van der Waals epitaxy and defect-charge manipulation of InSb islands on graphene-covered SiC(0001)

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Indium antimonide has attracted extensive interest due to its optical and electronic applications, and functions as a constituent block in exploring Majorana physics. Here, through molecular-beam epitaxy, we achieve van der Waals epitaxy of high-quality InSb islands on graphene-covered SiC(0001) substrate. As characterized with spectroscopic imaging scanning tunneling microscopy (STM), the islands have tens of nanometers in thickness and a 2 ×{} 2 surface reconstruction, exhibiting a narrow band gap of 0.315 ±{} 0.005 eV. Double concentric rings, whose diameters vary with the bias voltage of the STM tip, are observed in the spatially resolved conductance maps, which are explained as a charging process of solitary defects due to tip-induced band bending. Furthermore, high-temperature sample annealing induces a 3 ×{} 3 surface reconstruction, which possesses a larger gap of 0.40 ±{} 0.01 eV. Our work demonstrates the feasibility of van der Waals epitaxy of the InSb traditional semiconductor and enriches the understanding of charging process in single defects.