High-k and low-k nanocomposite gate dielectrics for low voltage organic thin film transistors

Abstract

Ce O 2 – Si O 2 nanocomposite films were used as the gate dielectrics in organic thin film transistors (OTFTs) with pentacene active semiconductor. CeO2–SiO2 composite films exhibited a high dielectric capacitance of 57nF∕cm2 with exceptionally low leakage current. Good device characteristics were obtained with saturation at low operating voltages (∼2V) and with a field effect mobility of 0.84cm2V−1s−1, a threshold voltage of ∼0.25V, an on/off current ratio of 103, and a subthreshold slope of 0.3V∕decade, whereas the gate leakage current density is considerably lowered. These results should therefore increase the prospects of using OTFTs in low power applications such as portable devices.

Orientation control of (001) and (101) in epitaxial tetragonal Pb(Zr,Ti)O3 films with (100)/(001) and (110)/(101) mixture orientations

“…(001) orientation is found to have smaller unit cell area than (100) one for all temperature range from T c to room temperature. These data show that (001) orientation become dominant in the mixture orientation of (001) and (100) due to the smaller unit cell area along in-plane direction in case of compressive stress, while (100) one with larger unit cell area in case of tensile stress, even if taking into account the possibility that the orientation change with the temperature below T c as pointed out by Kim et al 10) When films are grown on various substrates having different thermal expansion coefficients with the same bottom layers, the thermal strain is considered to mainly control the orientation of the films, especially in thick film case. In fact, the volume fraction of (001) orientation in (100)/(001) mixed orientation was found to be mainly determined by the thermal strain for 150 nm-thick Pb(Zr 0.35 Ti 0.65 )O 3 films.…”

Experimental evidence of strain relaxed domain structure in (100)/(001)-oriented epitaxial lead titanate thick films grown by metal organic chemical vapor deposition

“…5. This value is equal to that of the strain-free PbTiO 3 , which can be obtained as 2 ‫ء‬ arctan͑c / a͒ − 90°, where a and c are the lattice parameters of a strain-free state of PbTiO 3 . In fact, we found the inplane lattice parameters of a-and c-axes ͑a ʈ and c ʈ ͒ to be a ʈ = 0.4147 nm and c ʈ = 0.3896 nm, which are in good agreement with the strain-free values.…”

“…[2][3][4] In ferroelectric films with tetragonal perovskite structure, such as PbTiO 3 or Pb͑Zr, Ti͒O 3 ͑PZT͒, there are three possible domain types: c-domains with their polarization direction along the surface normal and two types of a-domains ͑defined as a and aЈ͒ with their polarization axes rotated by approximately 90°and oriented in the plane of the substrate. In such films, the phase transition from the cubic to tetragonal phase is accompanied by the formation of domain configurations consisting of a / aЈ or a / c or aЈ / c domains ͑90°domains͒ due to strain relaxation during the cooling process.…”

Kinetic Monte Carlo of transport processes in Al/AlOx/Au-layers: Impact of defects

“…While typically a value of ∼ 9.0 is cited for stoichiometric Al 2 O 3 , 10 our value is in good agreement with other plasma-grown AlO x dielectrics. 4 With ε r = 6.8, the thicknesses of different plasma-grown oxide layers could be estimated from CV-measurements, yielding capacitances of 0.9 µF/cm 2 and 1.04 µF/cm 2 and corresponding AlO x thicknesses of 5.8 nm and 6.7 nm, respectively. Reference values and variation ranges of these parameters are summarized in Table I.…”

“…1,2 In fact, aluminum oxide, AlO x , turned out to be useful for many electronic applications like silicon-onsapphire for CMOS technology, 3 organic devices, 4 THz-nano-rectennas, 5 nTP tunnel diodes, 6 gate metals on III/V-semiconductors 7,8 and for resistive switches. 9 In these applications AlO x films are mostly produced by ALD, 7,10 RIE-plasma-growth 6 or thermal oxidation.…”