抄録
Pt-catalyzed chemical etchings of SiC in hydrofluoric acid (HF) and water are investigated using density functional theory simulations. We investigated the kinetics of Pt-assisted HF/water dissociation and breaking of Si-C bonds based on the elastic and chemical interaction energies at the Pt-SiC interface, activation barriers of the Si-C bond breaking, and catalyst role of Pt. The etching is initiated by the dissociative adsorption of HF/water onto a step-edge Si, forming a five-fold coordinated Si moiety as a metastable state. This is followed by breaking of the Si-C back-bond by an H-transfer process. The results demonstrated that the gross activation barriers strongly depend on the Pt-SiC separation, characterized by the elastic and chemical interactions. However, chemical interactions are a dominant factor and a main contributor to the lowering of the activation barrier, leading to an enhancement of the etching reaction. The calculated activation barriers qualitatively agree well with the experimental results.
