Calculated total electronic densities of states for the considered In-Sn-Zn-O samples (a) in a wide range of the energy level and (b) near the valence and conduction band edges. With decreasing the sum of the In and Sn ratios from the ISZO#1, the density of states is shifted by +0.02 eV−1Å−3.
(a) Calculated top-most VBT levels (filled circles), CBM levels (filled rectangles), and energy gaps (solid line) in LDA+U are plotted as a function of the sum of the In and Sn ratios ( ). (b) Calculated electron effective masses (filled triangles) are plotted as a function of the .
Calculated (a) atomic-orbital portions (s-orbital projected DOS) of the CBM state and (b) average inter-atomic distances between the In and Sn atoms, as a function of the ratio in amorphous In-Sn-Zn-O.
Schematic diagram showing the In and Sn 5s orbital overlaps and the conduction band dispersions, when (a) the cations are isolated, (b) the inter-distances between the In and Sn atoms are closer, and (c) the inter-distances are furthermore closer.
Schematic diagram of the valence O-2p bands in (a) crystalline and (b) amorphous oxides. The lower part of the bands is and bonding states, while the upper part is and anti-bonding. In amorphous oxides, the highest level is the anti-bonding state resulting from the high energy p orbitals in the disordered structure.
Calculated charge densities of (a) the top-most valence state of the crystalline InGaZnO4, [(b)-(i)] the top-most VBT state of the amorphous In-Sn-Zn-O [(b)–(h)], and amorphous InGaZnO4 (i). The dashed lines connect two O atoms that have the orbital in the VBT state. The solid line in (a) indicates the orbital ordering.
Calculated rPDF between O atoms for amorphous In-Sn-Zn-O and InGaZnO4. In the parenthesis, the ratios are indicated. With decreasing the ratio from the ISZO#1 (67%), the rPDF is shifted by +1 ea.
Schematic diagrams showing the inter-site coupling between two high-energy (off-bond) O-2p orbitals, which depends on the O-M-O angles: (a) 180°, (b) ∼120°, and (c) 90°.
Local atomic configurations near a (a) Zn, (b) Ga, (c) Sn, and (d) In in amorphous ISZO#1 and amorphous InGaZnO4.
(a)–(h) O-M-O bond angle distributions for the amorphous In-Sn-Zn-O and amorphous InGaZnO4. The M is for In (circle), Sn (square), Zn (triangle), and Ga (diamond). (i) Volumetric densities of the acute O-M-O bond angles ( 90°) in the amorphous oxides, as a function of the ratio.
Seven considered amorphous In-Sn-Zn-O semiconductors in this work are listed. , , , and are the numbers of In, Sn, Zn, and O atoms, respectively, in the supercell. Nt is the total number of atoms in the supercell, and Vt is the total supercell volume. is the sum of the In and Sn composition ratios.
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