Resolution Rutherford Backscattering Research Articles

Spectroellipsometric detection of silicon substrate damage caused by radiofrequency sputtering of niobium oxide

Substrate surface damage induced by deposition of metal atoms by radiofrequency (rf) sputtering or ion beam sputtering onto single-crystalline silicon (c-Si) surface has been characterized earlier by electrical measurements. The question arises whether it is possible to characterize surface damage using spectroscopic ellipsometry (SE). In our experiments niobium oxide layers were deposited by rf sputtering on c-Si substrates in gas mixture of oxygen and argon. Multiple angle of incidence spectroscopic ellipsometry measurements were performed, a four-layer optical model (surface roughness layer, niobium oxide layer, native silicon oxide layer and ion implantation-amorphized silicon [i-a-Si] layer on a c-Si substrate) was created in order to evaluate the spectra. The evaluations yielded thicknesses of several nm for the i-a-Si layer. Better agreement could be achieved between the measured and the generated spectra by inserting a mixed layer (with components of c-Si and i-a-Si applying the effective medium approximation) between the silicon oxide layer and the c-Si substrate. High depth resolution Rutherford backscattering (RBS) measurements were performed to investigate the interface disorder between the deposited niobium oxide layer and the c-Si substrate. Atomic resolution cross-sectional transmission electron microscopy investigation was applied to visualize the details of the damaged subsurface region of the substrate.

Trace element quantification in high-resolution Rutherford backscattering spectrometry

The potential of high resolution Rutherford Backscattering (RBS) for identification and quantification of created elements in thin films was investigated. A beam of 250 keV d + ions from the AN700 van de Graaff accelerator in Linz was used to characterize the composition of an organic multi-element compound, i.e. a thin film of dried human blood on a carbon substrate. It was possible to identify more than 10 chemical elements with high accuracy, in the absence of any matrix effects. For instance, the Fe concentration was determined with a relative error <3% (400 ± 10 ppm), in perfect agreement with standard blood test values. The detection limit of heavy elements with atomic number higher than Fe was found to be below 50 ppm.

Structure and defects of epitaxial Si(111) layers on Y2O3(111)/Si(111) support systems

Single crystalline epitaxial Si(111)/Y2O3(111)/Si(111) heterostructures were grown by molecular beam epitaxy and the morphology, structure, and defects were characterized in detail. The growth of a closed and smooth layer system is demonstrated by means of reflection high energy electron diffraction measurements. X-ray reflectometry and high resolution Rutherford backscattering (RBS) experiments show low surface and interface roughnesses. Channeling RBS as well as x-ray diffraction pole figure studies demonstrate the type A/B/A epitaxy relationship of the Si(111)/Y2O3(111)/Si(111) heterostructure and reveal the existence of defects in the epitaxial Si(111) layer. These defects are studied in detail with high resolution transmission electron microscopy, disclosing microtwin formation and type B Si grains as the major defects.

Structural and compositional analysis of strain relaxed InGaAs/InP multi quantum wells

The structural and compositional analysis of strain relaxed InGaAs/InP multi quantum wells (MQWs) have been carried out using high resolution X-ray diffraction (HRXRD), Raman spectroscopy (RS) and Rutherford backscattering spectrometry (RBS). The surface morphology has been investigated by atomic force microscopy (AFM). No satellite peaks have been observed in the symmetrical X-ray scans indicating strong strain relaxation, highly mixed InGaAs/InP interfaces and no multilayer characteristics. This limits the structural as well as compositional analysis. Dynamical scattering theory based simulation package has been used to simulate the respective spectra and compared. The RS study shows huge Raleigh scattering induced background resulting low intense phonon modes. In spite of the background we could observe the GaAs and InAs type phonon modes which have been used for the analysis. The RBS studies also indicate the mixed InGaAs/InP interfaces with preferential GaAs and InP precipitation/segregation and the results are discussed in detail comparing with other complementary techniques. Also, AFM analysis has been utilized to obtain the composition in comparison with related literature.

