Tunable Electron Transport in Defect-Engineered PdSe$_\mathrm{2}$

TL;DR

This paper demonstrates how defect-engineering and chemical doping can tune electron and hole transport in PdSe$_2$, enabling control over its ambipolar behavior for potential high-performance transistor applications.

Contribution

It introduces a method to electrically and chemically tune charge carrier transport in PdSe$_2$ through defect-engineering and doping, supported by experimental and theoretical analysis.

Findings

Pristine PdSe$_2$ shows ambipolar behavior with slight electron dominance.

Chemical doping with HCl and EDTA effectively switches transport to p-type or n-type.

Low-temperature measurements reveal enhanced p-type behavior with higher ON/OFF ratio.

Abstract

Tuning the ambipolar behavior in charge carrier transport via defect-engineering is crucial for achieving high mobility transistors for nonlinear logic circuits. Here, we present the electric-field tunable electron and hole transport in a microchannel device consisting of highly air-stable van der Waals (vdW) noble metal dichalcogenide (NMDC), PdSe$_\mathrm{2}$, as an active layer. Pristine bulk PdSe$_\mathrm{2}$ constitutes Se surface vacancy defects created during the growth or exfoliation process and offers an ambipolar transfer characteristics with a slight electron dominance recorded in field-effect transistor (FET) characteristics showing an ON/OFF ratio < 10 and electron mobility ~ 21 cm$^2$/V.s. However, transfer characteristics of PdSe$_\mathrm{2}$ can be tuned to a hole-dominated transport while using hydrochloric acid (HCl) as a $p$-type dopant. On the other hand, the chelating agent EDTA, being a strong electron donor, enhances the electron-dominance in PdSe$_\mathrm{2}$ channel. In addition, $p$-type behavior with a 100 times higher ON/OFF ratio is obtained while cooling the sample down to 10 K. Low-temperature angle-resolved photoemission spectroscopy resembles the $p$-type band structure of PdSe$_\mathrm{2}$ single crystal. Also, first principle density functional theory calculations justify the tunability observed in PdSe$_\mathrm{2}$ as a result of defect-engineering. Such a defect-sensitive ambipolar vdW architecture may open up new possibilities towards future CMOS (Complementary Metal-Oxide-Semiconductor) device fabrications and high performance integrated circuits.