Abstract
Layered metal phosphochalcogenides of molecular formula, MPX3 (M = Mn, Fe, Co, Ni, etc and X = S, Se) have been emerging as new class of semiconductors towards various catalytic and optoelectronic applications. The low cleavage energy associated with these layered chalcogenides may lead to devices with very thin semiconductor channels. Herein, we report the first successful fabrication of field effect transistor (FET) using layered NiPS3 that reveals n-type semiconducting behavior. Devices using bulk and few-layer NiPS3 with gold contacts show on/off ratios of ~103–105 at 25 °C. The device characteristics reveal an increase in on-state current with decrease in threshold voltage and the Schottky barrier height is extracted to be 112 meV. Density functional theory calculations reveal various parameters that affect electron/hole doping in the layered phosphochalcogenide material.
Highlights
Calculations have been performed for neutral NiPS3 and electron/hole doping separately, and the values are tabulated in Table S1 (Supporting Information)
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Summary
Oriented crystals of NiPS3 obtained in the present study are shiny black in colour with high crystallinity and the X-ray diffraction pattern shows very high orientation in the (00 l) direction. The FET characteristics of transistors and the type of conduction (p- or n-type) will depend on the relative position of the frontier region with respect to the metal contacts To understand this aspect, the structural modulation of NiPS3 by electron/hole doping has been studied. It is seen that the addition of electron decreases the bond angle distortion in the NiS6 octahedra quite considerably to nearly zero (1.5°) while the hole doping increases the distortion angle by 12° from the neutral value of 26.02° This suggests that electron doping leads to stable octahedral geometry around Ni. The changes observed in NiS6 units confirm the earlier prediction based on DOS calculations that the doping affects the environment around Ni and S. Calculations have been performed for neutral NiPS3 and electron/hole doping separately, and the values are tabulated in Table S1 (Supporting Information)
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