Room temperature photoluminescence in plasma treated rutile TiO₂ (110) single crystals

Defects play a key role in tailoring the functional properties of metal oxides for next generation technologies. A comprehensive understanding and control of defects is therefore of vital importance in order to determine defect engineering strategies in materials and to allow for their technological realization. In this article, we report room temperature photoluminescence from plasma treated rutile TiO2 (110) single crystals. The effect of capacitively coupled radio frequency plasma etching on the luminescence properties of TiO2 (110) single crystals is discussed in detail. The plasma treatment modifies the surface of TiO2 (110) single crystals and introduces oxygen vacancies in the near surface region. The discharge parameters such as treatment time and pressure are correlated with the luminescence properties of treated TiO2 (110) single crystals. The Langmuir probe method is employed to determine the plasma electron density ion density 'ni', electron temperature 'L' and electron energy probability function (EEPF) of the plasma used to etch the TiO2 single crystals. Photoluminescence (PL) spectra reveal blue and green-light emission with an intensity dependent on the plasma treatment process. We hope that inducing defects through plasma treatment will be extended to other metal oxides surfaces, which may find utility in various applications.