Optical and microstructural studies of erbium-doped TiO2 thin films on silicon, SrTiO3, and sapphire

• DOI: 10.1063/5.0224010
• Publication Date: 2024-09-26T11:24:33Z
• Authors: Manish K. Singh; Gregory D. Grant; Gary Wolfowicz; Jianguo Wen; Sean E. Sullivan; Abhinav Prakash; Alan M. Dibos; F. Joseph Heremans; David D. Awschalom; Supratik Guha
• Keywords: Erbium; Silicon on sapphire

Rare-earth ion doped oxide thin films integrated on silicon substrates provide a route toward scalable, chip-scale platforms for quantum coherent devices. Erbium-doped TiO2 is an attractive candidate: the Er3+ optical transition compatible with C-band fiber communications, while insulating dielectric process technology. Through structural and studies of Er-doped grown via molecular beam deposition silicon, SrTiO3, sapphire substrates, we have explored impact polycrystallinity microstructure properties Er emission. Comparing polycrystalline TiO2(rutile)/Si single-crystalline TiO2(rutile)/r-sapphire TiO2(anatase)/Si TiO2(anatase)/SrTiO3, observe that inhomogeneous linewidth (Γinh) most prominent peak in spectrum (the Y1–Z1 transition, 1520 1533 nm rutile anatase TiO2) significantly narrower case. This implies relative insensitivity to extended defects grain boundaries such (as opposed to, e.g., point defects). We show growth undoped, underlying buffer Si can reduce Γinh by factor 4–5. Expectedly, also reduces decreasing concentrations: ∼2 order magnitude reduction from ∼1000 ppm ∼10 Er. then gets limited residual value ∼5 GHz insensitive further concentration. Based upon above results, argue these are presence high “grown-in” defect concentrations.