Accelerated/decelerated dynamics of the electric double layer at hydrogen-terminated diamond/Li+ solid electrolyte interface

The electrical response of the electric double layer (EDL) effect at the interface between a hydrogen-terminated diamond (H-diamond) and a Li+-conducting solid electrolyte [i.e., LiNbO3 and Li3PO4] was investigated by using an all-solid-state H-diamond-based EDL transistor (EDLT). A 5-nm-thick LiNbO3 or Li3PO4 interlayer was inserted between a H-diamond and a Li–Si–Zr–O (700 nm) Li+ solid electrolyte. We performed Hall measurements and pulse response measurements to investigate the EDL charging characteristics exhibited. The Hall measurements evidenced that all EDLTs exhibited EDL-induced hole density modulation, with a large EDL capacitance (CEDL) to 15 μF/cm2 in the Li + -deficient region (negative VG side). On the other hand, in the pulse response measurement, insertion of an LiNbO3 or Li3PO4 interlayer caused significant acceleration/deceleration of the switching response speed, ranging from τ = 61.4 ms to 229 μs? CEDL at the LiNbO3/H-diamond and Li3PO4/H-diamond interface, particularly on the Li+ rich side, was indicated as determining the switching response speed. The results indicate that the very thin EDL (i.e., 5 Å) can be formed at the solid/solid electrolyte interface, even when inorganic solid electrolytes are used instead of liquid electrolytes, and CEDL at the solid/solid electrolyte can be controlled by electrolyte compositions within a thickness of several Å from the interface.