A study on Ti-doped ZnO transparent conducting thin films fabricated by pulsed laser deposition

Effect of the Incorporation of Titanium on the Optical Properties of ZnO Thin Films: From Doping to Mixed Oxide Formation

“…These results indicate that the Ti atoms are incorporated as a dopant (electron donor) in the wurtzite structure, substituting the zinc atoms in the ZnO lattice and significantly improving the crystallinity of the doped ZnO sample. This interpretation is consistent with the smaller radius of Ti 4+ (0.068 nm) as compared to the Zn 2+ radius (0.074 nm) [7,16]. the position corresponding to the plane (002) of the ZnO but with much higher intensity than that obtained for the reference ZnO sample (note that the intensity of the spectrum is divided by a factor of 3).…”

“…These results indicate that the Ti atoms are incorporated as a dopant (electron donor) in the wurtzite structure, substituting the zinc atoms in the ZnO lattice and significantly improving the crystallinity of the doped ZnO sample. This interpretation is consistent with the smaller radius of Ti 4+ (0.068 nm) as compared to the Zn 2+ radius (0.074 nm) [7,16]. However, when the titanium concentration increases above 1.2 at.%, the intensity of the (002) peak decreases and widens, suggesting a progressive amorphization of the sample [16].…”

“…This is more apparent in the TZO samples with 4.1 at.% Ti, where the ZnO peaks suffer a shift towards lower diffraction angles. This fact has been explained by the compressive stress generated in the direction parallel to the surface, which induces an increase in the interplanar spacing, eventually leading to the peak displacement at lower angles, as detected in Figure 3 [16,17]. However, the presence of some zinc titanate crystallites cannot be discarded [18].…”

“…5.7 eV that can be attributed to Ti-O bonds [19]. However, when the titanium concentration increases above 1.2 at.%, the intensity of the (002) peak decreases and widens, suggesting a progressive amorphization of the sample [16]. This is more apparent in the TZO samples with 4.1 at.% Ti, where the ZnO peaks suffer a shift towards lower diffraction angles.…”

Structure, optical and electrical properties of Nb-doped ZnO transparent conductive thin films prepared by co-sputtering method

“…7,8 Doping Al, Ga, Sn, Ti, Nb and other elements in ZnO materials has become a hot research topic in the field of transparent conductive films. [9][10][11] Among these doping elements, Nb has great potential because the ionic radius of Nb 5þ is 0.64 Å, which is slightly smaller than the ionic radius of Zn 2þ (0.74 Å), 12 revealing theoretically there is a possibility of replacing Zn 2þ with Nb 5þ . In addition, the valence state difference between Nb 5þ and Zn 2þ is 3, which is quite attractive because one dopant atom can provide more electrons, indicating that NZO (Nb-doped ZnO) thin film has higher carrier concentration at the same doping concentration, 13 in other words, less amount of impurities to be incorporated in the NZO film at the same carrier concentration, so that defects in the film can be reduced, carrier mobility can be improved, and the resistivity of the film can be lowered.…”