Amorphous silicon exhibits a glass transition

Amorphous silicon is a semiconductor with a lower density than the metallic silicon liquid. It is widely believed that the amorphous–liquid transition is a first-order melting transition. In contrast to this, recent computer simulations and the experimental observation of pressure-induced amorphization of nanoporous silicon have revived the idea of an underlying liquid–liquid phase transition implying the existence of a low-density liquid and its glass transition to the amorphous solid. Here we demonstrate that during irradiation with high-energy heavy ions amorphous silicon deforms plastically in the same way as conventional glasses. This behaviour provides experimental evidence for the existence of the low-density liquid. The glass transition temperature for a timescale of 10 picoseconds is estimated to be about 1,000 K. Our results support the idea of liquid polymorphism as a general phenomenon in tetrahedral networks.

[1]  Ali Alavi,et al.  STRUCTURAL, DYNAMICAL, ELECTRONIC, AND BONDING PROPERTIES OF LASER-HEATED SILICON : AN AB INITIO MOLECULAR-DYNAMICS STUDY , 1997 .

[2]  S. Klaumünzer.  Plastic Flow of Amorphous Materials During Ion Bombardment , 2000 .

[3]  Schumacher,et al.  Dimensional changes of metallic glasses during bombardment with fast heavy ions. , 1990, Physical review. B, Condensed matter.

[4]  T. Morishita.  High density amorphous form and polyamorphic transformations of silicon. , 2004, Physical review letters.

[5]  S. Phillpot,et al.  Continuous thermodynamic-equilibrium glass transition in high-energy grain boundaries ? , 1997 .

[6]  Srikanth Sastry,et al.  Liquid–liquid phase transition in supercooled silicon , 2003, Nature materials.

[7]  David Turnbull,et al.  Heat of crystallization and melting point of amorphous silicon , 1983 .

[8]  Nobumasa Funamori,et al.  Pressure-induced structural change of liquid silicon. , 2002, Physical review letters.

[9]  A. Audouard,et al.  Atomic displacements and atomic motion induced by electronic excitation in heavy-ion-irradiated amorphous metallic alloys , 1993 .

[10]  S. Klaumünzer,et al.  Shape instability of amorphous materials during high-energy ion bombardment , 1997 .

[11]  N. Sobolev,et al.  Investigations of Radiation Damage Production in Ion Implanated Silicon , 1982 .

[12]  R. Yen,et al.  Picosecond laser‐induced melting and resolidification morphology on Si , 1979 .

[13]  Thermodynamic behavior of a model covalent material described by the environment-dependent interatomic potential , 2002, cond-mat/0206214.

[14]  Louis Hennet,et al.  Structural changes on supercooling liquid silicon , 2003 .

[15]  P. McMillan,et al.  Density-driven liquid–liquid phase separation in the system AI2O3–Y2O3 , 1994, Nature.

[16]  J. Ziegler,et al.  stopping and range of ions in solids , 1985 .

[17]  Doorn,et al.  Calorimetric evidence for structural relaxation in amorphous silicon. , 1989, Physical review letters.

[18]  Schumacher,et al.  Coulomb explosions in a metallic glass due to the passage of fast heavy ions? , 1986, Physical review letters.

[19]  A. Polman,et al.  Ion beam-induced anisotropic plastic deformation of silicon microstructures , 2004 .

[20]  J. D. Eshelby.  The determination of the elastic field of an ellipsoidal inclusion, and related problems , 1957, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[21]  P. McMillan,et al.  Pressure-induced amorphization and an amorphous–amorphous transition in densified porous silicon , 2001, Nature.

[22]  K. Sokolowski-Tinten,et al.  Femtosecond melting and ablation of semiconductors studied with time of flight mass spectroscopy , 1999 .

[23]  H. Trinkaus.  Local stress relaxation in thermal spikes as a possible cause for creep and macroscopic stress relaxation of amorphous solids under irradiation , 1995 .

[24]  Y. Waseda,et al.  Viscosity of molten silicon and the factors affecting measurement , 2003 .

[25]  C. R. Miranda,et al.  Transitions between disordered phases in supercooled liquid silicon. , 2004, The Journal of chemical physics.

[26]  P. McMillan.  Polyamorphic transformations in liquids and glasses , 2004 .

[27]  Jacobson,et al.  Structural relaxation and defect annihilation in pure amorphous silicon. , 1991, Physical review. B, Condensed matter.

[28]  H. Matsumura,et al.  Amorphous silicon produced by a new thermal chemical vapor deposition method using intermediate species SiF2 , 1985 .

[29]  S. K. Sundaram,et al.  Inducing and probing non-thermal transitions in semiconductors using femtosecond laser pulses , 2002, Nature materials.

[30]  G. Fuchs,et al.  High-energy heavy-ion irradiations of Fe85B15 amorphous alloy: evidence for electronic energy loss effect , 1987 .

[31]  H. Trinkaus,et al.  DYNAMICS OF VISCOELASTIC FLOW IN ION TRACKS : ORIGIN OF PLASTIC DEFORMATION OF AMORPHOUS MATERIALS , 1998 .

[32]  V. Pontikis,et al.  Multiscale phenomena in plasticity : from experiments to phenomenology, modelling and materials engineering , 2000 .

[33]  J. Poate,et al.  Homogeneous and interfacial heat releases in amorphous silicon , 1989 .

[34]  Toshio Mura,et al.  Micromechanics of defects in solids , 1982 .

[35]  G. J. Galvin,et al.  Melting temperature and explosive crystallization of amorphous silicon during pulsed laser irradiation , 1984 .

[36]  R. Masut,et al.  Directional effects during ion implantation: Lateral mass transport and anisotropic growth , 1997 .

[37]  G. Schumacher,et al.  Dramatic Growth of Glassy Pd 80 Si 20 during Heavy-Ion Irradiation , 1983 .

[38]  Ryazanov,et al.  Viscoelastic model for the plastic flow of amorphous solids under energetic ion bombardment. , 1995, Physical review letters.

[39]  S. Hosokawa,et al.  Sub-picosecond dynamics in liquid Si , 2003 .