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The embedded atom method (EAM) was applied to calculate the energy on Mg doping in polycrystalline Ni3Al. The EAM predicted the energy of Mg in Al site in grain boundary is lower than that of Mg in Ni site and much lower than that of Mg in Al or Ni site in bulk and in free surface. It means that Mg would segregate to grain boundary rather than bulk and free surface and Mg will favor to be the substitute of Al rather than of Ni in grain boundary. These results were consistent with the experiments that Mg segregated to grain boundaries with Al depletion and Ni enrichment.
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.
Ion beam controlled deposition (IBCD) or ion beam assisted deposition (IB AD) of Ti(C,N,O) films has been investigated much in the last decade for both the advantage of this advanced technology and the promising properties of such materials. Ti(C,N,O) films are various solid solutions of interstitial compounds TiC, TiN and TiO of F.C.C structure with lattice constants lying between the values of the pure compounds. Some content of oxygen improves their wear resistance due to the lower fn;e enthalpies of such films in comparison with pure TiC and TiN films . Many so-synthesizcd titanium carbide and titanium nitride films reported in published papers were actually of this sort as they often had more or less oxygen content from residual gas in vacuum. A number of papers were contributed to depict the texture and composition dependence of film on the arrival ratio of assisting ions versus deposited atoms (AR) as well as their mechanical properties [2–6]. However, the film formation mechanism in IBCD isn't quite clear yet, especially for cases with assisting ion energy of several to tens of keV. During a course to synthesize Ti(C,N,O) films by IBCD with the two beam technique, datum were accumulated. Based on a part of it, a previous paper on ion beam governed preferential growth in IBCD has been published . This paper was aimed to search for the origin of ion bombardment effect on film hardness.
Dual implantations of Si+ and P+ into InP:Fe were performed both at 200°C and room temperature. Si+ ions were implanted by 150keV with doses ranging from 5×1013 /cm2 to 1×1015 /cm2, while P+ ions were implanted by 110keV. 160keV and 180keV with doses ranging from 1×l013 /cm2 to 1×1015 /cm2. Hall measurements and photoluminescence spectra were used to characterize the silicon nitride encapsulated annealed samples. It was found that enhanced activation can be obtained by Si+ and P+ dual implantations. The optimal condition for dual implantations is that the atomic distribution of implanted P overlaps that of implanted si with the same implant dose. For a dose of 5×l014 /cm2, the highest activation for dual implants is 70% while the activation for single implant is 40% after annealing at 750°C for 15 minutes. PL spectrum measurement was carried out at temperatures from 11K to 100K. A broad band at about 1.26eV was found in Si+ implanted samples, of which the intensity increased with increasing of the Si dose and decreased with increasing of the co-implant P+ dose. The temperature dependence of the broad band showed that it is a complex (Vp-Sip) related band. All these results indicate that silicon is an amphoteric species in InP.
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.
A Monte-Carlo computer simulation has been performed to describe, at atomic level, the growth of titanium nitride films formed by ion beam enhanced deposition (IBED). The simulation is based on a random target, fixed free path of moving particles and binary collisions. An alternate process of deposition of titanium atoms and implantation of nitrogen ions is applied instead of the actual continuous and synchronous process of IBED. According to the actual conditions, the adsorption of nitrogen gas, which is leaked out from the ion source, at the fresh titanium layer surface has been considered. In addition, the change of the composition profile and the density profile during film growth is taken into account. It is demonstrated that the width of the intermixed region between the film and substrate increases with the increase of the atomic arrival ratio, R, of implanted nitrogen ions to deposited titanium atoms. When the titanium deposition rate is low, the nitrogen concentration of the film is relatively insensitive to R, indicating that a dominant contribution to the nitrogen concentration is derived from the nitrogen gas leaked out from the ion source. The results obtained in this study are in agreement with the experimental measurements.
150keV Si* ions and 160keV P* ions were implanted at 200°C with doses ranging from 5x1013 to 1x1015/cm2 to study the effect of dual implantations on the electrical properties of Fe doped InP. Samples encapsulated with Si3N4 films of about 1000Å were annealed in a halogen tungsten lamp RTA system under flowing N2 at different temperatures from 700 to 900°C for 5s. It has been found that Si*+P* dual implantations into InP can result in an enhanced activation, particularly significant at high dose of implantation. The maximum dopant activation and average electron mobility for Si*+P* dual implants at a dose of 1×1015/cm2 are 70% and 750cm2/vs, which corresponds to a peak electron concentration of 5×1019/cm3 while that for Si* single implant at the same dose are 29% and 870cm2/vs, which corresponds to a peak electron concentration of 1.2×10 19/cm3. The improvement of the electrical properties is discussed in terms of amphoteric behavior of silicon in InP.
Three types of ions with different atomic masses (B , Ar and As ) were chosen to irradiate polyimide films in similar conditions in order to check mechanisms of the formation of ion beam induced damage in polyimide. A four-point probe technique was used to measure sheet resistivities of implanted films. An ion mass effect on conductivity of ion irradiated polyimide film was discovered. The ion mass effect on ion beam induced change of conductivity and on the energy loss process of the ions in polyimide suggest that the electronic energy loss of incident ions is an important factor for the increase of conductivity of implanted polyimide, and the contributions of recoil ionization are restricted by the grave damages as a result of nuclear energy loss process of ions in targets. Our hypothesis is supported by automatic spreading resistance measurement of B implanted polyimide film coated on silicon substrate. The results of this work have been compared with the hypothesis of degradation through direct knock on of atoms in polyimide, proposed by D.Fink et al [Nucl. Instr. and Meths B32 (1988) 125]
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.
Titanium nitride films have been synthesized at room temperature by alternate deposition of titanium and bombardment by nitrogen ions with an energy of 40KeV. The component depth profiles and the structure of titanium nitride films were investigated by means of RBS, AES, TEM, XPS and X-ray diffraction. The results showed that titanium nitride films formed by ion beam enhanced deposition (IBED) had columnar structure and were mainly composed of TiN crystallites with random orientation. The oxygen contamination in titanium nitride films prepared by IBED was less than that of the deposited film without nitrogen ion bombardment. It was confirmed that a significant intermixed layer exists at the interface. The thickness of this layer was about 40 nm for the film prepared on iron plate. The mechanical properties of the film have been investigated. The films formed by IBED exhibited high hardness, improved wear resistance and low friction.
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