Chuan Yu Han

High-Performance Pentacene Thin-Film Transistor With High-

Pentacene organic thin-film transistor (OTFT) using high- k HfLaON gate dielectric is proposed, and the effects of varying its nitrogen content are studied. The HfLaON film is deposited using reactive sputtering of Hf-La target in Ar/O₂/N₂ ambience with different N₂ flow rates and then annealed in N₂. All the OTFTs can operate at low voltage with a threshold voltage as low as -0.53 V. The OTFT with an optimal nitrogen content can achieve a carrier mobility of 0.71 cm²/V·s, which is about twice that of its counterpart with HfLaO gate dielectric.

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Pentacene organic thin-film transistors (OTFTs) using LaxNb(1−x)Oy as gate dielectric with different La contents (x = 0.347, 0.648) have been fabricated and compared with those using Nb oxide or La oxide. The OTFT with La0.648Nb0.352Oy as gate dielectric can achieve a high carrier mobility of 1.14 cm2V−1s−1 (about 1000 times and 2 times those of the devices using Nb oxide and La oxide, respectively), and has negligible hysteresis of −0.130 V, small sub-threshold swing of 0.280 V/dec, and low threshold voltage of −1.35 V. AFM and XPS reveal that La can suppress the formation of oxygen vacancies in Nb oxide while Nb can alleviate the hygroscopicity of La oxide, which results in a more passivated and smoother dielectric surface, leading to larger pentacene grains grown and thus higher carrier mobility. The OTFT with Nb oxide has an anticlockwise hysteresis but the device with La oxide shows an opposite direction. This can be explained in terms of donor-like traps due to oxygen vacancies and acceptor-like tra...

HfLaON as Gate Dielectric

The effects of La incorporation in three transition-metal (TM = Y, Zr, and Nb) oxides as gate dielectric of pentacene organic thin-film transistor (OTFT) have been investigated. La incorporated in Zr oxide and Nb oxide greatly decreases their trap density (as confirmed by low-frequency noise measurement) by passivating their oxygen vacancies, resulting in larger pentacene grains grown on them (as shown by atomic force microscopy) and thus higher carrier mobility for the OTFT due to less grain-boundary scattering. The carrier mobility of the ZrLaO- and NbLaO-OTFTs is about 70 times and 300 times higher than that of their counterparts based on ZrO2 and Nb2O5, respectively. However, La incorporated in Y2O3 increases its trap density by roughening its surface, causing smaller pentacene grains grown and thus lower carrier mobility. On the other hand, all the three TM elements incorporated in La2O3 can result in more moisture-resistant gate dielectric with smoother surface, resulting in larger pentacene grains grown and thus higher carrier mobility for the OTFT.

High-performance organic thin-film transistor by using LaNbO as gate dielectric

Pentacene organic thin-film transistor (OTFT) with high-κ HfTiO gate dielectric has been fabricated. The effects of fluorine plasma and ammonia annealing on the properties of the OTFT have been studied. After treating the dielectric in the plasma, the carrier mobility of the transistor can be improved by about 5 times to 0.0883 cm2/V·s. Moreover, the fluorine plasma treatment can shift the threshold voltage of the device in the positive direction. Experimental results also show that NH3 annealing can enhance the OTFT performance in terms of higher mobility, smaller sub-threshold slope and larger on/off ratio.

A Study on La Incorporation in Transition-Metal (Y, Zr, and Nb) Oxides as Gate Dielectric of Pentacene Organic Thin-Film Transistor

Bottom-gate pentacene organic thin-film transistors (OTFTs) with HfLaO gate dielectric have been fabricated on different substrates with different gate materials (namely, Ti- or Al-coated vacuum tape, n-Si wafer, and ITO-coated glass) and the effects of the gate material on device performance have been studied. Although the dielectric surface and pentacene grain on the Ti- and Al-coated vacuum tapes are much rougher and much smaller, respectively, than those on the n-Si wafer, the OTFTs fabricated on the two vacuum tapes have much higher carrier mobility than that fabricated on the n-Si wafer, implying that the gate material can greatly affect the device performance. Like the case for MOSFET, the possible reason is that metal gate can screen the remote phonon scattering of HfLaO and avoid the remote Coulomb scattering of silicon gate, thus resulting in higher carrier mobility for the OTFTs with Al and Ti gate electrodes. As a result, a high-performance OTFT with a carrier mobility of 4.95 cm

Effects of fluorine plasma and ammonia annealing on pentacene thin-film transistor with HfTiO as gate dielectric

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A Study on Pentacene Organic Thin-Film Transistor With Different Gate Materials on Various Substrates

and threshold voltage of −1.31 V was successfully fabricated on vacuum tape by using Ti gate.

High-performance pentacene OTFT by incorporating Ti in LaON gate dielectric

Pentacene organic thin-film transistors (OTFT) using high-k LaTiON gate dielectric with different Ti contents are investigated. The LaxTi(1-x)ON films (with x = 1, 0.87, 0.76, and 0.67) are deposited by reactive sputtering followed by an annealing in N2 at 200 °C. The OTFT with La0.87Ti0.13ON can achieve a high carrier mobility of 2.6 cm2/V·s, a small threshold voltage of −1.5 V, a small sub-threshold swing of 0.07 V/dec, and a small hysteresis of 0.17 V. AFM and X-ray photoelectron spectroscopy reveal that Ti can suppress the hygroscopicity of La oxide to achieve a smoother dielectric surface, which can result in larger pentacene grains and thus higher carrier mobility. All the devices show a clockwise hysteresis because both the LaOH formation and Ti incorporation can generate acceptor-like traps in the gate dielectric.