Depth Scale

This signal is nearly square shaped because nickel exists from the front to the back surface. The depth scales are detennined from energy loss values, which are given in tabular fomi as a fiinction of energy [1, 2]. It is... 

Finally, it is difficult to caUbrate the depth scale in a depth profile. This situation is made more compHcated by different sputtering rates of materials. Despite these shortcomings, depth profiling by simultaneous ion sputtering/aes is commonly employed, because it is one of the few techniques that can provide information about buried interfaces, albeit in a destmctive manner. 

Due to the convoluted mass and depth scales present in an RBS spectrum, it may not be possible to accurately describe an unknown sample using a single RBS spectrum. For example. Figure 4a is an RBS spectrum acquired at a backscattering angle of 160° from a sample implanted with 2.50 x 10 atoms/cm of As at a depth of approximately 140 nm. If this were a totally unknown sample it would not be possible to determine positively the mass and depth of the implanted species from this spectrum alone, since the peak in the RBS spectrum also could have been caused by a heavier element at greater depth, such as Sb at 450 nm, or Mo at 330 nm, or by a... 

Generally. 5j. In this way, a depth scale may be associated with an ERS spectrum, as shown in the schematic spectrum of Figure 3c. That spectrum shows the H recoil rate (counts per energy channel of width AE) as a function of E y and hence as a function of depth below the sample surface (see Equation (3)). 

Fig. 3.47. Schematic back-scattering spectra for MeV He ions incident on a 100-nm Ni film on Si (top) and after reaction to form Ni2Si (bottom). Depth scales are indicated below the energy axes [3.120].

Fig. 3.48. Schematic diagram of particle trajectories undergoing scattering at the surface and channeling within the crystal. The depth scale is compressed relative to the width of the channel, to display the trajectories [3.120].

Knowing the composition of a layer, it is possible to establish a depth scale for the distribution of an element or to measure the layer thickness from the energy of the scattered particles. This depends on the energy loss of the projectile on its inward and outward paths, as described in Sect. 3.5.1. The energy difference, AE, for a particle scattered at the surface and a particle scattered at a depth x is given by ... 

A depth scale can be obtained from the energy of recoiled ions. If ions recoiled from a depth x are lower in energy by AE compared with ions recoiled from the surface, a simple relationship between AE and x can be found for thin layers, when constant stopping power is assumed ... 

Fig. 5.9. AFM image of a Lavsan filtration membrane. Image size 5 )xm x 5 )xm, depth scale 500 nm from black to white.

FIG. 42. Simulated depth distributions of (a) hydrogen and (b) silicon ions incident ona-Si H with energies of 10 and 50 eV. Note the difference in depth scale. Simulations were performed with TRIM92. 

Since ion beams (like electron beams) can be readily focussed and deflected on a sample so that chemical composition imaging is possible. The sputtered particles largely originate from the top one or two atom layers of a surface, so that SIMS is a surface specific technique and it provides information on a depth scale comparable with other surface spectroscopies. 

There are two parameters which are of primary importance in the analysis of SIMS data - the relationship between the secondary ion current and the elemental concentration in the sample surface, and the depth scale. 

Figure 2. Relative amounts of various iron species deduced from 57Fe Mossbauer spectra of the Fe-exchanged samples shown in relation to the progress of the hydrothermal crystallization process at 80°C (A), 57Fe Mossbauer spectra of the Fe-exchanged samples after 0 (a), 120 (b), 180 (c) and 240 min (d) of the hydrothermal crystallization process at 80°C (B) and RBS spectra collected on five different particles of the sample crystallized for 240 min (C). The position of surface Fe in Fig. 2C is marked by the vertical arrow. Depth scale (depth into each particle) is increasing toward left (marked with the horizontal arrow). Fit to experimental data with assumed homogeneous depth distribution of Fe is marked with the continuous line.

