Bulk gallium oxide (Ga₂O₃) has been widely used in lasers, dielectric coatings for solar cells, and deep-ultraviolet transistor applications due to the large bandgap over 4.5 eV. With the miniaturization of electronic devices, an atomically thin Ga₂O₃ monolayer has been unveiled recently, which features an asymmetric configuration with a quintuple-layer atomic structure. The superior stability, the strain-tunable electronic properties, high carrier mobility, and optical absorption indicate the promising applications in the electronic and photoelectronic devices. However, the strict investigation of lattice thermal conductivity $({\kappa }_L)$ of 2D Ga₂O₃ is still lacking, which has impeded the widespread use in practical applications. Here, we report the computational discovery of low ${\kappa }_L$ with a value of 10.28 W m⁻¹ K⁻¹ at 300 K in atomically thin Ga₂O₃. Unexpectedly, two quasi-acoustic shear phonon modes contribute as high as 27% to the ${\kappa }_L$ at 300 K, leading to 37% contribution of optical phonon modes, much larger than many other 2D materials. We also find that the quasi-acoustic shear mode can emerge in the system without van der Waals interactions. This work provides a new insight into the nature of thermal transport in non-van der Waals monolayer materials and predicts a new low ${\kappa }_L$ material of potential interest for thermal insulation in transistor applications.

中文翻译：

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准声剪切声子模式对新型单层 Ga2O3 热导率的巨大贡献

由于超过 4.5 eV 的大带隙，块状氧化镓 (Ga ₂ O ₃ ) 已广泛用于激光器、太阳能电池的介电涂层和深紫外晶体管应用。随着电子设备的小型化，最近出现了一种原子级薄的 Ga ₂ O ₃单层，其具有五层原子结构的不对称配置。优异的稳定性、应变可调的电子特性、高载流子迁移率和光吸收表明在电子和光电子器件中具有广阔的应用前景。然而，晶格热导率的严格研究$({\kappa }_{升})$2D Ga ₂ O ₃仍然缺乏，这阻碍了在实际应用中的广泛应用。在这里，我们报告了低的计算发现${\kappa }_{升}$在原子级薄的 Ga ₂ O _{3 中，}在 300 K 时具有 10.28 W m ^-1  K ^-1的值。出乎意料的是，两种准声剪切声子模式对${\kappa }_{升}$在 300 K 时，光学声子模式的贡献率为 37%，远大于许多其他 2D 材料。我们还发现准声剪切模式可以在没有范德瓦尔斯相互作用的情况下出现在系统中。这项工作提供了对非范德华单层材料中热传输性质的新见解，并预测了一个新的低${\kappa }_{升}$ 在晶体管应用中具有潜在热绝缘性的材料。