Fabrication and Light‐Emission Study of Ti‐δ‐Doped Quasi‐2D γ‐Alumina by Graphene‐Assisted Atomic Layer Deposition

Crystalline quasi‐2D Ti‐δ‐doped γ‐alumina (2D‐Ti:γ‐alumina) is synthesized by a facile, precursor‐alternating atomic‐layer‐deposition technique followed by a post‐growth air‐anneal at ≈800 °C. According to energy‐dispersive X‐ray spectroscopy maps, Ti atomic concentration remains uniform and approaches ≈1.5%. Subject to several UV‐light exposures, the samples are found to develop a full strength, stable emission in the ultrawide spectral range of ≈350–850 nm. The near‐infrared (NIR) emission band centered at ≈760 nm is assigned to Ti deep defect states introduced in the alumina host. According to photoluminescence excitation–emission studies, aggregate oxygen vacancies remain a primary excitation source of the NIR emission. In addition, a broad visible‐range emission band at ≈525 nm is registered in the temperature range of ≈108–348 K, but unlike the NIR band, its temperature dependence remains Arrhenius with the non‐radiative recombination activation energy of ≈73 ± 9 meV. The resultant 2D‐Ti:γ‐alumina holds promise for applications in low‐cost alumina‐based optoelectronics, photocatalytic remediation, and spectrally wide light sources.