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1.
Mo-Al-N films were deposited by a dc reactive magnetron sputtering technique. The effects of N2 partial pressure, substrate temperature, and aluminum content on the phase composition, microstructure, hardness and oxidation resistance of the films were studied. The MoAlN films as prepared are fcc Mo2N structure where partial Mo sites were substituted by Al, and the grain size of the crystallites increased from 8 to 30 nm when the Al concentration was increased from 6% to 33%. In the Mo0.94Al0.06N film, the hardness can reach 29 GPa, which is much higher than that in binary Mo-N systems. The oxidation resistance temperature of Mo-Al-N film with an Al content of 6% was higher than that of Mo-N films, and with further addition of Al content, the oxidation resistance temperature increased slightly. 相似文献
2.
Optical and structural characteristics of ZnO thin films grown by rf magnetron sputtering 总被引:1,自引:0,他引:1
S. Mandal 《Materials Research Bulletin》2008,43(2):244-250
Nanostructured ZnO thin films on Pyrex glass substrates were deposited by rf magnetron sputtering at different substrate temperatures. Structural features and surface morphology were studied by X-ray diffraction and atomic force microscopy analyses. Films were found to be transparent in the visible range above 400 nm, having transparency above 90%. Sharp ultraviolet absorption edges around 370 nm were used to extract the optical band gap for samples of different particle sizes. Optical band gap energy for the films varied from 3.24 to 3.32 eV and the electronic transition was of the direct in nature. A correlation of the band gap of nanocrystalline ZnO films with particle size and strain was discussed. Photoluminescence emission in UV range, which is due to near band edge emission is more intense in comparison with the green band emission (due to defect state) was observed in all samples, indicating a good optical quality of the deposited films. 相似文献
3.
Investigation of size dependent structural and optical properties of thin films of CdSe quantum dots
Cadmium selenide (CdSe) quantum dots were grown on indium tin oxide substrate using wet chemical technique for possible application as light emitting devices. The structural, morphological and luminescence properties of the as deposited thin films of CdSe Q-dot have been investigated, using X-ray diffraction, transmission electron microscopy, atomic force microscopy and optical and luminescence spectroscopy. The quantum dots have been shown to deposit in an organized array on ITO/glass substrate. The as grown Q-dots exhibited size dependent blue shift in the absorption edge. The effect of quantum confinement also manifested as a blue shift of photoluminescence emission. It is shown that the nanocrystalline CdSe exhibits intense photoluminescence as compared to the large grained polycrystalline CdSe films. 相似文献
4.
In this work, we report the preparation of lanthanum-modified lead zirconate titanate (PLZT) thin films by RF magnetron sputtering on platinized silicon (Pt/Ti/SiO2/Si) substrate. Sputtering was done in pure argon at 100 W RF power without external substrate heating. X-ray diffraction studies were performed on the films to study the effect of post-deposition furnace annealing temperature and time on the perovskite phase formation of PLZT. Annealing at 650 °C for 2 h was found to be optimum for the preparation of PLZT films in pure perovskite phase. The effect of different annealing conditions on surface morphology of the films was examined using AFM. The dielectric, ferroelectric and electrical properties of these films were also investigated in detail as a function of different annealing conditions. The pure perovskite film exhibits better properties than the other films which have some fraction of unwanted pyrochlore phase. The remanent polarization for pure perovskite film was found to be ∼29 μC/cm2 which is almost double compared to the films having mixed phases. The dc resistivity of the pure perovskite film was found to be 7.7 × 1010 Ω cm at the electric field of ∼80 kV/cm. 相似文献
5.
We report the resistive switching (RS) characteristics of tungsten nitride (WNx) thin films with excellent complementary metal-oxide-semiconductor (CMOS) compatibility. A Ti/WNx/Pt memory cell clearly shows bipolar RS behaviors at a low voltage of approximately ±2.2 V. The dominant conduction mechanisms at low and high resistance states were verified by Ohmic behavior and trap-controlled space-charge-limited conduction, respectively. A conducting filament model by a redox reaction explains the RS behavior in WNx films. We also demonstrate the memory characteristics during pulse operation, including a high endurance over >105 cycles and a long retention time of >105 s. 相似文献
6.
