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1.
Kwang‐Hwan Cho Min‐Gyu Kang Ho Won Jang Hyun Yong Shin Chong‐Yun Kang Seok‐Jin Yoon 《固体物理学:研究快报》2012,6(5):208-210
We report the fabrication of organic thin‐film transistors (OTFTs) with high‐k gate dielectrics of Mn‐doped Bi2Ti2O7 (BTO) films. 3% Mn‐doped BTO films deposited on polymer substrates by pulsed laser deposition at room temperature exhibit low leakage currents of 2.1 × 10–8 A/cm2 at an applied electric field of 0.3 MV/cm, while undoped BTO films show much higher leakage currents of 4.3 × 10–4 A/cm2. Mn doping effectively reduces the number of oxygen vacancies in the films and improves the electrical properties. Low operation voltage and significantly reduced leakage currents are demonstrated in pentacene‐based OTFTs with the Mn‐doped BTO gate dielectrics. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
The voltage relaxation of galvanic cells with zirconia based electrolytes polarised between an inert Pt electrode and a Pt/air
electrode is analysed to obtain the diffusion coefficients of holes and electrons. The hole diffusion coefficient can be reduced
by replacing zirconium with guest ions of different size, e.g. Nb5+ and Ti4+. The TZP phase with 3 mol% Y2O3 of dopant has a higher hole diffusion coefficient than the CYZ phase doped with 8 mol% Y2O3. 1 and 3 mol% p-type MnO1.5 doping increases the conductivity of holes in CYZ to a large extend, but does not influence the diffusivity. This indicates
that the doping increases the hole conductivity through an increased concentration of holes. In the case of 10 and 15 mol%
MnO1.5 doped Z3Y, the electronic conductivity is dominant. The chemical diffusion coefficients which are related to the oxygen vacancies
were determined by GITT. The results show that the chemical diffusion coefficient of oxygen vacancies is much larger than
that for holes in zirconia. 相似文献
3.
S. Wongsaenmai K. Kanchiang S. ChandarakY. Laosiritaworn S. RujirawatR. Yimnirun 《Current Applied Physics》2012,12(2):418-421
In this study, ceramics in Mn-doped ((Ka0.5Na0.5)0.935Li0.065)NbO3 ceramics (Mn content = 0.25, 0.50, 1.00 and 1.50 mol%) were successfully prepared by the conventional mixed-oxide technique. The crystal structure was identified by XRD as a single-phase perovskite structure with tetragonal symmetry. The valence of Mn ions, characterized by the synchrotron XAS technique, was seen to change from Mn4+ to Mn3+ during the formation of the crystal. The valence state of Mn strongly affected the crystal structure and ferroelectric properties of the ceramics. The ferroelectric parameters show the decrease of remnant polarization and the increase of the coercive field with increasing MnO2 content. The results confirm the Mn3+ in KNNL perovskite lattices, leading to the formation of oxygen vacancies and hardening effects. 相似文献
4.
Lee Ming-Kwei Yen Chih-Feng Chiu Shih-Chen 《Applied Physics A: Materials Science & Processing》2011,104(4):1175-1180
The electrical characteristics of thin TiO2 films prepared by metal–organic chemical vapor deposition grown on a p-type InP substrate were studied. For a TiO2 film of 4.7 nm on InP without and with ammonium sulfide treatment, the leakage currents are 8.8×10−2 and 1.1×10−4 A/cm2 at +2 V bias and 1.6×10−1 and 8.3×10−4 A/cm2 at −2 V bias. The lower leakage currents of TiO2 with ammonium sulfide treatment arise from the improvement of interface quality. The dielectric constant and effective oxide
charge number density are 33 and 2.5×1013 cm2, respectively. The lowest mid-gap interface state density is around 7.6×1011 cm−2 eV−1. The equivalent oxide thickness is 0.52 nm. The breakdown electric field increases with decreasing thickness in the range
of 2.5 to 7.6 nm and reaches 9.3 MV/cm at 2.5 nm. 相似文献
5.
