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1.
Kyung-Hoon Cho Chang-Hak Choi Joo-Young Choi Tae-Geun Seong Sahn Nahm Chong-Yun Kang Seok-Jin Yoon Jong-Hee Kim 《Journal of the European Ceramic Society》2010,30(2):513-516
The effect of oxygen partial pressure (OPP) on the leakage current density of Bi5Nb3O15 (B5N3) films grown on Pt electrodes was investigated. The leakage current density was very high for the film grown under a low OPP of 1.7 mTorr, but was significantly reduced by the subsequent annealing under a high oxygen pressure or for the film grown under high OPP of 5.1 mTorr. The variation of the leakage current density with OPP was explained by the number of oxygen vacancies, which produced electron trap sites at the interface between the Pt electrode and the B5N3 film. Schottky emission was postulated as the leakage current mechanism of the B5N3 films. The barrier height between the Pt electrode and the B5N3 film grown under a high OPP of 5.1 mTorr was approximately 1.55 eV, but decreased to 0.81 eV for the film grown under a low OPP of 1.7 mTorr due to the presence of the oxygen vacancy. 相似文献
2.
《Ceramics International》2017,43(8):6214-6220
CuxO thin films were deposited on glass and silicon substrates by High Power Impulse Magnetron Sputtering (HiPIMS) at room temperature from a metallic copper target. The influence of pulse off-time on the films’ structural, morphological and optoelectronic properties was investigated. It was found that the power intensity applied on the Cu target was strongly affected by pulse off-time, which had an important impact on the films’ composition. Upon increasing the pulse off-time from 500 μs to 3500 μs (pulse on-time fixed at 50 μs), the films’ crystallinity as well as transmittance in the visible region both ameliorate. Meanwhile, the conductivity type changed from n-type to p-type as the films’ composition changed. When the pulse off-time was fixed at 2000 μs, the optimal p-type conductivity of about 3 S × cm−1 was achieved, which is the highest p-type conductivity reported for Cu2O films in the last few years. The transition of the films’ conductivity type can be utilized for the fabrication of Cu2O-based p-n homojunction, and may also prove useful in developing other oxide films by using HiPIMS technology. 相似文献
3.
《Ceramics International》2017,43(2):2279-2287
We have investigated the characteristics of p-type Li-doped Cu2O (LCO) films grown by radio frequency magnetron sputtering to use as p-n heterojunction for flexible and semi-transparent piezoelectric nanogenerators (PENGs). Electrical, optical, morphological properties of the LCO films were examined as a function of Ar/O2 flow ratio as well as work function. The LCO films grown at Ar/O2 ratio of 20/4 sccm film showed a p-type behavior with resistivity of 2.12 Ω-cm, mobility of 0.364 cm2/V-s, and carrier concentration of 8.07×1019 cm-3. To overcome the piezoelectric potential screening effect of conventional ZnO-based PENGs, the p-type LCO layer was employed. Due to the enhanced piezoelectric potential coupled with the reduced total capacitance, the PENG with a p-LCO/n-ZnO heterojunction demonstrates the much higher output power up to ~52 μW than PENG only with ZnO layer (7 μW). The improved output power of PENGs indicates that sputtering of the p-type LCO layer on the n-type ZnO is the effective method to overcome the limit of the ZnO-based PENGs. 相似文献
4.
《Journal of the European Ceramic Society》1999,19(6-7):737-740
A series of doped Ruddlesden–Popper phases, of general formula Sr3Ti2-xMxO7-δ (M=Al, Ga, Co), were synthesized and their electrical conductivity characterized as a function of temperature and oxygen partial pressure. For fixed-valent dopants, p-type conductivity predominates at p(O2)> 10−5 atm, followed by a p(O2)-independent electrolytic regime, and n-type electronic conductivity at very low p(O2). The electrolytic regime exhibits activation energies in the range 1·7–1·8 eV. Doping with transition metals such as Co results in a very significant increase in total conductivity with a p-type conductivity at high p(O2). Furthermore, an apparent ionic regime at intermediate p(O2) is observed, characterized by high conductivity (> 10−2 S/cm at 700°C) and low activation energy (0·6 eV). This interpretation is consistent with iodometric measurements as interpreted by a defect chemical model. Other measurements are in progress to confirm this conclusion. 相似文献
5.
