Temperature‐Dependent Zinc Oxide Cathodoluminescence: Toward Compact Wavelength‐Tunable Solid‐State Photoionization Sources

Abstract When exciting cathodoluminescence from a material using an electron beam, the light emission is due to electronic transitions within the material. The fundamental transition is related to the bandgap, while other emissions can be related to material defects and/or impurities. Since the bandgap of materials is temperature‐ and strain‐dependent, cathodoluminescence emission can, in principle, be dynamically tuned. Herein, a proof‐of‐concept of a thermally tunable cathodoluminescence light source is demonstrated using a triode electron gun and a wide‐bandgap z ‐cut ZnO crystal as anode. At room temperature (295 K), an ultraviolet (UV) emission peak corresponding to the ZnO bandgap is identified (398 nm), and a wide emission in the visible range (centered at ≈510 nm) is also detected (recombination of electron‐hole pairs in singly occupied oxygen vacancies). Additionally, the cathodoluminescence emission spectrum is measured as a function of the ZnO anode temperature (295–373 K), resulting in a shift of the UV emission peak from 398 to ≈409 nm (3.115–3.032 eV), which translates to a temperature dependency of −1.06 ± 0.06 meV K ⁻¹ . The results establish the feasibility of a compact, wavelength‐tunable cathodoluminescence‐based UV source, with future potential for integration into field‐deployable systems for gas sensing and lab‐on‐chip spectroscopy applications.