Effects of O2/Ar ratio and annealing temperature on electrical properties of Ta2O5 film prepared by magnetron sputtering
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The effects of the oxygen-argon ratio on electric properties of Ta2O5 film prepared by radio-frequency magnetron sputtering were investigated.The Ta2O5 partially transforms from the amorphous phase into the crystal phase when annealing temperatures are 800℃ or higher.The lattice constant of Ta2O5 decreases with the increase of the O2/Ar ratio,which indicates that oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies during the deposition process.For the films deposited in working gas mixtures with different O2/Ar ratios and subsequently annealed at 700℃,the effective dielectric constant is increased from 14.7 to 18.4 with the increase of the O2/Ar ratio from 0 to 1.Considering the presence of an SiO2 layer between the film and the silicon substrate,the optimal dielectric constant of Ta2O5 film was estimated to be 31.Oxygen gas in the working gas mixture contributes to reducing the density of oxygen vacancies,and the oxygen vacancy density and leakage current of Ta2O5 film both decrease with the increase of the O2/Ar ratio.The leakage current decreases after annealing treatment and it is minimized at 700℃.However,when the annealing temperature is 800℃ or higher,it increases slightly,which results from the partially crystallized Ta2O5 layer containing defects such as grain boundaries and vacancies. 相似文献
6.
Fengzhen Huang Xiaomei Lu Zhe Wang Weiwei Lin Yi Kan Huifeng Bo Wei Cai Jinsong Zhu 《Applied Physics A: Materials Science & Processing》2009,97(3):699-704
Multiferroic BiFeO3/Bi3.25La0.75Ti3O12 films annealed in different atmospheres (N2 or O2) were prepared on Pt/Ti/SiO2/Si substrates via a metal organic decomposition method. Based on our experimental results, it is considered that, in the
films annealed in N2, fewer Fe2+ ions while more oxygen vacancies are involved. As a result, at room temperature, predominated by the reduced Fe2+ fraction, lower leakage current and dielectric loss, better ferroelectric property while reduced magnetization are observed.
However, the oxygen vacancies might be thermally activated at elevated temperature; thus, more strongly temperature-dependent
leakage current and a higher dielectric relaxation peak are observed for the films annealed in N2. 相似文献
7.
K.B. Ruan H.W. Ho R.A. Khan P. Ren W.D. Song A.C.H. Huan L. Wang 《Solid State Communications》2010,150(43-44):2158-2161
Carbon-doped In2O3 thin films exhibiting ferromagnetism at room temperature were prepared on Si (100) substrates by the rf-magnetron co-sputtering technique. The effects of carbon concentration as well as oxygen atmosphere on the ferromagnetic property of the thin films were investigated. The saturated magnetizations of thin films varied from 1.23 to 4.86 emu/cm3 with different carbon concentrations. The ferromagnetic signal was found stronger in samples with higher oxygen vacancy concentrations. In addition, deposition temperature and different types of substrates also affect the ferromagnetic properties of carbon-doped In2O3 thin films. This may be related to the oxygen vacancies in the thin film system. The experiment suggests that oxygen vacancies play an important role in introducing ferromagnetism in thin films. 相似文献
8.