《Ceramics International》2016,42(13):14543-14547
Cu(In1−xGax)Se2 (CIGS) thin films were prepared by RF magnetron sputtering from a single quaternary target at multiple processing parameters. The structural, compositional, and electrical properties of the as-deposited films were systematically investigated by XRD, Raman, SEM, and Hall effects analysis. The results demonstrate that by adjusting the processing parameters, the CIGS thin films with a preferential orientation along the (112) direction which exhibited single chalcopyrite phase were obtained. The films deposited at relatively higher substrate temperature, sputtering power, and Ar pressure exhibited favorable stoichiometric ratio (Cu/(In+Ga):0.8–0.9 and Ga/(In+Ga):0.25–0.36) with grain size of about 1–1.5 µm, and desirable electrical properties with p-type carrier concentration of 1016−1017 cm−3 and carrier mobility of 10–60 cm2/Vs. The CIGS layers are expected to fabricate high efficiency thin film solar cells. 相似文献
6.
《Ceramics International》2016,42(12):13555-13561
In this article, we report a comparative study of the influence of pressure-assisted (1.72 MPa) versus ambient pressure thermal annealing on both ZnO thin films treated at 330 °C for 32 h. The effects of pressure on the structural, morphological, optical, and gas sensor properties of these thin films were investigated. The results show that partial preferential orientation of the wurtzite-structure ZnO thin films in the [002] or [101] planes is induced based on the thermal annealing conditions used (i.e., pressure assisted or ambient pressure). UV–vis absorption measurements revealed a negligible variation in the optical -band gap values for the both ZnO thin films. Consequently, it is deduced that the ZnO thin films exhibit different distortions of the tetrahedral [ZnO4] clusters, corresponding to different concentrations of deep and shallow level defects in both samples. This difference induced a variation of the interface/bulk-surface, which might be responsible for the enhanced optical and gas sensor properties of the pressure-assisted thermally annealed film. Additionally, pressure-assisted thermal annealing of the ZnO films improved the H2 sensitivity by a factor of two. 相似文献
7.
Seon Mi Kong Rong Fan Sung Hee Jung Chee Won Chung 《Journal of Industrial and Engineering Chemistry》2013,19(4):1320-1324
Cu(In1?xGax)Se2 (CIGS) thin films were prepared using a single quaternary target by RF magnetron sputtering. The effects of deposition parameters on the structural, compositional and electrical properties of the films were examined in order to develop the deposition process without post-deposition selenization. From X-ray diffraction analysis, as the substrate temperature and Ar pressure increased and RF power decreased, the crystallinity of the films improved. The scanning electron microscopy revealed that the grains became uniform and circular shape with columnar structure with increasing the substrate temperature and Ar pressure, and decreasing the RF power. The carrier concentration of CIGS films deposited at the substrate temperature of 500 °C was 2.1 × 1017 cm?3 and the resistivity was 27 Ω cm. At the substrate temperature above 500 °C, In and Se contents in CIGS films decreased due to the evaporation and it led to the deterioration of crystallinity. It was confirmed that CIGS thin films deposited at optimal condition had similar atomic ratio to the target value even without post-deposition selenization process. 相似文献
8.
Highly nanocrystalline ZnO modified methyl glycol thin films have been deposited on a p-type silicon substrate via the sol–gel spin coating manner. The morphology of the as-deposited film was scrutinized using scanning electron microscopy. I–V characteristics of the as-prepared ZnO film under vacuum and in open air were monitored. The results showed that the ZnO films have a barrier height of 0.38 eV under vacuum and 0.62 eV in open air. The Schottky barrier height between ZnO grains was determined for different reducing gases. The ZnO film showed high sensitivity to H2S gas compared with other reducing gases due to the reduction of barrier height between ZnO grains. The as-prepared ZnO film was annealed at four different temperatures. X-ray diffraction manifested that the wurtzite hexagonal structure of ZnO deviated from ideality at annealing temperature greater than 650 °C. The barrier height of ZnO film decreased due to the increase of annealing temperature up to 650 °C and then decreased. The results also confirmed that the change of barrier height strongly affected the sensitivity of ZnO film. 相似文献
9.
