| 1. |
- Cho, C. R., et al.
(författare)
-
Ferroelectric Na0.5K0.5NbO3 thin films by pulsed laser deposition
- 2000
-
Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 31:1-4, s. 35-45
-
Tidskriftsartikel (refereegranskat)abstract
- Highly c-axis oriented single phase Na0.5K0.5NbO3 (NKN) thin films have been deposited onto polycrystalline Pt80Ir20 substrates and SiO2/Si(001) wafers using pulsed laser ablation of stoichiometric ceramic target. Strong self-assembling of NKN films along the [001] direction has been observed. Properties of NKN/Pt thin film structures have been successfully tailored by oxygen pressure control from the ferroelectric state, characterized by the remnant polarization of 12 muC/cm(2), dielectric constant epsilon similar to 520 and tan delta - 0.024 @ 100 kHz, to superparaelectric state with tan delta as low as 0.003 and epsilon = 210 with very small 1.7% dispersion in the frequency domain 0.4-100 kHz and less than 10% Variation in the temperature range 77-415 K. NKN films grown onto SiO2/Si(001) substrates show quadrupled super-lattice structure along c-axis, loss tan delta less than 0.01, and epsilon similar to 110 @ 1 MHz. C-V measure ments for Au/NKN(270nm)/SiO2/Si MFIS-diode structure yield memory window of 3.26 V at the programmable voltage of 8 V.
|
|
| 2. |
- Cho, C. R., et al.
(författare)
-
Na0.5K0.5NbO3 thin films for MFIS_FET type non-volatile memory applications
- 2002
-
Ingår i: Integrated Ferroelectrics. - 1058-4587 .- 1607-8489. ; 49, s. 21-30
-
Tidskriftsartikel (refereegranskat)abstract
- Na0.5K0.5NbO3(NKN) thin films have been prepared on Pt80Ir20, SiO2/Si, and Ta2O5/Si substrates for ferroelectric non-volatile memory applications. Ferroelectric hysteresis loops for Au/NKN/Pt80Ir20 vertical capacitor yielded remnant polarization of 12 muC/cm(2) and coercive field similar to20 kV/cm. Significant flat-band voltage V-FB shifts with buffer layer thickness in Au/NKN/SiO2/Si structures have been attributed to the intermixing between Na and K alkali ions and SiO2 layer. On the other hand, Au/NKN/Ta2O5/Si structure exhibited wide memory window without significant V-FB deviations, low leakage currents, and rather long retention time at zero bias.
|
|
| 3. |
- Koh, J. H., et al.
(författare)
-
Dielectric properties and Schottky barriers in silver tantalate-niobate thin film capacitors
- 2001
-
Ingår i: Integrated Ferroelectrics. - 1058-4587 .- 1607-8489. ; 39:1-4, s. 1361-1368
-
Tidskriftsartikel (refereegranskat)abstract
- Submicron thick ferroelectric Ag(Ta,Nb)O-3 films have been pulsed laser deposited on the bulk Pt80Ir20 polycrystalline substrates. They are ferroelectric at temperatures below 125 K with the remnant polarization of 0.4 muC/cm(2) @ 77K and paraelectric at higher temperatures with tandelta @ 100 kHz as low as 0.015. Extensive I-V characterization has been performed in a wide temperature range 77 K to 350 K for vertical Me/Ag(Ta,Nb)O-3/Pt80Ir20 capacitive cells, where the metals Me = Pd, Au, Cr, and Al have been used as a top electrode. The electronic transport in thin Me/Ag(Ta,Nb)O-3/Pt80Ir20 capacitors follows the Schottky emission mechanism with the barrier height for the Pd, Au, Cr, and Al of 0.85, 0.8, 0.74, and 0.69 eV, respectively.
|
|
| 4. |
|
|
| 5. |
- Klein, G., et al.
(författare)
-
Macrocognition
- 2003
-
Ingår i: IEEE Intelligent Systems & Their Applications. - 1094-7167. ; 18:3, s. 81-85
-
Forskningsöversikt (refereegranskat)abstract
- The importance of macrocognition in a cognitive system is discussed. Macrocognition is a term which indicates a level of description of the cognitive functions that are performed in natural decision-making settings. Macrocognition comprises the mental activities that must be successfully accomplished to perform a task or achieve a goal.
|
|
| 6. |
- Lee, S. K., et al.
(författare)
-
Electrical characterization of titanium-based ohmic contacts to 4H-Silicon carbide for high-power and high-temperature operation
- 2002
-
Ingår i: Journal of the Korean Physical Society. - 0374-4884 .- 1976-8524. ; 40:4, s. 572-576
-
Tidskriftsartikel (refereegranskat)abstract
- We report on titanium-based ohmic contacts (titanium carbide. titanium tungsten, and titanium) on both highly doped epilayers (n(+) and p(+)) and Al-ion-implanted layers. The TiC contact layer was epitaxially grown on epilayers as well as an Al-ion-implanted layers of 4H-SiC by co-evaporation Ti and C-60 under an ultra-high vacuum condition at low temperature (<500 degreesC). For comparison and long-term stability test, we also deposited TiW (weight ratio 30 : 710) ohmic contacts to p and n-type epilayers of 4H-SiC. The specific contact resistances (p(c)) were found to be as low as p- 5X10(-6), 2x10(-5), 2x10(-5), 3x10(-4), 4x10(-5), and 1X10(-4) Omegacm(2) for TiC contacts to n(+) epilayers, p(+) epilayers, and Al-ion-implanted layers, Ti contacts to p(+) epilayers, and TiW contacts to p(+) and to n(+) epilayers, respectively, by using linear transmission line method (TLM) measurements. During the long-term reliability tests in a vacuum chamber, we found that evaporated Au capping layers helped to keep the contacts from degrading.
|
|
