Charge transport, optical transparency, microstructure, and processing relationships in transparent conductive indium–zinc oxide films grown by low-pressure metal-organic chemical vapor deposition

Indium–zinc oxide films $({\mathrm{Zn}}_x{\mathrm{In}}_y{\mathrm{O}}_{\text{x+1.5y}}\mathrm{),}$ with $\text{x/y=0.08–12.0,}$ are grown by low-pressure metal-organic chemical vapor deposition using the volatile metal–organic precursors ${\mathrm{In(TMHD)}}_{\mathrm{3}}$ and ${\mathrm{Zn(TMHD)}}_{\mathrm{2}}$ $(\mathrm{TMHD}\text{=2,2,6,6}$ –tetramethyl–3,5–heptanedionato). Films are smooth (rms $\mathrm{roughness}\text{=40–50\hspace{0.17em}Å)}$ with complex microstructures which vary with composition. The highest conductivity is found at $\text{x/y=0.33,}$ with $\text{σ=1000\hspace{0.17em}}\mathrm{S/cm}$ (n-type; carrier ${\mathrm{density=3.7\times 10}}^{\mathrm{20}}{\mathrm{\hspace{0.17em}cm}}^{\mathrm{3}};$ ${\mathrm{mobility=18.6\hspace{0.17em}cm}}^{\mathrm{2}}\mathrm{/V\hspace{0.17em}s};$ $\text{dσ/dT<0).}$ The optical transmission window of such films is broader than Sn-doped ${\mathrm{In}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}},$ and the absolute transparency rivals or exceeds that of the most transparent conductive oxides. X-ray diffraction, high resolution transmission electron microscopy, microdiffraction, and high resolution energy dispersive X-ray analysis show that such films are composed of a layered ${\mathrm{Zn}}_k{\mathrm{In}}_{\mathrm{2}}{\mathrm{O}}_{\text{3+k}}$ phase precipitated in a cubic ${\mathrm{In}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}\mathrm{:Zn}$ matrix.