| AVS 60th International Symposium and Exhibition | |
| Transparent Conductors and Printable Electronics Focus Topic | Wednesday Sessions |
| Session TC+EM+EN+TF-WeA |
| Session: | Transparent Conductors and Photovoltaics |
| Presenter: | H. Makino, Kochi University of Technology, Japan |
| Authors: | H. Makino, Kochi University of Technology, Japan H. Song, Kochi University of Technology, Japan T. Yamamoto, Kochi University of Technology, Japan |
| Correspondent: | Click to Email |
Ga-doped ZnO (GZO) is promising candidate for alternative to ITO as transparent electrodes. We have reported that thermal desorption of Zn from polycrystalline GZO films starts at a little low temperature of 150 oC, which is close to the deposition temperature [1]. The amount of desorbed Zn from GZO films showed strong correlation with carrier concentration [1]. The Zn desorption also appeared in epitaxially grown GZO films deposited on sapphire substrates. In this paper, we reports thermal desorption of Zn in comparison between GZO films and ZnO films deposited on glass substrates.
The 150 nm thick GZO and ZnO films were deposited on glass at a substrate temperature of 200 oC using ion plating with DC arc discharge. The oxygen gas was introduced to the deposition chamber during the deposition process. The oxygen gas flow rate (OFR) was varied between 5 sccm and 25 sccm. Thermal desorption spectroscopy (TDS) was employed to evaluate characteristics of Zn desorption.
The TDS of Zn for the ZnO film deposited at 10 sccm showed a dominant desorption peak at 450 oC and a shoulder peak at 500 oC. The intensities decreased with increasing the OFR, and the peak at 500 oC disappeared with increasing the OFR to 20 sccm. On the other hand, the TDS of Zn for the GZO films deposited at the OFR of 10 sccm showed two peaks at 300 and 400 oC. The intensity of peak at 300 oC decreased with increasing the OFR, and the peak at 400 oC shifted to high temperature with increasing the OFR. Then, the TDS result of GZO deposited at 25 sccm showed one peak at 450 oC, which is similar to the dominant peak observed in the undoped ZnO films. The lower temperature of TDS peak of Zn suggests existence of weakly bounded Zn atoms in the GZO films. The weakly bounded Zn atoms are obvious in the GZO films deposited at low OFR conditions. It is possible to say that the weakly bounded Zn atoms were caused by high density of Ga doping to ZnO.
[1] H. Makino, Y. Sato, N. Yamamoto, T. Yamamoto, Thin Solid Films 520, 1407 (2011).