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Cu–Ag alloy films prepared by magnetron cosputtering were characterized by using x-ray diffraction. A two-phase nanocrystalline structure of Cu grains supersaturated with Ag and Ag grains saturated with Cu was always observed. When alloying Ag with Cu or Cu with Ag, the grain sizes decreased dramatically, and the supersaturation increased with the amount of the alloying element. On annealing, the grain sizes of the Cu–Ag films increased and the solubilities decreased. To shed light on the mechanisms in play during the phase formation and subsequent phase changes, additional in situ real-time measurements were carried out using a high-intensity x-ray beam from the synchrotron at the European Synchrotron Radiation Facility in Grenoble, France. Based on the experimental findings, the phase formation and the subsequent changes during annealing are discussed.
We show that low-energy (20 eV–20 keV) electron or photon irradiation extinguishes the characteristic physical and chemical properties of single-walled carbon nanotubes, indicating that the irradiation damages the nanotubes. The irradiation-induced defects convert the electric properties of metallic SWNTs to semiconducting, and the nominal bandgap can be tuned simply by the irradiation dose. The defects also have the following interesting properties. The damage and recovery are reversible, indicating that the number of carbon atoms is preserved. The damage and recovery strongly depend on the diameter, suggesting that the damage is prominent in a rolled up graphene sheet, but not in a planar one. The activation energy of the defect healing is so small, depending on the diameter, that the defects can be healed even at room temperature or below.
Using μ-Raman spectroscopy (μRS) and cathodoluminescence (CL) analyses, the impact of hydrogen plasma treatments on sintered zinc oxide (ZnO) samples was studied. 1 hour H-plasma treatments (150 W, 13.56 MHz) were applied at substrate temperatures between 250 °C and 500 °C. μRS and CL analyses show that plasma hydrogenation causes significant defects in ZnO samples; i) non-specified defect species are established with a maximal density upon H-plasma exposure at 350 °C substrate temperature, and ii) the formation of oxygen vacancies (VO) can be traced. Moreover, μRS reveals vibration modes of H2 molecules trapped in nano-voids. The experimental results indicate that those nano-voids are created by a coalescence of the VO defects.
We studied stress effects on As activation in silicon using density functional theory. Based on lattice expansion coefficient, we calculated formation energy change due to applied stress and plotted the stress dependence of AsmV concentration. We found that biaxial stress results in minimal impact on As activation, which is consistent with experimental observation by Sugii et al. [J. Appl. Phys. 96, 261 (2004)], who found no significant change in As activation under tensile stress.
Microwave heating is used to initiate the ion-cut process for transfer of coherent silicon-layers onto insulator substrates. Hydrogen and boron co-implanted silicon was bonded to an insulative substrate before processing inside a 2.45 GHz, 1300 W cavity applicator microwave system. Sample temperatures measured using a pyrometer were comparable to previous ion – cut studies. Selected samples were further annealed to repair any damage created in the ion implant process. Rutherford backscattering spectrometry and selective area electron diffraction patterns show high crystallinity in transferred layers. RUMP simulation of backscattering spectra and cross-sectional transmission electron microscopy demonstrate that thicknesses of the transferred layers are comparable to previous ion-cut exfoliation techniques. Surface quality as characterized by an atomic force microscope compares well with previous ion-cut studies. Hall measurements were used to characterize electrical properties of transferred layers. The mobility and carrier density of microwave activated ion – cut silicon on insulator processed samples compares well with previous annealing techniques.
We report that arsenic diffusion can be enhanced and retarded by surrounding interstitial rich and vacancy rich environments created by Si point defect engineering implant. The enhancement and retardation can be attributed to the dominant arsenic interstitial diffusion mechanism during post-implant anneal. Kinetic Monte Carlo simulations with newly implemented models show good match with experiments. Our study suggests the importance of arsenic interstitial mechanism and a possible approach for n-type ultra shallow junction fabrication.
Thermally grown SiO2 was implanted at room temperature with 220 keV Kr in order to generate bubbles/cavities in the sample. The formation and thermal stability of these bubbles/cavities is studied in this work. Transmission Electron Microscopy (TEM), Rutherford Backscattering Spectrometry (RBS) and Positron Annihilation Spectroscopy (PAS) were used to provide a comprehensive characterisation of defects (bubbles, vacancy, Kr and other types of defects) created by Kr implantation in SiO2 layer. These measurements suggest that the bubbles observed with TEM were a consequence of the interaction between Kr and vacancies (V), with VnXem complexes created in the whole of implanted zone. After annealing, bubbles/cavities disappear from SiO2 due to the strongly desorption of Kr and the decrease in vacancy concentration.
