Heavy ion-induced characteristic X-rays as a tool in solid state physics

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Characteristic X-ray generation by accelerated heavy ions offers some distinct advantages over conventional electron bombardment methods. For example, “clean” X-rays, free from background radiation, are generated; this allows the use of non-dispersive X-ray counting procedures. In addition the ability of heavy ions to generate X-rays can be coupled with their property of channeling through a crystalline lattice, thus yielding a probe for locating the atimic positions of impurity elements in a crystalline matrix. More recent studies have demonstrated that characteristic X-rays of a particular element can be generated selectively in the presence of other elements by bombardment with an appropriate beam of heavy ions. Since the resultant X-rays arise from near the surface of the target, there emerges a technique for elucidating, with high sensitivity, the concentration profile of an ion-implanted element. Finally, it should be noted that the X-rays involved in this work are normally in the soft-to-ultrasoft energy range, i.e. ranging from ≈ 2 kev to ≈ 200 eV. Some attention will be given therefore to a few of our recent developments in the design of gas flow proportional counters for the detection of these low-energy X-rays.