Disorder Depth Profiles Research Articles

RaDMaX online: a web-based program for the determination of strain and damage profiles in irradiated crystals using X-ray diffraction

RaDMaX online is a major update to the previously published RaDMaX (radiation damage in materials analysed with X-ray diffraction) software [Souilah, Boulle & Debelle (2016). J. Appl. Cryst. 49, 311–316]. This program features a user-friendly interface that allows retrieval of strain and disorder depth profiles in irradiated crystals from the simulation of X-ray diffraction data recorded in symmetrical θ/2θ mode. As compared with its predecessor, RaDMaX online has been entirely rewritten in order to be able to run within a simple web browser, therefore avoiding the necessity to install any programming environment on the users' computers. The RaDMaX online web application is written in Python and developed within a Jupyter notebook implementing graphical widgets and interactive plots. RaDMaX online is free and open source and can be accessed on the internet at https://aboulle.github.io/RaDMaX-online/.

Damage accumulation in MgO irradiated with MeV Au ions at elevated temperatures

The damage accumulation process in MgO single crystals under medium-energy heavy ion irradiation (1.2 MeV Au) at fluences up to 4 × 1014 cm−2 has been studied at three different temperatures: 573, 773, and 1073 K. Disorder depth profiles have been determined through the use of the Rutherford backscattering spectrometry in channeling configuration (RBS/C). The analysis of the RBS/C data reveals two steps in the MgO damage process, irrespective of the temperature. However, we find that for increasing irradiation temperature, the damage level decreases and the fluence at which the second step takes place increases. A shift of the damage peak at increasing fluence is observed for the three temperatures, although the position of the peak depends on the temperature. These results can be explained by an enhanced defect mobility which facilitates defect migration and may favor defect annealing. X-ray diffraction reciprocal space maps confirm the results obtained with the RBS/C technique.

Implantation damage study in ferromagnetic Mn-implanted Si

To investigate the influence of the residual implant damage and postimplant annealing upon the structure and magnetic properties of Mn-implanted Si, lattice disorder depth profiles were obtained from Rutherford backscattering spectroscopy (RBS)-channeling experiments on Mn-implanted ⟨100⟩ oriented p-type Si wafers. The defect concentration profiles were extracted from the RBS spectra using the two beam model. These profiles reveal a strong influence of the postimplant annealing temperatures upon the defects generated from implantation. Specifically, above 800°C, the backscattering yield from Si lattice defects decreases, which is coincident with a decrease in the magnetization. The evolution of the Mn concentration profiles and the magnetization suggest that the magnetization originates from Mn atoms located in the least damaged region.

Complementary use of ERDA and RBS/C for the determination of implanted atom and damage distributions in spinel

Crystalline oxide ceramics (particularly, zirconia and spinel) are promising matrices for nuclear waste immobilization and/or transmutation. The behavior of implanted ions and of radiation damage is a very important issue in the qualification of nuclear matrices. Ion beams provide very efficient tools for such an evaluation. This paper presents the results obtained for spinel single crystals implanted with He and Ar ions at fluences of 1017 and 2×1016cm−2, respectively. He and Ar depth profiles were measured by ERDA using high-energy Cu ions. The Ar depth profile was also determined by RBS. The evaluation of the amount of radiation damage induced in Al, Mg and O sublattices of spinel single crystals by ion implantation was done using both a classical analytical procedure and Monte-Carlo simulations of channeling data. The disorder depth profiles using the two methods are compared and correlated with He and Ar depth profiles.

Low-temperature silicon homoepitaxial growth by pulsed magnetron sputtering

Undoped silicon (Si) films have been deposited on Si (100) substrates by pulsed magnetron sputtering in pure Ar atmosphere at substrate temperatures TS between 300 and 450°C. Rutherford backscattering channeling (RBS-C) experiments reveal high structural order indicative of epitaxial growth at TS of 375–400°C. The disorder depth profiles derived from RBS-C exhibit defective initial film growth which is markedly reduced in the film volume. Homoepitaxial silicon film growth is observed in this optimal temperature range up to a thickness of 1.6μm and with growth rates of about 20nm/min. At higher and lower substrate temperatures, the disorder in the films is considerably enhanced.

