Isochronal Annealing Process Research Articles

Degradation and annealing characteristics of NPN SiGe HBT exposed to heavy ions irradiation

In this study, the performance degradation and annealing behavior of NPN SiGe HBT exposed to swift heavy ion irradiation were investigated. The direct current (DC) characteristics such as forward Gummel, junction leakage current and Early voltage were studied to quantify the irradiation tolerance. Base current and junction leakage current was found to increase after irradiation. The recovery of electrical parameters was characterized after room-temperature isothermal annealing and elevated-temperature isochronal annealing. An obvious temperature-dependence effect was found in the subsequent annealing process. Significant recovery existed in the high-temperature isochronal annealing process, while less was found in the room temperature self-annealing process. The different annealing behaviors of ionization damages and displacement damages are demonstrated to be responsible for various recoveries under room temperature and elevated temperature. The underlying physics mechanisms are discussed in detail.

Investigation of kinetic recovery process in low dose neutron-irradiated nuclear graphite by thermal annealing

ABSTRACT To investigate the kinetic recovery process of low dose neutron-irradiated graphite, nuclear-grade isotropic graphite IG-110U and ETP-10 were neutron irradiated using the JMTR up to 1.38 × 1023 n/m2 (En > 1 MeV) at ~473 K. In-situ measurement of macroscopic length was conducted during the isothermal and isochronal annealing process from room temperature up to 1673 K. From room temperature to 773 K for IG-110U, and to 1023 K for ETP-10, macroscopic lengths, lattice parameters, and unit cell volumes of both specimens recovered to their pre-irradiation values, and this recovery process subdivided into two stages. The activation energies of macroscopic volume recovery at 523–673 K and 673–773 K were determined to be ~0.22 eV and ~0.57 eV for IG-110U, respectively; ~0.13 eV and ~2.59 eV at 523–923 K and 923–1023 K for ETP-10, respectively. The migration of not only single interstitials but also interstitials dissociated from submicroscopic interstitial groups along basal planes followed by vacancy-interstitial recombination play a dominant role in the first stage. The second stage is suggested to proceed via the motion of carbon groups along basal planes for IG-110U, and migration of single interstitials along the c-axis for ETP-10. During 773 K or 1023 K up to 1673 K, macroscopic length continuously shrank with decreasing shrinking rate, even with a turnaround to swell at 1173 K for IG-110U.

Phase transformation and disorder effect on optical and electrical properties of Zn3P2 thin films

The phase transformation of zinc phosphide (Zn3P2) thin films was detected through isochronal annealing process. The effects on isochronal annealing on the internal structural, optical and electrical properties of deposited Zn3P2 thin films have been discussed. The films were prepared by thermal evaporation under constant preparation conditions of vacuum 1.3×10−5Torr, substrate temperature (300K), rate of deposition (∼1nm/s) and film thickness (480nm). The annealing process was carried out under vacuum for 2h at different temperatures ranging from 373 to 623K. X-ray diffraction patterns showed that the as-deposited films and those annealed at temperatures less than 623K exhibit amorphous structure, while the films annealed at 623K showed tetragonal polycrystalline structure. The optical transmission and reflection spectra were measured at the wavelength range of 190–2500nm. The absorption coefficient spectra and the degree of disorder as measured from the absorption edge were determined. The indirect and direct optical energy band gaps were evaluated for indirect allowed and direct allowed transitions for amorphous and polycrystalline films, respectively. The refractive index no increases with raising the annealing temperature which refers to more condensation in the material. The electrical resistivity for Zn3P2 films decreases exponentially with raising the annealing temperature up to 623K as influenced by structure transformation and decreasing the degree of disorder in the films.

Isochronal and isothermal crystallization kinetics of amorphous Fe-based alloys

Using the differential scanning calorimetry (DSC), the isochronal and isothermal crystallization kinetics of amorphous Fe 61Co 9− x Zr 8Mo 5W x B 17 ( x = 0 and 2) ribbons was investigated by the Kissinger equation and by the Kolmogorov–Johnson–Mehl–Avrami and Ranganathan–Heimendahl equations, respectively. The results show that tungsten can improve the activation energy E 1 K for the first crystallization in the isochronal annealing process and activation energy E n for the nucleation in the isothermal annealing process, which can be ascribed to the dissolution of tungsten in the amorphous phase. Meanwhile, tungsten can decrease the activation energy E 2 K for the second crystallization in the isochronal annealing process and growth activation energy E g in the isothermal annealing process, which is possibly associated with the formation of W-rich compound after the early nucleation process.

