Speaker
Description
Aluminum and lithium codoped zinc oxide ZnO (ALZO) thin films for transparent conductive oxides were coated on the Al$_{2}$O$_{3}$ (0001) substrate by using the radio frequency magnetron sputtering deposition methods. We employed the target ceramics Zn$_{1-x-y}$Al$_{x}$Li$_{y}$O (ALZO, x = 0.05, y = 0 ~ 0.10) which were prepared by using the conventional solid state reaction methods. All ALZO thin films were post-annealed in an Ar gas atmosphere at temperature of 500 °C using the rapid thermal heating system and were characterized by using the X-ray diffraction (XRD), scanning probe microscopy (SPM) and the ultraviolet-visible (UV-Vis) transmittance. The electrical properties were characterized by using the four-point probing surface conductivity and the Hall effect measurement with van der Pauw contact method.
When ALZO (y = 0.0 ~ 0.03) targets ceramics were employed,the n-type conductivity is expected, and the ALZO thin films showed only (0002) XRD peak of the Wurtzite phase. When the ZnO:Al,Li (y = 0.04 ~ 0.10) target ceramics were employed, the intensity of the (0002) XRD peak were decreased to the similar intensity of (10-11) XRD peaks and the (200) peak of zinc-blende phase was observed. The low angle grazing incident XRD measurements showed that the ZnO:Al,Li grains became nano-sized and randomly oriented with Li content increasing (y > 0.05) in the ALZO thin films. By analyses of the UV-Vis transmittance spectra, the optical band gap energies (𝑬𝒈) were estimated to be in the range of 𝑬𝒈 = 3.39 eV ~ 3.44 eV.
As the Li content in the ALZO targets was increased from x = 0 to 0.03, the bulk resistivity of ALZO thin films was increased from 𝝆 = 0.027 Ω/cm to 32 Ω/cm. When y is close to 0.05, the Al and Li are expected to be compensated, however the bulk resistivity was decreased to 𝝆 = 0.14 Ω/cm, which means that Li is less incorporated into thin film. Here, the zinc-blende phase was mixed with theWurtzite phase of the ZnO:Al,Li thin films.
