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1.
Metal-organic chemical vapour deposition (MOCVD) of various phases in PrOx system has been studied in relation with deposition temperature (450–750 °C) and oxygen partial pressure (0.027–100 Pa or 0.2–750 mTorr). Depositions were carried out by pulsed liquid injection MOCVD using Pr(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) precursor dissolved in toluene or monoglyme. By varying deposition temperature and oxygen partial pressure amorphous films or various crystalline PrOx phases (Pr2O3, Pr7O12, Pr6O11) and their mixtures can be grown. The pure crystalline Pr2O3 phase grows only in a narrow range of partial oxygen pressure and temperature, while high oxygen pressure (40–100 Pa) always leads to the most stable Pr6O11 phase. The influence of annealing under vacuum at 750 °C on film phase composition was also studied. Near 90% step coverage conformity was achieved for PrOx films on structured silicon substrates with aspect ratio 1:10. In air degradation of Pr2O3 films with transformation to Pr(OH)3 was observed in contrast to Pr6O11 films.  相似文献   

2.
A series of 0.2–0.6 μm thick SnOx films were deposited onto borosilicate and sodalime silica glass substrates by atmospheric plasma discharge chemical vapor deposition at 80 °C. SnOx films deposited from monobutyltin trichloride contained a large percentage of SnCl2:2H2O, and therefore were partially soluble in water. SnOx coatings deposited from tetrabutyltin were not soluble in water or organic solvents, had good adhesion even at growth rates as high as 2.3 nm/s, had high transparency of  90% and electrical resistivity of 107 Ω cm. As-grown tin oxide coatings were amorphous with a small concentration of SnO2, SnO and Sn crystalline phases as determined by grazing angle X-ray diffraction and X-ray photoelectron spectroscopy measurements. Upon annealing in air at 600 °C the resistivity of SnOx films decreased to 5–7 Ω cm. Furthermore, optical and X-ray measurements indicated that SnOx was converted into SnO2 (cassiterite) with a direct band gap of 3.66 eV. Annealing of as-grown SnOx films in vacuum at 340 °C led to formation of the p-type conductor SnO/SnOx. The indirect band gap of SnO was calculated from the optical spectra to be 0.3 eV.  相似文献   

3.
Transparent conducting fluorine-doped tin oxide (SnO2:F) films have been deposited on glass substrates by pulsed laser deposition. The structural, electrical and optical properties of the SnO2:F films have been investigated as a function of F-doping level and substrate deposition temperature. The optimum target composition for high conductivity was found to be 10 wt.% SnF2 + 90 wt.% SnO2. Under optimized deposition conditions (Ts = 300 °C, and 7.33 Pa of O2), electrical resistivity of 5 × 10− 4 Ω-cm, sheet resistance of 12.5 Ω/□, average optical transmittance of 87% in the visible range, and optical band-gap of 4.25 eV were obtained for 400 nm thick SnO2:F films. Atomic force microscopy measurements for these SnO2:F films indicated that their root-mean-square surface roughness ( 6 Å) was superior to that of commercially available chemical vapor deposited SnO2:F films ( 85 Å).  相似文献   

4.
The deposition behavior of silicon in hot wire chemical vapor deposition was investigated, focusing on the generation of negatively charged species in the gas phase using a gas mixture of 20% SiH4 and 80% H2 at a 450 °C substrate temperature under a working pressure of 66.7 Pa. A negative current of 6–21 µA/cm2 was measured on the substrate at all processing conditions, and its absolute value increased with increasing wire temperature in the range of 1400 °C–1900 °C. The surface roughness of the films deposited on the silicon wafers increased with increasing wire temperature in the range of 1510 °C–1800 °C. The film growth rate on the positively biased substrates (+ 100 V, + 200 V) was higher than that on the neutral (0 V) and negatively biased substrates (− 100 V, − 200 V, − 300 V). These results indicate that the negatively charged species are generated in the gas phase and contribute to deposition. The surface roughness evolved during deposition was attributed to the electrostatic interaction between these negatively charged species and the negatively charged growing surface.  相似文献   