I. O. Troyanchuk S. V. Trukhanov E. F. Shapovalova V. A. Khomchenko M. Tovar H. Szymczak 《Journal of Experimental and Theoretical Physics》2003,96(6):1055-1064
The crystal structure and magnetic and electric transport properties of polycrystalline La0.50D0.50MnO3?γmanganites (D=Ca, Sr) were studied experimentally depending on the concentration of oxygen vacancies. The La0.50Sr0.50MnO3?γ system of anion-deficient compositions was found to be stable and possess a perovskite structure only up to the γ=0.25 concentration of oxygen vacancies, whereas, for the La0.50Ca0.50MnO3?γ system, we were able to obtain samples with the concentrations of oxygen vacancies up to γ=0.50. The stoichiometric La0.50D0.50MnO3 (D=Ca, Sr) compositions had O-orthorhombic (Ca) and tetragonal (Sr) unit cells. The unit cell of the anion-deficient La0.50Sr0.50MnO3?γ manganites also became O-orthorhombic when the concentration of oxygen vacancies increased γτ;0.16). Oxygen deficiency in La0.50Sr0.50MnO3?γ first caused the transition from the antiferromagnetic to the ferromagnetic state γ~0.06) and then to the spin glass state γ~0.16). Supposedly, the oxygen vacancies in the reduced La0.50Sr0.50MnO3? γ samples with γ≥0.16 were disordered. The special feature of the La0.50Ca0.50MnO3?γ manganites was a nonuniform distribution of oxygen vacancies in the La0.50Ca0.50MnO2.75 phase. In the La0.50Ca0.50MnO2.50 phase, the type of oxygen vacancy ordering corresponded to that in Sr2Fe2O5, which led to antiferromagnetic ordering. The specific electric resistance of the La0.50D0.50MnO3?γ anion-deficient samples increased with increasing oxygen deficiency. The magnetoresistance of all samples gradually increased as a result of the transition to the magnetically ordered state. Supposedly, the La0.50Ca0.50MnO3?γ manganites in the range of oxygen vacancy concentrations 0.09≤γ≤0.50 had a mixed state and contained microdomains with different types of magnetic ordering. The experimentally observed properties can be interpreted based on the model of phase layering and the model of superexchange magnetic ordering. 相似文献
9.
Choon-W. Nahm 《Journal of Physics and Chemistry of Solids》2012,73(7):834-838
The effect of Ta2O5 addition on microstructure, electrical properties, and dielectric characteristics of the quaternary ZnO–V2O5–MnO2 vaistor ceramics was investigated. Analysis of the microstructure indicated that the quaternary ZnO–V2O5–MnO2–Ta2O5 ceramics consisted of mainly ZnO grain and minor secondary phases such as Zn3(VO4)2, ZnV2O4, TaVO5, and Ta2O5. As the amount of Ta2O5 increased, the sintered density increased from 94.8 to 97.2% of the theoretical density (5.78 g/cm3 for ZnO), whereas the average grain size decreased from 7.7 to 6.0 μm. The ceramics added with 0.05 mol% Ta2O5 exhibited the highest breakdown field (2715 V/cm) and the highest nonlinear coefficient (20). However, further increase caused α to abruptly decrease. The Ta2O5 acted as a donor due to the increase of electron concentration in accordance with the amount of Ta2O5. The donor concentration increased from 1.97×1018 to 3.04×1018cm?3 with increasing the amount of Ta2O5 and the barrier height exhibited the maximum value (0.95 eV) at 0.05 mol% Ta2O5. 相似文献
10.
The effects of vanadium(V) doping into SrBi4Ti4O15 (SBTi) thin films on the structure, ferroelectric, leakage current, dielectric, and fatigue properties have been studied. X-ray diffraction result showed that the crystal structure of the SBTi thin films with and without vanadium is the same. Enhanced ferroelectricity was observed in the V-doped SrBi4Ti4O15 (SrBi4−x/3Ti4−xVxO15, SBTiV-x (x = 0.03, 0.06, and 0.09)) thin films compared to the pure SrBi4Ti4O15 thin film. The values of remnant polarization (2Pr) and coercive field (2Ec) of the SBTiV-0.09 thin film capacitor were 40.9 μC/cm2 and 105.6 kV/cm at an applied electric field of 187.5 kV/cm, respectively. The 2Pr value is over five times larger than that of the pure SBTi thin film capacitor. At 100 kHz, the values of dielectric constant and dielectric loss were 449 and 0.04, and 214 and 0.06 for the SBTiV-0.09 and the pure SBTi thin film capacitors, respectively. The leakage current density of the SBTiV-0.09 thin film capacitor measured at 100 kV/cm was 6.8 × 10−9 A/cm2, which is more than two and a half orders of magnitude lower than that of the pure SBTi thin film capacitor. Furthermore, the SBTiV-0.09 thin film exhibited good fatigue endurance up to 1010 switching cycles. The improved electrical properties may be related to the reduction of internal defects such as bismuth and oxygen vacancies with changes in the grain size by doping of vanadium into SBTi. 相似文献
11.
