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1.
C. R. Foschini R. Tararam A. Z. Simões L. S. Rocha C. O. P. Santos E. Longo J. A. Varela 《Journal of Materials Science: Materials in Electronics》2016,27(3):2175-2182
Calcium copper titanate, CaCu3Ti4O12, CCTO, thin films with polycrystalline nature have been deposited by RF sputtering on Pt/Ti/SiO2/Si (100) substrates at a room temperature followed by annealing at 600 °C for 2 h in a conventional furnace. The crystalline structure and the surface morphology of the films were markedly affected by the growth conditions. Rietveld analysis reveal a CCTO film with 100 % pure perovskite belonging to a space group Im3 and pseudo-cubic structure. The XPS spectroscopy reveal that the in a reducing N2 atmosphere a lower Cu/Ca and Ti/Ca ratio were detected, while the O2 treatment led to an excess of Cu, due to Cu segregation of the surface forming copper oxide crystals. The film present frequency -independent dielectric properties in the temperature range evaluated, which is similar to those properties obtained in single-crystal or epitaxial thin films. The room temperature dielectric constant of the 600-nm-thick CCTO films annealed at 600 °C at 1 kHz was found to be 70. The leakage current of the MFS capacitor structure was governed by the Schottky barrier conduction mechanism and the leakage current density was lower than 10?7 A/cm2 at a 1.0 V. The current–voltage measurements on MFS capacitors established good switching characteristics. 相似文献
2.
X. H. Zheng J. Xiao X. Huang D. P. Tang X. L. Liu 《Journal of Materials Science: Materials in Electronics》2011,22(8):1116-1119
The formation behavior of CaCu3Ti4O12 (CCTO) had been investigated via solid state reaction from CaTiO3, CuO and TiO2 powders. In the temperature range from 750 to 1,200 °C, the reaction sequence was traced by XRD, and the microstructure evolution
of calcined powders was also investigated by SEM. CCTO began to form owing to the reaction between CaTiO3, CuO and TiO2 at around 850 °C, and became the major phase at 1,000 °C. Finally, the single phase CCTO was obtained at 1,150 °C. However,
CCTO was decomposed at CaTiO3, CuO and TiO2 when the temperature increased to 1,200 °C. In addition, no other intermediate phases occurred in the synthesized process.
The formation behaviors indicated that CaTiO3 prevented the formation and growth of CCTO. 相似文献
3.
Wen Feng Qin Wan Yong Ai Jun Zhu Jie Xiong Jinlong Tang Ying Zhang Yan Rong Li 《Journal of Materials Science》2007,42(20):8707-8713
Conductive SrRuO3 (SRO) thin films have been grown on (100) MgO substrates by pulsed laser deposition (PLD) technique. Effects of oxygen pressure
and deposition temperature on the orientation of SRO thin film were investigated. X-ray diffraction (XRD) θ/2θ patterns and
the temperature dependent resistivity measurements indicated that oxygen pressure of 30 Pa and deposition temperature of 700 °C
were the optimized deposition parameters. A parallel-plate capacitor structure was prepared with the SRO films deposited under
optimized condition as an electrode layer and Ba0.60Sr0.40TiO3 (BST) thin film as the dielectric layer. XRD Φ scans indicated a
epitaxial relationship between BST and SRO on MgO substrate. The dielectric constant and loss tangent measured at 10 kHz
and 300 K was 427 and 0.099 under 0 V bias, and 215 and 0.062 under 8 V bias, respectively. A tunability of 49.6% has been
achieved with DC bias as low as 8 V. The C–V hysteresis curve and the P–E hysteresis loop suggested that the BST films epitaxially grown on SRO/MgO have ferroelectricity at room temperature. The
induced ferroelectricity was believed to originate from the compressive strain between the epitaxial BST and SRO thin films.
These results show the potential application of the BST/SRO heterostructures in microelectronic devices. 相似文献
4.
In the present study, different catalysts (∼ 10 nm thick) including metals, noble metals and metal oxides, were loaded in
dotted island form over SnO2 thin film for LPG gas detection. A comparison of various catalysts indicated that the presence of platinum dotted islands
over SnO2 thin film deposited by r.f. sputtering exhibited enhanced response characteristics with a high sensitivity, ∼ 742, at an
operating temperature of ∼ 280°C. Different characterization techniques have been employed such as atomic force microscopy,
X-ray diffraction and UV-vis spectroscopy, to study the surface morphology, grain size and optical properties of the deposited
thin films. The results suggest the possibility of utilizing the sensor element with the present novel method of catalyst
dispersal for the efficient detection of LPG. 相似文献
5.