Structural and optical properties of GaAs quantum dots formed in SiO 2 matrix

A shallow sequential ion implantation of As and Ga ions into pure silica substrates was conducted to form GaAs quantum dots near the substrate surface. The main efforts were made to understand how the post thermal annealing affects the formation, thermal stability, and chemical composition of nanoparticles in a silica host. When the sample was annealed at 600 °C under 96% Ar + 4% H 2, X-ray diffraction (XRD), infrared reflectance (IR reflectance), and tunneling electron microscopy (TEM) confirmed the formation of GaAs quantum dots near the silica surface. X-ray photoemission spectroscopy (XPS) showed 3d electron binding energies of Ga and As at 18.8 eV and 40.75 eV suggesting GaAs nanocrystal formation. An additional band was also observed at ∼ 20.12 eV which was attributed to the presence of GaO x . At 1000 °C, however, an additional peak is also observed near 44.1 eV indicating As 2O 3 formation. It was argued that the formation of GaO x at 600 °C and As 2O 3 at 1000 °C was primarily due to the volatile nature of the Ga and its related compounds. High resolution Rutherford back scattering (RBS) using 14N 3+ ions showed that 1000 °C annealing resulted in 50% loss of Ga and a 35% position shift toward the surface while As concentration is unchanged with a 25% position shift toward the surface.

プラズマベースイオン注入法を用いた窒素イオン注入表面の高分解能ラザフォード後方散乱分光法による評価

プラズマベースイオン注入法を用いた窒素イオン注入表面の高分解能ラザフォード後方散乱分光法による評価

KrF laser epitaxy of silicon germanium alloy layers by irradiation of Si(1−x)Gex/Si (100) structures

KrF excimer laser pulses at 248 nm were used to irradiate Ge and SiGe films grown on Si (100) by ultrahigh vacuum chemical vapor deposition (CVD) or to assist the CVD growth itself. In both cases the laser energy density was sufficiently high (0.5 J/cm2) to melt the whole CVD film. The CVD growth either without or with laser assistance, as well as the post-growth irradiation were monitored by online single wavelength ellipsometry, which allowed to follow in real time the modification of the film morphology induced by the laser treatment. Effective smoothing of the surface islands upon laser irradiation was revealed in every case. Particularly, for the laser-assisted CVD growth, the influence of the laser irradiation modality on the surface microroughness during growth was evidenced and the irradiation condition for optimal surface planarization identified. The microstructural properties of the SiGe layers were investigated by high resolution x-ray diffraction and Rutherford backscattering spectrometry. In the case of the laser-assisted CVD growth, the solidification of alloys exhibiting excellent epitaxial quality and graded Ge profiles was attained. The alloys resulted fully strained for Ge content of 5 at %. This growth technique which allows to design the Ge profile inside the alloyed layer, by adjusting precursor gas fluxes and laser irradiation conditions, results particularly attracting for the production of compositionally graded SiGe film, to be applied as buffer layers in SiGe based devices.

Josephson junctions fabricated by oxygen ion irradiation of YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin films

Ion irradiated microbridges are an interesting type of Josephson junction, because their technological requirements can be very low. In this paper a specialized fabrication process and the electrical characterization of the fabricated devices are reported on. The I/sub C/R/sub N/ product at 77 K is about 24 /spl mu/V. The phase coherence was proven by measurements on DC-SQUIDs made of these junctions. To get a deeper insight of the damage produced by ion irradiation, YBa/sub 2/Cu/sub 3/O/sub 7-x/, thin films have been investigated by high resolution transmission electron microscopy (HRTEM) and Rutherford backscattering spectroscopy (RBS).

Growth of Epitaxical SiC Layers onto on and off Axis 6H SiC Substrates by Ion Beam Deposition

ABSTRACTThin films of β SiC have been grown epitaxically onto on axis (0001) 6H α SiC substrates using ion beam deposition. The ion beam deposition technique involves the direct deposition of alternating layers of 13C+ and 30Si+. The carbon and silicon ions were obtained from an ion implanter by decelerating mass analyzed ion beams to 40 eV. The SiC substrate was held at ∼973 K. Thin films of α-SiC (a mixture of α- polytypes) were obtained following deposition onto off axis (∼2°) 6H α-SiC. High resolution electron microscopy and Rutherford backscattering techniques were used to determine the structure and crystalline perfection of the resulting layers.

Investigation of the interstitial site in As+-ion-implanted GaAs by means of a multidirectional and high-depth resolution RBS/channelling technique

The double-yield peak and the site exchange of the responsible interstitial atoms on annealing have been observed for the first time in a low-dose As+-ion-implanted GaAs crystal by means of a high-depth resolution and multidirectional Rutherford back-scattering (RBS)/channelling technique. The newly observed second peak is located deeper than the conventional first peak around the projected range Rp. After annealing at 200-250 degrees C, it is found that the interstitial atoms responsible for both peaks change their sites during aging at a low temperature (RT approximately 40 degrees C) and occupy a more stable bond-centred interstitial site for the first peak and a mixed site of the bond-centred and a split (100) one for the second peak. It is concluded that a split (100) site may be one of the most stable sites in the GaAs even at a higher temperature.

