Curran Kalha

University College London

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Anna Regoutz

University College London

P. Thakur

Diamond Light Source

Nathalie Fernando

University College London

Tien‐Lin Lee

Diamond Light Source

Aysha A. Riaz

University College London

Christoph Schlueter

Deutsches Elektronen-Synchrotron DESY

Laura E. Ratcliff

Argonne National Laboratory

María Ibáñez

Institute of Science and Technology Austria

Mahsa Parvizian

University of Basel

Jonathan De Roo

University of Basel

Cooperative Institutions

University College London

Diamond Light Source

Imperial College London

University of Oxford

Universitat Politècnica de Catalunya

Barcelona Supercomputing Center

Technical University of Darmstadt

Research Complex at Harwell

Transnational Press London

Lawrence Berkeley National Laboratory

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Digitisation of Trzhaskovskaya Dirac-Fock Photoionisation Parameters for HAXPES Applications

Figshare (2020)

Joe Willis Curran Kalha M. B. Trzhaskovskaya V. G. Yarzhemsky David O. Scanlon

This document provides a digitised version of the tabulated Dirac-Fock photoionisation parameters for HAXPES applications (2018), calculated by M.B. Trzhaskovskaya and V.G. Yarzhemsky. The data from the original paper was mined, checked and deposited into a Microsoft Excel spreadsheet for easy access.

10.6084/m9.figshare.13292144

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Capturing the Dynamics of Ti Diffusion Across Ti_xW_1−x/Cu Heterostructures using X‐Ray Photoelectron Spectroscopy

Advanced Physics Research (2023)

Curran Kalha P. Thakur Tien‐Lin Lee Michael Reisinger Johannes Zechner

Abstract Interdiffusion phenomena between adjacent materials are highly prevalent in semiconductor device architectures and can present a major reliability challenge for the industry. To fully capture these phenomena, experimental approaches must go beyond static and post‐mortem studies to include in situ and in‐operando setups. Here, soft and hard X‐ray photoelectron spectroscopy (SXPS and HAXPES) is used to monitor diffusion in real‐time across a proxy device. The device consists of a Si/SiO 2 /Ti x W 1−x (300 nm)/Cu(25 nm) thin film material stack, with the Ti x W 1−x film ( x = 0.054, 0.115, 0.148) acting as a diffusion barrier between Si and Cu. The interdiffusion is monitored through the continuous collection of spectra whilst in situ annealing to 673 K. Ti within the TiW is found to be highly mobile during annealing, diffusing out of the barrier and accumulating at the Cu surface. Increasing the Ti concentration within the Ti x W 1−x film increases the quantity of accumulated Ti, and Ti is first detected at the Cu surface at temperatures as low as 550 K. Surprisingly, at low Ti concentrations (x = 0.054), W is also mobile and diffuses alongside Ti. By monitoring the Ti 1 s core level with HAXPES, the surface‐accumulated Ti was observed to undergo oxidation even under ultra‐high vacuum conditions, highlighting the reactivity of Ti in this system. These results provide crucial evidence for the importance of diffusion barrier composition on their efficacy during device application, delivering insights into the mechanisms underlying their effectiveness and limitations.

Diffusion barrier

10.1002/apxr.202300008

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Revealing the Bonding Nature and Electronic Structure of Early-Transition-Metal Dihydrides

PRX Energy (2024)

Curran Kalha Laura E. Ratcliff Giorgio Colombi Christoph Schlueter B. Dam

By combining experiment and theory, this study unveils a direct link between the electronic states in metal hydrides and their enthalpy of formation, advancing our understanding and potential applications in energy materials, catalysis, and gas storage.

10.1103/prxenergy.3.013003

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The influence of stabiliser concentration on the formation of In₂O₃ thin films

Journal of Materials Chemistry C (2024)

Aysha A. Riaz Curran Kalha Maria Basso Máté Füredi Anna Regoutz

In 2 O 3 is the parent oxide semiconductor for many transparent conducting oxides owing to its comparatively wide band gap and reasonable conductivity. The ability to fabricate thin films of In 2 O 3 utilising...

Stabiliser

10.1039/d4tc03116d

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Digitisation of Trzhaskovskaya Dirac-Fock Photoionisation Parameters for HAXPES Applications, Part II

Figshare (2020)

Joe Willis Curran Kalha M. B. Trzhaskovskaya V. G. Yarzhemsky David O. Scanlon

This document provides a digitised version of the tabulated Dirac-Fock photoionisation parameters for HAXPES applications, Part II: Inner atomic shells (2019), calculated by M.B. Trzhaskovskaya and V.G. Yarzhemsky. The data from the original paper was mined, checked and deposited into a Microsoft Excel spreadsheet for easy access.

10.6084/m9.figshare.13292174.v1

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Revealing the bonding nature and electronic structure of early transition metal dihydrides

arXiv (Cornell University) (2023)

Curran Kalha Laura E. Ratcliff Giorgio Colombi Christoph Schlueter B. Dam

Hydrogen as a fuel plays a crucial role in driving the transition to net zero greenhouse gas emissions. To realise its potential, obtaining a means of efficient storage is paramount. One solution is using metal hydrides, owing to their good thermodynamical absorption properties and effective hydrogen storage. Although metal hydrides appear simple compared to many other energy materials, understanding the electronic structure and chemical environment of hydrogen within them remains a key challenge. This work presents a new analytical pathway to explore these aspects in technologically relevant systems using Hard X-ray Photoelectron Spectroscopy (HAXPES) on thin films of two prototypical metal dihydrides: YH$_{2-\delta}$ and TiH$_{2-\delta}$. By taking advantage of the tunability of synchrotron radiation, a non-destructive depth profile of the chemical states is obtained using core level spectra. Combining experimental valence band spectra collected at varying photon energies with theoretical insights from density functional theory (DFT) calculations, a description of the bonding nature and the role of d versus sp contributions to states near the Fermi energy are provided. Moreover, a reliable determination of the enthalpy of formation is proposed by using experimental values of the energy position of metal s band features close to the Fermi energy in the HAXPES valence band spectra.