5.
HfO2 thin films with columnar microstructure were deposited directly on ZnS substrates by electron beam evaporation process. SiO2 thin films, deposited by reactive magnetron sputtering, were used as buffer layers, HfO2 thin films of granular microstructure were obtained on SiO2 interlayer by this process. X-ray diffraction patterns demonstrate that the as-deposited HfO2 films are in an amorphous-like state with small amount of crystalline phase while the HfO2 films annealed at 450 °C in O2 for 30 min and in Ar for 150 min underwent a phase transformation from amorphous-like to monoclinic phase. Antireflection effect in certain infrared wave band, such as 3–6 μm, 4–12 μm, 4–8 μm and 3–10 μm, can be observed, which was dependent on the thickness of thin films. The cross-sectional images of HfO2 films, obtained by field emission scanning electron microscopy, revealed that there was no distinct morphological change upon annealing.  相似文献   

6.
An all alkoxide based sol–gel route was investigated for preparation of epitaxial La0.5Sr0.5CoO3 (LSCO) films on 100 SrTiO3 (STO) substrates. Films with 20–30 to 80–100 nm thickness were prepared by spin-coating 0.2–0.6 M (metal) solutions on the STO substrates and heat treatment to 800 °C at 2 °C min− 1, 30 min, in air. The films were epitaxial with a cube-on-cube alignment and the LSCO cell was strained to match the STO substrate of 3.905 Å closely; a and b = 3.894 Å and 3.897 Å for the 20–30 and 80–100 nm films, respectively. The c-axis was compressed to 3.789 Å and 3.782 Å for the 20–30 and 80–100 nm films, respectively, which resulted in an almost unchanged cell volume as compared to polycrystalline film and nano-phase powders prepared in the same way. The SEM study showed mainly very smooth, featureless surfaces, but also some defects. A film prepared in the same way on an -Al2O3 substrate was dense and polycrystalline with crystallite sizes in the range 10–50 nm and gave cubic cell dimensions of ac = 3.825 Å. The conductivity of the ca 30–40 nm thick polycrystalline film was 1.7 mΩcm, while the epitaxial 80–100 nm film had a conductivity of around 1.9 mΩcm.  相似文献   

7.
Electrochromic properties of nanocrystalline MoO3 thin films   总被引:1,自引:0,他引:1  
Electrochromic MoO3 thin films were prepared by a sol–gel spin-coating technique. The spin-coated films were initially amorphous; they were calcined, producing nanocrystalline MoO3 thin films. The effects of annealing temperatures ranging from 100 °C to 500 °C were investigated. The electrochemical and electrochromic properties of the films were measured by cyclic voltammetry and by in-situ optical transmittance techniques in 1 M LiClO4/propylene carbonate electrolyte. Experimental results showed that the transmittance of MoO3 thin films heat-treated at 350 °C varied from 80% to 35% at λ = 550 nm (ΔT =  45%) and from 86% to 21% at λ ≥ 700 nm (ΔT =  65%) after coloration. Films heat-treated at 350 °C exhibited the best electrochromic properties in the present study.  相似文献   

8.
An effective method is developed for low temperature metal oxide deposition through thermal decomposition of metal diketonates in supercritical carbon dioxide (scCO2) solvent. The rates of Al(acac)3 (Aluminum acetyl acetonate) and Ga(acac)3 (Gallium acetyl acetonate) thermal decomposition in scCO2 to form conformal Al2O3 and Ga2O3 thin films on planar surfaces were investigated. The thermal decomposition reaction of Al(acac)3 and Ga(acac)3 was found to be initialized at  150 °C and 160 °C respectively in scCO2 solvent, compared to  250 °C and 360 °C in analogous vacuum-based processes. By measuring the temperature dependence of the growth rates of metal oxide thin films, the apparent activation energy for the thermal decomposition of Al(acac)3 in scCO2 is found to be 68 ± 6 kJ/mol, in comparison with 80–100 kJ/mol observed for the corresponding vacuum-based thermal decomposition reaction. The enhanced thermal decomposition rate in scCO2 is ascribed to the high density solvent which effectively reduces the energy of the polar transition states in the reaction pathway. Preliminary results of thin film deposition of other metal oxides including ZrOx, FeOx, Co2O3, Cr2O3, HfOx from thermal decomposition of metal diketonates or fluorinated diketonates in scCO2 are also presented.  相似文献   

