From: hackbard Date: Thu, 23 Sep 2010 15:49:31 +0000 (+0200) Subject: movie ... X-Git-Url: https://hackdaworld.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0a9d3950d67d44d045abf76030e2538028ad17f8;p=lectures%2Flatex.git movie ... --- diff --git a/posic/publications/sic_prec.tex b/posic/publications/sic_prec.tex index 8a6d36d..3696eae 100644 --- a/posic/publications/sic_prec.tex +++ b/posic/publications/sic_prec.tex @@ -325,19 +325,36 @@ No significant change in structure is observed. However, the decrease of the cut-off artifact and slightly sharper peaks observed with increasing temperature, in turn, indicate a slight acceleration of the dynamics realized by the supply of kinetic energy. However, it is not sufficient to enable the amorphous to crystalline transition. In contrast, even though next neighbored C bonds could be partially dissolved in the system exhibiting low C concentrations the amount of next neighbored C pairs even increased in the latter case. -Moreover the peak at \unit[0.252]{nm}, which gets slightly more distinct, equals the second next neighbor distance in diamond and indeed is made up by a structure of two C atoms interconnected by a third C atom. -Obviously conducive rearrangements of C are hindered in a system, in which high amounts of C are incoorporated within a too short period of time. -Thus, for these systems even larger time scales are necessary for an amorphous to crystalline transition and structural evolution in general, which is not accessible by the traditional MD technique. +Moreover the C-C peak at \unit[0.252]{nm}, which gets slightly more distinct, equals the second next neighbor distance in diamond and indeed is made up by a structure of two C atoms interconnected by a third C atom. +Obviously processes that appear to be non-conducive are likewise accelerated in a system, in which high amounts of C are incoorporated within a short period of time, which is accompanied by a concurrent introduction of accumulating, for the reason of time non-degradable, damage. +% non-degradable, non-regenerative, non-recoverable +Thus, for these systems even larger time scales, which are not accessible within traditional MD, must be assumed for an amorphous to crystalline transition or structural evolution in general. % maybe put description of bonds in here ... +Nevertheless, some results likewiese indicate the acceleration of other processes that, again, involve C$_{\text{s}}$. +The increasingly pronounced Si-C peak at \unit[0.35]{nm} corresponds to the distance of a C and a Si atom interconnected by another Si atom. +Additionally the C-C peak at \unit[0.31]{nm} corresponds to the distance of two C atoms bound to a central Si atom. +For both structures the C atom appears to reside on a substitutional rather than an interstitial lattice site. +However, huge amount of damage hampers identification. +The alignment of the investigated structures to the c-Si host is lost in many cases, which suggests the necissity of much more time for structural evolution to maintain the topotaptic orientation of the precipitate. +\section{Discussion} +Investigations are targeted on the initially stated controversy of SiC precipitation, i.e. whether precipitation occurs abrubtly after ehough C$_{\text{i}}$ agglomerated or a successive agglomeration of C$_{\text{s}}$ on usual Si lattice sites (and Si$_{\text{i}}$) followed by a contraction into incoherent SiC. +Results of a previous ab initio study on defects and defect combinations in C implanted Si\cite{zirkelbach10b} sugeest C$_{\text{s}}$ to play a decisive role in the precipitation of SiC in Si. +To support previous assumptions MD simulations, which are capable of modeling the necessary amount of atoms, i.e. the precipitate and the surrounding c-Si structure, have been employed in the current study. +In a previous comparative study\cite{zirkelbach10a} we have schown that the utilized empirical potential fails to describe some selected processes. +Thus, limitations of the employed potential have been further investigated and taken into account in the present study. +We focussed on two major shortcomings: the overestimated activation energy and the poor description of intrinsic and C point defects in Si. -\section{Discussion} Sii stress compensation ... +Concluded that C sub is very probable ... +Alignment lost, successive substitution more probable to end up with topotactic 3C-SiC. + + Both, low and high, acceleration not enough to either observe C agglomeration or amorphous to crystalline transition ... The first-principles results are in good agreement to previous work on this subject\cite{burnard93,leary97,dal_pino93,capaz94}.