In-depth profiles

Roughness from sputtering causes loss of depth resolution in depth profiling for Auger Electron Spectroscopy (AES), X-Ray Photoelectron Spectroscopy (XPS), and SIMS. 

Current practice in depth profiling is to use positively charged argon ions at energies between 0.5 and 10 keV, focused into a beam of 2-5-p.m diameter, which is then ras-... 

Like XPS, the application of AES has been very widespread, particularly in the earlier years of its existence more recently, the technique has been applied increasingly to those problem areas that need the high spatial resolution that AES can provide and XPS, currently, cannot. Because data acquisition in AES is faster than in XPS, it is also employed widely in routine quality control by surface analysis of random samples from production lines of for example, integrated circuits. In the semiconductor industry, in particular, SIMS is a competing method. Note that AES and XPS on the one hand and SIMS/SNMS on the other, both in depth-profiling mode, are complementary, the former gaining signal from the sputter-modified surface and the latter from the flux of sputtered particles. 

Because of the complex nature of the discharge conditions, GD-OES is a comparative analytical method and standard reference materials must be used to establish a unique relationship between the measured line intensities and the elemental concentration. In quantitative bulk analysis, which has been developed to very high standards, calibration is performed with a set of calibration samples of composition similar to the unknown samples. Normally, a major element is used as reference and the internal standard method is applied. This approach is not generally applicable in depth-profile analysis, because the different layers encountered in a depth profile of ten comprise widely different types of material which means that a common reference element is not available. 

In summary, such simple classification schemes for drug-likeness can, in a very fast and robust manner, help to enrich compound selections with drug-like molecules. These filters are very general and cannot be interpreted any further. Thus, they are seen rather as a complement to the more in-depth profiling of leads and drugs by using molecular properties and identifying trends in compound series. 

Latitudinal variations in depth profiles of salinity in the (a) Atlantic, (b) Pacific, and (c) tropical oceans High-latitude salinities are given by the dashed lines. Source After Pickard, G. L, and W. J. Emery (1999). Descriptive Physicai Oceanography An Introduction, 5th ed. Butterworth-Heinemann, p. 52. 

The development of surface analytical techniques such as LA-ICP-MS, GDMS and SIMS focuses on improvements to sensitivity and detection limits in order to obtain precise and accurate analytical data. With respect to surface analytical investigations, an improvement of spatial and depth resolution is required, e.g., by the establishment of a near field effect or the apphcation of fs lasers in LA-ICP-MS. There is a need for the improvement of analytical techniques in the (j,m and nm range, in depth profiling analysis and especially in imaging mass spectrometry techniques to perform surface analyses faster and provide more accurate data on different materials to produce quantitative 3D elemental, isotopic and molecular distribution patterns of increased areas of interest with high spatial and depth resolution over an acceptable analysis time. 

Because the technique is essentially a mass spectrometer, the detection sensitivity can be quite high, approaching 1 ppb for many elements. This advantage, the capability of analyzing all elements and readily distinguishing between isotopes, and the built-in depth-profiling ability make SIMS a very powerful qualitative surface probe. 

A new method of interpreting Auger electron spectroscopy (AES) sputter profiles of transition metal carbides and nitrides is proposed. It is shown that the chemical information hidden in the shape of the peaks, and usually neglected in depth profiles, can be successfully extracted by factor analysis (FA). The various carbide and nitride phases of model samples were separated by application of FA to the spectra recorded during AES depth profiles. The different chemical states of carbon, nitrogen and metal were clearly identified. 

In depth profiling using Ar+ sputtering, it is not easy to take the XPS data while actually sputtering. 

Figure 13.9 Seasonal and spatial variability in depth profiles of potential NH4+ (pNTR) and CH4 (pMOx) rates in Galveston Bay sediments, for (a) August 1998 and (b) November 1998. (Modified from Carini et al., 2003.)...

Identifying different water strata in depth profiles. 

From the above, make a list of compounds that are introduced into the ground along with each type of applied fertilizer (e.g., K, S04). These compounds should be analyzed, along with nitrate, in accessible wells in depth profiles of the type shown in Fig. 16.1. 

Kromer JO, Sorgenfrei O, Klopprogge K et al (2004) In-depth profiling of lysine-producing Corynebacterium glutamicum by combined analysis of the transcriptome, metabolome, and fluxome. J Bacteriol 186 1769-1784... 

In depth profile the quantity of interest is the concentration r, expressed in natural units (e.g. atoms cm jig-l) it is related to the number of counts AC in a layer according to the relation... 

Figure 2. SIMS in depth profile of carbon (polyimide) and Copper introduced during RF sputter cleaning.

Urban MW, Gaboury SR, McDonald WF, Tiefenthaler AM (1990) Adv Chem Ser 227 287 Urban MW, Koenig JL (1990) Recent Developments in Depth Profiling from Surfaces Using FT-IR Spectroscopy. In Durig JR (ed) Applications of FT-IR Spectroscopy, Vibrational Spectra and Structure, vol 18, p 127... 

The superior corrosion performance and strong adhesion of the plasma coating system can be attributed to the coating properties and, more importantly, to the nature of interfacial chemistry. Two techniques were applied to study the surface and interfacial chemistry of the plasma coating system (1) in situ plasma deposition and XPS analysis and (2) in-depth profiling of sputtered neutral mass spectroscopy (SNMS). 

GD-AES was found to surpass the energy dispersive X-ray (EDX) linescan technique in depth profiling capabilities the former exhibited better turnaround time and spatial resolution, and required less sample preparation [281]. 

Fig. 9.17. In-depth profiles obtained by LIBS and definition of in-depth resolution (DR).

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