9.
Chang Jung Kim   《Thin solid films》2004,450(2):261-264
Ferroelectric bismuth lanthanum titanate (Bi3.25La0.75Ti3O12; BLT) thin films were deposited on Pt/TiO2/SiO2/Si substrate by chemical solution deposition method. The films were crystallized in the temperature range of 600–700 °C. The spontaneous polarization (Ps) and the switching polarization (2Pr) of BLT film annealed at 700 °C for 30 min were 22.6 μC/cm2 and 29.1 μC/cm2, respectively. Moreover, the BLT capacitor did not show any significant reduction of hysteresis for 90 min at 300 °C in the forming gas atmosphere.  相似文献   

10.
(100)-oriented 0.462Pb(Zn1/3Nb2/3)O3–0.308Pb(Mg1/3Nb2/3)O3–0.23PbTiO3 (PZN-PMN-PT) perovskite ferroelectric thin films were prepared on La0.7Sr0.3MnO3/LaAlO3 (LSMO/LAO) substrate via a chemical solution deposition route. The perovskite LSMO electrode was found to effectively suppress the pyrochlore phase while promote the growth of the perovskite phase in the PZN-PMN-PT film. The film annealed at 700 °C exhibited a high dielectric constant of 2130 at 1 kHz, a remnant polarization, 2Pr, of 29.8 μC/cm2, and a low leakage current density of 7.2 × 10− 7 A/cm2 at an applied field of 200 kV/cm. The ferroelectric polarization was fatigue-free at least up to 1010 cycles. Piezoelectric coefficient, d33, of 48 pm/V was also demonstrated. The results showed that much superior properties could be achieved with the PZN-PMN-PT thin films on the solution derived LSMO electrode than on Pt electrode by sputtering.  相似文献   

11.
Samarium-doped ceria (SDC) thin films were prepared from Sm(DPM)3 (DPM = 2,2,6,6-tetramethyl-3,5-heptanedionato) and Ce(DPM)4 using the aerosol-assisted metal–organic chemical vapor deposition method. -Al2O3 and NiO-YSZ (YSZ = Y2O3-stabilized ZrO2) disks were chosen as substrates in order to investigate the difference in the growth process on the two substrates. Single cubic structure could be obtained on either -Al2O3 or NiO-YSZ substrates at deposition temperatures above 450 °C; the similar structure between YSZ and SDC results in matching growth compared with the deposition on -Al2O3 substrate. A typical columnar structure could be obtained at 650 °C on -Al2O3 substrate and a more uniform surface was produced on NiO-YSZ substrate at 500 °C. The composition of SDC film deposited at 450 °C is close to that of precursor solution (Sm : Ce = 1 : 4), higher or lower deposition temperature will both lead to sharp deviation from this elemental ratio. The different thermal properties of Sm(DPM)3 and Ce(DPM)4 may be the key reason for the variation in composition with the increase of deposition temperature.  相似文献   

12.
La0.5Sr0.5CoO3−δ (LSCO) thin films were deposited on yttria stabilized zirconia (YSZ) substrates by pulsed laser deposition (PLD) for application to thin film solid oxide fuel cell electrodes. During the deposition, the substrate temperature was varied from 450 to 750°C, and the oxygen pressure in the chamber was varied from 80 to 310 mTorr. Films deposited at 650°C and an oxygen background pressure of 150 mTorr were mostly (100) oriented. Deposition at higher temperatures or under lower oxygen pressures lead to mostly (110) oriented films. Films with low electrical resistivity of 10−3 Ω·cm were obtained.  相似文献   

13.
Pt-PtOx thin films were prepared on Si(100) substrates at temperatures from 30 to 700°C by reactive r.f. magnetron sputtering with platinum target. Deposition atmosphere was varied with O2/Ar flow ratio. The deposited films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. Resistively of the deposited films was measured by d.c. four probe method. The films mainly consisted of amorphous PtO and Pt3O4 (or Pt2O3) below 400°C, and amorphous Pt was increased in the film as a deposition temperature increased to 600°C. When deposition temperature was thoroughly increased, (111) oriented pure Pt films were formed at 700°C. Compounds included in the films strongly depended on substrate temperature rather than O2/Ar flow ratio. Electrical resistivity of Pt-PtOx films was measured to be from the order of 10−1 Ω cm to 10−5 Ω cm, which was related to the amount of Pt phase included in the deposited films.  相似文献   