Effect of oxygen partial pressure on the structural and optical properties of sputter deposited ZnO nanocrystalline thin films 总被引:1,自引:0,他引:1
We report the influence of deposition parameters such as oxygen partial pressure and overall sputtering pressure on the structural and optical properties of the as-grown ZnO nanocrystalline thin films. The films were prepared by dc magnetron sputtering using Zn metal target under two different argon and oxygen ratios at various sputtering pressures. Microstructure of the films was investigated using X-ray diffraction and scanning electron microscopy. Optical properties of the films were examined using UV-Visible spectrophotometer. The results show that the films deposited at low oxygen partial pressure (10%) contain mixed phase (Zn and ZnO) and are randomly oriented while the films deposited at higher oxygen partial pressure (30%) are single phase (ZnO) and highly oriented along the c-axis. We found that the oxygen partial pressure and the sputtering pressure are complementary to each other. The optical band gap calculated from Tauc's relation and the particle size calculation were in agreement with each other. 相似文献
7.
La0.67Ca0.33MnO3 (LCMO) thin films were successfully fabricated by a DC magnetron sputtering technique on Si (1 0 0) substrates from chemically synthesized compacted powders. Powders of proper stochiometry composites were synthesized by a novel chemical technique [D.R. Sahu, B.K. Roul, P. Pramanik, J.L. Huang, Physica B 369 (2005) 209] and were found to be nanosized (≈40-50 nm). The sinterability of the powders were improved significantly due to their large surface area with a reduction of sintering temperature (up to 500 °C) as compared to the powders prepared by other solid-state reaction route. Bulk LCMO targets were prepared and preliminary structural and magnetic properties of target were investigated for colossal magnetoresistance (CMR) properties. Films deposition parameters like DC power, gas flow rate, deposition time, etc., were critically optimized to achieve desired thickness of film using above LCMO target by DC magnetron sputtering. LCMO films fabricated on Si (1 0 0) substrates showed enhanced magnetoresistance (MR) at low temperature. Maximum MR of about 1000% was observed at 100 K. Paramagnetic to ferromagnetic transitions were observed in films below room temperature and were found at approximately 240 K. However, as compared to bulk target prepared by a chemical route, it was found that Curie temperature (Tc) and MR response of bulk target were higher than the thin films. Preliminary point chemical analysis revealed the deficiency of Ca2+ ions in CMR films. 相似文献
8.
M.K. Suresh H. Sreemoolanadhan Annamma John P.R.S. Wariar 《Materials Research Bulletin》2010,45(7):761-3095
Nanocrystalline magnesium titanate was synthesized through an auto-ignited combustion method. The phase purity of the powder was examined using X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy and Raman spectroscopy. The transmission electron microscopy study showed that the particle size of the as-prepared powder was in between 20 and 40 nm. The nanopowder could be sintered to 98% of the theoretical density at 1200 °C for 3 h. The microstructure of the sintered surface was examined using scanning electron microscopy. The dielectric constant (?r) of 16.7 and loss factor (tan δ) of the order of 10−4 were obtained at 5 MHz when measured using LCR meter. The quality factor (Qu × f) 73,700 and temperature coefficient of resonant frequency (τf) −44.3 ppm/°C, at 6.5 GHz are the best reported values for sintered pellets obtained from phase pure nanocrystalline MgTiO3 powder. 相似文献
9.
L.J. Li H. Deng L.P. Dai J.J. Chen Q.L. Yuan Y. Li 《Materials Research Bulletin》2008,43(6):1456-1462
Al-doped ZnO films were deposited by RF magnetron sputtering. From the X-ray diffraction and scanning electron spectrometer studies, wurtzite structure with (0 0 2) orientation ZnO thin films were obtained at Al concentration below 15 atomic percent (at.%). As the Al concentration above 15 at.%, the thin films did not fully crystallize. Two new emission peaks occurred at 351 nm and 313 nm when the Al doping above 15 at.% from the photoluminescence spectrum, and the peaks shift towards the shorter wavelengths with increasing the Al concentration. X-ray photonic spectra of O 1s conformed the amount of oxygen captured by Al3+ increasing as the Al3+ concentration increasing due to the dominant Al3+ possess high charge in competition with Zn2+ in the matrix of ZnO. 相似文献
10.
