Wang Li-Wen, Chu Sheng-Yuan
Department of Electrical Engineering, National Cheng Kung University, Tainan 700, Taiwan.
Materials (Basel). 2023 Sep 28;16(19):6463. doi: 10.3390/ma16196463.
This study presents gallium-doped zinc oxide (ZnO:Ga, GZO) thin films. GZO thin films with both high transparency and low sheet resistance were prepared by RF sputtering and then post-annealed under nitrogen and hydrogen forming gas. With post-annealing at 450 °C, the proposed films with a film thickness of 100 nm showed high transparency (94%), while the sheet resistance of the films was reduced to 29 Ω/square, which was comparable with the performances of commercial indium tin oxide (ITO) samples. Post-annealing under nitrogen and hydrogen forming gas enhanced the films' conductivity while altering the thin-film composition and crystallinity. Nitrogen gas played a role in improving the crystallinity while maintaining the oxygen vacancy of the proposed films, whereas hydrogen did not dope into the thin film, thus maintaining its transparency. Furthermore, hydrogen lowered the resistance of GZO thin films during the annealing process. Then, the detailed mechanisms were discussed. Hydrogen post-annealing helped in the removal of oxygen, therefore increasing the Ga content, which provided extra electrons to lower the resistivity of the films. After the preferable nitrogen/hydrogen forming gas treatment, our proposed films maintained high transparency and low sheet resistance, thus being highly useful for further opto-electronic applications.
本研究展示了镓掺杂氧化锌（ZnO:Ga，GZO）薄膜。通过射频溅射制备出具有高透明度和低方块电阻的GZO薄膜，然后在氮气和氢气混合形成气体的氛围下进行后退火处理。在450℃进行后退火处理时，所制备的厚度为100nm的薄膜显示出高透明度（94%），同时薄膜的方块电阻降低至29Ω/□，这与商业氧化铟锡（ITO）样品的性能相当。在氮气和氢气混合形成气体氛围下的后退火处理提高了薄膜的导电性，同时改变了薄膜的成分和结晶度。氮气在提高结晶度的同时保持了所制备薄膜的氧空位，而氢气并未掺入薄膜中，从而保持了其透明度。此外，氢气在退火过程中降低了GZO薄膜的电阻。随后，对详细机制进行了讨论。氢气后退火有助于去除氧，因此增加了Ga含量，这提供了额外的电子以降低薄膜的电阻率。经过优选的氮气/氢气混合形成气体处理后，我们所制备的薄膜保持了高透明度和低方块电阻，因此对于进一步的光电子应用非常有用。