14.
High quality epitaxial GaAs films of 1.8 and 6.3 μm thickness on silicon substrates were examined for lattice distortion, misalignment and curvature by X-ray diffraction (Bond method) at 20–400 °C. These films were deposited by the metal-organic chemical vapour deposition method on the (001) plane of silicon using a buffer layer produced at Tb = 370 or 460 °C. A top layer was then grown at Tt = 560 or 650 °C. The GaAs films contract more strongly on cooling than the substrate, which causes a curvature and a tetragonal distortion below a critical temperature Tc. This temperature varies on thermal treatment at 200–400 °C and approaches Tb, the growth temperature of the buffer layer. The tetragonal distortion can be stabilized, so that Tc approximates Tb, if the GaAs films are annealed for several days at 400 °C.  相似文献   

15.
We have investigated the stress behaviors and a mechanism of void formation in TiSix films during annealing. TiSix thin films were prepared by DC magnetron sputtering using a TiSi2.1 target in the substrate temperature range of 200–500 °C. The as-deposited TiSix films at low substrate temperature (<300 °C) have an amorphous structure with low stress of 1×108 dynes/cm2. When the substrate temperature increases to 500 °C, the as-deposited TiSix film has a mixture of C49 and C54 TiSi2 phase with stress of 8×109 dynes/cm2. No void was observed in the as-deposited TiSix film. Amorphous TiSix film transforms to C54 TiSi2 phase with a random orientation of (311) and (040) after annealing at 750 °C. The C49 and C54 TiSi2 mixture phase transforms to (040) preferred C54 TiSi2 phase after annealing over 650 °C. By increasing substrate temperature, the transformation temperature for C54 TiSi2 can be reduced, resulting in relieved stress of TiSi2 film. The easy nucleation of the C54 phase was attributed to an avoidance of amorphous TiSix phase. We found that amorphous TiSix→C54 TiSi2 transformation caused higher tensile stress of 2×1010 dynes/cm2, resulting in more voids in the films, than C49→C54 transformation. It was observed that void formation was increased with thermal treatment. The high tensile stress caused by volume decreases in the silicide must be relieved to retard voids and cracks during C54 TiSi2 formation.  相似文献   

16.
Calcium oxide and calcium hafnium oxide thin films were grown by atomic layer deposition on borosilicate glass and silicon substrates in the temperature range of 205–300 °C. The calcium oxide films were grown from novel calcium cyclopentadienyl precursor and water. Calcium oxide films possessed refractive index 1.75–1.80. Calcium oxide films grown without Al2O3 capping layer occurred hygroscopic and converted to Ca(OH)2 after exposure to air. As-deposited CaO films were (200)-oriented. CaO covered with Al2O3 capping layers contained relatively low amounts of hydrogen and re-oriented into (111) direction upon annealing at 900 °C. In order to examine the application of CaO in high-permittivity dielectric layers, mixtures of Ca and Hf oxides were grown by alternate CaO and HfO2 growth cycles at 230 and 300 °C. HfCl4 was used as a hafnium precursor. When grown at 230 °C, the films were amorphous with equal amounts of Ca and Hf constituents (15 at.%). These films crystallized upon annealing at 750 °C, showing X-ray diffraction peaks characteristic of hafnium-rich phases such as Ca2Hf7O16 or Ca6Hf19O44. At 300 °C, the relative Ca content remained below 8 at.%. The crystallized phase well matched with rhombohedral Ca2Hf7O16. The dielectric films grown on Si(100) substrates possessed effective permittivity values in the range of 12.8–14.2.  相似文献   

