Professor Paine's research interests are in thin film characterization and processing with a focus on interfaces and interface stability in electronic thin film systems. The evolution of microstructure as a function of processing conditions is being studied in a wide range of materials synthesized by physical vapor deposition techniques. Key characterization techniques include x-ray diffraction, electron microscopy, semiconductor device measurements.

Amorphous metal oxides with the (n-1)d10ns0 (n≥4) electronic configuration are being used for the fabrication of thin film transistors (TFT's) with superior performance when compared to current amorphous Si-based devices. These new materials are optically transparent and have important application to organic light emitting-based displays which, as current-driven devices, require a higher on/off current ratio than field-driven LCD-based displays. Amorphous oxides such as ZnO-rich ZnO : In2O3 (a−ZIO, molar ratio of 2:1), ZnO : SnO2 (a-ZSO, molar ratios of 1:1 and 1:2) and In2O3 : Ga2O3 : ZnO ternary oxide (a-IGZO, In1.1:Ga1.1:Zn0.9) all have field effect mobilities of ~6–50 cm2 / V s which is very attractive relative to amorphous Si .
Amorphous In2O3-10wt%ZnO (a-IZO) is a particularly attractive candidate material due to its high electron mobility, room temperature processing, high surface planarity, and isotropic etch characteristics. We are investigating a-IZO channel / a-IZO metallization structured TFT's since, with IZO's carrier concentration tunable between ~ 1E15 / cm3 to ~ 5E20 / cm3, the same IZO target can be used to deposit both the semiconducting channel and source/drain metallization layers by simply adjusting the process oxygen during deposition. Also, compositionally homogeneous IZO/IZO channel metallization has favorable band alignment which may contribute to a low specific contact resistance. For TFT applications, amorphous IZO channel material must be deposited with low carrier density, high carrier mobility, and good ohmic source-drain channel contact must be achieved by finding source/drain metals with a minimum specific contact resistance to the IZO channel. One challenge that limits the implementation of a-IZO channel devices is the difficulty in achieving low enough carrier concentrations to limit enhancement mode TFT off-state current. One approach has been to utilize very thin channel layers, while another is to add Ga as a third cation species to IZO (IGZO) to suppress native defect-based carrier formation. The addition of cation species increases scattering and significantly decreases channel carrier mobility. On the other hand, the use of very thin (10 – 30 nm) IZO channel layers poses processing and device design challenges.

 

S. Lee, K. Park, and D. C. Paine, "Metallization Strategies for In2O3-based amorphous oxide semiconductor materials", J. Materials Research, in press (2012).

S. Lee, S. Park, and D.C. Paine, "A Study of the Specific Contact Resistance and Channel Resistivity of Amorphous IZO thin film transistors with IZO source-drain metallization", J. Appl. Phys. J. Appl. Phys. 109, 063702 (2011).

S. Lee and D. C. Paine, "On the effect of Ti on the stability of amorphous indium zinc oxide used in thin film transistor applications", Appl. Phys. Lett. 98(26), 262108 (2011).

D.C. Paine, B. Yaglioglu, Z. Beiley, and S. Lee, "Amorphous IZO-based transparent thin film transistors", Thin Solid Films, 516(17,) 5894-5898 (2008).

B. Yaglioglu, H. Y. Yeom, R. Beresford, and D. C. Paine, "High-mobility amorphous In2O3-10 wt %ZnO thin film transistors," Applied Physics Letters, 89, 062103(2006).

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Materials Research Society
Institute of Electrical and Electronics Engineers (IEEE)
The Minerals, Metals and Materials Society (TMS)

Prof Paine teaches courss in in the Division of Engineering in materials characterization (EN0240: Electron microscopy); in thermodynamics of phase equilibrium (EN0141 and EN0241); in electronic materials (EN0145); and occasionally teaches courses in crystallography, physical metallurgy, and introductory materials (EN0041).