P. Thomas L. N. Sathapathy K. Dwarakanath K. B. R. Varma 《Bulletin of Materials Science》2007,30(6):567-570
CaCu3Ti4O12 (CCTO) was synthesized and sintered by microwave processing at 2·45 GHz, 1·1 kW. The optimum calcination temperature using
microwave heating was determined to be 950°C for 20 min to obtain cubic CCTO powders. The microwave processed powders were
sintered to 94% density at 1000°C/60 min. The microstructural studies carried out on these ceramics revealed the grain size
to be in the range 1–7 μm. The dielectric constants for the microwave sintered (1000°C/60 min) ceramics were found to vary
from 11000–7700 in the 100 Hz–00 kHz frequency range. Interestingly the dielectric loss had lower values than those sintered
by conventional sintering routes and decreases with increase in frequency. 相似文献
6.
G. Alarcón-Flores M. Aguilar-Frutis M. García-Hipolito J. Guzmán-Mendoza M. A. Canseco C. Falcony 《Journal of Materials Science》2008,43(10):3582-3588
Yttrium oxide thin films are deposited on silicon substrates using the ultrasonic spray pyrolysis technique from the thermal
decomposition of a β-diketonate, yttrium acetylacetonate (Y(acac)3). The decomposition of Y(acac)3 was studied by thermogravimetry, differential scanning calorimetry, mass spectrometry, and infrared spectroscopy. It was found
that a β-diketone ligand is lost during the initial steps of decomposition of the Y(acac)3. The rest of the complex is then dissociated or degraded partially until Y2O3 is obtained in the final step with the presence of carbon related residues. Then the Y(acac)3 was used to synthesize Y2O3 thin films using the spray pyrolysis technique. The films were deposited on silicon substrates at temperatures in the range
of 400–550 °C. The films were characterized by ellipsometry, infrared spectroscopy, atomic force microscopy, and X-ray diffraction.
The films presented a low surface roughness with an index of refraction close to 1.8. The crystalline structure of the films
depended on the substrate temperature; films deposited at 400 °C were mainly amorphous, but higher deposition temperatures
(450–550 °C), resulted in polycrystalline with a cubic crystalline phase. 相似文献
7.
H. Z. Chen M. C. Kao S. L. Young C. C. Yu C. H. Lin C. R. Ou C. M. Lee 《Journal of Superconductivity and Novel Magnetism》2010,23(6):933-935
Bi4Ti3.96Nb0.04O12 thin films were successfully deposited on Pt(111)/Ti/SiO2/Si(100) substrates by a sol–gel method and rapid thermal annealing. The effects of Nb-substitution and annealing temperature
(500–800°C) on the microstructure and ferroelectric properties of bismuth titanate thin films were investigated. X-ray diffraction
analysis reveals that the intensities of (117) peaks are relatively broad and weak at annealing temperatures smaller than
700°C. With the increase of annealing temperature from 500°C to 800°C, the grain size of Bi4Ti3.96Nb0.04O12 thin films increases. The Bi4Ti3.96Nb0.04O12 thin films annealed at 700°C exhibit the highest remanent polarization (2P
r), 36 μC/cm2 and lowest coercive field (2E
c), 110 kV/cm. The improved ferroelectric properties can be attributed to the substitution of Nb5+ to Ti4+ in Bi4Ti3O12 assisting the elimination of defects such as oxygen vacancy and vacancy complexes. 相似文献
8.
M. Bleiweiss J. Amirzadeh M. Yin A. Lungu T. Datta 《Journal of Superconductivity and Novel Magnetism》2005,18(4):567-572
Synthesis and optical transmission of MgB2 thin films on optically transparent glass are reported. In the 400–1000 nm regime as deposited films show high metallic reflectivity
and very little transmission. After deposition, the films were annealedex situ and rendered superconducting withT
c of 38 K, approaching that of the bulk material. The reaction conditions where quite soft ∼ 10 min at 550°C. The optical absorption
coefficient,α and photon energy,E followed a Tauc-type behavior, (αE)1/2=β
T(E −E
g). The band gap (E
g) was observed to peak at 2.5 eV; but, the slope parameterβ
Tbehaved monotonically with reaction temperature. Our results indicate that an intermediate semiconducting phase is produced
before the formation of the superconducting phase; also optical measurements provide valuable information in monitoring the
synthesis of MgB2 from its metallic constituents. In addition these films have interesting optical properties that may be integrated into optoelectronics. 相似文献
9.
