Yuanyuan Jin,Jian Sun,Ling Zhang,Junqiang Yang,Yangwu Wu,Bingying You,Xiao Liu,Kai Leng,Song Liu
High-κ materials that exhibit large permittivity and band gaps are needed as gate dielectrics to enhance capacitance and prevent leakage current in downsized technology nodes. Among these, monoclinic ZrO 2 (m-ZrO 2 ) shows good potential because of its inertness and high-κ with respect to SiO 2 , but a method to produce ultrathin single crystal is lacking. Here, the controllable preparation of ultrathin m-ZrO 2 single crystals via the in situ thermal oxidation of ZrS 2 is achieved. As-grown m-ZrO 2 presents an equivalent oxide thickness of ≈0.29 nm, a high dielectric constant of ≈19, and a breakdown voltage ( E BD ) of ≈7.22 MV cm −1 . MoS 2 field effect transistor (FET) by using m-ZrO 2 as a dielectric layer shows comparable mobility to that using SiO 2 dielectric. The ultraclean interface of m-ZrO 2 /MoS 2 and high crystalline quality of m-ZrO 2 lead to negligible hysteresis in transfer curves. Single crystal m-ZrO 2 dielectric shows potential application in digital complementary metal oxidesemiconductor (CMOS) logic FET.
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 (Sm 2 O 2 SO 4 ) 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 Sm 2 O 2 SO 4 nanoplates with 2D molybdenum disulfide (MoS 2 ) 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 ~10 9 , 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 MoS 2 /h-BN/MLG/Sm 2 O 2 SO 4 /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 Sm 2 O 2 SO 4 as a high- κ dielectric in future 2D devices, with implications for low-power, high-performance electronics.
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