Single-crystal antimonene flakes are observed on sapphire substrates after the postgrowth annealing procedure of amorphous antimony (Sb) droplets prepared by using molecular beam epitaxy at room temperature. The large wetting angles of the antimonene flakes to the sapphire substrate suggest that an alternate substrate should be adopted to obtain a continuous antimonene film. By using a bilayer MoS/sapphire sample as the new substrate, a continuous and single-crystal antimonene film is obtained at a low growth temperature of 200 °C. The results are consistent with the theoretical prediction of the lower interface energy between antimonene and MoS. The different interface energies of antimonene between sapphire and MoS surfaces lead to the selective growth of antimonene only atop MoS surfaces on a prepatterned MoS/sapphire substrate. With similar sheet resistance to graphene, it is possible to use antimonene as the contact metal of 2D material devices. Compared with Au/Ti electrodes, a specific contact resistance reduction up to 3 orders of magnitude is observed by using the multilayer antimonene as the contact metal to MoS. The lower contact resistance, the lower growth temperature, and the preferential growth to other 2D materials have made antimonene a promising candidate as the contact metal for 2D material devices.

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Organometal halide perovskite materials are one of the promising candidates for next generation solar energy conversion and optoelectronics applications. Controlling perovskite film morphologies is the key toward promoting device performance, and the sequential deposition method has been extensively used for fabricating high quality perovskite films. Nevertheless, the conversion processes of perovskite from PbI 2 and methylammonium iodide (MAI) precursor remains unclear. In this study, we investigated the nucleation pathway as well as barriers by performing a series of density functional theory (DFT) calculations. DFT calculations suggested that MAI intercalation allows fluctuation in the lateral dimensions between PbI 2 layers, which facilitates nucleation of perovskite nuclei with crystalline orientations complied with recent experiments. By computing perovskite nucleus formation energies with different nucleus sizes, we found that the formation of perovskite nuclei must overcome a nucleation barrier for further growth. The perovskite nucleation barriers are sensitive to both MAI intercalation concentration and perovskite nuclei densities. High MAI intercalation concentration yields high nucleation barriers, and this can be mitigated by forming perovskite films with fine perovskite grains, which is consistent with experimental observations. The present study therefore reveals the atomistic structures of perovskite nuclei embedded in MAI-intercalated PbI 2 , and provides insights into the conversion pathway of perovskite from sequential deposition processes.