The effect of Sb addition on the morphology of self-catalyzed InAsSb nanowires (NWs) is systematically investigated. InAs NWs were grown by molecular beam epitaxy with and without antimony (Sb) flux. It is demonstrated that trace amount of Sb flux is capable of tuning the geometry of NWs, i.e. it enhances lateral growth and suppresses axial growth. We attributed these behaviors to the surfactant effect of Sb which results in modifications to the kinetic and thermodynamic processes. The thermodynamic mechanism that accounts for Sb segregation in InAsSb NWs is also elucidated. This study opens a new route towards precisely controlled NW
geometry by Sb addition.