Electronic structure calculations of positron lifetimes in SiC: Self-consistent schemes and relaxation effect

Abstract We present electronic structure calculations of positron lifetimes in various neutral and negative monovacancies in 3 C and 6 H silicon carbide. Self-consistent positron lifetime calculation schemes were used and full defect relaxation due to the creation of the vacancy and the presence of the positron was considered. Formation energies of the various possible charges of the defects were also calculated to predict their detectability in PAS. Lifetimes between 170 ps and 195 ps for V C and between 222 ps and 227 ps for V Si were obtained. Based on these results we propose new interpretations of the experimental PAS signals observed in n-type 3 C and 6 H -SiC samples.

[1]  M. Barthe,et al.  Optical transitions of the silicon vacancy in 6H-SiC studied by positron annihilation spectroscopy , 2002 .

[2]  S. Dannefaer,et al.  Positron annihilation investigation of electron irradiation-produced defects in 6H-SiC , 2004 .

[3]  Brauer,et al.  Positron studies of defects in ion-implanted SiC. , 1996, Physical review. B, Condensed matter.

[4]  C. Ling,et al.  Isochronal annealing studies of n-type 6H-SiC with positron lifetime spectroscopy , 2000 .

[5]  Risto M. Nieminen,et al.  Theory of Positrons in Solids and on Solid Surfaces , 1994 .

[6]  Friedhelm Bechstedt,et al.  Vacancies in SiC: Influence of Jahn-Teller distortions, spin effects, and crystal structure , 1999 .

[7]  Brauer,et al.  Evaluation of some basic positron-related characteristics of SiC. , 1996, Physical review. B, Condensed matter.

[8]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

[9]  M. Barthe,et al.  Negatively charged vacancy defects in 6H–SiC after low-energy proton implantation and annealing , 2001 .

[10]  Fabien Bruneval,et al.  Understanding and correcting the spurious interactions in charged supercells , 2011 .

[11]  A. Rempel,et al.  Identification of lattice vacancies on the two sublattices of SiC. , 2002, Physical review letters.

[12]  F. Carré,et al.  Structural materials challenges for advanced reactor systems , 2009 .

[13]  G. E. Matthews,et al.  A Projector Augmented Wave (PAW) code for electronic structure calculations, Part I: atompaw for generating atom-centered functions , 2001 .

[14]  Wolfgang J. Choyke,et al.  Static Dielectric Constant of SiC , 1970 .

[15]  Xavier Gonze,et al.  Implementation of the projector augmented-wave method in the ABINIT code: Application to the study of iron under pressure , 2008 .

[16]  Stefan Goedecker,et al.  ABINIT: First-principles approach to material and nanosystem properties , 2009, Comput. Phys. Commun..

[17]  Car,et al.  Ab initio study of positron trapping at a vacancy in GaAs. , 1994, Physical review letters.

[18]  R. Nieminen,et al.  Electron-positron density-functional theory. , 1986, Physical review. B, Condensed matter.

[19]  C. Lam,et al.  Decomposition of positron lifetime spectra generated by Monte Carlo method: The case study of 6H silicon carbide , 2006 .

[20]  T. Ohshima,et al.  Silicon vacancies in 3C-SiC observed by positron lifetime and electron spin resonance , 1998 .

[21]  Zhang,et al.  Chemical potential dependence of defect formation energies in GaAs: Application to Ga self-diffusion. , 1991, Physical review letters.

[22]  Nieminen,et al.  Electron-positron Car-Parrinello methods: Self-consistent treatment of charge densities and ionic relaxations. , 1995, Physical review. B, Condensed matter.

[23]  F. Bruneval.  Methodological aspects of the GW calculation of the carbon vacancy in 3C-SiC , 2012 .

[24]  C. Ling,et al.  Positron lifetime spectroscopic studies of as-grown 6H-silicon carbide , 2000 .

[25]  M. Puska.  Ab-initio calculation of positron annihilation rates in solids , 1991 .

[26]  Marjorie Bertolus,et al.  Electronic structure investigation of energetics and positron lifetimes of fully relaxed monovacancies with various charge states in 3C-SiC and 6H-SiC , 2013 .

[27]  M Leslie,et al.  The energy and elastic dipole tensor of defects in ionic crystals calculated by the supercell method , 1985 .

[28]  Xavier Gonze,et al.  A brief introduction to the ABINIT software package , 2005 .

[29]  M. Barthe,et al.  Silicon vacancy-type defects in as-received and 12-MeV proton-irradiated 6H-SiC studied by positron annihilation spectroscopy , 2003 .

[30]  L. Giancarli,et al.  Candidate blanket concepts for a European fusion power plant study , 2000 .

[31]  H. Okumura,et al.  Annealing processes of vacancy‐type defects in electron‐irradiated and as‐grown 6H‐SiC studied by positron lifetime spectroscopy , 1996 .

[32]  Alex Zunger,et al.  Accurate prediction of defect properties in density functional supercell calculations , 2009 .

[33]  Matthieu Verstraete,et al.  First-principles computation of material properties: the ABINIT software project , 2002 .

[34]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[35]  T. Higuchi,et al.  Positron study of electron irradiation-induced vacancy defects in SiC , 2006 .