GANESH E PATIL D D KAJALE D N CHAVAN N K PAWAR P T AHIRE S D SHINDE V B GAIKWAD G H JAIN 《Bulletin of Materials Science》2011,34(1):1-9
In this work, SnO2 thin films were deposited onto alumina substrates at 350°C by spray pyrolysis technique. The films were studied after annealing
in air at temperatures 550°C, 750°C and 950°C for 30 min. The films were characterized by X-ray diffraction (XRD), scanning
electron microscopy (SEM) and optical absorption spectroscopy technique. The grain size was observed to increase with the
increase in annealing temperature. Absorbance spectra were taken to examine the optical properties and bandgap energy was
observed to decrease with the increase in annealing temperature. These films were tested in various gases at different operating
temperatures ranging from 50–450°C. The film showed maximum sensitivity to H 2S gas. The H2S sensing properties of the SnO2 films were investigated with different annealing temperatures and H 2S gas concentrations. It was found that the annealing temperature significantly affects the sensitivity of the SnO2 to the H 2S. The sensitivity was found to be maximum for the film annealed at temperature 950°C at an operating temperature of 100°C.
The quick response and fast recovery are the main features of this film. The effect of annealing temperature on the optical,
structural, morphological and gas sensing properties of the films were studied and discussed. 相似文献
10.
Noor Shahina Begum H. M. Farveez Ahmed O. M. Hussain 《Bulletin of Materials Science》2008,31(5):741-745
Boron doped TiO2 thin films have been successfully deposited on glass substrate and silicon wafer at 30°C from an aqueous solution of ammonium
hexa-fluoro titanate and boron trifluoride by liquid phase deposition technique. The boric acid was used as an F
− scavenger. The resultant films were characterized by XRD, EDAX, UV and microstructures by SEM. The result shows the deposited
film to be amorphous which becomes crystalline between 400 and 500°C. The EDAX and XRD data confirm the existence of boron
atom in TiO2 matrix and a small peak corresponding to rutile phase was also found. Boron doped TiO2 thin films can be used as photocatalyst for the photodegradation of chlorobenzene which is a great environmental hazard.
It was found that chlorobenzene undergoes degradation efficiently in presence of boron doped TiO2 thin films by exposing its aqueous solution to visible light. The photocatalytic activity increases with increase in the
concentration of boron. 相似文献
11.
Li Jia Yu Jun Wang Yunbo Peng Gang Li Jianjun 《Journal of Materials Science: Materials in Electronics》2010,21(2):137-140
Bi3.15Nd0.85Ti3O12 (BNT) thin film with a thin LaNiO3 film as buffer layer was fabricated by sol–gel method on Pt/TiO2/SiO2/Si substrate. The BNT thin films have a perovskite phase with a dense microstructure. The P
r and V
c value are 25.5 μc/cm2 and 3.7 V, respectively under the applied voltage of 15 V. After the switching of 2 × 109 cycles, the P
r value decreases to 86% of its pre-fatigue value. The leakage current density of the BNT thin films with LaNiO3 buffer layer were generally in the order of 10−8 to 10−6 A/cm2. The fatigue and leakage current properties were improved dramatically compared with the BNT film without a LaNiO3 buffer layer that we prepared before. The measured residual stress was tensile stress and its value was 176 MPa. 相似文献
12.
Gd3+ was chosen as a substitute for Bi3+ in BiNbO4 ceramics, and the substitution effects on the sintering performance and microwave dielectric properties were studied in this
paper. The high temperature triclinic phase was observed only in the Bi0.98Gd0.02NbO4 ceramics when sintered at 920 °C. Both bulk densities and dielectric constant (εr) increased with the sintering temperature, while decreased with the Gd content. The quality factor (Q) exhibited a correlation to the Gd content and the microstructures of Bi1−x
Gd
x
NbO4 ceramics. At the sintering temperature of 900 °C, Bi0.992Gd0.008NbO4 ceramics exhibited microwave dielectric properties of εr ∼ 43.87, Q × f ∼ 16,852 GHz (at 4.3 GHz), and its temperature coefficient of resonant frequency (τf) was found to be near-to-zero. 相似文献
13.
