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A novel sol-gel-hydrothermal process for preparation of highly oriented thin films of Pb(Zr0.52Ti0.48)O3 is reported. Pb(Zr0.52Ti0.48)O3 thin films with fully (111) orientation were successfully prepared on platinized silicon substrates at low temperature (100–200 °C) by combining a conventional sol-gel process and hydrothermal method, i.e., sol-gel-hydrothermal technique. The x-ray rocking curve for the (111) reflection as measured by a high-resolution four-crystal diffractrometer showed a narrow full width at half-maximum value of 0.20° for the as-prepared films. A dense, pinhole-free, and uniform surface morphology was observed from atomic force microscopy images of the films. The low leakage current density of the prepared films was also found.
Crystalline 3C-SiC thin films were successfully grown on (100) and (111) Si substrates by using ArF pulsed laser ablation from a SiC ceramic target combined with a vacuum annealing process. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were employed to study the effect of annealing on the structure of thin films deposited at 800°C. It was demonstrated that vacuum annealing could transform the amorphous SiC films into crystalline phase and that the crystallinity was strongly dependent on the annealing temperature. For the samples deposited on (100) and (111) Si, the optimum annealing temperatures were 980 and 920°C, respectively. Scanning electron microscope (SEM) micrographs exhibited different characteristic microstructure for the (100) and (111) Si cases, similar to that observed for the carbonization layer initially formed in chemical vapor deposition of SiC films on Si. This also showed the presence of the epitaxial relationship of 3C-SiC//Si and 3C-SiC//Si in the direction of growth.
Ferroelectric thin films of Pb(Zr, Ti)O3 (PZT) were fabricated on platinum-coated silicon using the process of direct-current glow discharge assisted laser deposition, where the substrate was electrically grounded. The films deposited at 730 °C with +800 V discharge voltage are oriented mostly with the c-axis perpendicular to the substrate surface, and exhibit good ferroelectric hysteresis loops. A possible mechanism for the improvement of the deposition process has been proposed.
Well-crystallized polycrystalline thin films of cubic barium titanate (BaTiO3) have been synthesized on Ti-covered Si substrates by exposing the substrates to a Ba(OH)2 aqueous solution at 160 °C and a low pressure less than 1 MPa. It was presumed that the film formation of BaTiO3 involved a dissolution-crystallization mechanism, which provides an attractive approach to produce other titanate films and powders. Also, we have used for the first time this hydrothermal technique to deposit epitaxial (001)-textured PbTiO3 thin films on SrTiO3(100) substrates.
Stoichiometric films of Pb(Zr0.52Ti0.48)O3 (PZT) were successfully deposited on Si-on-Insulator (SOI) substrates, with and without a platinum electrode, by an ArF (λ=193nm) pulsed excimer laser. Rapid thermal annealing (RTA) was used to transform amorphous or pyrochlore phase into ferroelectric perovskite phase. The film structure, composition, morphology, interface and electrical properties were studied by x-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM) and Sawyer-Tower circuit, respectively. It was found that there was a narrow operational window of annealing time for PZT films at fixed annealing temperature. Pure ferroelectric perovskite phase with mainly (100) and (110) orientations could be obtained in PZT films on Pt coated SOI substrates. The interfaces between the PZT films and both Si and Pt//Si were very abrupt, indicating there was no interdiffusion between them. Ferroelectric hysteresis loops showed a remanent polarization of 15μC/cm2 and a coercive field of 50KV/cm.
A slow positron beam was used to investigate the solid state reaction of Co/Si and Co/Ti/Si. Variable-energy (0-20 keV) positrons were implanted into samples at different depths. The Doppler broadening of the annihilation -y-ray energy spectra, measured at a number of different incident positron energies were characterized a line-shape parameter “5”. It was found that the measured S parameters were sensitive to thin film reaction and crystalline characteristics. In particular, the S parameter of epitaxial CoSi2 formed by the ternary reaction was quit different from that of the polycrystalline CoSi2 formed by direct reaction of Co with Si.
The effect of ion implantation on the formation and light emitting properties of porous silicon is reported. Si + , F+ ions were implanted into silicon wafers before electrochemical etching process. The experiments showed that porous structure can be formed on the wafer containing amorphous layer, while the porosity distribution with the depth changed greatly compared with the anodized crystalline Si. The implantation of F+ ions greatly affects the formation mechanism. The creation of point defects leads to red-shift in photoluminescence measurements.
