Density Functional Theory study of leaching efficiency of acids on Si(110) surface with adsorbed boron

• DFT calculations are used to identify the best leaching agent for boron removal from metallurgical grade silicon.
• Optimized structure of boron on Si(110) surface interacted with Cl−, NO3− or SO42−  was obtained respectively.
• Bond strength of Si–B was obviously weakened by different ions with the order of NO3− > SO42− > Cl−.

The Density Functional Theory (DFT)-based leaching efficiency of impurity boron from metallurgical grade silicon (MG-Si) by HCl, HNO3, and H2SO4 was investigated. The boron-doped Si(110) surface was selected as the interaction interface, and respective interactions of Cl−, NO3−, and SO42−  with boron were performed. The principle of boron removal by hydrometallurgy was discussed in the context of a theoretical model and a comprehensive explanation for changes in the density of states (DOS) and bond population was provided. Based on the analysis of the effect of interactions on the electronic structure and properties of the boron-doped Si(110) surface, it was found that all three types of acid ions interact strongly with boron and NO3− registers the strongest interaction. The analysis of the bond population of Si–B showed that these bonds are more easily broken by NO3− than by either Cl− or SO42−, and the formation of B –O bonds is promoted. Furthermore, the effects of the three types of acid agents on the removal of boron from MG-Si were discussed. Acid leaching of porous silicon was performed and the results from inductively coupled plasma (ICP) analysis indicated that the removal efficiency of boron follows the order of HNO3 > H2SO4 > HCl. In addition, the experimental results concur with those of the calculations.

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