Experimental Study on the Role of Hydrogen in the Breakdown of Low-Temperature Si Epitaxy

AbstractHomoepitaxial Si layers were grown on Si(100) at temperatures of 325 - 500 °C by Electron-Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposition (ECR PECVD) from a gas mixture of SiH4,H2 and Ar. Ar was added in order to realize high growth rates where the breakdown of epitaxy was well observed. Si disorder depth profiles derived from RBS channeling spectra were compared with hydrogen depth distributions measured by Heavy-Ion Elastic Recoil Detection Analysis (HI-ERDA) and Secondary Ion Mass Spectroscopy (SIMS). The results suggest that the transition from epitaxial to amorphous growth proceeds through two stages: (1) a highly defective but still ordered growth with the defect density increasing as the growth proceeds and (2) the formation of conically shaped precipitates of amorphous Si. Both regions act as an increasingly effective sink for excessive hydrogen which diffuses from the growth surface into the bulk of the sample. In perfectly grown epitaxial films, where the overall concentration of excessive hydrogen was low, the hydrogen diffusion tail was found to extend far beyond the interface into the Si substrate.

Effect of Oxygen Ion Implantation in Gallium Nitride

Epitaxial single crystal GaN films (2.0 μm thick) were implanted 60° off the <0001> surface normal with 600 keV O+ ions at 190 or 210 K over a range of ion fluences from 4.8×1017 to 5.0×1020 ions/m2. The implantation damage, as determined by in-situ Rutherford Backscattering Spectrometry in a <0001> channeling geometry (RBS/C), ranged from dilute defects up to the formation of a disorder saturation state that was not fully amorphous. The relative disorder on the Ga sublattice exhibited a sigmoidal dependence on ion fluence. Results show that GaN crystals are extremely resistant to the ion implantation damage as compared to other ceramic materials like SiC. An asymmetric shape in the angular scan curve around the <0001> axis, which might be associated with the Ga lattice distortion in the crystal structure, was observed for the as-irradiated material to the highest ion fluence (5.0×1020 O+/m2) at 210 K. Comparisons of Ga disorder depth-profiles from the experiment and SRIM97 simulations suggest that the damage peaks shift to greater depths at the low irradiation temperature (210 K). Significant recovery of these defects was not observed in the isochronal annealing steps (20-min) up to 970 K.

Effect of Oxygen ION Implantation in Gallium Nitride

AbstractEpitaxial single crystal GaN films (2.0 μtm thick) were implanted 60° off the <0001> surface normal with 600 keV O+ ions at 190 or 210 K over a range of ion fluences from 4.8x 1017 to 5.0 × 1020 ions/m2. The implantation damage, as determined by in-situ Rutherford Backscattering Spectrometry in a <0001> channeling geometry (RBS/C), ranged from dilute defects up to the formation of a disorder saturation state that was not fully amorphous. The relative disorder on the Ga sublattice exhibited a sigmoidal dependence on ion fluence. Results show that GaN crystals are extremely resistant to the ion implantation damage as compared to other ceramic materials like SiC. An asymmetric shape in the angular scan curve around the <0001> axis, which might be associated with the Ga lattice distortion in the crystal structure, was observed for the as-irradiated material to the highest ion fluence (5.o× 1020 O+/m2) at 210 K. Comparisons of Ga disorder depth-profiles from the experiment and SRIM97 simulations suggest that the damage peaks shift to greater depths at the low irradiation temperature (210 K). Significant recovery of these defects was not observed in the isochronal annealing steps (20-min) up to 970 K.

Radiation damage in Ge induced by Te + implantation near channeling conditions

Samples of (100), (111) and (110) oriented Ge-crystals were implanted with 40 keV Te + ions at fluences between 5 × 10 13 and 5 × 10 14 cm −2. The beam alignment during the implantation was α = 0 ° or within 6 to 7° from the surface normal. The disorder depth profiles were analysed by using conventional and high depth resolution RBS channeling of 2 MeV helium ions. The damage profiles for implantation at α smaller than the critical angle for axial channeling (ψ c) show an increase in the average penetration depth and a reduction in the damage peak in comparison to the case of α exceeding ψ c. In parallel, a MARLOWE based computer code is applied to simulate the atomic collision cascades and resulting impurity and disorder depth distributions.

The influence of dose rate and implantation temperature on the damage produced by N+ion irradiation of silicon

Abstract Low angle exit (9°) Rutherford backscattering geometry and channelling of 2 MeV 4He+ has been employed to investigate the disorder depth profiles generated by N+ implantation of Si. It is shown that the measured damage, following N+ irradiation, depends significantly upon the ion dose rate as well as substrate temperature during irradiation. A beam heating effect during implantation also influences defect formation.