A.S. Khomane 《Materials Research Bulletin》2011,46(10):1600-1603
Synthesis of cadmium selenide thin films by CBD method has been presented. The deposited film samples were subjected to XRD, SEM, UV-vis-NIR and TEP characterization. X-ray diffraction analysis showed that CdSe film sample crystallized in zinc blende or cubic phase structure. SEM studies reveal that the grains are spherical in shape and uniformly distributed all over the surface of the substrates. The optical band gap energy of as deposited film sample was found to be in the order of 1.8 eV. The electrical conductivity of the film sample was found to be 10−6 (Ω cm)−1 with n-type of conduction mechanism. 相似文献
11.
Structural and optical studies of yttrium oxide nanoparticles synthesized by co-precipitation method
Ramasamy Srinivasan 《Materials Research Bulletin》2010,45(9):1165-749
Yttrium oxide (yttria) nanoparticles were successfully synthesized by co-precipitation method. As-synthesized and annealed powders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), UV-visible (UV-vis), photoluminescence (PL) spectra and Fourier transform infrared spectrometer (FTIR). The XRD results show that the as-prepared sample has mixed phase of Y(OH)3 and yttria (Y2O3). However, cubic yttrium oxide phase alone is found for annealed samples. The strain values are calculated from Williamson-Hall (W-H) plot for annealed samples. SEM and TEM micrographs show that the samples are composed of aggregated nanoparticles with different shapes and sizes. From the UV-vis spectra, it is found that the position of the absorption peak is shifted towards the lower wavelength side when particle size decreases. In the PL spectra, the broad emission bands are observed between 340 and 380 nm and the presence of metal oxide is confirmed by FTIR spectra. 相似文献
12.
Ru-Bing Zhang 《Materials Research Bulletin》2005,40(9):1584-1590
Fe-doped titania films are prepared by RF magnetron sputtering on Si wafers with specifically designed TiO2 targets containing different amounts of Fe2O3 powder as a dopant source. The physical properties of the films are investigated in terms of the preparation conditions, such as Fe2O3 content in the target, RF power, substrate temperature and working pressure. The films show the typical crystallographic orientation. The growth rate increases with increasing RF power, but decreases with working pressure. Films with 40 nm and the transmittance over 90% at the visible region are prepared by using Fe-doped titania target. 相似文献
13.
Ultrathin films of nanocrystalline α-Fe2O3 have been deposited on glass substrates from an inorganic precursor, iron nitropruside. This is a novel route of synthesis for iron oxide thin films on glass substrates, by annealing the precursor thin film in air at 650 °C for 15 min. The films were characterized using TG-DTA analysis, X-ray diffraction, UV-visible, FESEM, AFM and Raman measurements. X-ray diffraction and Raman analyses revealed that the deposited films contain α-phase of Fe2O3 (hematite). The synthetic route described here provides a very simple and cost-effective method to deposit α-Fe2O3 thin films on glass substrates with band gap energy of about 2.75 eV. The deposited films were found to show catalytic effect for the photo-degradation of phenol. 相似文献
14.
NdOHCO3 dodecahedral microcrystals with an orthorhombic structure have been successfully synthesized by the hydrothermal method used urea as the precipitator. Experimental parameters, such as the reaction temperature, the reaction time, and the molar ratio of the starting reagents were examined. The as-synthesized products were characterized by powder X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence. The possible growth process of NdOHCO3 dodecahedral microcrystals was discussed. 相似文献
15.
A facile one-pot synthesis of ZnS hollow spheres has been carried out via a chemical transformation induced inside-out Ostwald ripening process from a single source precursor. The size and shell thickness of the ZnS hollow spheres can be controlled by adjusting the reaction temperature and reaction time, respectively. Photoluminescence spectra show a dominant emission peak at 470 nm accompanied by several weaker peaks. UV-vis measurement reveals that the obtained ZnS hollow spheres exhibit “hollow effect”. The formation process of ZnS hollow spheres has been discussed. 相似文献
16.
