Atomically Thin Metal–Dielectric Heterostructures by Atomic Layer Deposition

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 angstroms 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, we 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 interfaces of Ir/Al2O3 heterostructures was addressed, indicating an extension of the material portfolio available for novel optical functionalities.

Light-Field-Controlled PHz Currents in Metals

“…The relevant findings for this work are that the Ir percolates rather fast and forms homogeneous layers rather than nanoparticles. The presence of a Bragg peak in the X-ray reflectivity measurements evidenced the continuous metallic layers in the samples [22]. After the deposition of a pair of gold electrodes a µm-sized gap is formed.…”

“…In this work the number of cycles for the Al 2 O 3 is fixed to 35, while the number of cycles of Ir is # = {0, 8, 16, 32, 64}, which leads to f = {0 %, 11 %, 21 %, 34 %, 51 %} fractional content respectively. The detailed investigation of the sample properties was carried out elsewhere [22]. The relevant findings for this work are that the Ir percolates rather fast and forms homogeneous layers rather than nanoparticles.…”

“…We use the carrier-envelope phase (CEP) of a few-cycle laser pulse to drive currents within a volume enclosed by gold electrodes connected to an external circuit. Our samples comprise alternating layers of iridium (Ir) metal and Al 2 O 3 dielectric, fabricated using the atomic layer deposition technique [22]. This material exhibits a high third-order nonlinear susceptibility and we have previously demonstrated its applicability in a CEP-scanning device for characterizing few-cycle laser beams [23].…”

Carrier-envelope phase on-chip scanner and control of laser beams

“…We implemented tapered electrodes, see Fig. 1a, b , on a thin metal−dielectric heterostructure of Ir and Al 2 O 3 made by atomic-layer deposition (ALD) on a fused silica substrate 42 . The heterostructure has a nanolaminate structure and possesses a high χ (3) that enhances the magnitude of CEP-sensitive currents, as already indicated in refs.…”