Bi₂O₂Se is a promising material for next-generation semiconducting electronics. It exhibits premature metallicity on the introduction of a tiny amount of electrons, the physics behind which remains elusive. Here we report on transport and dielectric measurements in Bi₂O₂Se single crystals at various carrier densities. The temperature-dependent resistivity (ρ) indicates a smooth evolution from the semiconducting to the metallic state. The critical concentration for the metal-insulator transition (MIT) to occur is extraordinarily low (n_c∼10¹⁶ cm⁻³). The relative permittivity of the insulating sample is huge (ϵ_r ≈ 155(10)) and varies slowly with temperature. Combined with the light effective mass, a long effective Bohr radius (a ^*_B ≈ 36(2)) is derived, which provides a reasonable interpretation of the metallic prematurity according to Mott’s criterion for MITs. The high electron mobility (µ) at low temperatures may result from the screening of ionized scattering centers due to the huge ≈_r. Our findings shed light on the electron dynamics in two dimensional (2D) Bi₂O₂Se devices.

Bi ₂ O ₂ Se是用于下一代半导体电子产品的有前途的材料。在引入少量电子时，它表现出过早的金属性，其背后的物理原理仍然难以捉摸。在这里，我们报告了在不同载流子密度下Bi ₂ O ₂ Se单晶中的传输和介电测量。随温度变化的电阻率（ρ）指示从半导体状态到金属状态的平稳演变。用于金属-绝缘体转变（MIT）发生的临界浓度是非常低的（Ñ _ç〜10 ¹⁶厘米^-3）。绝缘样品的相对介电常数很大（ε _{- [R} ≈155（10））和具有温度变化缓慢。与光有效质量，长有效玻尔半径（组合一个^*_乙≈36（2））被导出，它提供了一种根据莫特的准则的MITs金属早产的合理解释。高电子迁移率（μ在低温下）可能导致的电离散射中心筛选由于庞大≈ _{- [R} 。我们的发现揭示了二维（2D）Bi ₂ O ₂ Se器件中的电子动力学。