On the mechanism of {111}-defect formation in silicon studied by in situ electron irradiation in a high resolution electron microscope

Abstract

The initial stages of point defect cluster formation on {111} habit planes in Si crystals have been investigated during in situ electron irradiation in a high resolution electron microscope to elucidate their nature and origin. It was observed that k 110 l interstitial chains located in {111} planes at regular spacing are formed by the agglomeration of self-interstitial atoms to the core of vacancy or interstitial Frank partial dislocation loops and by the insertion of interstitial chains between two perfect {111} planes. Based on experimental and calculated high resolution electron microscopy images a structural model for the {111}-defect is proposed which includes a regular sequence of double ® ve-membered and single eight-membered rings in which no dangling bonds are involved. A dependence of the displacement vector of the {111}-defect on the formation mechanism is observed. An isolated {111}-defect is characterized by the fully relaxed atomic structure with a displacement vector of ( a /5 ) k 111 l . The aggregation of self-interstitials in the core of Frank partial dislocations results in the relaxation of the strongly deformed crystal lattice by decreasing the displacement vector of initial defects. §

Atomic structure of extended defects in boron-implanted silicon layers

“…Embedding of I s into the defect plane occurs in the form of individual 110 -chains separated by eight-member channels and connected to the matrix by doubled fivemember rings, which ensures the 2 × 1 periodicity. We discovered this mechanism in studying the processes of PD clustering in Si with in situ irradiation by electrons in the JEM-4000EX microscope [10].…”

“…4 shows the HREM images of the V -type Frank loops after boron implantation (a) and during irradiation by electrons in the course of interaction with I s (b and c), as well as the computer model of such a defect (d). This unusual defect, which was called the {111} defect, in contrast to the classical V -type Frank dislocation loop, has a very small displacement vector a/8 111 and small excess energy, which does not exceed 0.3-0.4 eV per atom in this defect [10]. Such an extended defect may form in the core of any dislocation owing to kinetic restrictions of embedding of I s into the dislocation loop plane, where I s occupy substitutional positions [11].…”

Atomistic Calculation of Defect Thermodynamics in Crystalline Silicon

“…While vacancy clusters are characterized by the octahedral morphology across all sizes, no single morphological motif describes self-interstitial clusters. [61][62][63][64][65][66][67][68][69][70][71][72]. Small clusters containing up to about 15 self-interstitials are compact and three-dimensional and exhibit magic sizes, particularly at sizes that are integer multiples of four (i.e., 4, 8, and 12) [46,50,59].…”

In situHREM irradiation study of point-defect clustering in MBE-grown strainedSi1−xGex/(Fedina1, Lebedev2, Tendeloo3 et al. 2000Phys. Rev. BSelf Cite340280View full textAdd to dashboardCite

“…31 Furthermore, at room temperature both interstitials and vacancies cluster on a ͕113͖ plane if their diffusion to the surface is blocked by covering films. [14][15][16][17] According to these results the aggregation of point defects on ͕113͖ in Si layers close to the Si-Si 3 N 4 interface can be considered rather as an additional way of point-defect recombination in an extended form in the presence of a high concentration of both types of point defects. At the initial stage, vacancies cluster in the form of ͓110͔ chains located on ͕113͖ and further act as traps for interstitials.…”

“…Recently, clustering of intrinsic point defects at room temperature in thin Si specimens covered with Si 3 N 4 films was shown to be much more complex than earlier assumed and included a combined aggregation of vacancies and interstitial atoms on ͕111͖ and ͕113͖ habit planes. [14][15][16] The driving force proposed for this process is either a compensation of large strains caused by initial clustering of vacancies on ͕111͖ or a slow recombination of point defects in extended shape on ͕113͖. 17 In general, however, the role of strain in point-defect clustering is not yet clear.…”