High-κ samarium oxysulfate dielectric for two-dimensional electronics with enhanced gate coupling.

Layered dielectric materials and their van der Waals (vdW) heterostructures offer high potential for next-generation two-dimensional (2D) electronic devices, but materials that combine a wide bandgap and high dielectric constant are rare. Here, we present the controllable synthesis of quasi-vdW layered samarium oxysulfate (Sm2O2SO4) single crystals via a molten-salt-assisted chemical vapor deposition (CVD) method. These atomically thin crystals exhibit remarkable dielectric properties, including a wide bandgap (~5.54 eV), high dielectric constant (~18), robust breakdown voltage (>12 MV cm-1) and good thermal reliability. By integrating ultrathin Sm2O2SO4 nanoplates with 2D molybdenum disulfide (MoS2) via vdW forces, we fabricate field-effect transistors (FETs) showing a subthreshold swing down to 65.2 mV dec-1, hysteresis down to 5.4 mV, on/off current ratios of ~109, and gate leakage currents down to around 7 × 10-7 A cm-2. Furthermore, a high gate coupling ratio (GCR ~ 0.83) non-volatile memory device was developed based on the MoS2/h-BN/MLG/Sm2O2SO4/MLG heterostructure. The flash memory achieves ultrafast (~50 ns) programming/erasing operations, robust endurance (>2000 cycles) and long-term retention (>10 years). This work shows promising results for the integration of Sm2O2SO4 as a high-κ dielectric in future 2D devices, with implications for low-power, high-performance electronics.