Raman study of As outgassing and damage induced by ion implantation in Zn-doped GaAs

Abstract : Room temperature micro-Raman investigations of LO phonon and LO phonon-plasmon coupling is used to study the AsAs outgassing mechanism and the disordering effects induced by ion implantation in ZnZn-doped GaAsGaAs with nominal doping level p=7×1018cm−3p=7×1018cm−3. The relative intensity of these two peaks is measured right after rapid vacuum thermal annealings (RVTA) between 200 and 450°C450°C, or after ion implantations carried out at energies of 40keV40keV with P+P+, and at 90 and 170keV170keV with As+As+. These intensities provide information regarding the Schottky barrier formation near the sample surface. Namely, the Raman signature of the depletion layer formation resulting from AsAs desorption is clearly observed in samples submitted to RVTA above 300°C300°C, and the depletion layer depths measured in ion implanted GaAs:ZnGaAs:Zn are consistent with the damage profiles obtained through Monte Carlo simulations. Ion channeling effects, maximized for a tilt angle set to 45°45° during implantation, are also investigated. These results show that the Raman spectroscopy is a versatile tool to study the defects induced by postgrowth processes in multilayered heterostructures, with probing range of about 100nm100nm in GaAsGaAs-based materials

Formation of Pd2Si on single-crystalline Si (100) at ultrafast heating rates : an in-situ analysis by nanocalorimetry

The kinetics of intermediate phase formation between ultrathin films of Pd (12 nm) and single-crystalline Si (100) is monitored by in-situ nanocalorimetry at ultrafast heating rates. The heat capacity curves show an exothermic peak related to the formation of Pd2Si. A kinetic model which goes beyond the conventional linear-parabolic growth to consider independent nucleation and lateral growth of Pd2Si along the interface and vertical growth mechanisms is developed to fit the calorimetric curves. The model is used to extract the effective interfacial nucleation/growth and diffusion coefficients at the unusually high temperatures of silicide formation achieved at very fast heating rates

Effect of elevated substrate temperature deposition on the mechanical losses in tantala thin film coatings

Brownian thermal noise in dielectric multilayer coatings limits the sensitivity of current and future interferometric gravitational wave detectors. In this work we explore the possibility of improving the mechanical losses of tantala, often used as the high refractive index material, by depositing it on a substrate held at elevated temperature. Promising results have been previously obtained with this technique when applied to amorphous silicon. We show that depositing tantala on a hot substrate reduced the mechanical losses of the as-deposited coating, but subsequent thermal treatments had a larger impact, as they reduced the losses to levels previously reported in the literature. We also show that the reduction in mechanical loss correlates with increased medium range order in the atomic structure of the coatings using x-ray diffraction and Raman spectroscopy. Finally, a discussion is included on our results, which shows that the elevated temperature deposition of pure tantala coatings does not appear to reduce mechanical loss in a similar way to that reported in the literature for amorphous silicon; and we suggest possible future research directions

Exploration of co-sputtered Ta 2 O 5 -ZrO 2 thin films for gravitational-wave detectors

We report on the development and extensive characterization of co-sputtered tantala–zirconia (Ta2O5-ZrO2) thin films, with the goal to decrease coating Brownian noise in present and future gravitational-wave detectors. We tested a variety of sputtering processes of different energies and deposition rates, and we considered the effect of different values of cation ratio η = Zr/(Zr + Ta) and of post-deposition heat treatment temperature T a on the optical and mechanical properties of the films. Co-sputtered zirconia proved to be an efficient way to frustrate crystallization in tantala thin films, allowing for a substantial increase of the maximum annealing temperature and hence for a decrease of coating mechanical loss φ c. The lowest average coating loss was observed for an ion-beam sputtered sample with η = 0.485 ± 0.004 annealed at 800 °C, yielding φ¯c=1.8×10−4 rad. All coating samples showed cracks after annealing. Although in principle our measurements are sensitive to such defects, we found no evidence that our results were affected. The issue could be solved, at least for ion-beam sputtered coatings, by decreasing heating and cooling rates down to 7 °C h−1. While we observed as little optical absorption as in the coatings of current gravitational-wave interferometers (0.5 parts per million), further development will be needed to decrease light scattering and avoid the formation of defects upon annealing

PACS: 61.72.Cc; 61.72.Ji; 61.80

Abstract 10 Defects produced in 8 MeV proton irradiated silicon were studied using Fourier transform infrared spectroscopy 11 (FTIR) and positron annihilation measurements (PAS). Isothermal annealing of the divacancy absorption band 12 monitored using FTIR, has been compared with PAS on similar samples. The two methods agree perfectly during 13 isothermal annealing at 150°C, but at 250°C the 1.8 lm absorption band disappears after annealing for 60 min, 14 whereas positron lifetime and trapping rate remain constant, and annealing to 500°C is required to remove the di-15 vacancy response. Since divacancies are not mobile at 150°C their annealing can be ascribed to recombination with 16 mobile interstitials. The discrepancy observed during annealing at 250°C is suggested to be a consequence of some sor

NlWil B Beam Interactions with Materials 8 Atoms Quantitative depth profiling of light elements by means of the ERD E X B technique

Abstract ERDA [J. L'kuyer et al., J. Appl. Phys. 47 (1976) 3811 is a technique of great interest for quantitative depth profiling of light elements in matter. The use of crossed electric and magnetic fields (E X B filter) [G.G. Ross et al. J. Nucl. Mater. 128/129 (1992) 484; G.G. Ross and L. Leblanc, Nucl. Instr. and Meth. B 62 (1992) 4841 in place of the traditional absorber, enhances the resolution by eliminating the straggling induced normally by the absorber and removes the uncertainty on the absorber thickness. The E X B filter allows the simultaneous detection of different particles such as H, D and He. This work presents the first ERD E X B depth profiling by means of a heavy ion beam. Compared with the usual ERD E X B with 350 keV He, the 2.54 MeV 15N beam enhances scattering cross section by a factor of 3, has equivalent depth resolution (l-3 nm at surface) and gives a depth probe twice deeper