《Ceramics International》2016,42(5):5762-5765
Crystalline CaLa4(Zr0.05Ti0.95)4O15 thin films deposited on n-type Si substrates byRF magnetron sputtering at a fixed RF power of 100 W, an Ar/O2 ratio of 100/0, an operating pressure of 3 mTorr, and different substrate temperatures were investigated. The surface structural and morphological characteristics analyzed by X-ray diffraction and atomic force microscopy were sensitive to the deposition conditions, such as the substrate temperature. The diffraction pattern showed that the deposited films had a polycrystalline microstructure. As the substrate temperature increased, the quality of the CaLa4(Zr0.05Ti0.95)4O15 thin films improved, and the kinetic energies of the sputtered atoms increased, resulting in a structural improvement of the deposited CaLa4(Zr0.05Ti0.95)4O15 thin films. A high dielectric constant of 16.7 (f=1 MHz), a dissipation factor of 0.19 (f=1 MHz), and a low leakage current density of 3.18×10−7 A/cm2 at an electrical field of 50 kV/cm were obtained for the prepared films. 相似文献
10.
《Journal of the European Ceramic Society》1999,19(6-7):687-691
High temperature current-voltage characteristics were investigated with a Nb doped SrTiO3 (Nb–STO) single crystal. The conductivity of the 0·5 wt% Nb doped SrTiO3 showed high n-type conductivity with a negative temperature coefficient. The Pt/Nb–STO interface freshly prepared by laser ablation at 973 K in high vacuum condition showed ohmic behavior. However, it turned to show a Schottky type non linearity when annealed in oxygen gas at temperatures higher than 773 K. The I–V curve in the forward direction was well fitted with the equation based on the thermionic emission model. At high temperatures, the I–V behavior was dependent on the oxygen partial pressure. The lower oxygen partial pressure resulted in a lower barrier height. The change in the I–V curve with oxygen potential was almost reversible at 873 K, and was frozen below 673 K. Those phenomena suggested that the Schottky barrier formation at the Pt/STO interface has a strong relation with the oxygen transport in Nb–STO. 相似文献
11.
《Journal of the European Ceramic Society》2007,27(13-15):3815-3818
ZnO thin films were successfully deposited on SiO2/Si substrate by sol–gel technology. The as-grown ZnO thin films were annealed under an ambient atmosphere from 600 to 900 °C by rapid thermal annealing (RTA) process. X-ray diffraction and scanning electron microscopy analyses reveal the physical structures of ZnO thin films. From PL measurement, two ultraviolet (UV) luminescence bands were obtained at 375 and 380 nm, and the intensity became stronger when the annealing temperature was increased. The strongest UV light emission appeared at annealing temperature of 900 °C. The chemical bonding state in ZnO films was investigated by using X-ray photoelectron spectrum. The mechanism of UV emission was also discussed. 相似文献
12.
Novel chemo-resistive gas sensors based on reduced graphite oxide (rGO) thin films have been fabricated and evaluated for hydrogen detection. The rGO materials were thermally treated at various conditions and analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy techniques to investigate the change of functional groups. The semiconductor type of the rGOs treated at different conditions were checked by flowing hydrogen gas at 20 cm3/min (sccm) under 10 Torr partial pressure. The rGOs treated at 70 °C in atmosphere (rGO070a), 200 °C in a vacuum (rGO200v), and 500 °C in a vacuum (rGO500v) exhibited n-type, ambipolar, and p-type behavior, respectively. The rGO500v was adopted as active sensing element without any rare metal decoration, and its sensing response to hydrogen was studied by using air as carrier gas. The rGO500v exhibited good sensitivity (~4.5%), response time (~20 s), and recovery time (~10 s) to 160 ppm hydrogen gas at room temperature. 相似文献
13.
《Ceramics International》2017,43(12):8831-8838
The effect of deposition conditions on the photocatalytic activity of TiO2-ZnO thin films was studied. By using a (Ti)90-(Zn)10 alloy target, the samples were deposited at room temperature on glass substrates by dc reactive magnetron sputtering and post-annealed in air at 500 °C. The dependence of the physical properties of the films on the O2/Ar gas ratio and the deposition working pressure was investigated. XRD patterns showed mainly the formation of the anatase phase of TiO2. Optical absorption measurements exhibited a blue shift of the band-gap energy with increasing working pressure. XPS spectra indicated the presence of the Ti4+ and Zn2+ oxidation states, which correspond to TiO2 and ZnO, respectively. The chemical state of Ti was further analyzed by means of the modified Auger parameter, α’, which gave a value of ca. 873 eV. The photocatalytic property of the films was assessed by the degradation of a methylene blue aqueous solution. The maximum photocatalytic performance was observed for the samples deposited at 3.0 mTorr and O2/Ar gas ratio of 10/90. These results are explained in terms of the structural, optical, and morphological properties of the films. 相似文献
14.
