April 7 - 11, 2025
Seattle, Washington
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2025 MRS Spring Meeting & Exhibit
QT06.01.03

Growth and Characterization of Er Doped CaMoO4 Thin Films on Silicon for Quantum Applications

When and Where

Apr 8, 2025
2:30pm - 2:45pm
Summit, Level 4, Room 444

Presenter(s)

Co-Author(s)

Ignas Masiulionis1,2,Bonnie Lin3,Sungjoon Kim2,Gregory Grant1,2,Angel Yanguas-Gil2,Jeffrey Elam2,Jiefei Zhang2,James LeBeau3,David Awschalom1,2,Supratik Guha1,2

The University of Chicago1,Argonne National Laboratory2,Massachusetts Institute of Technology3

Abstract

Ignas Masiulionis1,2,Bonnie Lin3,Sungjoon Kim2,Gregory Grant1,2,Angel Yanguas-Gil2,Jeffrey Elam2,Jiefei Zhang2,James LeBeau3,David Awschalom1,2,Supratik Guha1,2

The University of Chicago1,Argonne National Laboratory2,Massachusetts Institute of Technology3
The Er3+ ion–embedded in a solid-state host dielectric is an excellent - candidate for qubits in quantum communication due to the well-shielded Er3+ 4f-4f telecom c-band transition. CaWO4 has emerged as an intriguing host material, demonstrating promising optical and spin properties in bulk samples [1,2]. In contrast, CaMoO4 is a compound similar to CaWO4 that has yet to be explored as a host for rare earth based quantum emitters. Both compounds have a tetragonal (scheelite) structure, with lattice parameters that exhibit low mismatch (~3.1%) with silicon (CaMoO4 : a = b = 0.521 nm, c = 1.14 nm; CaWO4 : a = b = 0.525 nm, c = 1.13 nm), presenting a unique opportunity for epitaxial growth on silicon and future on-chip integration.
Precise stoichiometric control is essential for high quality host materials for such applications. This control is best ensured via self-limiting growth methods rather than pre-calibrated control of the flux delivery, which can lack adequate precision. In this work, we present our results of obtaining stoichiometric growth of CaMoO4 on silicon substrates via self limiting methods, making the first step towards epitaxial growth of these complex oxides. We utilize Ca, MoO3, oxygen (atomic or molecular) for the growth of CaMoO4 using molecular beam deposition, followed by post-growth anneals in oxidizing environments. This allows efficient control of the two relevant reactions: Ca + MoO3 + ½O2 = CaMoO4; MoO3 = MoO2 + ½ O2 via control of the molecular fluxes and adjustment of the growth temperature to control the sticking coefficients of Ca and MoO3 . Structural characterization was carried out using X-ray diffraction to confirm the desired CaMoO4 phase. During growth, thin films were doped with Er (1 - 20 ppm range) and extensive optical characterization studies were carried out to study its 4f-4f emission. This includes energy level assignment, transient spectral hole burning (TSHB), and time-resolved photoluminescence. We observe TSHB linewidths as low as 30 MHz, inhomogeneous linewidths ~ 20 GHz, and T1 optical lifetimes up to 7 ms in the annealed films. These results merit further characterization of CaMoO4 thin films to explore its suitability for spin control.

[1] Marianne Le Dantec et al.,Twenty-three–millisecond electron spin coherence of erbium ions in a natural-abundance crystal. Sci. Adv. 7, eabj9786 (2021). DOI: 10.1126/sciadv.abj9786

[2] Mahmet T. Uysal et al., Spin-photon entanglement of a single Er3+ ion in the telecom band. arXiv:2406.06515v2

Keywords

molecular beam epitaxy (MBE) | oxide

Symposium Organizers

Jeffrey McCallum, University of Melbourne
Yuan Ping, University of Wisconsin-Madison
Kai-Mei Fu, University of Washington
Christopher Anderson, University of Illinois at Urbana-Champaign

Symposium Support

Platinum
Gordon and Betty Moore Foundation

Session Chairs

Benjamin Pingault
Yaser Silani

In this Session