Backscattering spectrum

Figure Bl.24.5. Backscattering spectrum of a thin Ni film (950 A) with near monolayers ( 30 x 10 at cm of An on the front and back surfaces of the Ni film. The signals from the front and back layers of An are shown and are separated in energy from each other by nearly the same energy width as the Ni signal.

Figure Bl.24.10. Random and aligned (chaimelled) backscattering spectrum from a single crystal sample of silicon. The aligned spectrum has a peak at the high energy end of the Si signal. This peak represents helium...

As an example, we show in Figure 3 a backscattering spectrum from GaAs (110), obtained vwth a 300-keV Li ion beam. This is a well-chosen test example of energy resolution, as the atomic numbers of the two constituents are quite close (31 and 33 for Ga and As, respectively). Not only are these two species well resolved, but the two common isotopes of Ga are also well separated. Note that the peaks are asymmetric due to contributions from lower layers. Resolving power of this kind surely will find many new applications in materials science. 

Fig. 3.16 Schematic drawing of the MIMOS II Mossbauer spectrometer. The position of the loudspeaker type velocity transducer to which both the reference and main Co/Rh sources are attached is shown. The room temperature transmission spectrum for a prototype internal reference standard shows the peaks corresponding to hematite (a-Fe203), a-Fe, and magnetite (Fe304). The internal reference standards for MIMOS II flight units are hematite, magnetite, and metallic iron. The backscatter spectrum for magnetite (from the external CCT (Compositional Calibration Target) on the rover) is also shown...

That these ideas have some merit is indicated by the work of Hart, Dunlap, and Marsh . These investigators deposited a fraction of a monolayer of copper onto a silicon wafer and then monitored the position and concentration of the copper using Rutherford backscattering. After deposition, the copper, which was then located on the immediate surface, was bombarded with 20 keV Ne ions to a fluence sufficient to sputter 90 A of Si from the surface. The Rutherford backscattering spectrum, which was taken after this bombardment, showed that the copper was uniformly distributed to a depth of 600 A which corresponds roughly to the projected range of the Ne" " ions, i.e., the depth of the altered layer was approximately equal to the projected range of the Ne. 

Figure 1. A Rutherford backscattering spectrum for a thin (40/ig/cm2) MoSt sputter-deposited film. Conditions 4He ions normally incident at 3.0 MeV, and scattered ions detected at a 135° angle by a surface-barrier diode detector. Note the scale factor for other than the Mo peak and the Si substrate. The sample layer configuration is indicated at the upper left.

Figure 2. A partial Rutherford backscattering spectrum for a relatively thick (430jxg/cm2) sputter-deposited solid lubricant thin film with conditions as in Fig. 1.

Current research interest is in the solid phase epitaxial regrowth of amorphous Si using laser processing. RBS has been used to follow the melting and recrystallization of the crystal-amorphous interface (12). This is accomplished by monitoring the backscattered spectrum+with the substrate oriented in a direction that will allow the He to channel along the crystal planes. 

Special attention should be paid to the amplitude of the experimental curves, which roughly equals that predicted theoretically. In inelastic spectroscopy the amplitude of the EPI spectrum is an order of magnitude lower than expected one (see Fig. (1) in Ref. [14] and the discussion cited therein). This discrepancy may be explained either by the diffusive regime of current flow with and unknown mean free path (j, or by the specific PC-transport character of the EPI function obtained from the inelastic backscattering spectrum. 

Fig. 24. o-backscattering spectrum from steel implanted with Pb ... 

Fig. 6.3 The backscattering spectrum of liquid hydrogen at 14. IK. Note that the rotational line has disappeared and a sharp edge is now seen at 118 cm". ...

Fig. 2.13. Result of a Kirkendall marker experiment carried out by Rutherford backscattering spectroscopy. The upper part shows the marker shifts (A m and A ) for the tungsten marker and the Zr edge from the backscattering spectrum. The lower part compares the experimental data with the expected behavior of the marker shift when only one species moves (dashed lines). Within experimental error, it is found that only Ni moves (see [2.46] for details)...

An example of the change in composition of a silicide layer is shown in Fig. 12.5 for PtSi that was sputtered with 20keV argon ions and then analyzed with 2 MeV 4He ions. The Rutherford backscattering spectrum shows an enrichment of the Pt concentration in the surface region. The ratio of Pt/Si increased from the value of unity associated with that of the bulk to a value near two in the surface region. The increased concentration of Pt at the surface occurs because the partial... 

Particle- or proton-induced. X-ray emission (PIXE) is another modern powerful yet non-destructive elemental analysis technique used to determine the elemental make-up of a sample material. When a material is exposed to a particle or proton beam, atomic interactions occur that give off electromagnetic radiation of wavelengths in the X-ray part of the electromagnetic spectrum characteristic of an element. Three different types of spectra can be collected from a PIXE experiment an X-ray emission spectrum, a Rutherford (proton) backscattering spectrum and a proton transmission spectrum. 

The essentially non-destructive nature of Rutherford backscattering spectrometry, combined with the its ability to provide both compositional and depth information, makes it an ideal analysis tool to study thin-film, solid-state reactions. In particular, the non-destructive nature allows one to perform in situ RBS, thereby characterizing both the composition and thickness of formed layers, without damaging the sample. Since only about two minutes of irradiation is needed to acquire a Rutherford backscattering spectrum, this may be done continuously to provide a real-time analysis of the reaction [6]. 

Figure 1 Rutherford backscattering spectrum ( = 2MeV, 0lab = 14O) from an Si crystal with thin layers of Cr (3x 10 atoms cm and Au (8 x 10 atoms cm evaporated onto the surface. The continuum at low energies is due to ions backscat-tered from Si after penetration into the bulk. The energy of such ions can be related to the scattering depth.

Figure 3 Backscattering spectrum for incidence of a 500 keV He+ ion beam aiong a <1 00> direction of a W crystai. A surface peak, corresponding to backscattering from the surface iayers, appears in the high-energy end of the spectrum.

Figure 1.23 Raman backscattering spectrum of as-grown single-costal ZnO after background subtraction. The sample was irradiated with the 488 nm line of an Ar laser and a power of 190 mW. The solid line represents a least-square fitofsixGaussian lines to the data. The dashed lines indicate the individual local vibrational modes. The peak positions are indicated in the plot.

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