Nasrin Talebian Mohammad Reza Nilforoushan Zahra Salehi 《Ceramics International》2012,38(6):4623-4630
In the present study, the effects of the heterojunctions on the optical and structural characteristics and the resulting photocatalytic properties of multilayered ZnO-based thin films were investigated. The junctions were composed of semiconducting ZnO nano-porous films coated on the In2O3 and SnO2 counterpart layers. The multilayered ZnO films based on the triple-layered Ag-doped indium oxide (AIO)/tin oxide (TO)/zinc oxide (ZnO), indium oxide (IO)/Ag-doped tin oxide (ATO)/zinc oxide (ZnO), indium oxide (IO)/tin oxide (TO)/zinc oxide (ZnO) and tin oxide (TO)/indium oxide (IO)/zinc oxide (ZnO) have been fabricated by subsequent sol–gel dip coating. Their structural and optical properties combined with photocatalytic characteristics were examined toward degradation of Solantine Brown BRL (C.I. Direct Brown), an azo dye using in Iran textile industries as organic model under UV light irradiation. Effects of operational parameters such as initial concentration of azo dye, irradiation time, solution pH, absence and presence of Ag doping and consequent of sublayers on the photodegradation efficiencies of ZnO nultilayered thin films were also investigated and optimum conditions were established. It was found that the photocatalytic degradation of azo dye on the composite films followed pseudo-first order kinetics. Photocatalytic activity of AIO/TO/ZnO interface composite film was higher compared with other films and the following order was observed for films activities: AIO/TO/ZnO > IO/TO/ZnO > ATO/IO/ZnO > TO/IO/ZnO. Differences in the film efficiencies can be attributed to differences in crystallinity, interfacial lattice mismatch, and surface morphology. Besides, the presence of Ag doping between layers that may act as trap for electrons generated in the ZnO over layer thus preventing electron–hole recombination. 相似文献
15.
G. Balakrishnan S. Tripura Sundari R. Ramaseshan R. Thirumurugesan E. Mohandas D. Sastikumar P. Kuppusami T.G. Kim J.I. Song 《Ceramics International》2013,39(8):9017-9023
Aluminum oxide (Al2O3) thin films were deposited on silicon (100) and quartz substrates by pulsed laser deposition (PLD) at an optimized oxygen partial pressure of 3.0×10?3 mbar in the substrate temperatures range 300–973 K. The films were characterized by X-ray diffraction, transmission electron microscopy, atomic force microscopy, spectroscopic ellipsometry, UV–visible spectroscopy and nanoindentation. The X-ray diffraction studies showed that the films deposited at low substrate temperatures (300–673 K) were amorphous Al2O3, whereas those deposited at higher temperatures (≥773 K) were polycrystalline cubic γ-Al2O3. The transmission electron microscopy studies of the film prepared at 673 K, showed diffuse ring pattern indicating the amorphous nature of Al2O3. The surface morphology of the films was examined by atomic force microscopy showing dense and uniform nanostructures with increased surface roughness from 0.3 to 2.3 nm with increasing substrate temperature. The optical studies were carried out by ellipsometry in the energy range 1.5–5.5 eV and revealed that the refractive index increased from 1.69 to 1.75 (λ=632.8 nm) with increasing substrate temperature. The UV–visible spectroscopy analysis indicated higher transmittance (>80%) for all the films. Nanoindentation studies revealed the hardness values of 20.8 and 24.7 GPa for the films prepared at 300 K and 973 K respectively. 相似文献
16.
《Ceramics International》2017,43(2):1802-1808
The SnO thin films were deposited at low RF power densities by RF magnetron sputtering. According to XRD and XPS analyses, the SnO thin film comprised nanocrystalline orthorhombic SnO with a (110) orientation. Reducing RF power density resulted in better nanocrystallinity, changing hydrophobicity to hydrophilicity, and increasing the optical transmission in the UV–vis–NIR region. After annealing, the SnO thin film favored p-type conductivity and hydrophilicity. As the annealing temperature increased, the coexistence of nanocrystalline orthorhombic SnO and tetragonal SnO2 in the film clearly increased the optical transmission in the ultraviolet region. The SnO thin films after annealing at 500 ℃ in vacuum and N2 (200 sccm) exhibited a higher hole mobility and a better optical selection in the ultraviolet region, respectively. 相似文献
17.