An isochronal kinetic study of intermetallic compound growth in Sn/Cu thin film couples

Growth kinetics of Cu6Sn5 and Cu3Sn compounds in Cu/Sn thin film couples was studied by in situ resistivity measurements and X-ray diffraction analysis. The Cu6Sn5 and Cu3Sn intermetallic compounds were found to form in sequence when the Cu/Sn bimetallic samples were isochronally annealed from room temperature to 220 °C. A kinetic model was presented to explain sequential appearance of the Cu6Sn5 phase and the Cu3Sn phase during the isochronal annealing process. The activation energies of Cu6Sn5 and Cu3Sn compound growth in Cu/Sn thin film couples were determined from the in situ resistivity measurements to be 0.87 eV and 1.05 eV, respectively.

Effects of Ti Interlayer on Ni/Si Reaction Systems

The effects of Ti interlayer on the formation of Ni silicides on Si(100) substrate was investigated. The phase and microstructure of Ni silicides during isochronal annealing treatment are monitored in situ by curvature measurement and characterized ex situ by other measurements. The addition of a thin Ti layer which formed an amorphous layer with the Si substrate acted as a diffusion barrier for the Ni atom in the early phase transformation process. The transformation temperature for the NiSi is significantly increased in an isochronal annealing process. When the NiSi phase is formed, the Ti-related layer moves to the surface of the silicide film. The temperature for the transformation of NiSi to is relatively irrelevant to the presence of the Ti interlayer. A preferential orientation of (200) and (002) was found in the NiSi phase formed via the Ti interlayer, which significantly improved the epitaxial quality of on Si(100) substrate with a stepwise interface bounded by (111) and (100) planes. The top continuous Ti-related layer causes the incomplete accommodation of the thermal stress for the system. Upon disintegration of the Ti-related layer, the thermal stress of the system could be completely accommodated by relaxation of the NiSi layer. © 2004 The Electrochemical Society. All rights reserved.

Metastable phase accompanying crystallisation of amorphous Al85Ni10Ce5 alloy

Isochronal annealing and isothermal annealing of melt spun amorphous Al85Ni10Ce5 alloy were carried out to investigate the crystallisation behaviour. It has been found that a metastable phase occurring in the crystallisation process, may exist for a certain time but in due course disappears either acting as a nucleus of another phase or transforming into another stable phase with an increase in either annealing temperature or annealing time. Transmission electron microscopy results reveal that Al3Ce may be one of the metastable phases during the isochronal annealing process. Furthermore, microhardness measurements reveal that the specimens containing metastable phases exhibit higher microhardness than the as quenched and as crystallised alloy.

Stress evolution of Ni /Pd /Si reaction system under isochronal annealing

The stress evolutions of Ni /Pd /Si samples under isochronal annealing condition were studied. We have used a laser scanning method for substrate curvature measurements to measure the total force per unit width ( F/W) of the film produced during isochronal annealing. With the introduction of a thin Pd interlayer into the Ni /Si reaction system, the curve of F/W versus temperature shows two additional abrupt changes, one is associated with the formation of the Pd 2Si phase and the other is associated with the initial stage of the Ni 2Si formation. With increasing thickness of the Pd interlayer (up to 5 nm), the temperatures for the complete formation of Ni 2Si and NiSi were increased, while the threshold temperature for the formation of NiSi 2 was not significantly changed. The thin Pd 2Si layer formed at low temperature acts as a diffusion barrier to retard the formation of Ni 2Si and subsequently delay the formation of NiSi. The maximum difference of the total force per width in the film, during the whole isochronal annealing process, was significantly reduced with increasing Pd layer thickness.

