Simultaneous optimization of phononic and electronic transport in two-dimensional Bi2O2Se by defect engineering

Defect engineering represents one degree of freedom to tune the physical and chemical properties of two-dimensional (2D) materials. Here, we demonstrate that the thermal and electronic properties of 2D Bi2O2Se can be optimized simultaneously by introducing oxygen defects. 2D Bi2O2Se and its oxygen-deficient counterpart (Bi2OxSe, x < 2) can be controllably synthesized by the chemical vapor deposition (CVD) method. By introducing oxygen defects, the thermal conductivity of 2D Bi2O2Se is reduced by nearly three times, achieving an extremely low thermal conductivity of 0.68 +/- 0.06 W/mK at room temperature via the thermal bridge technique. This low thermal conductivity is enabled by the scattering of phonons by targeting of high-, mid-, and low-frequency phonons due to oxygen defects, strong anharmonicity, and nanostructure boundaries, respectively. Meanwhile, the mobility is also improved to 260-500 cm(2)center dot V-1 center dot s(-1) and the usual polar optical phonon scattering in 2D Bi2O2Se is weakened owing to the introduction of oxygen defects. Our results promise potential applications for thermoelectric design, nanoelectronics, and thermal barrier coating devices based on emerging 2D materials.