The results are summarized in Figure 4, where gradual F passivation increases the formation energy to a positive value of 2 eV, thus indicating destabilization of the structure, whereas the O and OH passivations exhibit a gradual decrease in the formation energy with respect to the full H case, indicating that the structure is further stabilized by the insertion of O in either radical (OH) or atomic (=O) form.
For such applications, it is critical to understand the effects of surface modifications on the electronic band structure of pSiC; however the theoretical characterization of the effects of chemical agents on the electronic structure of C-terminated SiC is nonexistent (to the best of our knowledge); hence, this work discusses the effects of different surface passivation species on the structure and electronic properties of pSiC.
To study the effects of different chemical passivation agents on the electronic and structural properties of pSiC, the hydrogen atoms of the surface were gradually replaced with F (H + F), OH radicals (H + OH), and O (H + O) atoms.
Figure 2 presents the electronic band structures of pSiC with different chemical passivation schemes alongside the bulk crystalline SiC calculated on a 32-atom supercell; notice that the gap is direct due to the folding of the Brillouinzone.
Figure 3 presents the evolution of the band gap energy with respect to the number of passivation agents other than H per supercell.
To verify the most stable surface passivation, formation energies calculations were performed using the following expression :
Trivalent chromium passivation is used after zinc plating for enhancing corrosion resistance of parts.
At first, we found that in parts produced from an older solution, the passivation layer has cracks which are not seen in parts from a fresh/new solution.
These metal ions deposit into the passivation as hydroxides, and the larger the quantity in this layer the more the layer contracts by heating, meaning the newer the solution the less the layer contracts.
So, we investigated developing a new solution to improve the corrosion resistance after heating through the reduction of metal ion deposits in the passivation layer.
et al., "Development of Trivalent Chromium Passivation for Zn Platng with High Corrosion Resistance after Heating," SAE Int.