Energetic ion beam analysis

First, because of the large energy difference, this method is completely insensitive to chemical binding effects. While other conventional surface analysis techniques which are sensitive to the chemical state are unquestionably frequently required, it is also true that methods thus dependent on the chemical state may suffer from difficulties in calibration, particularly in transition regions where an element is found in more than one chemical state. Energetic ion beam analysis, on the other hand, offers an absolute technique independent of these effects. As such, this technique and other conventional techniques (e.g. Auger, ESCA etc.) may often prove to be complementary, each supplying information not available by the other techniques. 

Third, the requirement of accelerating an ion to the MeV range of energies must necessarily entail a larger size, more expensive and often more complex acceleration apparatus. Thus, the technique of energetic ion beam analysis grew in the... 

The use of elastic backscattering, which is the primary technique for energetic ion beam analysis, is the normal method of choice when it will produce satisfactory results. Some other ion beam techniques which may be useful in supplementing backscattering in specific cases will be discussed later in this paper. 

Near Surface Analysis with Energetic Ion Beams... 

The field of materials analysis by energetic ion beams has begun to mature in the last decade after arising within the nuclear physics community. The basic method, Rutherford back-scattering, has been the subject of a text (1 ), and the field has also engendered a useful handbook (2). Publications are scattered throughout the literature with much of the output in articles relating to the properties of materials. In these the ion beam analysis may form only a part of the work. New developments in technique and applications continue and have been the subject of a series of international conferences (see for example (3) for the latest of these). 

Because all phases of the interaction of the incident energetic ion beam with materials, including kinematics and cross section of the elastic collision and the energy losses by means of inelastic interaction with the electrons are readily calculable, the analysis lends itself to computer simluation. One of the first such programs, developed at IBM (4), is used at NRL, while other programs have also been developed at a number of other laboratories. 

It has been shown that energetic ion beams may be utilized to "nondesthuctively" determine the profile of composition vs. depth in a wide variety of near surface situations. The major difficulties and limitations of the method have been delineated with descriptions of alternative methods applicable in difficult cases. The advantages of using these techniques as complementary to other surface analysis methods has also been pointed out. 

In addition, many characterization techniques utilize energetic beams that can accelerate this process if carried out in ambient air or even vacuum (see handbook chapter Effects of Irradiation on Porous Silicon ). In some cases, such as ion beam analysis in vacuo of chemical composition, capping of layers is required to provide reliable data (Giaddui et al. 1998). 

Principles and Characteristics The basic and most mature method of materials analysis by energetic ion beams is elastic Rutherford backscattering spectroscopy (RBS). As it is practised today to interrogate a sample RBS uses typically a well collimated mono-energetic beam of O -particles from a Van der Graaf accelerator or from a variety of small accelerators, with energy 0 1-5 MeV [233]. The He + particles backscattered... 

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