Wen Chiao Chin Kuan Yew Cheong 《Journal of Materials Science: Materials in Electronics》2011,22(12):1816-1826
Samarium oxide (Sm2O3) thin films with thicknesses in the range of 15–30 nm are deposited on n-type silicon (100) substrate via radio frequency
magnetron sputtering. Effects of post-deposition annealing ambient [argon and forming gas (FG) (90% N2 + 10% H2)] and temperatures (500, 600, 700, and 800 °C) on the structural and electrical properties of deposited films are investigated
and reported. X-ray diffraction revealed that all of the annealed samples possessed polycrystalline structure with C-type
cubic phase. Atomic force microscope results indicated root-mean-square surface roughness of the oxide film being annealed
in argon ambient are lower than that of FG annealed samples, but they are comparable at the annealing temperature of 700 °C
(Argon—0.378 nm, FG—0.395 nm). High frequency capacitance–voltage measurements are carried out to determine effective oxide
charge, dielectric constant and semiconductor-oxide interface trap density of the annealed oxide films. Sm2O3 thin films annealed in FG have smaller amount of effective oxide charge and semiconductor-oxide interface trap density than
those oxide films annealed in argon. Current–voltage measurements are conducted to obtain barrier heights of the annealed
oxide films during Fowler–Nordheim tunneling. 相似文献
14.
For the first time, sputtered zinc oxide (ZnO) thin films have been used as a CO2 gas sensor. Zinc oxide thin films have been synthesized using reactive d.c. sputtering method for gas sensor applications,
in the deposition temperature range from 130–153°C at a chamber pressure of 8·5 mbar for 18 h. Argon and oxygen gases were
used as sputtering and reactive gases, respectively. ZnO phase could be crystallized using a pure metal target of zinc. The
structure of the films determined by means of X-ray diffraction method indicates that the zinc oxide single phase can be fabricated
in this substrate temperature range. The sensitivity of the film synthesized at substrate temperature of 130°C is 2·17 in
the presence of CO2 gas at a measuring temperature of 100°C. 相似文献
15.
Choon-W. Nahm 《Journal of Materials Science: Materials in Electronics》2011,22(8):1010-1015
The microstructure, electrical properties, and DC-accelerated aging behavior of the ZnO-V2O5-Mn3O4 ceramics were investigated at different sintering temperatures of 850–925°C. The microstructure of the ZnO-V2O5-Mn3O4 ceramics consisted of ZnO grain as a primary phase, and Zn3(VO4)2 which acts as a liquid-phase sintering aid, in addition to Mn-rich phase as secondary phases. The maximum value (3,172 V/cm)
and minimum value (977 V/cm) of breakdown field were obtained at sintering temperature of 850 and 900°C, respectively. The
nonlinear coefficient exhibited the highest value, reaching 30 at 925°C and the lowest value, reaching 4 at 850°C. The optimum
sintering temperature was 900°C, which exhibited not only high nonlinearity with 24 in nonlinear coefficient, but also the
high stability, with %ΔE1mA = −0.9% and %∆α = −12.5% for DC-accelerated aging stress of 0.85 E1mA/85°C/24 h. 相似文献
16.
Guo-Hua Chen 《Journal of Materials Science》2007,42(17):7239-7244
The effects of replacement of MgO by CaO on the sintering and crystallization behavior of MgO–Al2O3–SiO2 system glass-ceramics were investigated. The results show that with increasing CaO content, the glass transition temperature
firstly increased and then decreased, the melting temperature was lowered and the crystallization temperature of the glass-ceramics
shifted clearly towards higher temperatures. With the replacement of MgO by less than 3 wt.% CaO, the predominant crystalline
phase in the glass-ceramics fired at 900 °C was found to be α-cordierite and the secondary crystalline phase to be μ-cordierite.
When the replacement was increased to 10 wt.%, the predominant crystalline phase was found to be anorthite and the secondary
phase to be α-cordierite. Both thermal expansion coefficient (TCE) and dielectric constant of samples increases with the replacement
of MgO by CaO. The dielectric loss of sample with 5 wt.% CaO fired at 900 °C has the lowest value of 0.08%. Only the sample
containing 5 wt.% and10 wt.% CaO (abbreviated as sample C5 and C10) can be fully sintered before 900 °C. Therefore, a dense
and low dielectric loss glass-ceramic with predominant crystal phase of α-cordierite and some amount of anorthite was achieved
by using fine glass powders (D50 = 3 μm) fired at 875–900 °C. The as-sintered density approaches 98% theoretical density. The flexural strength of sample
C5 firstly increases and then decreases with sintering temperature, which closely corresponds to its relative density. The
TCE of sample C5 increases with increasing temperature. The dielectric property of sample C5 sintered at different temperatures
depends on not only its relative density but also its crystalline phases. The dense and crystallized glass-ceramic C5 exhibits
a low sintering temperature (≤900 °C), a fairly low dielectric constant (5.2–5.3), a low dielectric loss (≤10−3) at 1 MHz, a low TCE (4.0–4.25 × 10−6 K−1), very close to that of Si (∼3.5 × 10−6 K−1), and a higher flexural strength (≥134 MPa), suggesting that it would be a promising material in the electronic packaging
field. 相似文献
17.