Density of states

Fermi energy

10.48550/arxiv.2305.16053

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Digitisation of Scofield Hartree-Fock Normalizations and Binding Energies Tabulated Data

Figshare (2020)

Curran Kalha Nathalie Fernando Anna Regoutz

This document provides a digitised version of the tabulated Hartree-Fock normalizations and binding energies (Table A1) calculated by J. H. Scofield (1973) from Lawrence Livermore National Laboratory (LLNL). The data from the original paper was mined, checked and deposited into a Microsoft Excel spreadsheet for easy access.

10.6084/m9.figshare.13057904

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Data for "The chemistry of Cu3N and Cu3PdN nanocrystals"

Zenodo (CERN European Organization for Nuclear Research) (2022)

Mahsa Parvizian Alejandra Durán Balsa Rohan Pokratath Curran Kalha Seungho Lee

Data underlying the figures in the publication "The chemistry of Cu₃N and Cu₃PdN nanocrystals" Table of contents: The .pxp documents contain the experimental data of the figures in the manuscript and they can be opened/edited with the software IGOR Pro 8.0 or higher. Figure 2.pxp. TEM images of (A) Cu₃N and (B) Cu₃PdN. The histograms are shown as an inset. The cube edge length is used as a measure for size. (C) DLS and (D) powder XRD measurements. Figure 3.pxp. ¹H NMR spectra of aliquots after degassing, at 190°C after the color change, 220°C, 240°C, 260°C and at the end of the reaction. Aldimine formation is observed starting from the color change. The aldimine reference is shown for comparison. Figure 4.pxp. XRD spectra of the syntheses with different amines. The reference of bulk Cu₃N (blue) and bulk Cu₂O (green) are shown. Figure 5.pxp. XPS core level spectra of Cu₃N and Cu₃PdN, including (A) Cu 2p_3/2, (B) Pd 3d, (C) N 1s, and (D) O 1s Figure 6.pxp. Nuclear magnetic resonance spectroscopy of the purified Cu₃N and Cu₃PdN NCs. (A) ¹H-NMR of the NCs indicating the presence of oleyl chain. (B) Diffusion ordered NMR spectroscopy of the Cu₃PdN NCs showing a slow and a fast diffusing species. Figure 7.pxp. (A) Valence region of Cu₃N and Cu₃PdN, including XPS valence spectra and the broadened and cross section weighted sum of the projected density of states (PDOS) from density functional theory (DFT). The position of the valence band maximum (VBM) of Cu₃N and the position of the Fermi energy (E_F) are also shown. (B)-(C) UV-Vis absorption spectra of Cu₃N in cyclohexane and Cu₃PdN in tetrachloroethylene with their corresponding Tauc plots as an inset, respectively. Indirect bandgaps were determined from linear fitting to the low energy region of the Tauc plots (shown in dotted green line).

10.5281/zenodo.6542907

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Rapid laser-induced low temperature crystallization of thermochromic VO2 sol-gel thin films

Applied Surface Science (2023)

Maria Basso Elena Colusso Chiara Carraro Curran Kalha Aysha A. Riaz

The thermochromic properties of vanadium dioxide (VO2) offer great advantages for energy-saving smart windows, memory devices, and transistors. However, the crystallization of solution-based thin films at temperatures lower than 400°C remains a challenge. Photonic annealing has recently been exploited to crystallize metal oxides, with minimal thermal damage to the substrate and reduced manufacturing time. Here, VO2 thin films, obtained via a green sol-gel process, were crystallized by pulsed excimer laser annealing. The influence of increasing laser fluence and pulse number on the film properties was systematically studied through optical, structural, morphological, and chemical characterizations. From temperature profile simulations, the temperature rise was confirmed to be confined within the film during the laser pulses, with negligible substrate heating. Threshold laser parameters to induce VO2 crystallization without surface melting were found. With respect to furnace annealing, both the crystallization temperature and the annealing time were substantially reduced, with VO2 crystallization being achieved within only 60 s of laser exposure. The laser processing was performed at room temperature in air, without the need of a controlled atmosphere. The thermochromic properties of the lasered thin films were comparable with the reference furnace-treated samples.

Thermochromism

Pulsed Laser Deposition

10.1016/j.apsusc.2023.157507

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The Chemistry of Cu₃N and Cu₃PdN Nanocrystals**

Angewandte Chemie International Edition (2022)

Mahsa Parvizian Alejandra Durán Balsa Rohan Pokratath Curran Kalha Seungho Lee

The precursor conversion chemistry and surface chemistry of Cu3 N and Cu3 PdN nanocrystals are unknown or contested. Here, we first obtain phase-pure, colloidally stable nanocubes. Second, we elucidate the pathway by which copper(II) nitrate and oleylamine form Cu3 N. We find that oleylamine is both a reductant and a nitrogen source. Oleylamine is oxidized by nitrate to a primary aldimine, which reacts further with excess oleylamine to a secondary aldimine, eliminating ammonia. Ammonia reacts with CuI to form Cu3 N. Third, we investigated the surface chemistry and find a mixed ligand shell of aliphatic amines and carboxylates (formed in situ). While the carboxylates appear tightly bound, the amines are easily desorbed from the surface. Finally, we show that doping with palladium decreases the band gap and the material becomes semi-metallic. These results bring insight into the chemistry of metal nitrides and might help the development of other metal nitride nanocrystals.

Oleylamine

10.1002/anie.202207013

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Citations (24)