Fig. 6: Electronic structure properties of MgO/MgF₂:Cr³⁺ obtained by first-principles calculations.

a Hall effect measurement comparing key electrical properties of MgF₂:0.005Cr³⁺ and MgO/MgF₂:0.005Cr³⁺, including the F-factor, carrier concentration, carrier mobility, and resistivity; b UPS spectra of MgF₂:0.005Cr³⁺ and MgO/MgF₂:0.005Cr³⁺, with the extracted IE and VBM indicated. The inset shows the actual UPS measurement setup. c Schematic illustration of the electronic band structure, highlighting the definitions and relative positions of the IE, work function (WF), and electron affinity (EA). d Front and side views of the charge density difference of MgO/MgF₂:Cr³⁺. The purple and yellow areas represent electron depletion and accumulation, respectively. e Energy band diagram of MgO/MgF₂:Cr³⁺. f Density of states distribution of MgO/MgF₂:Cr³⁺. g Comparison of the band gap of MgF₂:Cr³⁺ and MgO/MgF₂:Cr³⁺ as the strain increases from −5% to 5% along the y-axis. h Electron/hole mobility of MgF₂:Cr³⁺ and MgO/MgF₂:Cr³⁺. Source data are provided as a Source Data file.