Defect and dopant depth profiles in boron-implanted silicon studied with channeling and nuclear reaction analysis

Single crystals of silicon were implanted at RT with 1 MeV boron ions to a dose of 1 × 10 15 ions/cm 2. The depth profile of the boron was measured using the 2060-keV resonance of the 11B(α, n) 14N nuclear reaction. The distribution of the lattice disorder as a function of depth was determined from channeling of MeV α-particles. This was done in the as-implanted case and after furnace annealing at temperatures up to 1000°C. A short description of the applied techniques is presented. The crystal disorder was found to almost vanish during annealing at 600°C and to reappear at higher annealing temperatures at a depth coinciding with the projected range of the boron ions. Both the boron and the disorder depth profiles are broadened after annealing at 1000°C. The results agree with recent findings on defect annealing in silicon.

Ion-beam-induced epitaxial regrowth of amorphous layers in silicon on sapphire

A neon ion beam has been used to regrow epitaxially a ~1700-\AA{}-thick amorphous surface layer in silicon on sapphire at low temperatures. The damaged layer was produced by implanting 80-keV silicon ions to a dose of $2\ifmmode\times\else\texttimes\fi{}{10}^{15}$ ions/${\mathrm{cm}}^{2}$ at room temperature. The channeling technique with 315-keV protons was used to investigate the depth distribution of the damage, and disorder depth profiles were extracted from the backscattering spectra using calculations based on multiplescattering theory. The epitaxial regrowth was quantitatively determined from the extracted profiles. Many of the parameters which influence the regrowth rate, such as dose, dose rate, target temperature, energy, and random or channeled direction for the annealing beam, were varied. The results were compared with energy deposition calculations which indicated strongly that the annealing rate depends on the energy deposited in elastic collisions by the annealing ion beam. A defect annealing model based on vacancy diffusion is discussed.

The radiation damage in high-dose argon-implanted silicon

Abstract Measurements of the depth profiles of disorder produced in silicon by argon ions implanted at energies of 20-300 keV and with a fluence of 1016 to 1017/cm2 were made by profiling the oxide growth rate.

Depth profile studies of extended defects induced by ion implantation in Si and Al

Depth profiles of disorder characterized by extended defects can be obtained by ion channeling and this capability provides an important extension to studies of implanted systems. A planar channeling analysis technique using 2 MeV /sup 4/He backscattering is developed and applied to two cases. In both cases transmission electron microscopy (TEM) is used to confirm the nature and density of extended defects present. The first case is for channeled implants of P into Si which produces a known density of dislocations at a fixed depth below the surface upon annealing. The second case is Ni-implanted Al, and the first determination of the depth profile of the disorder induced by implantation in Al is obtained.

Disorder production and amorphisation in ion implanted silicon

Abstract Measurements of the depth profiles of disorder and the depth integrated disorder produced in Si at 40 K or 300 K by low energy (15 keV-60 keV) ions of a range of masses from the light (N+ and P+), intermediate (Ar+ and As+) to heavy (In+, Sb+, As+ 2, Bi and Sb+ 2) were made using Rutherford scattering-dechannelling techniques. Studies of both the ‘surface peak’ disorder and the dechannelling minimum indicate a gradual change in the process of disorder production from one of point defect generation for light projectiles to direct impact amorphisation for heavy projectiles. In the lower mass ion cases it is concluded that amorphisation is produced by overlap of more lightly disordered regions and it is shown how all the data can be encompassed within a generalized model of amorphousness production which occurs when local defect densities lie in the range 2–18%.

The application of low angle Rutherford backscattering and channelling techniques to determine implantation induced disorder profile distributions in semiconductors

Low angle exit (9°) Rutherford backscattering geometry and chanelling of 2 MeV 4He + are employed to investigate the disorder depth profiles created by 40 keV N + implantation in (111) silicon and (100) GaAs targets. Parameters which can influence the disordering rate and its spatial distribution, such as ion fluence, flux, substrate type and substrate temperature are examined. Under certain implantation conditions, the damage profile distributions are asymmetric — exhibiting a bimodal form in silicon targets or confined much closer to the GaAs surface than the normally expected mean range of 40 keV N + ions.

Fluence dependence of disorder depth profiles in Pb implanted Si

Abstract The total, depth integrated disorder, induced by Pb implantation into Si at room temperature, initially increases rapidly with implantation fluence and then reaches a quasi saturation level where the increase with fluence is slow. Measurements of the depth distributions of the disorder, using high resolution low angle exit Rutherford Backscattering/Channelling analysis, suggest that the quasi saturation results from overlapping of disordered zones generated deep in the tail of the disorder-depth profiles. The depth of the disordered solid-crystal boundary, XD increases with ion fuence φ, according to the relation XD = x- + f[φ).[sgrave]., where x- is the most probable projected depth and [sgrave] the projected standard deviation of disorder generation. It is shown that this relationship is consistent with an approximately Gaussian depth distribution of disorder production.