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, Bi2TeO5, that uniquely combines high-κ with pronounced anisotropy. By adjusting the precursor mass during chemical vapor deposition, we can controllably synthesize Bi2TeO5 with orientations ranging from in-plane to out-of-plane. As a dielectric in MoS2 top-gate FETs, Bi2TeO5 achieves Ion/Ioff exceeding 107, 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 m0). The FET shows stable performance over 1000 cycles. Additionally, Bi2TeO5 with in-plane anisotropy induces gate-tunable electrical anisotropic behaviors in monolayer MoS2 through interface coupling. Our findings introduce a high-performance dielectric for next-generation FETs and demonstrate its potential applications in anisotropic electronics.