Early Stages Of Reaction Between Amorphous Ni-Nb And Crystalline Au Films

ABSTRACTThin film interactions between a-(Ni-Nb) and polycrystalline Au over-layers have been studied with high depth resolution (≤1.7nm) Rutherford backscattering (RBS) and TEM to obtain information on the early stages of reaction at the interface. The RBS spectra from Au indicated that the interdiffused samples consisted of two layers: an Au-Nb binary layer on the surface and a ternary Au-Ni-Nb compound layer beneath the binary layer. The growth kinetics of the ternary compound layer differed in samples which had been relaxed prior to Au deposition from the kinetics for unrelaxed samples. Furthermore, cross section TEM micrographs showed that relaxed and unrelaxed samples exhibit different microstructures after the early stages, of annealing. We interpret this result to indicate that the reaction stages in relaxed samples are not as advanced as those in the unrelaxed samples.

Ion implantation process modelling

A simulation program for implantation (IMPLAN) has been developed as part of a complete silicon planar technology simulation program (STEP, Silicon Technology Evaluation Program). The input parameters of IMPLAN are the type of implanted ions, the target material, the kind of the eventual covering surface layer and its thickness, the energy of the ion implantation and the dose. The output is the dopant profile in numerical or graphical format. Joined half-Gaussian and Pearson distributions are used in the program in order to get high accuracy. To measure implanted depth profiles we used a high resolution Rutherford backscattering (RBS) technique. Comparison of the experimental results ans simulations shows that the difference between theory and experiment is mostly less than the errors of the measurements.

Low-temperature annealing behavior of Se-implanted GaAs studied by high resolution Rutherford backscattering channeling

High resolution Rutherford backscattering (RBS) and channeling measurements have been used to study the recrystallization of Se-implanted GaAs layers. Investigation of the solid phase growth kinetics at temperatures between 200 and 600 °C showed that the amorphous layer starts to regrow at 200 °C epitaxially from the crystalline-amorphous interface but stops, at 200 °C, after about 30% of the layer has regrown. For temperatures of 250 °C and above complete regrowth occurs. Although various amounts of disorder remain, it decreases in amount with increasing temperature. One step annealing at 600 °C for 30 minutes results in a RBS channeling quality comparable to the undamaged crystal.

The corrosion behaviour and rutherford backscattering analysis of palladium-implanted titanium

The corrosion behaviour of Pd-implanted Ti in boiling 1M H 2SO 4 has been investigated by means of high resolution Rutherford backscattering (RBS) profiles of the Pd concentration as a function of corrosion time, and by electrochemical methods consisting of corrosion potential vs time curves and potentiostatic polarization data. Employing ion-implanted Xe as a surface ‘marker’, absolute corrosion rates were determined by RBS analysis and compared to corrosion rates determined from the polarization curves. The rate of Ti dissolution is found to be reduced by about three orders of magnitude for Pd-implanted samples. The corrosion potential-time curves and high resolution RBS data both show that soon after immersion, the Pd surface concentration rises to 20 at.% because of preferential dissolution of Ti and that the Pd is retained in the surface for corrosion times of up to 9 h. The steady state corrosion potential of implanted samples is close to that of pure Pd and 800 mV anodic with respect to the corrosion potential of pure Ti. The protection is explained by the fact that the mixed electrode potential is more noble than the critical potential for passivity of Ti, resulting in a markedly reduced dissolution rate.

Diffusion behaviour of Pb in high dose implanted silicon layers during isothermal annealing

Abstract High depth resolution Rutherford backscattering (RBS) has been employed to investigate the diffusion behaviour of Pb in high dose implanted (111) Si during isothermal annealing. Results indicate that rapid Pb outdiffusion accompanies the recrystallization of surface layers rendered amorphous by high dose Pb implantation. The timescale of the rapid outdiffusion process, which may be related to the period of recrystallization of the amorphous layers has been found to be about 110 minutes for 80 keV, 1016” cm−2 and 5 × 1015 cm”: Pb-implanted (111) Si layers isothermally annealed at 565°C. Following an initial dead time, during which no diffusion occurs, the subsequent initial rate of Pb outdiffusion apparently increases linearly with implantation dose. The “dead” time was observed to vary with annealing temperature in the range 500–600°C.