Diebel and Dunham Reply:

Abstract

Diebel and Dunham Reply: Fiorentini and Lopez [1] have identified a lower energy structure for the F 4 V complex than the higher symmetry structure which we considered in Ref. [2]. Our calculations using the methods described in Ref.[2] confirm the lower energy of this structure. By exploring a range of configurations, we also found lower energy structures for F 3 V, F 4 V 2 , F 5 V 2 , and F 6 V 2 . The energy differences are most significant for higher F to V ratios, and these F n V m structures have rotated Si-F bonds similar to F 4 V, which allow larger F-F spacing as noted in the Comment [1]. In this Reply, we have updated Table I and Fig. 3 from Ref.[2] to include these values. While some of the numbers have changed, the overall conclusions of our work on F in Si [2,3] remain valid (and are, in fact, confirmed in a recent paper by the authors of the Comment [4]): The strong binding of F to vacancies leads to immobilization and segregation of F in V-rich regions during ion implant annealing, giving rise to apparent uphill F diffusion and reduction of B transient enhanced diffusion.In Table I, the formation and binding energies for different F n V m configurations are listed. For two or more F atoms, F n V m structures are favored over the interstitial configurations. For the F n V structures, the binding energy gained by adding additional fluorine atoms is approximately constant (ÿ 2 eV). For F n V 2 , the binding energies of F to V 2 are similar to that for F n V, with slightly larger binding energies for the first two F atoms. The lower energy asymmetric structures show greater bond angle distortion but much smaller changes in bond length compared to the structures analyzed in Ref. [2]. With the updated values, the saturated F 4 V structure (rather than the F 6 V 2 ) is stable in the presence of interstitials (apparent once Table II of Ref. [2] is updated with values of Table I).In Fig. 1, estimated equilibrium concentrations of F structures versus total F concentration are shown. The fully saturated clusters F 6 V 2 and F 4 V are the most important in equilibrium. Out of equilibrium, a cascade of reactions involving point defects and F n V m clusters determine the dynamic behavior [3]. In the presence of nonequilibrium point-defect concentrations, the local equilibrium F n V m concentrations need to be multiplied by C V =C V m . Thus, in the presence of excess vacancies during initial stages of implant annealing, almost all fluorine will reside in F n V m structures.

Fluorine codoping in germanium to suppress donor diffusion and deactivation

“…[22][23][24] We also carried out some calculations for F n V m clusters in Si and found binding energy values that were very similar to those reported previously. 13,14 For example, our predicted binding energy of the FV pair in Si is Ϫ2.23 eV, which is in excellent agreement with the DFT study of Lopez et al 14 ͑Ϫ2.0 eV͒ and the experimental value of Pi et al 9 ͑Ϫ2.2 eV͒.…”

“…These predictions agree with previous results for F interstitials in Si. 13,14 As the bond-center F interstitials are positively charged, they should repel each other, whereas the tetrahedral F interstitials should repel each other because they are negatively charged. Conversely, F interstitial pairs consisting of a bondcenter and a tetrahedral interstitial should be bound ͑F 2 ͒.…”

“…A number of experimental [9][10][11] and theoretical [12][13][14][15][16][17] studies address the issue of doping Si with F. These provide evidence that F n V m clusters are stable in Si. In particular, simulation studies suggested that the most abundant F n V m clusters are those in which all the V dangling bonds are saturated by F. 16 Interestingly, recent experimental work 10 on F-implanted preamorphized Si determined that the predicted F n V m clusters do not exist in detectable concentrations.…”

Lattice site investigation of F in preamorphized Si

“…Up to now, it is known that the slowing down of boron TED occurs by the interaction between F and point defects, and it has been suggested that F atoms form complexes with these defects. [3][4][5][6][7][8][9] By ab initio calculations, several authors 5,7,8,10 have found that the lowest-energy state for a single interstitial F in Si is at the bond-centered the ͑BC͒ site in the +1 charge state or at the tetrahedral ͑T͒ site in the −1 charge state, depending on the Fermi energy. However, in Refs.…”

Multifunctional silicon inspired by a wing of male Papilio ulysse

“…In the RIE process, structural defects such as fluorinevacancy complexes are formed by penetrating fluorine into silicon lattice at or near the surface structure. [16][17][18][19][20] The defects created and the high concentration of fluorine impurity as detected by XPS can modify surface states by introducing impurity states in the bandgap. Hence, the surface of the nanocones can be considered as an absorber for photons which has energy lower than the bandgap energy.…”