Lijuan Liu Panli You Guangfu Yin Xiaoming Liao Zhongbing Huang Xianchun Chen Yadong Yao 《Current Applied Physics》2012,12(4):1045-1051
A series of Eu2+ and Sm3+ co-doped Li2SrSiO4 phosphors are prepared by the high temperature solid-state reaction. The morphology, structure and spectroscopic properties of the prepared samples are characterized by scanning electron microscopy, X-ray diffraction, diffuse reflection spectra, photoluminescence spectra and electron paramagnetic resonance spectra, respectively. The effect of Sm3+ doping concentration on the photoluminescence intensity of the prepared samples is also investigated. The results indicate that the crystal structure of Li2SrSiO4 is not changed with the Eu2+, Sm3+ co-doping. The spherical-like particle size of the obtained product is about 20–30 nm in diameter. When the Sm3+ concentration is 0.3 mol% and the Eu2+ concentration is 0.7 mol%, the phosphors show the maximum emission intensity, which is 50% higher than that of Eu2+ doped Li2SrSiO4. Excited at 420 nm, the phosphor presents a single broad emission band peaking at 558 nm, which is ascribed to the 4f65d1 → 4f7 transitions of Eu2+ and 4G5/2 → 6H5/2 and 4G5/2 → 6H7/2 transitions of Sm3+. The Commission International de I′Eclairage chromaticity coordinates of Li2SrSiO4:0.7 mol% Eu2+, 0.3 mol% Sm3+ are x = 0.28, y = 0.28. 相似文献
12.
Kazuhisa Sato Ken Suzuki Keiji Yashiro Tatsuya Kawada Hiroo Yugami Toshiyuki Hashida Alan Atkinson Junichiro Mizusaki 《Solid State Ionics》2009,180(20-22):1220-1225
The conductivity and elastic modulus of (CeO2)1 − x(YO1.5)x for x values of 0.10, 0.15, 0.20, 0.30, and 0.40 were investigated by experiments and molecular dynamics simulations. The calculated conductivity exhibited a maximum value at approximately 15 mol% Y2O3; this trend agreed with that of the experimental results. In order to clarify the reason for the occurrence of the maximum conductivity, the paths for the transfer of oxygen vacancies were counted. The numerical result revealed that as the content of Y2O3 dopant increases, the number of paths for the transfer of oxygen vacancies decreases, whereas the number of oxygen vacancies for conductivity increases. Thus, the trade-off between the increase in the number of vacancy sites and the decrease in the vacancy transfer was considered to be the reason for the maximum conductivity occurring at the Y2O3 dopant content of approximately 15 mol%. The calculated elastic modulus also exhibited a minimum value at approximately 20 mol% Y2O3, which also agreed with the experimental results. It was shown that the Y–O–Y bonding energy increased with the increasing content of Y2O3 dopant. Thus, the trade-off between the increase in the number of vacancy sites and that in the Y–O–Y bonding energy was considered to be the reason for the minimum elastic modulus occurring at the Y2O3 dopant content of approximately 20 mol%. 相似文献
13.
S. Canulescu T. Lippert A. Wokaun 《Applied Physics A: Materials Science & Processing》2008,93(3):771-778
The mass distributions of the species generated by laser ablation from a La0.6Ca0.4MnO3 target using laser irradiation wavelengths of 193 nm, 266 nm and 308 nm have been investigated with and without a synchronized
gas pulse of N2O. The kinetic energies of the species are measured using an electrostatic deflection energy analyzer, while the mass distributions
of the species were analyzed with a quadrupole mass filter.
