# Stability, efficiency, and mechanism of n-type doping by hydrogen adatoms in two-dimensional transition metal dichalcogenides

## TL;DR

This study uses first-principles calculations to demonstrate that hydrogen adatoms can effectively dope two-dimensional TMDCs by donating electrons without creating defect states, offering a promising method for electronic device development.

## Contribution

It reveals the stability, diffusion barriers, and doping mechanism of hydrogen adatoms in TMDCs, highlighting their potential for stable n-type doping in 2D semiconductors.

## Key findings

- Hydrogen atoms are most stable at interstitial sites on Mo/W planes.
- Hydrogen doping results in high electron donation efficiency, one electron per adatom.
- No defect states are introduced inside the band gap by hydrogen doping.

## Abstract

Mono- and few-layer transition-metal dichalcogenides (TMDCs) provide opportunities for ideal two-dimensional semiconductors for electronic and optoelectronic devices. For electronic devices on TMDCs, it is essential to incorporate n- and/or p-type dopants which are stable in positions after patterned doping. Here we investigate hydrogen doping for TMDC (MX2 with M = Mo, W and X = S, Se, Te) nanosheets by first-principles calculations to address diffusion and doping properties. We find that adsorbed hydrogen atoms in TMDCs are energetically most stable at the interstitial site right on the Mo or W plane and have substantial energy barriers against diffusion that increase in the order of sulfides, selenides, and tellurides. Located at the most stable interstitial site on the Mo or W plane, the hydrogen atoms produce electrons in the conduction bands in the extremely high rate of one electron per hydrogen atom, without any defect state inside the band gap remarkably. We analyze the chemical bonding character around the dopant and the mechanism for such high efficiency of electron doping. We also consider properties of hydrogen molecules and Te vacancies for comparison. Our work shows that hydrogen doping is the promising pathway to development of highly integrated electronic devices on TMDCs