PHYSICAL REVIEW B VOLUME 49, NUMBER 18 1 MAY 1994-II Track formation in SiOz quartz and the thermal-spike mechanism A. Meftah Centre Interdisciplinaire de Recherches avec les Ions Lourds, Brie Postale 5133, 14040 Caen Cedex, France F. Brisard and J. M. Costantini Commissariat a I' Energie Atomique, Service PTN, BcAie Postale 12, 91680 Bruyeres-le-Chattel, France E. Dooryhee Centre Interdisciplinai re de Recherches avec les Ions Lourds, BcA~e Pos tale 5133, 14040 Caen Cedex, France M. Hage-Ali Centre de Recherches Nucleaires, Groupe Phase, 67037 Strasbourg Cedex, France M. Hervieu J. P. Stoquert Centre de Recherches Nucleaires, Group Phase, 67037 Strasbourg Cedex, France F. Studer CRISMA T, Institut des Sciences de la Matiere et du Rayonnement, Boulevard du Marechal Juin, 14050 Caen Cedex, France M. Toulemonde Centre Interdisciplinaire de Recherches avec les Ions Lourds, Bdiie Postale 5133, 14040 Caen Cedex, Finance (Received 1 November 1993) a-quartz has been irradiated with heavy ions: ' F, ' S, and 'Cu at an energy of about 1 MeV/amu in order to cover a range of electronic stopping powers dE/dx between 2. 4 and 9 keV/nm and "Ni, ' Kr, Te, ' Xe, ' 'Ta, and Pb between 1 and 5. 8 MeV/amu for dE/dx ) 7 keV/nm. The extent of the in- duced damage is determined using Rutherford backscattering ion channeling with a 2-MeV 4He beam. The damage cross section A is obtained using a Poisson law Fd = 1 — exp( — A Pt ), where P is the flux and t the irradiation time. This damage cross section is linked to the effective radius R, through the relation A =m. R„where R, is the radius of an equivalent cylinder of damage. Using high-resolution electron mi- croscopy, cylinders of amorphous matter have been observed, whose radius corresponds to R, when the track is continuous (i. e. , for A ) 1.3 X 10 ' cm; R, & 2 nm). A thermal-spike model is applied to calcu- late the radii of the observed tracks assuming that the observed amorphous cylinders correspond to a rapid quench of a molten liquid phase along the ion path. The model is applied only when the latent track is continuous and cylindrical. A good agreement is obtained taking into account that the initial spatial energy deposition on the electrons depends on the ion velocity. I. I¹RODUcaxON In most insulators a strongly damaged zone is induced along the ion path by the slowing down of a swift heavy ion. Although much work has been done over the past 30 years' in order to describe the latent tracks, the damage mechanism is still unclear. Several authors have proposed different models in order to explain these mech- anisms. For insulators resistant to radiolysis one may think of the thermal spike, the ionic spike' (where atom- ic motion is induced by the electrostatic repulsion of close neighbor ionized atoms) or more reflned models. ' For example, the role of target inner-shell electron excita- tions was invoked, as a source of local intense ionizations, which trigger the damage formation process. However it has been shown experimentally' that it is not neces- sary to invoke the inner-shell electron excitation as the major cause of the damage formation process. If the ionic-spike model was proposed to account for the track formation, ' Sigrist and Balzer" have shown later on that the electronic stopping power threshold as deduced from the chemical etching of several insulators cannot be scaled by the parameters governing the ionic spike. On the contrary a better correlation appears between this threshold and the thermal conductivity of these insula- tors. In the same way, the electronic sputtering' ' was 0163-1829/94/49(18)/12457(7)/$06. 00 49 12 457 1994 The American Physical Society