Quantum Materials - 10

Abstract

Moiré superlattices, caused by a crystal orientation or lattice mismatch, emerge moiré potentials with longer periods than the lattice. The moiré miniband can cause the formation of flat band [1].
In our previous research, we find that by growing single or double-bilayer (BL) Sb honeycomb lattices on a Bi(111) surface grown on Si(111), we can get a moiré pattern due to a lattice mismatch between antimonene and Bi(111). Our group studied the property of the band structure by means of STM and ARPES measurement. Results showed a significant peak near Fermi level caused by saddle-point in the band structure. [2]
The purpose of the present research is to improve the homogeneity of our sample to supply four-electrode conductivity measurements.
First, We changed thickness of the substrate Bi layer. It is found by STM measurement that for thin Bi film at around 10 BL, moiré might appear a smaller lattice constant than that of bulk, which further affects moiré period size.
As our next experiment, we designed an experiment using mask to evaporate Bi on Si(111) substrate to obtain a Bi-thickness gradation structure (Fig.1). Result shows that moiré pattern trends to disappear at Bi thickness of around 4 BL. This phenomena may come from the variation in Bi(111) lattice constant due to the strong effect of the Si(111) substrate. With good homogeneity of Sb/Bi structure, this kind of sample may realize our calculation model without moiré pattern, which requires a further study.