Electronic self-passivation of single vacancy in black phosphorus

Black phosphorus exhibits an electronic self-passivation phenomenon by re-arranging its vacancies. The charge mobility of the material may be improved by this.

Ultra-thin, high-speed and energy-efficient electronics and optoelectronics devices can be developed with 2D semiconductors with high carrier mobility. Many of the existing materials synthesis and device fabrication processes introduce surface defects, particularly vacancies with dangling bonds. The defects act as sinks for charge carriers and nonradiative recombination centers, limiting device performance. It's important to maintain their high- performance device characteristics by effective passivation of the surface vacancies. A type of high-mobility 2D material with many uses in optoelectronic and photovoltaic applications is called bpm. It displays unique defect passivation behaviors which are different from other 2D semiconductors made of two or more elements.

A research team led by Associate Professor Jiong LU from the Department of Chemistry, National University of Singapore used both scanning tunneling microscopy and non-contact atomic force microscopy techniques to show the local reconstruction and ionization of a single vacancy. This self-passivation mechanism can be triggered by mild thermal annealing or by STM tip manipulation and it relies on the formation of a special type of chemical bond at the defect site. The work is being done in collaboration with the research group from the Yale-NUS College and the Institute of Physics, Czech Academy of Sciences.

The research team evaluated the impact of the self-passivation effect on the carrier mobility performance by measuring a field-effect transistor made of BP. Before and after self-passivation at the site of the defect, they compared the local electronic structure and scattering behavior. The researchers observed an increase in hole mobility of up to 43% after the self-passivation mechanism is triggered. The quenching of its associated in-gap electronic states is likely to be the reason for this.

Chemical functionalization and surface coating have been used to passivate surface vacancies in 2D Semiconductors to remove the associated detrimental in-gap electronic states. Most passivation schemes improve the photoluminescence quantum yield without significant enhancement in charge transport properties. The electronic performance is degraded by altering the van der Waals structure.

Prof. Lu said that the new passivation scheme reported may be an ideal surface passivation strategy, which can only affect the defect states, without leaving a permanent crystal lattice change. Our work opens up a new route for electronic self-passivation of defects, which is crucial for the further improvement of carrier mobility.

More information: Hanyan Fang et al, Electronic Self-Passivation of Single Vacancy in Black Phosphorus via Ionization, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.128.176801 Journal information: Physical Review Letters Citation: Electronic self-passivation of single vacancy in black phosphorus (2022, May 25) retrieved 25 May 2022 from https://phys.org/news/2022-05-electronic-self-passivation-vacancy-black-phosphorus.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.