| AVS 59th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM+SS+AS+NS-ThM |
| Session: | Nanoelectronic Interfaces, Materials, and Devices |
| Presenter: | E.X. Zhang, Vanderbilt University |
| Authors: | C.X. Zhang, Vanderbilt University D.M. Fleetwood, Vanderbilt University M.L. Alles, Vanderbilt University R.D. Schrimpf, Vanderbilt University E.B. Song, University of California at Los Angeles S. Kim, University of California at Los Angeles K. Galatsis, University of California at Los Angeles K.L. Wang, University of California at Los Angeles E.X. Zhang, Vanderbilt University |
| Correspondent: | Click to Email |
Graphene based materials are promising candidates for integration into future integrated circuit technologies. Initial studies of the effects of electron-beam and proton irradiation have been performed on graphene materials, but there remain significant questions about the nature of the conductivity and the defects that influence its material and electronic properties. We have found that low-energy x-ray irradiation can lead to significant shifts in the charge neutral point and increases in resistance of suspended graphene layers and graphene layers on SiO2. For graphene-on-SiO2 structures, the reaction oxygen atoms may be supplied either by ozone in the ambient air, or by the adjacent SiO2 substrate. Similar reactions may be observed for hydrogen, for devices exposed to x-ray and/or UV ozone (UVO) irradiation. Moreover, we also have found that graphene/PZT ferroelectric field-effect transistors (FFETs) are sensitive to UVO irradiation. The conducting channel in these devices is a single graphene layer. The device functions as a nonvolatile memory with reverse hysteresis, where charge trapping and detrapping in the PZT layer leads to a large memory window that is robust to x-ray irradiation and/or memory state cycling. When these devices are exposed to UVO irradiation, the memory window of the device decreases slightly with exposure time. In addition, an increase is observed in the slope of the I-V curves, along with a small positive shift in current-voltage characteristics. These results are consistent with the formation of negatively charged surface states on the graphene layer during the UVO exposure, which are most likely associated with adsorbed oxygen. The degradation in the I-V characteristics recovers somewhat with room temperature annealing. At the AVS meeting, the detailed electrical response will be described, and a physical model will be presented for the UVO degradation and recovery mechanisms.