《Diamond and Related Materials》2000,9(3-6):654-657
Hydrogenated amorphous carbon (a-C:H) films have been deposited from acetylene gas in a microwave electron cyclotron resonance (ECR) plasma reactor. The films were deposited at a pressure of 0.2 mTorr and at radio frequency (r.f.) induced substrate biases from 80–300 V. Selected film properties, including optical bandgap and bonded hydrogen content, were measured. At r.f. induced biases from 150 to 300 V, corresponding to ion energies for C2H2+ of approximately 150–300 eV, the hydrogen content remains constant and the optical bandgap peaks at a bias of 200 V, or approximately 100 eV per carbon in the C2H2+ ions. This ECR system result is in agreement with those observed by other researchers using different deposition methods where an optical bandgap maximum and an sp3 maximum occurs at ion energies of 90–100 eV per carbon atom. The discharge properties measured include a partial pressure analysis of the residual exit gas and the substrate current density. 相似文献
18.
Benjamin W. Schmidt Bridget R. Rogers William J. Sweet Cameron K. Gren Timothy P. Hanusa 《Journal of the European Ceramic Society》2010,30(11):2301-2304
Results from an investigation of chemical vapor deposition of aluminum oxide from dimethylaluminum isopropoxide as a function of deposition temperature at a total pressure of 1.5 mTorr are reported. An effective activation energy for this process was determined to be 85 kJ/mol. Deposited films were shown to be oxygen-rich compared to Al2O3, with higher deposition temperatures resulting in films closer to stoichiometric alumina. Carbon content of the films increased from approximately 1 to 8 at.% at substrate temperatures of 417 and 659 °C, respectively. 相似文献
19.
Chang-Hak Choi Joo-Young Choi Kyung-Hoon Cho Myong-Jae Yoo Jae-Hong Choi Sahn Nahm Chong-Yun Kang Seok-Jin Yoon Jong-Hee Kim 《Journal of the European Ceramic Society》2010,30(2):517-520
Bi6Ti5TeO22 (BTT) thin films were grown on a Pt/Ti/SiO2/Si(1 0 0) substrate under various conditions and the valence state of the Te ion was investigated. For the BTT films grown at 300 °C, most of the Te ions existed as Te4+ ions. However, for the 10 mol% Mn-added BTT films grown at 300 °C, Te6+ ions were found even in the film grown under low oxygen partial pressure (OPP) and their number increased with increasing OPP. This increase was attributed to the presence of Mn2+ ions, which assisted the transition of Te4+ ions to Te6+ ions in order to maintain the charge balance of the Ti4+ sites. Furthermore, in the films grown at 300 °C under a high OPP of 80.0 Pa and subsequently annealed at 600 °C under a high oxygen pressure of 101 kPa, most of the Te ions existed as Te6+ ions. However, for the film grown at 300 °C under low OPP, even though the film was annealed under a high oxygen pressure of 101 kPa, only a few of Te6+ ions were formed, whereas most of Te ions remained as the Te4+ ions. 相似文献
20.
《Carbon》2013
We prepared and characterized flexible thermoelectric (TE) materials based on thin films of single-walled carbon nanotube (SWCNT) composites with polyvinylalcohol. While pristine SWCNTs incorporated in a polymer matrix generated a p-type TE material, chemical functionalization of SWCNTs by using polyethyleneimine produced an n-type TE material. TE modules made of both p- and n-type composite were fabricated to demonstrate TE voltage and power generation. A single p–n junction made of two composite strips containing 20 wt.% of SWCNTs generated a high TE voltage of 92 μV per 1 K temperature gradient (ΔT). By combining five electrically connected p–n junctions an output voltage of 25 mV was obtained upon the applying ΔT = 50 K. Furthermore, this module generated a power of 4.5 nW when a load resistance matched the internal module resistance of 30 kΩ. These promising results show the potential of TE energy conversion provided by the SWCNT composite films connected in scalable modules for applications that require light weight and mechanical flexibility. 相似文献