Oriented Growth of BiOCl High-κ Dielectrics for Pristine Van der Waals Electronics

High-κ dielectric materials are pivotal for next-generation two-dimensional (2D) electronics. However, integrating high-κ dielectrics with 2D semiconductors remains challenging in terms of simultaneously achieving superior dielectric properties and high-quality interfaces. Here, we demonstrate that ultrathin bismuth oxychloride (BiOCl) crystals grown by chemical vapor deposition (CVD) can serve as excellent gate dielectrics, showing a high dielectric constant (>40) and a wide bandgap (∼3.9 eV). Remarkably, the CVD growth mode of BiOCl can be regulated from horizontal to vertical orientation by tuning nucleation rates, enabling residue-free dry transfer for pristine device integration. Top-gated BiOCl/MoS 2 field-effect transistors exhibit a high on/off ratio exceeding 10 8 , a near-ideal subthreshold swing of 61.2 mV/dec, minimal gate leakage currents of 10 −8 A/cm 2 , and nearly zero hysteresis. This reliable approach to integrating ultrathin single-crystalline high-κ dielectrics paves the way for realizing the full theoretical performance of 2D electronics.