An in situ optical microspectroscopy investigation of the growth and oxidation of silver nanoparticles (NPs) embedded in SiO2 thin films deposited on soda-lime glass has been conducted in real time during thermal processing in air. Variation of Ag NP size is followed by fitting of surface plasmon resonance (SPR) with spectra calculated by Mie theory, and analysed concurrently with the time evolution of SPR peak intensity. The NP transformations appeared to be temperature and time dependent. Silver NPs were indicated to grow at relatively high temperatures (e.g. 600 °C) due to Ostwald ripening, followed by a plateau and a gradual decrease in size resulting in SPR vanishing due to oxidation. The three phases were well separated in time. Oxidation appeared dominant at lower temperatures (e.g. 400 °C) as indicated by a continuous decrease in Ag particle size. The product of Ag NP oxidation was revealed by photoluminescence spectroscopy as single Ag+ ions. Furthermore, the data indicated that: (i) Ag+ ions are formed during heat treatment under an Ag/Ag+ redox equilibrium; (ii) the ions diffuse from the SiO2 matrix towards the soda-lime substrate where they stabilize; and (iii) the continuous removal of these ions from the matrix is necessary in order for the equilibrium to be displaced towards oxidation. 相似文献
17.
《Materials Research Bulletin》2002,37(10):1749-1754
The growth of manganese(II) sulfide films by radiofrequency sputtering are shown for the first time. Polycrystalline, nearly stoichiometric films of the metastable hexagonal γ-MnS phase were obtained when the substrate temperature was approximately 26°C. For higher substrate temperatures, 120 and 180°C, the films were amorphous and sulfur deficient. The sulfur loss is substrate-temperature dependant. This behavior is discussed in terms of the dissociation of the MnS molecules during the sputtering process and the phase diagram of sulfur. An analysis of the optical transmission spectrum of the γ-MnS films allowed us to estimate their index of refraction in the non-absorbing region of the spectrum and the electronic band gap in the high absorbance region, obtaining an Eg value of 3.47±0.01 eV at room temperature. 相似文献
18.
《Materials Research Bulletin》2013,48(11):4444-4448
Nanocrystalline ɛ-Fe3N and Co4N nitride phases are synthesized first time by using tris(1,2-diaminoethane)iron(II) chloride and tris(1,2-diaminoethane)cobalt(III) chloride precursors, respectively. To prepare ɛ-Fe3N and Co4N nitride phases, the synthesized precursors were mixed with urea in 1:12 ratio and heat treated at various temperatures in the range of 450–900 °C under the ultrapure nitrogen gas atmosphere. The precursors are confirmed by FT-IR study. The ɛ-Fe3N phase crystallizes in hexagonal structure with unit cell parameters, a = 4.76 Å and c = 4.41 Å. The Co4N phase crystallizes in face centred cubic (fcc) structure with unit cell parameters, a = 3.55 Å. The estimated crystallite size for ɛ-Fe3N and Co4N phases are 29 nm and 22 nm, respectively. The scanning electron microscopy (SEM) studies confirm the nanocrystalline nature of the materials. The values of saturation magnetization for ɛ-Fe3N and Co4N phases are found to be 28.1 emu/g and 123.6 emu/g, respectively. The reduction of magnetic moments in ultrafine materials compared to bulk materials have been explained by spin pairing effect, lattice expansion, superparamagnetic behaviour and canted spin structures at the surface of the particles. 相似文献
19.
Structural and microstructural analyses of nanocrystalline titania thin films prepared by pulsed laser deposition have been carried out. At lower oxygen partial pressures (≤10−4 mbar), rutile films were formed, whereas at 1.2 × 10−3 mbar of oxygen partial pressure, the thin films contained both rutile and anatase phases. At 0.04 and 0.05 mbar of oxygen partial pressure, the film was purely anatase. Addition of oxygen has also shown a profound influence on the surface morphology of the as deposited titania films. Modified Rietveld method has been used to determine crystallite size, root mean square strain and fractional coordinates of oxygen of the anatase films. The influence of crystallite size and strain on the rutile to anatase phase transition is investigated. 相似文献
20.
Reza Keshavarzi Majid Moghadam Shahram Tangestaninejad Hamid Reza Fallah Hamed Reza Modayemzadeh 《Materials Research Bulletin》2011,46(4):615-620
In this work, the preparation of In2O3-ZnO thin films by electron beam evaporation technique on glass substrates is reported. Optical and electrical properties of these films were investigated. The effect of dopant amount and annealing temperature on the optical and electrical properties of In2O3-ZnO thin films was also studied. Different amount of ZnO was used as dopant and the films were annealed at different temperature. The results showed that the most crystalline, transparent and uniform films with lowest resistivity were obtained using 25 wt% of ZnO annealed at 500 °C. 相似文献