| AVS 60th International Symposium and Exhibition | |
| Advanced Surface Engineering | Wednesday Sessions |
| Session SE+PS-WeA |
| Session: | Atmospheric Pressure Plasmas |
| Presenter: | J.Z. Chen, National Taiwan University, Taiwan, Republic of China |
| Authors: | S.T. Lien, National Taiwan University, Taiwan, Republic of China H.C. Li, National Taiwan University, Taiwan, Republic of China Y.J. Yang, National Taiwan University, Taiwan, Republic of China C.C. Hsu, National Taiwan University, Taiwan, Republic of China I.C. Cheng, National Taiwan University, Taiwan, Republic of China J.Z. Chen, National Taiwan University, Taiwan, Republic of China |
| Correspondent: | Click to Email |
MgZnO/ZnO heterostructures have shown great potential for optoelectronic device applications. The polarization field at MgZnO/ZnO heterojunction can induce charge accumulation at the interface to form two-dimensional electron gases (2DEGs). This has been observed in high quality materials grown by molecule beam epitaxy (MBE) or pulse laser deposition (PLD) as well as in defective MgZnO/ZnO heterostructure system deposited by rf-sputtering. Although high quality MgZnO/ZnO is desirable for its high electron mobility, the required deposition technique such as MBE or PLD is not suitable for the processing of large-area electronics. In regard to large-area deposition, rf-sputtering technique is the preferred process in spite of the more defective nature of the deposited materials. In our previous studies, we have demonstrated that the electron Hall mobility of ~40 cm2V-1s-1 and field-effect mobility of ~84 cm2V-1s-1 in the rf-sputtered Mg0.4Zn0.6O/ZnO heterostructure and the top-gated Mg0.2Zn0.8O/ZnO thin film transistor, respectively. The mobility exceeds the typical value (6 to 9 cm2V-1s-1) of a-InGaZnO TFT, which is the most promising technique for large-area oxide electronics nowadays.
One key step to obtain 2DEGs in the defective rf-sputtered MgZnO/ZnO heterostructures is the thermal annealing process on ZnO prior to the deposition of MgZnO material. This paper reports that atmospheric pressure plasma jet (APPJ) treatment can be used for the same purpose with a much shorter processing time. A thirty-second APPJ anneal on ZnO with a maximum temperature of 340 oC can replace a 30 min, 400 oC furnace-anneal to promote the formation of 2DEGs in the rf-sputtered MgZnO/ZnO heterostructure. The APPJ treatment also increases the crystallinity of ZnO films and releases the compressive residual stresses, verified by XRD and UV–Vis transmission measurements. The ultra-short processing time is attributed to the synergy of plasma reactivity and temperature of APPJ.