Polycrystalline MnNiCuFeO was implanted by B+, P+ and Si+ ion beams and thermally annealed. The structure and electrical properties of the sample were measured using SEM, Microprobe (MP), Low Frequency Impedance Analyzer (LFIA) and Spreading Resistance Probe (SRP). The results show that the resistance of grain boundaries is much higher than that of grains. The spreading resistance of the implanted samples is lower by factor of 2 than that of the unimplanted ones. The ratio of the real part Rs (grain effect) to imaginary part Xs (grain boundary effect) decreases with ion beam implantation. From these results, we came to the conclusion that the behavior of the grain boundaries is important to the bulk properties of polycrystalline MnNiCuFeO.
Amorphous CoMnNiO film is doposited on oxidized Si substrate by RF sputtering equipment. Structure relaxation occurs in the amorphous CoMnNiO film when it is annealed below 550°C. Annealed in the range from 600°C to 1000°C, the amorphous film is converted into the polycrystal. After annealing in rich oxygen atmosphere, the amorphous film is transformed into spinel solid solution with stable structure and good electrical properties. The electrical conductivity will be reduced due to formation of low valence oxides when annealed without oxygen. As annealing temperature is higher than 1000°C, some spinel solid solutions will be resolved into low valence oxides CoO and NiO, reducing the conductivity of the CoMnNiO film.
The damage behavior of <100>-Si implanted with P2+ and P+ ions at equivalent energies were investigated by 2MeV He* backscattering and channeling analysis. Different incident energies (25-90keV/atom) and intermediate doses (1013–1014/cm2) were used for the implantation with sample holder being kept at temperatures ranging from 77k to 483K. It has been shown that the damage created by P2* implants is always greater than that of P2+ implants when the dosage is below the threshold fluence at which amorphization takes place. This damage enhancement phenomenon is strongly related to implantation temperature. A striking damage enhancement induced by 90 keV/atom P2+ implants in the surface region of the sample was observed, and it has been attributed to the multiple collision effect between diatomic ions and host atoms.
The damage and annealing behavior of <100> Si implanted at room temperature by and P+ at different energies (5-600KeV) and intermediate dose (∼1014/cm2) has been investigated. Experimental results show that the damage created by implantation is always greater than that of P+ implantation. The ratio of total displaced atoms of the target cuased by molecular and atomic implantation, ND(mol)d/ND(atom) reached a maximal value at 100KeV () and 50KeV (P+) after rapid thermal annealing, the carrier concentration profiles measured by spreading resistance measurements are also different for the and P+ implanted samples. We attribute essentially this phenomenon to the displacement spike, but the multiple collision effect and the interaction between two molecular fragments should be considered while the incident energy is high.
A novel material SOM (Silicon on Metal) was obtained by laser recrystallization. 0.5miti amorphous-Si film was deposited by glow discharge on a metal substrate covered with lym CVD Si02 Boron ions were implanted in a-Si at an energy of 60KeV and a dose of 5xl015cm-2. A CW argon laser was used to recrystal-lize a-Si film. After CW argon laser irradiation, a-Si was recrystallized and the grain size was increased to 10x40ym, the concentration profile of impurities became uniform and the electrical properties of SOM were improved significantly, sheet resistance lower than 60Ω/⃞n was obtained. The gauge factor of recrystallized SOM materials measured by a cantilever transducer was higher than 30. The devices made of this material have pressure sensitivity of 6mV/V for pressure range 1 bar.
Mo-Si films on silicon substrates has been prepared by the CO2 laser-initiated aluminothermic reaction. The features of these films have been characterized by RBS, AES, etc. The formation mechanism is discussed.
The InP films with thickness of 1-2 µm and resistivity of 10-10−3Ω-cm were sputtered on oxidized Si substrates heated at about 300°C to form as InP SOI. Using X-ray diffraction, ED, TEM, Hall and RBS, we have investigated the grain size, compositions, thermal stability and electrical characteristics of InP SOI before and after CW Ar+ laser recrystallization. The sputtered InP SOI films appear as polycrystalline and its grain size increases with increasing of irradiated laser power from 5.8 to 7.0 W at a beam diameter of 70 µm. After irradiation at 7 W the single crystal ED patterns are obtained, the mobility and carrier concentrations amount to 103cm2/Vs and 1017cm−3, respectively, and the compositions are stoichiometric.
GaAs SOI consisting of a sputtered GaAs film on a SiO2 −Si or sapphire substrate is irradiated by CW Ar+ laser beam with a view to investigating its recrystallization. Using AES, x-ray diffraction, TEM and ED, we have studied the compositions, crystal orientations and grain size of the laser-irradiated GaAs films. The possible application of GaAs SOI to devices is discussed on the basis of the experimental results.
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