Zinc oxide based composites and methods for their fabrication
View Patent ↗A transparent, electrically conductive composite includes a layer of molybdenum oxide or nickel oxide deposited on a layer of zinc oxide layer. The molybdenum component exists in a mixed valence state in the molybdenum oxide. The nickel component exists in a mixed valence state in the nickel oxide. The composite may be utilized in various electronic devices, including optoelectronic devices. In particular, the composite may be utilized as a transparent conductive electrode. As compared to conventional transparent conduct oxides such as indium tin oxide, the composite exhibits superior properties, including a higher work function.
1. A transparent, electrically conductive composite, comprising:
a first layer including ZnO; and
a second layer disposed on the first layer and including a component selected from the group consisting of MoO x where x ranges from 2.0 to 2.75 and NiO x where x ranges from 0.8 to 1.2.
2. The composite of claim 1 , wherein the ZnO is doped with a dopant selected from the group consisting of gallium, aluminum, and both gallium and aluminum.
3. The composite of claim 2 , wherein the dopant has a concentration ranging from 0.05 to 5 atomic %.
4. The composite of claim 1 , wherein the composite has a work function ranging from 4.4 to 5.3 eV.
5. The composite of claim 1 , wherein the composite has an optical transmittance ranging from 80% or greater.
6. The composite of claim 1 , wherein the second layer includes MoO x and has a thickness ranging from 0.5 to 10 nm.
7. The composite of claim 1 , wherein the second layer includes MoO x and the MoO x includes a combination of Mo 4+ , Mo 5+ and Mo 6+ species.
8. The composite of claim 7 , wherein the ratio of (Mo 4+ , Mo 5+ ) species to Mo 6+ species ranges from 2:1 to 4:1.
9. The composite of claim 1 , wherein the second layer includes MoO x and the MoO x is doped with an electron-donating species having a higher valence state than the Mo species of the MoO x .
10. The composite of claim 1 , wherein the second layer includes MoO x and the MoO x is doped with a dopant selected from the group consisting of manganese and rhenium.
11. The composite of claim 10 , wherein the dopant has a concentration ranging from 0.5 to 5.0 atomic %.
12. The composite of claim 1 , wherein the second layer includes NiO x and has a thickness ranging from 0.4 to 8 nm.
13. The composite of claim 1 , wherein the second layer includes NiO x and the NiO x includes a combination of Ni 2+ and Ni 3+ species.
14. The composite of claim 13 , wherein the ratio of Ni 3+ species to Ni 2+ species ranges from 2:1 to 4:1.
15. The composite of claim 1 , wherein the second layer includes NiO x and the NiO x is doped with a dopant that increases the conductivity of the NiO x .
16. The composite of claim 15 , wherein the second layer includes NiO x and the NiO x is doped with a dopant selected from the group consisting of lithium and sodium.
17. The composite of claim 16 , wherein the dopant has a concentration ranging from 0.5 to 8.0 atomic %.
18. A method for fabricating a transparent, electrically conductive composite, the method comprising:
depositing a first layer including ZnO on a substrate; and
depositing a second layer on the first layer, the second layer including a component selected from the group consisting of MoO x where x ranges from 2.0 to 2.75 and NiO x where x ranges from 0.8 to 1.2.
19. The method of claim 18 , further comprising tuning the work function of the composite by a step selected from the group consisting of controlling the thickness of the second layer, controlling the relative concentrations of Mo 4+ , Mo 5+ and Mo 6+ valence states or Ni 2+ and Ni 3+ valence states, controlling a plasma flume parameter, controlling a position of an outlet of an O 2 supply source relative to a laser plume, controlling deposition temperature, controlling laser energy, controlling O 2 partial pressure, annealing the composite, and combinations of two or more of the foregoing.
20. An electronic device, comprising:
a semiconductor-based structure including a semiconductor material; and
a transparent, electrically conductive composite disposed on the semiconductor-based structure and comprising a first layer including ZnO, and a second layer disposed on the first layer and including a component selected from the group consisting of MoO x where x ranges from 2.0 to 2.75 and NiO x where x ranges from 0.8 to 1.2, wherein the second layer contacts the semiconductor-based structure.