Figure 8.4. TM-AFM images of SILAR-grown ZnS on (100)Si after (a) 0, (b) 2, (c) 5, (d) 10, (e) 20, (f) 50, and (g) 100 cycles. Depth scale lOnm (a)-(c), 25nm (d)-(f), and 75 nm (g) from black to white. Reprinted from Valkonen, Lindroos, Resch, Leskela, Friedbacher and Grasserbauer. 1998. Applied Surface Science 136, Copyright (1998) with permission from Elsevier.

However, the validity of a similar assumption has to be questioned, in case the skin has previously been treated with a topically applied formulation [126], Opinions differ, whether the distinct curvature of the steady-state stratum corneum concentration gradient, reported in literature, may be an artifact of a wrong depth scale, since such a behavior cannot be reasonably explained by the established diffusion theory. 

Vertical diffusivity coefficient used to numerically model the physical process of turbulence over depth scales in the water column. 

Depth scale calibration of an SIMS depth profile requires the determination of the sputter rate used for the analysis from the crater depth measurement. An analytical technique for depth scale calibration of SIMS depth profiles via an online crater depth measurement was developed by De Chambost and co-workers.103 The authors proposed an in situ crater depth measurement system based on a heterodyne laser interferometer mounted onto the CAMECA IMS Wf instrument. It was demonstrated that crater depths can be measured from the nm to p,m range with accuracy better than 5 % in different matrices whereas the reproducibility was determined as 1 %.103 SIMS depth profiling of CdTe based solar cells (with the CdTe/CdS/TCO structure) is utilized for growing studies of several matrix elements and impurities (Br, F, Na, Si, Sn, In, O, Cl, S and ) on sapphire substrates.104 The Sn02 layer was found to play an important role in preventing the diffusion of indium from the indium containing TCO layer. 

Figure 7.4 Generalized profiles of concentration and isotope ratio changes for dissolved sulfate and carbon species in anoxic marine sediments. Depth scale is arbitrary with depth units ranging from 10 1 to 102 m. (Reproduced from Claypool, G.E., Kvenvolden, K.A., Ann. Rev. Earth Planet Sci., 11, 299 (1983). With permission from Annual Reviews, Inc.)...

Not every phenomenon was assessed on every 10-point interval on the depth scale, so curves are shown as dotted where data points are missing. 

The researcher planning work with self-report depth scales should note some other precautions outlined in my chapter in Fromm and Shor s book 114. (back)... 

Figure 10. Profiles generated from the 1005-keV resonance of the 52Cr(p,y)ssMn reaction in pure Fe samples implanted with fluences of 1 X 1017 and 1 X l 16 52Cr atoms/cm2 at 150 keV. (Note the scale factor for the latter.) The incident energy at which the y-ray yield for each point was obtained is on the lower abcissa scale and an equivalent depth scale is on the upper. Conditions 1H ions normally incident, and y-rays detected at a 0° angle to the beam with a Ge(Li) detector. (Reproduced, with permission, from Ref. 6. Copyright 1980, North-Holland Publishing...

In this idealized case, the profile can be obtained by varying the incident particle energy E0 stepwise within a certain interval. Yield calibration is done by a standard in an analogous way as described in equation (4). Close to the surface equation (5) can be simplified by the so-called surface approximation which consists in replacing S(E) by S(E0), i.e. by the value of the energy loss at the surface. The expression for the depth scale is then simply dR(E0) — (E0—ER)/S(E0). 

The suboxic zone is defined as the region between where oxygen decreases to near zero (O2 < 10 xM) and where sulfide first appears (H2S > 1 iM) [16, 17]. Many important redox reactions involving Fe, Mn, N, and other intermediate redox elements occur in the suboxic zone. Similar redox reactions take place in sediments throughout the world s oceans, but they are easier to study in the Black Sea because they are spread out over a depth scale of tens of meters (rather than centimeter or millimeter scales as in sediments). The Black Sea suboxic layer hydrophysical structure is very stable compared with other ocean redox regions such as Cariaco Trench, which is influenced by mesoscale eddies, or the Baltic Sea that is influenced by inflows of the North Sea saline oxygenated waters in cold winters. 

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