Controllable Synthesis of Out-of-Plane Grown Bi₂TeO₅ with High-κ and Anisotropy for High-Performance Field-Effect Transistors

Two-dimensional (2D) van der Waals (vdW) dielectrics with high-κ and anisotropy are crucial for advanced field-effect transistors (FETs) and other anisotropic electronic devices. Here, we demonstrate a 2D vdW dielectric, Bi 2 TeO 5, that uniquely combines high-κ with pronounced anisotropy. By adjusting the precursor mass during chemical vapor deposition, we can controllably synthesize Bi 2 TeO 5 with orientations ranging from in-plane to out-of-plane. As a dielectric in MoS 2 top-gate FETs, Bi 2 TeO 5 achieves I on / I off exceeding 10 7, a subthreshold swing of 65.2 mV dec –1, a small hysteresis of 15 mV, and ultralow leakage current density below 10 –5 A cm –2, attributed to its large effective electron mass ( m * = 27.4 m 0 ). The FET shows stable performance over 1000 cycles. Additionally, Bi 2 TeO 5 with in-plane anisotropy induces gate-tunable electrical anisotropic behaviors in monolayer MoS 2 through interface coupling. Our findings introduce a high-performance dielectric for next-generation FETs and demonstrate its potential applications in anisotropic electronics.