Termination-Dependent HF Activation on 4H-SiC (112−0): Pt–Ni–C–N ₄ Dual-Atom Catalysts Promote Etching Kinetics─A First-Principles Study

Attributed to the high conductivity of the (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>11</mml:mn><mml:mover><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mover><mml:mn>0</mml:mn></mml:math>) face of 4H-SiC, understanding the HF-assisted wet etching mechanism of this crystal face is crucial for semiconductor processing by clarifying the influence of surface terminations and functional groups on the etching process. In this study, we performed a first-principles investigation of the stepwise HF etching process on the (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>11</mml:mn><mml:mover><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mover><mml:mn>0</mml:mn></mml:math>) face with OH or coexisting F and OH terminations. By elucidating the etching reaction pathway, we identified key transition states, intermediates, and rate-determining steps. Analysis of adsorption configurations, charge transfer, and bonding characteristics reveals that HF dissociation strongly depends on surface termination, with the activation energy on the F-OH coterminated surface (2.51 eV) markedly lower than that on the OH-terminated surface (2.86 eV). In both cases, etching favors Si over C, with Si preferentially volatilized as SiF₄ rather than SiHF₃, highlighting a strong selectivity for complete fluorination. Importantly, the Pt-Ni-C-N₄ dual-atom catalyst, distinguished by excellent stability and economic advantage over pure Pt, lowers the energy barrier by ∼1 eV, rendering etching possible at ambient temperature. These findings shed light on termination-dependent etching behavior and guide the design of efficient low-temperature etching strategies for the nonpolar <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>(</mml:mo><mml:mn>11</mml:mn><mml:mover><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mover><mml:mn>0</mml:mn><mml:mo>)</mml:mo></mml:math> face of 4H-SiC.