Nanoporous SiO2/Si thin layers produced by ion track etching: Dependence on the ion energy and criterion for etchability

Faculty of Physics, Catholic University of Rio Grande do Sul, Av. Ipiranga 6681, 90619-900 Porto Alegre, Brazil
Journal of Applied Physics (Impact Factor: 2.18). 08/2008; 104(2):024307 - 024307-8. DOI: 10.1063/1.2957052
Source: IEEE Xplore

ABSTRACT Vitreous SiO 2 thin films thermally grown onto Si wafers were bombarded by Au ions with energies from 0.005 to 11.1 MeV/u and by ions at constant velocity (0.1 MeV/u 197 A u , 130 T e , 75 A s , 32 S , and 19 F ). Subsequent chemical etching produced conical holes in the films with apertures from a few tens to ∼150 nm . The diameter and the cone angle of the holes were determined as a function of energy loss of the ions. Preferential track etching requires a critical electronic stopping power Se th ∼2 keV / nm , independent of the value of the nuclear stopping. However, homogeneous etching, characterized by small cone opening angles and narrow distributions of pore sizes and associated with a continuous trail of critical damage, is only reached for Se≫4 keV / nm . The evolution of the etched-track dimensions as a function of specific energy (or electronic stopping force) can be described by the inelastic thermal spike model, assuming that the etchable track results from the quenching of a zone which contains sufficient energy for melting. The model correctly predicts the threshold for the appearance of track etching Se th if the radius of the molten region has at least 1.6 nm. Homogeneous etching comes out only for latent track radii larger than 3 nm.

Download full-text


Available from: P. F. P. Fichtner, May 11, 2015
1 Follower
20 Reads
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Processes for making nanoporous SiO2 layers on Si via the irradiation of thermally oxidized silicon wafers with fast ions followed by chemical treatment in a solution or vapor of hydrofluoric acid are presented. It is shown that the density, shape, diameter, and length-to-diameter ratio of channels etched in silicon dioxide can be controlled by varying the regimes of fast ion irradiation or chemical treatment of SiO2/Si structures. Track parameters calculated using the thermal spike model are compared with the chemical etching data.
    Bulletin of the Russian Academy of Sciences Physics 05/2012; 76(5). DOI:10.3103/S1062873812050267
  • [Show abstract] [Hide abstract]
    ABSTRACT: The work reports on experimental features and theoretical studies of swift-heavy-ion-induced shaping of Ge nanospheres into disks. A stack of alternating Ge and SiO2 layers was sputtered on an oxidized Si wafer. The Ge layer thicknesses varied from 2.5 to 7.5 nm. Thermal treatment above the melting temperature of Ge transformed each Ge layer into a layer of Ge nanospheres. With growing Ge layer thickness the mean diameter increases from 8 to 37 nm. Irradiation with low fluences (∼1014 cm−2) of 38 MeV I7+ shaped medium-sized Ge nanospheres into disks, whereas smaller ones became rod-like and larger ones remained unchanged. At higher fluences, the larger Ge nanospheres shrink due to Ge loss and shape into disks too. A new model is presented and atomistic Monte-Carlo simulations are shown which describe the shaping evolution and the size thresholds for shaping quantitatively. The volume change of Ge upon melting has been identified as driving force.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 05/2009; 267(8-9-267):1345-1348. DOI:10.1016/j.nimb.2009.01.062 · 1.12 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recent experimental works devoted to the phenomena of mixing observed at metallic multilayers Ni/Si irradiated by swift heavy ions irradiations make it necessary to revisit the insensibility of crystalline Si under huge electronic excitations. Knowing that Ni is an insensitive material, such observed mixing would exist only if Si is a sensitive material. In order to extend the study of swift heavy ion effects to semiconductor materials, the experimental results obtained in bulk silicon have been analyzed within the framework of the inelastic thermal spike model. Provided the quenching of a boiling (or vapor) phase is taken as the criterion of amorphization, the calculations with an electron–phonon coupling constant g(300K)=1.8×1012W/cm3/K and an electronic diffusivity De(300K)=80cm2/s nicely reproduce the size of observed amorphous tracks as well as the electronic energy loss threshold value for their creation, assuming that they result from the quenching of the appearance of a boiling phase along the ion path. Using these parameters for Si in the case of a Ni/Si multilayer, the mixing observed experimentally can be well simulated by the inelastic thermal spike model extended to multilayers, assuming that this occurs in the molten phase created at the Ni interface by energy transfer from Si.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 08/2009; 267(16):2719-2724. DOI:10.1016/j.nimb.2009.05.063 · 1.12 Impact Factor
Show more