Atomically Thin Metal-Dielectric Heterostructures by Atomic Layer Deposition

TL;DR

This study reports the fabrication and characterization of atomically thin Ir/Al2O3 heterostructures with tunable optical properties, revealing layer-by-layer growth and interface bonding, advancing materials for optoelectronic applications.

Contribution

It introduces a method to create atomically thin Ir/Al2O3 heterostructures with controlled composition and demonstrates their tunable dielectric and metallic properties for optoelectronic use.

Findings

Layer-by-layer growth of Ir confirmed by XRR and HRTEM.

Formation of Ir-O-Al bonds at interfaces at lower Ir concentrations.

Transition from dielectric to metallic behavior at 2-4 nm Ir thickness.

Abstract

Heterostructures increasingly attracted attention over the past several years to enable various optoelectronic and photonic applications. In this work, atomically thin interfaces of Ir/Al2O3 heterostructures compatible with micro-optoelectronic technologies are reported. Their structural and optical properties were determined by spectroscopic and microscopic techniques (XRR, XPS, HRTEM, spectroscopic ellipsometry, and UV/VIS/NIR spectrophotometry). The XRR and HRTEM analyses reveal a layer-by-layer growth mechanism of Ir in atomic scale heterostructures, which is different from the typical island-type growth of metals on dielectrics. Alongside, XPS investigations imply the formation of Ir-O-Al bonding at the interfaces for lower Ir concentrations, in contrast to the nanoparticle core-shell structure formation. Precisely tuning the ratio of the constituents ensures the control of the dispersion profile along with a transition from effective dielectric to metallic heterostructures. The Ir coating thickness was varied ranging from a few {\AA} to films of about 7 nm in the heterostructures. The transition has been observed in the structures containing individual Ir coating thicknesses of about 2-4 nm. Following this, show epsilon-near-zero metamaterials with tunable dielectric constants by precisely varying the composition of such heterostructures. Overall, a comprehensive study on structural and optical properties of the metal-dielectric interface of Ir/Al2O3 heterostructures was addressed indicating an extension of the material portfolio available for optical system design.