The influence of sintering conditions on the microstructural features and impedance characteristics of the giant dielectric
constant material CaCu3Ti4O12 (CCTO) was investigated. The microstructure and impedance characteristics were found to be strongly dependent on the sintering
conditions. Sintering of the CCTO ceramics at elevated temperatures (>1100 °C) for prolonged durations resulted in the segregation
of Cu-rich phase, mostly confined to the surface, which was in concomitance with the appearance of the additional semicircle
at the low frequency end in Impedance (Z*) plots. The absence of this additional semicircle in the Cu-deficient CCTO ceramics
and the appearance of the same in Cu-rich CCTO ceramics that were deliberately fabricated corroborated the above observations.
Also, La2/3Cu3Ti4O12 (LCTO), a low dielectric constant member of CCTO family, which consisted of small grains without the segregation of Cu-rich
phase at the grain boundary, did not reveal the presence of additional semicircle in the Z*plots. 相似文献
18.
Oblique deposition and exposure to photons of energy greater than the bandgap have a marked effect on the structure and consequently
on electrical and optical properties of amorphous chalcogenides. This paper presents a detailed study of photoinduced effect
and oblique deposition effect on electrical and optical properties of a-GeSe2 films deposited at different angles (0°–80°). The indirect-optical bandgap energy (2.18 eV) was found to be independent of
angle of incidence. The spectral response of refractive index and extinction coefficient has been determined in the wavelength
range of 0.6–1 μm using the transmission spectra. Refractive index decreases with the increase in angle of incidence. The
value of refractive index was observed to be 2.28 for 0° and 2.00 for 80° films at 0.646 μm. An increase in bandgap was also
observed on exposure to the UV light for ∼120 min. The change in bandgap became more significant with the increase in angle
of incidence (∼ 2.3% for 0° and ∼10.6% for 80°). The temperature dependence of conductivity along with time dependence and
spectral response of photocurrent has also been investigated. 相似文献
19.
Gangqiang Zhu Xijin Huang Mirabbos Hojamberdiev Peng Liu Yun Liu Guoqiang Tan Jian-ping Zhou 《Journal of Materials Science》2011,46(3):700-706
In this work, self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) were applied to induce the nucleation and
growth of the antimony sulfide (Sb2S3) films on the functional ITO glass substrate at low temperature. The structure, morphology, and optical properties of the
Sb2S3 films were investigated by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, and UV–vis
spectroscopy. After thermal treatment at 200 °C for 1 h in air, the orthorhombic Sb2S3 was formed as a predominant phase in the deposited thin films. When the deposited films were thermally treated at 400 °C
for 1 h in air, the orthorhombic Sb2S3 was decomposed and a cubic Sb2O3 was formed. The optical band energies of the as-deposited and thermally treated Sb2S3 films at 200 °C for 1 h in air and nitrogen were found to be 2.05 eV, 1.77, and 1.76 eV, respectively. As chemical templates,
the OTS-functionalized SAMs played an important role in controlling the nucleation and growth of Sb2S3 films at low temperature. The results obtained from different preparation parameters applied in the present work will allow
controlling the growth of the Sb2S3 films with uniform surface. 相似文献
20.
Guo-hua Chen Jun-tao Liu Hua-rui Xu Chang-rong Zhou Min-hong Jiang Xin-yu Liu 《Journal of Materials Science: Materials in Electronics》2011,22(8):915-919
Ultrafine strontium barium niobate (Sr0.3Ba0.7Nb2O6, SBN30) powders were prepared by urea method starting from a precursor solution constituting of Sr (NO3)2, Ba (NO3)2, NbF5, urea and polyvinyl alcohol (PVA) as surfactant. Their structural behavior and morphology were examined by means of X-ray
diffractometry (XRD) and Scanning electron microscopy (SEM). The results showed that the SBN30 powders crystallized to a pure
tetragonal phase at annealing temperatures as low as 750 °C. The average particle size of SBN powders subjected to 750 °C
was of the order of 150–300 nm. With increasing calcination temperature,however, the average particle size of the calcined
powders increased. The SBN30 ceramic prepared from urea method can be sintered at temperature as low as 1,225 °C. The transition
temperature from the ferroelectric phase to the paraelectric phase and the relative dielectric permittivity of the SBN30 powder
were less than the corresponding values of the bulk ceramic. The permittivity and loss tangent (tan δ) at room temperature
(1 kHz) was found to be 930 and below 0.025. 相似文献