Atomic displacements and atomic motion induced by electronic excitation in heavy-ion-irradiated amorphous metallic alloys

Abstract

AbslraeLIn amorphous melallic alloys inadiated with swift heavy ions, electronic excitation induces atomic displacemenu at the beginning of the irradiation and anisotmpic growth above an incubation Ruence. We provide here an extensive review of our data on amorphous F e s B u (including work that i s already published), as well as a general description of the lopic. Samples were inadiated at various temperatures (20 K, 90 K, 223 K) with a large variety of highonergy (GeV) heavy ions (Ar to U). The atomic rearrangements occuning during irradiation were studied by br dm electrim1 mistan= experiments. The influence of the inadiation geometry as well as of a uniaxial stress applied lo the sample was investigated. The whole set of data is accounted for with a Wohit phenomenological model allowing one U) extracl physical pammeters A description of the ion-target interaction on the basis of the Coulomb explosion mechanism is also provided. 1

Incubation Dose for Ion Beam Induced Anisotropic Growth of Amorphous Alloys: Insight into Amorphous State Modifications

“…Therefore, in the electron temperature region e f , T e , 5e f the heating radius R 2 T Ӎ 4D e t ea depends only weakly on the initial electron temperature and the electronic energy loss S e and we neglect below this dependence in Eq. (6 1.34 3 10 212 s, and obtain R T 35 nm which is in a reasonable agreement for the heating radius (R T 20 nm) resulting from a fitting to the experimental data [6].…”

“…In this energy range, heavy ions with sufficiently high electronic stopping power (S e . 5 keV͞nm) induce in amorphous materials at low temperatures (T irr # 200-300 K) two striking deformation phenomena: (i) anisotropic expansion ("growth") of unstressed amorphous foil samples perpendicular to the ion-beam direction [2][3][4][5][6][7][8] and (ii) creep of stressed amorphous samples with creep or stress relaxation rates [7][8][9][10][11][12][13] which are larger by orders of magnitude than those in crystalline or polycrystalline materials.…”

“…At medium electronic stopping power (5-30 keV͞nm) the occurrence of both deformation phenomena, i.e., (i) and (ii), requires some incubation fluence (dose) f c which depends on the electronic and nuclear stopping powers, irradiation temperature, and amorphous material properties [2,3,5,6].…”

“…To our knowledge, the only system for which a satisfactory number of data are available for testing the stopping power dependence of the incubation dose is the amorphous metallic alloy Fe 85 B 15 [6] irradiated at low irradiation temperatures ͓T irr 90 K, w͑T irr ͒ ! 1͔.…”

“…In this energy range, heavy ions with sufficiently high electronic stopping power (S e . 5 keV͞nm) induce in amorphous materials at low temperatures (T irr # 200-300 K) two striking deformation phenomena: (i) anisotropic expansion ("growth") of unstressed amorphous foil samples perpendicular to the ion-beam direction [2-8] and (ii) creep of stressed amorphous samples with creep or stress relaxation rates [7][8][9][10][11][12][13] which are larger by orders of magnitude than those in crystalline or polycrystalline materials.At medium electronic stopping power (5-30 keV͞nm) the occurrence of both deformation phenomena, i.e., (i) and (ii), requires some incubation fluence (dose) f c which depends on the electronic and nuclear stopping powers, irradiation temperature, and amorphous material properties [2,3,5,6].Recently, ion-beam induced anisotropic growth [14-17] and creep (or stress relaxation) [16][17][18] of amorphous materials have been described in terms of viscous flow and shear stress relaxation in locally heated and damaged regions in the vicinity of the ion trajectories. In the case of anisotropic growth, the shear stress, assumed to relax upon temporal local heating in the vicinity of the projectile trajectory, is due to the thermal expansion in the heated cylindrical track whereas in the creep (stress relaxation) it is given simply by the externally applied macroscopic stress.…”