# Theoretical Prediction of Stable Cluster-assembled CdSe Bilayer and its Functionalization with Co and Cr Adatoms

## TL;DR

This study theoretically predicts the stability, electronic properties, and functionalization effects of a CdSe bilayer assembled from clusters, revealing potential for magnetic and tunneling applications.

## Contribution

It introduces a novel stable bilayer structure of CdSe clusters and explores its magnetic and electronic modifications through transition metal functionalization.

## Key findings

- Bilayer remains stable at room temperature.
- Functionalization induces ferromagnetism and half-metallicity.
- Bilayer exhibits tunnel diode-like I-V characteristics.

## Abstract

In this article, we present our results on bilayers assembled upon strategic placement of Cd$_6$Se$_6$ clusters. These bilayers are studied for their stability and electronic structure with the help of density functional theory and are further analyzed using Bardeen, Tersoff and Hamann formalism for their tunneling properties. Our calculations show that the hexagonal arrangement of these clusters prevails as the most stable geometry showing all real phonon modes. First-principles molecular dynamics studies on this 2D structure show that it remains intact even at room temperature. This bilayer shows an indirect semiconducting band gap of 1.28~eV with the current-voltage (I-V) characteristics similar to a tunnel diode. Further, we functionalized this bilayer using transition metal atoms, Co and Cr. The aim was to seek whether the bilayer sustains magnetism and how the concentration affects its electronic and magnetic properties. Co functionalization brings ferromagnetic ordering in the bilayer which turns near half-metallic upon increasing the concentration. On the other hand, Cr functionalization shows a transition from antiferro- to ferromagnetic ordering upon increasing the concentration. The I-V characteristics of all these functionalized bilayers show negative differential conductance similar to a tunnel diode.