Deciphering the Complexity of Step Profiles on Vicinal Si(001) Surfaces Through Multiscale Simulations

Abstract The behavior of vicinal Si(001) surfaces are a subject of intense research for years, yet the mechanism behind its step modulation remains unresolved. Step B, in particular, can meander randomly or form a periodic zigzag profile, a surface phenomenon that has eluded explanation due to the lack of appropriate simulation tools. Here, a multiscale simulation strategy, enhanced by machine learning potentials are proposed, to investigate this mesoscale behavior. The study reveals a phase transition in the step profile on vicinal Si(001) surfaces from random meandering to a zigzag wave pattern as the miscut angle decreases. This step‐profile transition is corroborated by Monte Carlo simulations and experimental observations. Remarkably, this transition is robust across various surface conditions, including bare, hydrogen‐saturated, boron‐doped, or strained surfaces. The findings resolve the long‐standing puzzle of step polymorphism on vicinal Si(001) surfaces and pave the way for exploring mesoscale phenomena using multiscale simulations.