Thin-film transistors (TFTs) are primarily used as a switching element in liquid crystal
displays. Currently, amorphous silicon is the dominant TFT technology for displays, but
higher performance TFTs will become necessary to enable ultra-definition resolution
high-frequency large-area displays. Amorphous zinc tin oxide (ZTO) TFTs were
fabricated by RF magnetron sputter deposition. In this study, the effect of both deposition
and post annealing conditions have been evaluated in regards to film structure,
composition, surface contamination, and device performance. Both the variation of
oxygen partial pressure during deposition and the temperature of the post-deposition
annealing were found to have a significant impact on TFT properties. X-ray diffraction
data indicated that the ZTO films remain amorphous even after annealing to 600° C.
Rutherford backscattering spectrometry indicated that the Zn:Sn ratio of the films was
~1.7:1 which is slightly tin rich compared to the sputter target composition. X-ray
photoelectron spectroscopy data indicated that the films had significant surface
contamination and that the Zn:Sn ratios changed depending on sample annealing
conditions. Electrical characterization of ZTO films using TFT test structures indicated
that mobilities as high as 17 cm² V⁻¹ s⁻¹ could be obtained for depletion mode devices. It
was determined that the electrical properties of ZTO films can be precisely controlled by
varying the deposition conditions and annealing temperature. It was found that the ZTO
electrical properties could be controlled where insulating, semiconducting and conducting
films could be prepared. This precise control of electrical properties allowed us to
incorporate sputter deposited ZTO films into resistive random access memory (RRAM)
devices. RRAM are two terminal nonvolatile data memory devices that are very
promising for the replacement of silicon-based Flash. These devices exhibited resistive
switching between high-resistance states to low-resistance states and low-resistance states
to high-resistance states depending on polarity of applied voltages and current
compliance settings. The device switching was fundamentally related to the defect states
and material properties of metal and insulator layers, and their interfaces in the metalinsulator-metal (MIM) structure. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Jan. 6, 2012 - Jan. 6, 2013
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26517 |
| Date | 06 January 2013 |
| Creators | Rajachidambaram, Jaana Saranya |
| Contributors | Herman, Gregory S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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