Figure 2.

Work function versus Fermi level position plots. Solid lines follow constant ionization potentials, dotted vertical lines mark the intrinsic bandgap, and symbol size corresponds to substrate temperature during deposition (smallest = room temperature, largest = $400{}^{\circ }$C ($500{}^{\circ }$C for (b)). (a) upper left graph RF magnetron sputtered SnO${}_2$ (triangles) and SnO${}_2$:Sb (diamonds) grown at $400{}^{\circ }$C, and sintered ceramic SnO${}_2$:Sb (squares); (b) lower left graph DC magnetron sputtered ZnO (triangles) and ZnO:Al (diamonds) thin films, and sintered ceramic ZnO:Al (bowtie); (c) upper right graph In${}_2$O${}_3$ reactively evaporated (open triangles), RF magnetron sputtered (closed triangles), sintered (filled squares), and air-annealed (crossed squares); (d) lower right ITO sintered ceramic samples (filled squares), air-annealed thin films (crossed squares), ozone-trated thin films (crossed circle), and RF magnetron sputtered 2% doped ITO (open triangles) and 10% doped ITO (filled triangles).