experiment. Current study shows that the subsequent surface isomerizations are the key reactions to better understand the complex surface structures and their properties.