F. Meyer

Raman scattering and stress measurements in Si1−xGex layers epitaxially grown on Si(100) by ion‐beam sputter deposition

Si1−xGex thin films have been grown on silicon substrates by ion‐beam sputter deposition (IBSD). Film stress has been determined from the change in deflection curvature of the substrate after deposition and strain has been investigated by using Raman scattering spectroscopy. These properties have been studied as a function of different parameters: growth temperature, layer thickness, and annealing conditions. Raman and stress results are in close correspondence with regard to effects of deposition temperature. Si‐rich films (0≤x≤0.3) were compressively strained for all deposition temperatures. A compressive to tensile stress change was observed in the Ge‐rich alloys (x=0.6) when the growth temperature reached Tg ≊ 500u2009°C. In addition, the strain as a function of depth from the surface has been studied by changing the laser wavelength. The strain has been shown to increase from the surface to the interior of the film. The origin of the stress observed in IBSD films is discussed and we show that this stress...

Ion beam sputtering deposition of tungsten: energy and mass effects of primary ions

Abstract The present work reports a study on the dependence of the properties of ion beam sputter deposited (IBSD) tungsten on silicon upon energy and mass effects of primary ions. Properties of thin W films ( t = 100–3000 A ) such as morphology (SEM), microstructure (XRD), impurity content (RBS) and resistivity were investigated. XRD patterns exhibit only the bcc α-W whatever the experimental parameters. The use of xenon leads to the best electrical characteristics; in this case resistivity depends weakly on incident ion energy and its variation versus thickness is rather well described in terms of a grain boundary scattering mechanism, whereas layers obtained with argon exhibit higher resistivities, which strongly depend on ion energy. We show that back-scattered ions from the target can account for the observed argon content. The more efficient electron-scattering centers appear to be argon atoms embedded in the growing film. This explanation agrees fairly well with results we obtained for DC magnetron sputter deposition and post deposition 45 keV Ar+ implantation.

Epitaxial growth of single-crystal Si1−xGex on Si(100) by ion beam sputter deposition

The first results are reported on Si1−xGex epitaxial layers grown on Si(100) by ion beam sputter deposition in ultrahigh vacuum. Growth temperatures were varied from 300 to 700°C, for compositions in the range 0.05 < x < 0.5. The properties of the grown films, such as morphology and structure, were studied by scanning electron microscopy and reflection high-energy electron diffraction respectively. Results indicate good monocrystallinity for the entire range of deposition temperature used. For deposition temperatures over 300°C, the films have smooth surfaces for all compositions and thicknesses. The distorted lattice parameters of epitaxial Si0.7Ge0.3 layers were measured by double-crystal diffractometry and the tetragonal strain was calculated. Increasing deposition temperature results in strain relaxation. Layers 3000 A thick grown at 400°C still retain a larger strain than that measured in a similar layer grown by molecular beam epitaxy. All these results may show the effects of energetic bombardment on the growing film.

Local strains in Si1−x−yGexCy alloys as deduced from vibrational frequencies

Abstract Raman spectroscopy has been used to study the bond structure of Si 1− x − y Ge x C y alloys. An anharmonic model for the force constants is applied to interpret the results. It is well established that the Ge and C concentrations in these alloys can be chosen so that their average lattice constants may be equal to, or even smaller than that of the Si lattice. Our Raman results show that the C local mode vibrational energy increases rapidly with increasing C concentration, at a rate of 3.2 cm −1 /at%. Additional fine structure is observed near the Si–C main peak in samples grown by rapid thermal chemical vapor deposition (RTCVD). This fine structure is absent in samples grown by pulsed laser induced epitaxy (PLIE). In agreement with previous studies, the satellite structure of the Si–C peak is interpreted as an indication for short-range order. Our analysis shows that pronounced differences exist in the microscopic structures of SiGeC alloys grown by different growth techniques.

