Atomic-Scale Characterization and Dynamics of Two dimensional In-Se Materials.

Zhongchang Wang

Atomic-Scale Characterization and Dynamics of Two dimensional In-Se Materials.

Zhongchang Wang

Received Date: 2022-04-02 | Accepted Date: 2022-04-11 | Published Date: 2022-04-30

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Abstract

III-VI semiconductors are currently being investigated as potential candidates for optoelectronic and phase change memory devices. Among several III-VI semiconductors, In-Se systems are an interesting type of material due to their multiple phases and excellent optical properties. For example, In₂Se₃ is a direct bandgap material with a layered structure. There are at least five different phases of In₂Se₃ (α, β, γ, δ, and κ). The α and β -phases can crystallize in both α(3R) and α(2H) crystal structures while the γ -phase has a defective wurtzite structure. The κ–phase is reported to have a structure more similar to the α-phase with a larger unit cell. On the other hand, one also has several different phases, which hold substantial potential device applications. For the suitability of device applications, it is important to have single-phase materials which is still a great challenge because different phases of In₂Se₃ can co-exist with each other. We investigate how the growth temperature, fluxes, and type of substrates (GaAs (100), GaAs (111) A, and Mica) influence the growth of In₂Se₃and find the optimum parameters for obtaining phase-controlled In₂Se₃ by using molecular beam epitaxy (MBE). We have found that Se-rich and high temperatures favor the growth of β phase In₂Se₃ while γ phase is obtained in In-rich conditions and low temperatures on GaAs (100) substrates. Within the same parameter range, the γ phase was predominant on GaAs (111) A substrates. We are now combining state-of-the-art scanning transmission electron microscopy (STEM) with density functional theory (DFT) calculations to systematically investigate the atomic structure of the grown In₂Se₃ and the possible defects in the material. Moreover, we also conduct in-situ TEM and STEM studies of 2D InSe materials upon heating and will present some interesting direct in-situ observations.