Bi $_2$ O $_2$ Se单晶的巨介电常数和过早金属性
Huge permittivity and premature metallicity in Bi$_2$O$_2$Se single crystals
摘要：
Bi $_2$ O $_2$ Se是下一代半导体电子学的有前途的材料。它在引入少量电子时表现出过早的金属性，其背后的物理学仍然难以捉摸。在这里，我们报告在不同的载流子密度的Bi $_2$ O $_2$ Se单晶的传输和介电测量。随温度变化的电阻率（$ρ$）表明从半导体到金属状态的平滑演变。发生金属-绝缘体转变（MIT）的临界浓度非常低（$n_\textrm{c}\sim10^{16}$ cm $^{-3}$）。绝缘样品的相对介电常数很大（$ε_\textrm{r}\approx155(10)$），随温度变化缓慢。结合轻有效质量，导出了长有效玻尔半径（$a_\textrm{B}^*\approx36(2)$ $\textrm{nm}$），根据Mott判据对金属的金属早熟现象给出了合理的解释.低温下的高电子迁移率（$μ$）可能是由于巨大的$ε_\textrm{r}$屏蔽电离散射中心的结果。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。
英文摘要：
Bi$_2$O$_2$Se 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 Bi$_2$O$_2$Se 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 ($n_\textrm{c}\sim10^{16}$ cm$^{-3}$). The relative permittivity of the insulating sample is huge ($ε_\textrm{r}\approx155(10)$) and varies slowly with temperature. Combined with the light effective mass, a long effective Bohr radius ($a_\textrm{B}^*\approx36(2)$ $\textrm{nm}$) 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 $ε_\textrm{r}$. Our findings shed light on the electron dynamics in two dimensional (2D) Bi$_2$O$_2$Se devices.
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