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<p>Realizing the potential for 2D SnSe optoelectronics requires understanding the thickness dependence of structure, defects, and optical properties. We investigate the thickness-dependent crystal structure, band gap, and carrier lifetime of SnSe films deposited by molecular beam epitaxy (MBE) on (100) MgO. MBE enables stoichiometric (<i>2h</i>00)-oriented SnSe films with tunable thicknesses from 80 nm down to 4 nm. As thickness decreases, out-of-plane covalent bonds contract, while in-plane bonding and the van der Waals gap expand with a concurrent increase in stacking fault density, consistent with theoretical predictions of reduced stacking fault energies. Below 8 nm, the band gap transitions from indirect to direct, increasing from 1.4 eV to 1.8 eV, primarily driven by a combination of structural changes and confinement effects. Our results demonstrate how the thickness and structural distortion of 2D materials can be used to modulate the optical properties relevant to optoelectronics.</p>

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Thickness-modulated crystal structure and band gap of 2D SnSe deposited by molecular beam epitaxy

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月27日

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  • Marshall B. Frye,
  • Jonathan R. Chin,
  • Walter J. Smith,
  • Stephen Daniel Funni,
  • Joshua D. Wahl,
  • Anaranya Ghorai,
  • Charles Paillard,
  • Anna M. Österholm,
  • Judy J. Cha,
  • Thomas E. Beechem,
  • Lauren M. Garten

摘要

Realizing the potential for 2D SnSe optoelectronics requires understanding the thickness dependence of structure, defects, and optical properties. We investigate the thickness-dependent crystal structure, band gap, and carrier lifetime of SnSe films deposited by molecular beam epitaxy (MBE) on (100) MgO. MBE enables stoichiometric (2h00)-oriented SnSe films with tunable thicknesses from 80 nm down to 4 nm. As thickness decreases, out-of-plane covalent bonds contract, while in-plane bonding and the van der Waals gap expand with a concurrent increase in stacking fault density, consistent with theoretical predictions of reduced stacking fault energies. Below 8 nm, the band gap transitions from indirect to direct, increasing from 1.4 eV to 1.8 eV, primarily driven by a combination of structural changes and confinement effects. Our results demonstrate how the thickness and structural distortion of 2D materials can be used to modulate the optical properties relevant to optoelectronics.