17.
We use the glancing angle deposition technique (GLAD) to grow CuInS2 thin films by a vacuum thermal method onto glass substrates. During deposition, the substrate temperature was maintained at 200 °C. Due to shadowing effect the oblique angle deposition technique can produce nanorods tilted toward the incident deposition flux. The evaporated atoms arrive at the growing interface at a fixed angle θ measured from the substrate normal. The substrate is rotated with rotational speed ω fixed at 0.033 rev s− 1. We show that the use of this growth technique leads to an improvement in the optical properties of the films. Indeed high absorption coefficients (105–3.105 cm− 1) in the visible range and near-IR spectral range are reached. In the case of the absence of the substrate rotation, scanning electron microscopy pictures show that the structure of the resulting film consists of nanocolumns that are progressively inclined towards the evaporation source as the incident angle was increased. If a rapid azimuthal rotation accompanies the substrate tilt, the resulting nanostructure is composed of an array of pillars normal to the substrate. The surface morphology show an improvement without presence of secondary phases for higher incident angles (θ > 60°).  相似文献   

18.
We report on the properties of (1−x)SrBi2Ta2O9xBi3TaTiO9 solid solution thin films for ferroelectric non-volatile memory applications. The solid solution thin films fabricated by modified metalorganic solution deposition technique showed much improved properties compared to SrBi2Ta2O9. A pyrochlore free crystalline phase was obtained at a low annealing temperature of 600°C and grain size was found to be considerably increased for the solid solution compositions. The film properties were found to be strongly dependent on the composition and annealing temperatures. The measured dielectric constant of the solid solution thin films was in the range 180–225 for films with 10–50% of Bi3TaTiO9 content in the solid solution. Ferroelectric properties of (1−x)SrBi2Ta2O9xBi3TaTiO9 thin films were significantly improved compared to SrBi2Ta2O9. For example, the observed remanent polarization (2Pr) and coercive field (Ec) values for films with 0.7SrBi2Ta2O9–0.3Bi3TaTiO9 composition, annealed at 650°C, were 12.4 μC/cm2 and 80 kV/cm, respectively. The solid solution thin films showed less than 5% decay of the polarization charge after 1010 switching cycles and good memory retention characteristics after about 106 s of memory retention. The improved microstructural and ferroelectric properties of (1−x)SrBi2Ta2O9xBi3TaTiO9 thin films compared to SrBi2Ta2O9, especially at lower annealing temperatures, suggest their suitability for high density FRAM applications.  相似文献   

19.
Highly conducting and transparent indium tin oxide (ITO) thin films were prepared on SiO2 glass and silicon substrates by pulsed laser ablation (PLA) from a 90 wt.% In2O3-10 wt.% SnO2 sintered ceramic target. The growths of ITO films under different oxygen pressures (PO2) ranging from 1×10−4–5×10−2 Torr at low substrate temperatures (Ts) between room temperature (RT) and 200°C were investigated. The opto-electrical properties of the films were found to be strongly dependent on the PO2 during the film deposition. Under a PO2 of 1×10−2 Torr, ITO films with low resistivity of 5.35×10−4 and 1.75×10−4 Ω cm were obtained at RT (25°C) and 200°C, respectively. The films exhibited high carrier density and reasonably high Hall mobility at the optimal PO2 region of 1×10−2 to 1.5×10−2 Torr. Optical transmittance in excess of 87% in the visible region of the solar spectrum was displayed by the films deposited at Po2≥1×10−2 Torr and it was significantly reduced as the PO2 decreases.  相似文献   

20.
For growth temperatures in the range of 275°C to 425°C, highly conductive RuO2 thin films with either (110)- or (101)-textured orientations have been grown by metal-organic chemical vapor deposition (MOCVD) on both SiO2/Si(001) and Pt/Ti/SiO2/Si(001) substrates. Both the growth temperature and growth rate were used to control the type and degree of orientational texture of the RuO2 films. In the upper part of this growth temperature range ( 350°C) and at a low growth rate (< 3.0 nm/min.), the RuO2 films favored a (110)-textured orientation. In contrast, at the lower part of this growth temperature range ( 300°C) and at a high growth rate (> 3.0 nm/min.), the RuO2 films favored a (101)-textured orientation. In contrast, higher growth temperatures (> 425°C) always produced randomly-oriented polycrystalline films. For either of these low-temperature growth processes, the films produced were crack-free, well-adhered to the substrates, and had smooth, specular surfaces. Atomic force microscopy showed that the films had a dense microstructure with an average grain size of 50–80 nm and a rms. surface roughness of 3–10 nm. Four-probe electrical transport measurements showed that the films were highly conductive with resistivities of 34–40 μΩ-cm (at 25°C).  相似文献   

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