3.3.1 Band Structure
We measured the band structures of pure SrTiO3 as well as effect for Ag atom doping upon the electronic properties of SrTiO3. The band structure of both pure and doped SrTiO3 are shown in Fig 2 (a) & (b), respectively. We can see that maximum of valance band (VB) present at point R and the minima of conduction band (CB) present at point G, which confirms the indirect band gap of pure SrTiO3. Taking such two approximation points into consideration, the calculated bandgap of pure SrTiO3 is 1.91eV and Ag-doped SrTiO3 is 2.18 eV. This indirect band gap findings are nearly matched with previous study. As we can see that in the case of pure SrTiO3, the value of direct band gap is lesser than the value which is obtained by experiment which is 3.2 eV [22]. From Fig 2(b), both minima of conduction band and the maxima of the valence band present at same point ā€œGā€ throughout the observed results of Ag-doped SrTiO3 and after doping the indirect band gap was converted to direct band gap. The graph reveals that the VB of Ag-SrTiO3, especially at point G, is transferred up than that of pure SrTiO3 [15,16].