【International Papers】Suboxides and subselenides: Intermediate reaction products to form Ga₂O₃、Ga₂Se₃、In₂O₃、In₂Se₃、SnO₂ and SnSe₂ during molecular-beam epitaxy

      Researchers from the University of Bremen have published a dissertation titled "Suboxides and subselenides: Intermediate reaction products to form Ga₂O₃, Ga₂Se₃, In₂O₃, In₂Se₃, SnO₂, and SnSe₂ during molecular-beam epitaxy" in Physical Chemistry Chemical Physics.

Abstract

      The molecular-beam epitaxial (MBE) growth of III-O and IV-O materials (e.g., Ga₂O₃, In₂O₃, and SnO₂) is known to be reaction-limited by complex 2-step kinetics and the desorption of volatile suboxides (e.g., Ga₂O, In₂O, SnO). We find that the different surface reactivities of suboxides and respective elements (e.g., Ga, In, Sn) with active oxygen define the film-growth-windows (FGWs) and suboxide-formation-windows (SFWs) of III-O and IV-O materials, respectively. To generalize, we provide elementary reaction pathways and respective Gibbs energies to form binary III-O, III-Se, IV-O, and IV-Se ground-states as well as their subcompounds during their MBE growth. We apply the 2-step kinetics model established for oxides to identify the subselenide-limited growth of Ga₂Se₃ as the specific example for III-Se materials. Our kinetic and thermodynamic conclusions suggest subcompound-limited growth may be an inherent property for the growth of III–VI and IV–VI thin films by MBE and related epitaxial growth techniques.

FIG. 1. (a) Calculated partial pressures of the gas species C=Ga, In, Sn, A = O, Se, C_y-x A_y-x= GaO, InO, InSe, SnO, SnSe, and C_x A_y-x= Ga₂O, In₂O, In₂Se.

FIG. 2. MBE reaction scheme for binary III-VI and IV-VI materials, showing impinging φc and φa, resulting cation nc, anion na, respective subcompound reservoirs, and the final compound Cx Ay.

DOI：

doi.org/10.1039/D4CP01702A