Enhanced Transport and Optoelectronic Properties of van der Waals Materials on CaF<sub>2</sub> Films
Haizeng Song, Fei Zhou, Shancheng Yan, Xin Su, Han Wu, Qi Wu, Yuan Gao, Rui Chen, Tianhong Chen, Jie Yao, Yi Shi
Abstract
To achieve better properties of van der Waals (vdW) devices, vdW heterointerfaces with substrates such as hexagonal boron nitride (h-BN) were introduced to alleviate adverse substrate effects. However, the premature dielectric breakdown and its scale limitation make wider application of h-BN substrates challenging. Here we report a fluoride-based substrate that substantially improves optoelectronic and transport properties of dichalcogenide devices, with enhancement factors comparable to those of h-BN. A model system of wafer-scale fluoride calcium (CaF 2 ) ultrathin films with the preferable growth direction along [111] is prepared by the magnetron sputtering method. Results show that the constructed SnS 2 /CaF 2 and WS 2 /CaF 2 devices exhibit 1 order of magnitude higher than devices based on the SiO 2 substrate in electronic mobility and photoresponsivity. Theoretical calculations reveal that devices based on fluoride substrates are immune from the Coulomb impurity scattering by forming quasi-vdW interfaces, exhibiting great potential for high responsivity and mobility of photogenerated carriers in 2D vdW devices.