Defect-free germanium has been demonstrated in SiO2 trenches on silicon via aspect ratio trapping, whereby defects arising from lattice mismatch are trapped by laterally confining sidewalls. Results were achieved through a combination of conventional photolithography, reactive ion etching of SiO2, and selective growth of Ge as thin as 450 nm. It was revealed that facets, when formed early on in the growth process, play a dominant role in determining the configurations of threading dislocations in the films. This approach shows great promise for the integration of Ge and/or III-V materials, sufficiently large for key device applications, onto silicon substrates.
(100)–oriented Czochralski germanium (Cz Ge) wafers were implanted with hydrogen at en-ergies up to 100 keV (related to H+) at a doses of D = 4·106 H+/cm2. Post-hydrogen annealing in normal air atmosphere on a hotplate was employed for 10 min at various temperatures between 350 °C and 600 °C to investigate the samples with regard to blistering and layer exfoliation having in mind the Smart-Cut™ technology for GOI structure formation. The generation and evolution of blisters and craters (“exploded” blisters demonstrating layer exfoliation) were investigated in dependence on the annealing temperature by atomic force microscopy and μ-Raman spectroscopy. The latter method points out the appearance of strong tensile stress upon H+ implantation and subsequent annealing. If the tensile stress exceeds about 1.2 GPa layer exfoliation occurs.
Electron-hole recombination enhanced glide of Shockley partial dislocations bounding expanding stacking faults and their interactions with threading dislocations in 4H silicon carbide epitaxial layers have been studied using synchrotron white beam X-ray topography and in situ electroluminescence. The mobile silicon-core Shockley partial dislocations bounding the stacking faults are able to cut through threading edge dislocations leaving no trailing dislocation segments in their wake. However, when the Shockley partial dislocations interact with threading screw dislocations, trailing 30o partial dislocation dipoles are initially deposited in their wake due to the pinning effect of the threading screw dislocations. These dipoles spontaneously snap into their screw orientation, regardless the normally immobile carbon-core Shockley partial dislocation components in the dipoles. They subsequently cross slip and annihilate, leaving a prismatic stacking fault in (2-1-10) plane with the displacement vector 1/3[01-10].
An evaluation of an algorithm used to extract Threading Screw Dislocation defect data from Synchrotron White Beam X-Ray Topographical images of SiC wafers is reported. This extraction involves a two-fold process; firstly the algorithm highlights the appropriate defect and secondly updates the counter to provide a final result of defect count. The result of the automated algorithm is compared to hand counts in all cases, this allowing a critical analysis of the technique. Improvements to this algorithm have been made since last reported by the same authors, which are discussed. The analysis herein was also performed on a much larger sample of SiC wafer images than previously used by the same authors  allowing a better judgment of performance and critical evaluation. The algorithm is also compared with a previous algorithm that was used. Advantages and deficiencies in the algorithm are outlined and other potential avenues for extraction of the data are also discussed.
High-power semiconductor lasers are required to be more and more powerful, efficient and reliable for applications such as solid-state lasers pumping, materials processing, and thermal printing among others. The understanding of the degradation mechanisms is essential to improve the high power laser reliability. The highest power emission is achieved with multi-emitter laser cm-bars, which present problems related to packaging induced stress. A very harmful defect in this type of devices is the so-called V defect. We present herein a study of these defects using cathodoluminescence imaging, the role of packaging is discussed.
Indium nitride (InN) is a promising yet technologically challenging material with a high defect density and unusual material properties. Its high electron mobility may be utilized in high power electronic devices, and its high absorbance and low energy optical response make it a promising candidate for multi-junction, high-efficient solar cell technology. Studies of absorption and photoluminescence optical response of epitaxial InN resulted in a large correction of the fundamental bandgap from the originally proposed 1.9 eV to now below 0.7 eV. Yet, it is still debated if the commonly measured optical transitions below the original high bandgap values are actually caused by a large concentration of defects, on the order of 1020/cm3, rather than reflecting a low fundamental bandgap. Many applications of this material, e.g. in high-efficient solar cell technology, are primarily dependent on the successful production of a contacted p-n junction, which has not yet been achieved. This contribution addresses the controversy in the bandgap discussion of InN. Valence electron energy loss spectroscopy (VEELS) of InN allows spatially resolved analysis of the density of states in the transmission electron microscope (TEM). Standard optical characterization is compared with results from TEM characterization.
