Showing papers by "Werner Wesch published in 2016"

Direction-dependent RBS channelling studies in ion implanted LiNbO3

Abstract: Damage formation in ion implanted LiNbO 3 was studied by Rutherford backscattering spectrometry (RBS) along various directions of the LiNbO 3 crystal. From the results obtained it can be unambiguously concluded that Nb atoms being displaced during ion implantation preferably occupy the free octahedron sites of the LiNbO 3 lattice structure and most likely also form Nb Li antisite defects.

Swift Heavy Ion Irradiation of Amorphous Semiconductors

Abstract: In this chapter, the interaction of swift heavy ions (SHIs) with amorphous semiconductors is reviewed. While crystalline Si and Ge are insensitive to SHI irradiation, the higher electron-phonon coupling efficiency of their amorphous counterparts can result in ion track formation due to transient melting along the ion path. The cumulative effect of multiple SHI irradiations can then lead to plastic deformation and porous layer formation. After a review of plastic deformation in amorphous materials (including a theoretical description), results for ion track formation, plastic deformation and porous layer formation in selected amorphous Group IV and III-V materials are summarized. Complementary molecular dynamics simulations provide additional understanding and in combination with experiment enables new mechanistic insight at the atomic scale.

Ion-implantation-induced amorphization of InxGa1−xP alloys as functions of stoichiometry and temperature

Abstract: Rutherford Backscattering Spectrometry/Channeling and Extended X-ray Absorption Fine Structure measurements have been combined to investigate the amorphization of InxGa1−xP alloys at 15 and 300 K for selected stoichiometries representative of the entire stoichiometric range. The amorphization kinetics differs considerably for the two temperatures: at 15 K, the amorphization kinetics of InxGa1−xP is intermediate between the two binary extremes while at 300 K, InxGa1−xP is more easily amorphized than both InP and GaP. Direct impact and stimulated amorphization both contribute to the amorphization process at 15 K. Dynamic annealing via thermally induced Frenkel pair recombination reduces the influence of direct impact amorphization at 300 K such that the stimulated amorphization is dominant. At this temperature, stimulated amorphization in ternary InxGa1−xP alloys is supported by the structural disorder inherent from the bimodal bond length distribution.

Swift Heavy Ion Irradiation of Crystalline Semiconductors

Abstract: In this chapter the structural modification of crystalline semiconductors due to swift heavy ion (SHI) irradiation induced high electronic excitation is discussed. After a short description of the energy deposition processes, experimental results on ion track and damage formation in various semiconductors are presented. The results highlight the different susceptibility of the materials to SHI induced damage formation and the existence of material specific threshold values of the electronic energy deposition for track formation. The results are discussed in the framework of existing models and it is shown that the experimental data can be well described using an extended inelastic thermal spike model.

Primary Processes of Damage Formation in Semiconductors

Abstract: In this chapter damage formation and amorphisation in various semiconductors are reviewed with special focus on primary processes. Trends are shown how the parameters during ion implantation influence damage formation and to what extend the results for the various semiconductors can be generalised. It is shown that three groups of semiconductors can be identified. One group of materials exhibits a continuous transition towards amorphisation at sufficiently low temperatures. In these materials comparable mechanisms of defect formation are observed provided the implantation temperature is similarly close to or below the corresponding critical temperature of amorphisation, T c, the concept of which is discussed in this chapter. In a second group, amorphisation can be achieved at low temperatures only and only by secondary processes resulting in a discontinuous transition to amorphisation. And in a third group of materials amorphisation by ion implantation is not observed even not at low temperatures for moderate ion fluences which do not significantly alter the stoichiometry of the material. Various models are applied for describing the damage evolution. This represents a further step towards a prediction of damage to be expected for certain irradiation conditions in the corresponding materials.