Argon incorporation effects on the conductivity of metal layers

Almost all plasma- and ion-beam-based deposition techniques involve energetic particle bombardment of the growing film and lead to a more or less significant incorporation of noble gas. This incorporation is considered by most researchers to have a negligible effect on the electron mobility in the films. It is clearly established that the conductivity of metals is limited by oxygen contamination and, for very thin films, by the reflection of electrons on the film interfaces and on the grain boundaries. We studied tungsten films deposited by ion beam sputter deposition, with Ar+ or Xe+ energies ranging from 0.3 keV to 20 keV. We also studied silver deposited by ion-beam-assisted deposition (IAD) with Ar+ over the energy range 0.25–1 keV. The incorporation of noble gas depends on the mass and on the energy of primary ions for sputtering and on the energy and the ion:neutral flux ratio for IAD: it is found to vary between 0% to 5% and may be modified by post-deposition implantation at 45 keV. For film thicknesses above 50-100 nm, the resistivities of argon-free layers are 2.5 μΩ cm and 9 μΩ cm for silver and tungsten respectively. The incorporation of argon results in an increase in the resistivity proportional to the concentration (2.9 μΩ cm and 11 μΩ cm per percentage unit for silver and tungsten respectively), whatever the energy of the incorporated particles. In the case of tungsten, we show that the linear relation ϱ([Ar]) we determined appears as a lower limit for a lot of previously published papers when oxygen contamination is avoided

WNx films prepared by reactive ion-beam sputter deposition

Abstract WN x thin films (0.5⩽ x ⩽1) were deposited at room temperature on clean silicon substrates by reactive ion-beam sputter deposition in an UHV set-up. Properties such as morphology, microstructure, density, composition, mechanical stress and resistivity have been investigated as functions of ion-beam energy. Thermal stability of very thin films during sequential annealings and Schottky diodes were respectively characterized by in situ Auger electron spectrometry and C(V) measurements. It is demonstrated that a subnitridation of the silicon substrate occurs during the initial growth of the WN x layers. This may explain the absence of silicon out-diffusion up to more than 700°C and some anomalies observed during the electrical measurements of the Schottky diodes.

A complete study of the v 1, v 2, 2v 2 bands of ClCN with their associated hot bands

The 378 cm-1 and 780 cm-1 bands of ClCN, have been remeasured with a resolution of about 0·002 cm-1, using a Bruker Fourier transform spectrometer. Sixteen transitions in the region of the v 2 band and twenty in the region of the v 1 and 2v 2 bands have been analysed for 35ClCN and 37ClCN. The Fermi resonance between the states |v 1, v 2, l 2, v 3> and |v 1 - 1, v 2 + 2, l 2, v 3> has been investigated. The accuracy of the calculated band origins is better than 0·0003 cm-1 for most bands. New molecular constants are obtained.

EFFECT OF GROWTH CONDITIONS ON THE STRUCTURAL PROPERTIES OF ION BEAM SPUTTER DEPOSITED SIGE EPILAYERS

Structural properties of Si1−xGex layers epitaxially grown on Si(100) by Ion Beam Sputter Deposition were studied as a function of growth temperature and film thickness. It was shown that the structure of defects strongly depends on the growth temperature, Tg. The dislocations cross grid which is observed at the SiGe/Si interface for layers grown at high (700u2009°C) Tg is missing in layers grown at low (≲550u2009°C) Tg, while a new type of defects parallel to {001} and {113} lattice planes appear at these temperatures. The optimal Tg for a Ge content of 20‐25 at. % was found to be close to 550‐625u2009°C. Surface roughness for all the growth temperatures was found to be less than that for such a ‘‘smooth’’ technique as MBE. Photoluminescence studies revealed, to the best of our knowledge for the first time, two peaks on the low energy side in the neighborhood of the Si(TO) peak of the epilayers. The evolution of the intensity of these peaks is strongly correlated with the dynamics of strain relaxation and can be att...

Structural disorder in SiGe films grown epitaxially on Si by ion beam sputter deposition

Abstract SiGe/Si heterostructures grown by ion beam sputter deposition were characterized by high-resolution X-ray diffraction and transmission electron microscopy. Agglomerates of point defects, formed under ion bombardment during growth, were observed in electron microscopy images. These specific defects resulted in structural disorder which could be described in terms of local fluctuations of interplanar distances. The averaged magnitudes of the fluctuations were derived from X-ray diffraction spectra using a novel simulation procedure based on the direct summation of scattered waves in imperfect heterostructures. This approach allowed us to characterize quantitatively the degree of the structural disorder, and to follow defect transformations as a function of growth and annealing temperatures.

Diode-Laser spectrum of CICN in the ν1 and 2ν2 spectral range

Abstract The spectrum of CICN has been recorded in the region from 670 to 820 cm −1 using a diode-laser spectrometer with Doppler-limited resolution. The ν 1 and 2 ν 2 bands and the associated hot bands have been analyzed.