Rutherford backscattering spectrometry of the light elements and limits of their determination in the compound materials / A.V.Frantskevich, A.A.Kikinev

Обсуждаются возможности применения методики Резерфордовского обратного рассеяния (POP) для исследования образцов с неравномерным распределением элементов по глубине, пределы чувствительности обнаружения легких примесей. Предлагается нетрадиционная методика, позволяющая повысить чувствительность и разрешение по легким элементам (при модификации различных свойств конструкционных материалов с помощью высокодозной и высокоэнергетической имплантации).High energy or MeV ion implantation has attracted more and more attention in recent years. It offers many potential applications in compound semiconductor technology especially for the formation of buried layers with different physical properties or for the modification of the mechanical, chemical and electrical characteristics of materials. High energy ion implantation permits to control directly the concentration of the implanted impurities. But it is necessary to identify the implanted elements and to investigate their depth distribution. Rutherford backscattering spectrometry (RBS) is widely used for such aims, but there are a lot of difficulties in the interpretation of the backscattering spectra obtained from the analysis of the bulk compound materials with the inhomogeneous depth distribution of elements. Practically it is impossible to perform without using other methods of analysis (SIMS, PIXE). A proposed method allows to avoid these difficulties and to increase sensibility for the depth distribution of the light elements up to 1016 at/cm2. The sample preparation procedure permits to decrease a treated thickness up to 200-2000 nm using mechanical polishing and ion sputtering from the back side of the sample. Thickness is controlled by the RBS measurements simultaneously with the specimen sputtering. If the prepared samples have enough mechanical strength spectra are measured from the self-supported films or from the films, deposited on the light substrate (Be, C). In order to distinguish signals from the heavy and the light elements, to facilitate and to accurate the calculations of the spectra target tilting and glancing incidence were used. This procedure, of course, reduces the actual accessible depth for analysis, but can result in dramatic improvements in depth resolution for near-surface analysis. The RBS measurements also included the channeling techniques, which allows to determine amount and depth distribution of lattice disorder, location of impurity atoms in the lattice sites, composition and thickness of amorphous surface layers. The mentioned methods differ from the other ways of the investigation of the different properties of materials and permits to avoid problems during the creation of the films. Peculiarities of the backscattering spectra measured from the compound materials are discussed