In vacuum (pressure 10−7 mbar), the ablation plume consists of metal atoms and ions such as La, Ca, Mn, O, LaO, as well as multiatomic species, e.g.
LaMnO+. The LaO+ diatomic species are by far the most intense diatomic species in the plume, while CaO and MnO are only detected in small
amounts.
The interaction of a reactive N2O gas pulse with the ablation plume leads to an increase in plume reactivity, which is desired when thin manganite films are
grown, in order to incorporate the necessary amount of oxygen into the film. The N2O gas pulse appears to have a significant influence on the oxidation of the Mn species in the plume, and on the creation of
negative ions, such as LaO−,O− and O2−. 相似文献
14.
The effect of CO2 laser irradiation on La0.67Ba0.33MnO3 epitaxial thin film was investigated. Epitaxial thin films grown by pulsed laser deposition were irradiated by a CO2 laser in air for 10-60 s. It is shown that after CO2 laser irradiation treatment, the crystallinity of the film is strongly enhanced. It is found that a dramatic decrease in the resistivity of the CO2-laser-irradiated film is accompanied by a remarkable increase in its insulator-metal transition temperature and the temperature coefficient of resistance. This significant improvement of its structure and properties is achieved in several dozens of seconds and surpasses that observed in films annealed in an oxygen atmosphere at 900 °C for 12 h, suggesting that CO2 laser irradiation is a new and effective tool to optimize CMR manganites for bolometric applications. 相似文献
15.
We have developed an in-situ method using sonication (3 mm probe sonicator, 30 W, 20 kHz) and auto-reduction (control) to study the mechanism of the formation of manganese dioxide (MnO2) on a solid template (silk film), and its resulting enzymatic activity on tetramethylbenzidine (TMB) substrate. The fabrication of the silk film was first optimized for stability (no degradation) and optical transparency. A factorial approach was used to assess the effect of sonication time and the initial concentration of potassium permanganate (KMnO4). The result indicated a significant correlation with a fraction of KMnO4 consumed and MnO2 formation. Further, we found that the optimal process conditions to obtain a stable silk film with highly catalytic MnO2 nanoparticles (NPs) was 30 min of sonication in the presence of 0.5 mM of KMnO4 at a temperature of 20–24 °C. Under the optimal condition, we monitored in-situ the formation of MnO2 on the silk film, and after thorough rinsing, the in-situ catalysis of 0.8 mM of TMB substrate. For control, we used the auto-reduction of KMnO4 onto the silk film after about 16 h. The result from single-wavelength analysis confirmed the different kinetics rates for the formation of MnO2 via sonication and auto-reduction. The result from the multivariate component analysis indicated a three components route for sonication and auto-reduction to form MnO2-Silk. Overall, we found that the smaller size, more mono-dispersed, and deeper buried MnO2 NPs in silk film prepared by sonication, conferred a higher catalytic activity and stability to the hybrid material. 相似文献
16.
Min Hyuk Park Han Joon Kim Yu Jin Kim Taehwan Moon Keum Do Kim Cheol Seong Hwang 《固体物理学:研究快报》2014,8(10):857-861
With increasing annealing temperature (Tanneal), the magnitude of the electric fields for the antiferroelectric‐to‐ferro‐electric (EAF) and ferroelectric‐to‐antiferroelectric (EFA) transition of a 9.2 nm thick Hf0.3Zr0.7O2 film decreased. The energy storage densities of the Hf0.3Zr0.7O2 films crystallized at 400 °C, 500 °C, and 600 °C were as large as 42.2 J/cm3, 40.4 J/cm3, and 28.3 J/cm3, respectively, at the electric field of 4.35 MV/cm. The maximum dielectric constant of the Hf0.3Zr0.7O2 film crystallized at 600 °C was the largest (~46) as it had the smallest EAF and EFA, whereas the leakage current density of the film crystallized at 400 °C was the smallest. The 400 °C of Tanneal was the optimum condition for energy storage application. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
17.