反跳粒子検出法，陽電子消滅測定法による黒鉛中の水素，重水素と欠陥の研究

Behavior of deuterium atoms implanted in graphite has been investigated by ERD (elastic recoil detection) method and the defect behavior has also been studied by positron annihilation method. It was found that diffusion of deuterium atoms shows a significant anisotropy, i.e., very high diffusivity along the direction parallel to the basal plane and very low diffusivity along the direction perpendicular to the basal plane. Deuterium atoms are considered to be trapped at the boundaries between adjacent crystallites and the sites of radiation induced defects and are released from the specimen through three stages in the isochronal annealing process depending on the depth of the trapping potential. The isochronal annealing curve of the positron lifetime for HOPG irradiated with electrons at 77 K can be divided into two stages, i.e., below 1200°C and above 1200°C. In the former the increase of positron lifetime corresponding to the growth of interstitital type loops is observed and in the latter that corresponding to the growth of vacancy type loops (and also to interstitial type loops) is observed. Positron lifetime calculation for a vacancy and vacancy clusters was made and the comparison with the experimental results was also made to clarify the fundamental aspects of radiation induced defects in graphite.

Effects of isochronal thermal annealing and hydrogenation on photoluminescence from n-type GaN films grown by metalorganic vapor phase epitaxy

We have investigated the behavior of three emission bands located at around 375, 580 and 750 nm in photoluminescence (PL) spectra from n-type GaN films grown by the metalorganic vapor phase epitaxy method in the isochronal annealing process and in a similar process after the films have been hydrogenated using a hydrogen plasma. The PL intensities of the two bands located at around 375 nm and 750 nm vs isochronal annealing temperature show similar rules, but the isochronal annealing behavior of PL intensity for the band located at around 580 nm differs obviously from that of the two bands mentioned above. Hydrogenation has an obvious effect on the isochronal annealing behavior of PL intensity, e.g. decreases the number of peaks in the curves of PL intensity vs isochronal annealing temperature.

Thermal and Ar ion beam annealing of surface amorphous layers produced by Sb implanted into 〈100〉 Ni single crystal

The thermal and ion beam annealing of amorphous layers produced by the implantation of 10 17 ions cm −2 of Sb at 80 keV into 〈100〉 Ni was investigated using RBS/channelling techniques. The isochronal annealing process was carried out in the temperature range from 250 to 1100°C, whereas the ion beam process involved the use of 1.5 MeV Ar + ions up to a fluence of 2.4 × 10 17 ions cm −2 at a constant temperature of 350°C. The results indicated that irrespective of the anneal process involved, the initial surface amorphous disorder caused by the implantation annealed out in two distinct stages. For Sb peak concentrations above a critical value of 8–9 at.%, there was evidence of some possible form of segregation process occurring particularly during the isothermal annealing at 350°C. During this process, a partial recovery of the crystalline lattice was observed together with only very slight diffusion of Sb atoms. When the Sb peak concentration fell below this critical value, there was a second rapid anneal process which was accompanied with a long range diffusion of the Sb impurities in the Ni lattice. This further restoration of the crystalline lattice was by no means perfect as the high dechannelling level of the observed RBS spectra indicated that an extensive number of dislocation networks still persisted in the surface layer even after prolonged annealing. Following the long range diffusion, the Sb atoms were observed to occupy substitutional sites in the good crystalline region of the Ni lattice.

The trapping of deuterium in argon-implanted nickel

Argon ions with energy 250 keV were implanted at fluences of 2×1016 cm−2 at temperatures of 500, 250, and 21 °C, in a specimen of relatively pure polycrystalline nickel. Deuterium was introduced into the surface and implanted regions by making the specimen the negative electrode of an electrolytic cell containing 1-N pure deuterated sulfuric acid. Deuterium trapped in the vacancy complexes of the implanted regions was analyzed as a function of temperature using the 2H(3He,1H)4He nuclear reaction during an isochronal annealing process. The results indicate that the types of traps and trap densities found in the regions implanted at 21 and 250 °C were essentially identical while the trap density found in the region implanted at 500 °C was approximately 40% of that found in the other regions. Math model comparison with the experimental results suggests the existence of at least two types of traps in each region. Trap binding enthalpies used in the math model to fit the experimental data were slightly higher for the region implanted with argon at 500 °C than for the regions implanted at the lower temperatures. TEM studies revealed the presence of small voids in the region implanted at 500 °C as well as dislocation loops similar to those found in the regions implanted at the lower temperatures.

Decomposition of a supersaturated aluminum-rich aluminum-iron solid solution during annealing

The decomposition of a supersaturated Al-0.68 at. % (1.4 wt. %) Fe solid solution in the isochronal annealing process is studied by electron microscope technique. The stability of the solid solution and the type and development of the precipitation pattern are discussed. The decomposition temperature range is established and compared to the disintegration of some amorphous and metastable crystalline structures.