The segregation of As atoms at the Si/SiO2 interface during annealing was investigated by grazing incidence X-ray fluorescence spectroscopy in combination with successive removal of silicon layers by etching with thicknesses on the order of a nanometer. With this method it is possible to clearly distinguish between the segregated atoms and the As atoms in the bulk over a large range of implantation doses from 3·12 cm−2 to 1·16 cm−2. The samples were annealed at 900 °C and 1000 °C, respectively, for times sufficiently long to ensure that the segregation reflects an equilibrium effect. The results were confirmed by medium energy ion scattering, Z-contrast measurements and electron energy loss spectroscopy.
Copper is one of the most concerned contaminants for silicon process, due to its detrimental effects on device performance if present in active regions. Gettering of Cu by changing the surface conditions at the wafer surface is commonly used. Acceleration of Cu out-diffusion and surface precipitation was observed with changes of the surface potential, which could be altered by both existing Cu precipitates and organics at the surface. In this work, physically based models are developed to describe the Cu evolution at the wafer surface including the dependence of surface potential. These models are verified by comparison to the experiment measurements from Ohkubo et al. [Jpn. J. Appl. Phys. 1 44, 3793 (2005)].
Four boron-implanted p-n junction silicon light-emitting diode structures were designed and simulated under an identical process flow by using Silvaco simulators. In the simulation, only boron-implant parameters and post-implant anneal conditions were varied to identify and compare the physical, electrical, and optical properties of the structures. It was found that a pillar structure with a wrapped p-n junction has the greatest radiative recombination rate. Regardless the structure type, the maximum radiative recombination rate always occurs within the p+ region. There exists a peak in the maximum radiative recombination rate when the anneal temperature increases from 700 to 1100 °C, and the anneal temperature at peak increases while the implant dose increases. Furthermore, the radiative recombination rate always increases with the implant dose but it saturates at a high dose. However, the radiative recombination rate does not change significantly with the implant energy.
A series of isothermal annealing experiments have been performed in the range 790–920°C under N2 flow in order to study the deuterium out-diffusion kinetics of Mg-doped GaN grown on sapphire under deuterated ammonia. The deuterium concentration was measured by SIMS analysis before and after each annealing step. The kinetics closely follow a first-order law. The activation energy related to the deuterium out-diffusion process is 3.1 eV. In addition, deuterium effusion measurements were performed measuring the molecular HD flux while the specimens were annealed in ultra high vacuum with a linear heating rate. In contrast to SIMS, this method detects the species that migrated out of the sample. Effusion peaks of the HD flux at 360 and 490°C are attributed to the fragmentation of adsorbed CHxDy complexes. The molecular HD flux starts increasing at 800°C which is the onset of the GaN decomposition and has its maximum at 920°C. This HD flux is accompanied by the desorption of H and D containing radicals and molecules desorbing above 900°C.
B12As2 epitaxial layers grown on (0001) 6H-SiC and (1120) 6H-SiC substrates have been studied using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and synchrotron white beam x-ray topography (SWBXT) and investigated with the aid of crystal visualization software. SWBXT showed that B12As2 adopted  growth orientation, parallel to SiC, on c-plane 6H-SiC and adopted  growth orientation, parallel to SiC, on a-plane 6H-SiC. However, SWBXT also revealed the twins in both sets of the B12As2 films, consistent with the SEM observation of the surface morphology. Cross-sectional HRTEM also confirmed the presence of twins in both cases and also revealed the existence of an intermediate layer between the c-plane 6H-SiC and the B12As2 film. By correlating the HRTEM observation and crystal visualization, the atomic configurations across the twin boundaries in both samples as well as those in the intermediate layer in the c-plane sample were proposed.
We report the observation of threading dislocation de-multiplication process by transmission electron microscopy (TEM). The GaN films used in this study were grown on (0001) sapphire substrates with LT-GaN buffer layers by reduced pressure organometallic vapor phase epitaxy. By using g · Db = 0 invisibility criterion, it was found that some of TDs were de-multiplicated by interactions among themselves. In particular, type a+c TDs were found to nucleate through the interactions between type a and type c TDs in GaN near the GaN/sapphire interface so that the de-multiplication of TDs in GaN films was achieved.
The techniques of small angle X-ray scattering and transmission electron microscopy are applied to characterize the size distribution of nanocavities in a (111) Si wafer multi-implanted with He+ in the Mev range energy. The comparison between both methods shows that they all give access to the same structural information but small angle X-ray scattering additionally offers the possibility to monitor the cavity size distribution during a thermal treatment. Moreover, providing that the collected data are of good quality, the former method also allows the knowledge of the porosity of the implanted Si wafer.