The kinetics of the oxygen exchange reaction and the reduction of NO at La0.8Sr0.2CoO3−, La0.8Sr0.2MnO3− and Ag-electrodes on stabilized zirconia (8mol% Y203=YSZ) has been studied by means of electrochemical methods (impedance, I-U characteristics). For La0.8Sr0.2CoO3 electrodes the oxygen exchange was found to proceed via the bulk of the electrode with a rate limiting oxygen exchange at
the electrode surface. Electrodes based on La0.8Sr0.2MnO3 change their electrode characteristics with the applied potential. At low cathodic polarization the electrode reaction is
limited to the three-phase boundary electrode/YSZ/gas. At high cathodic potentials oxygen vacancies are created and consequently
additional oxygen is exchanged via the electrode bulk. Furthermore, a significant NO reduction was observed which indicate
a reaction with the oxygen vacancies at the electrode surface. For Ag a rate limiting transport of oxygen atoms through the
bulk of the electrode was found. As a consequence the oxygen concentration at the electrode surface remains nearly constant.
In this context, the observed inactivity for the NO reduction of Ag-electrodes may be explained.
Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995 相似文献
18.
《Solid State Ionics》2006,177(19-25):1687-1690
The local coordination structure around Yttrium ions in yttria stabilized zirconia (YSZ) has been investigated by 89Y MAS-NMR. The NMR spectrum showed multiple peaks corresponding to yttrium ions in different coordination numbers. The compositional dependence of spectra was observed. Yttrium ions of different oxygen coordination number were quantified. The oxygen vacancy concentration around the cations was determined. It was found that the vacancies were distributed around Zirconium ions in lower Y2O3 concentrations, and the vacancy concentration located to Yttrium began increasing at concentrations above 10 mol% Y2O3. The local structure change was able to be directly observed by 89Y NMR measurements. 相似文献
19.
S.-H. Lim M. Murakami A.J. Zambano I. Takeuchi 《Journal of magnetism and magnetic materials》2009,321(13):1955-1958
We have fabricated exchange-biased Co/Pt layers ((0.3 nm/1.5 nm)×3) on (0 0 1)-oriented Cr2O3 thin films. The multilayered films showed extremely smooth surfaces and interfaces with root mean square roughness of ≈0.3 nm for 10 μm×10 μm area. The Cr2O3 films display sufficient insulation with a relative low leakage current (1.17×10−2 A/cm2 at 380 MV/m) at room temperature which allowed us to apply electric field as high as 77 MV/m. We find that the sign of the exchange bias and the shape of the hysteresis loops of the out-of-plane magnetized Co/Pt layers can be delicately controlled by adjusting the magnetic field cooling process through the Néel temperature of Cr2O3. No clear evidence of the effect of electric field and the electric field cooling was detected on the exchange bias for fields as high as 77 MV/m. We place the upper bound of the shift in exchange bias field due to electric field cooling to be 5 Oe at 250 K. 相似文献
20.
Ta2O5/Al2O3 stacked thin film was fabricated as the gate dielectric for low-voltage-driven amorphous indium–gallium–zinc-oxide (IGZO) thin film transistors (TFTs). The Ta2O5/Al2O3 stacked thin film exhibits a combination of the advantages of Al2O3 and Ta2O5. The IGZO TFT with Ta2O5/Al2O3 stack exhibits good performance with large saturation mobility of 26.66 cm2 V−1 s−1, high on/off current ratio of 8 × 107, and an ultra-small subthreshold swing (SS) of 78 mV/decade. Such small SS value is even comparable with that of submicrometer single-crystalline Si MOSFET. 相似文献