Anatase TiO₂-based two-dimensional electron gases generated by low-energy argon-ion irradiation

Two-dimensional electron gas (2DEG) has abundant properties, which motivate not only fundamental physical interest but also concepts for device designing. While most of the reported 2DEGs are based on SrTiO₃, here we report on a systematic investigation on anatase TiO₂-based 2DEG generated by ion irradiation. By irradiating the surface layer of the anatase TiO₂ films with appropriate argon ion beams, we gained the 2DEGs with a thickness of 4 nm. Unique transport behaviours of a T^-1/3 or ln(1/T) sheet resistance dependence below 100 K are observed depending on irradiation time. Unusually large positive MR is observed for which the magnetic field causes a strong shrinkage of electron wave functions, and fairly large negative MR is detected in the 2DEG, arising from the depression of magnetic scattering.