СЕМИНАР: др Станко Недић

У среду, 18. септембра, у 13 часова у библиотеци „др Драган Поповић“, др Станко Недић ће одржати семинар

Zinc oxide nanowire field effect transistors for UV photodetector and
non-volatile memory applications


Transistor scaling is rapidly reaching its physical limitations and
alternative device designs at the nanoscale are required for the “after
Moore” regime. In particular, zinc oxide (ZnO) nanowires (NWs) are
considered as excellent candidates for future nanoscale building blocks
with applications ranging from optoelectronics to sensing.
As-synthesized ZnO NWs are intrinsically n-type doped due to the
presence of oxygen vacancies and/or zinc interstitials [1, 2]. ZnO NWs
were reproducibly synthesized by thermal chemical vapor deposition and
electrical characteristics of different ZnO NW field effect transistor
(FET) configurations were studied. Parylene C passivated devices
exhibited low power consumption and excellent field effect mobilities up
to ~189.2 cm^2/Vs. Time-resolved drain current response to periodic
ultraviolet illumination was evaluated for conventional and surface
passivated back-gate ZnO NW FETs. The effects of surface passivation,
gate voltage bias, temperature, and ambient pressure were examined with
regard to the photosensitivity, photoconductive gain and the
photocarrier relaxation dynamics of the ZnO NW FET based photodetectors.
Non-volatile memory functionality of ZnO NW FETs has been previously
demonstrated using ferroelectric nanoparticles [3] and mobile protons in
the gate dielectric layer [4]. High performance ferroelectric
non-volatile memory devices based on top-gate ZnO NW FETs were
fabricated on glass substrates by spin coating the ZnO NW channel with a
200 nm thick poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE))
film acting as a top-gate dielectric [5]. Electrical conductance
modulation and memory hysteresis are achieved by a gate electric field
induced reversible electrical polarization switching of the
ferroelectric thin film. Remarkably, the device exhibited a large memory
window of ~16.5 V, a high drain current on/off ratio of ~10^5, a gate
leakage current below ~300 pA, and excellent retention characteristics
for over 10^4 s.

[1] Chang, P.-C., and Lu, J. G., “ZnO nanowire field-effect
transistors”, IEEE Transaction on Electron Devices 55, pp. 2977-2987
[2] Goldberger, J., Sirbuly, D. J., Law, M., and Yang, P., “ZnO nanowire
transistors”, J. Phys. Chem. Lett. B 109, pp. 9-14 (2005).
[3] Sohn, J. I., Choi, S. S., Morris, S., Bendall, J. S., Coles, H. J.,
Hong, W.-K., Jo, G., Lee, T., and Welland, M. E., “Novel nonvolatile
memory with multibit storage based on a ZnO nanowire transistor”, Nano
Lett. 10, pp. 4316-4320 (2010).
[4] Yoon, J., Hong, W.-K., Jo, M., Jo, G., Choe, M., Park, W., Sohn, J.
I., Nedic, S., Hwang, H., Welland, M. E., and Lee, T., “Nonvolatile
memory functionality of ZnO nanowire transistors controlled by mobile
protons”, ACS Nano 5, pp. 558-564 (2011).
[5] Nedic, S., Chun, Y. T., Hong, W.-K., Chu, D., and Welland, M. E.,
“High performance non-volatile ferroelectric copolymer memory based on a
ZnO nanowire transistor fabricated on a transparent substrate”, Appl.
Phys. Lett. 104, 033101 (2014).