Structure and mechanical properties of a Σ= 51 [011] tilt boundary in germanium

HAL Id: jpa-00245830

https://hal.archives-ouvertes.fr/jpa-00245830

Submitted on 1 Jan 1988

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Structure and mechanical properties of a Σ= 51 [011] tilt boundary in germanium

W. Skrotzki, H. Wendt, C.B. Carter, D.L. Kohlstedt

To cite this version:

W. Skrotzki, H. Wendt, C.B. Carter, D.L. Kohlstedt. Structure and mechanical properties of a Σ=

51 [011] tilt boundary in germanium. Revue de Physique Appliquée, Société française de physique / EDP, 1988, 23 (4), pp.681-681. �10.1051/rphysap:01988002304068100�. �jpa-00245830�

681

STRUCTURE AND MECHANICAL PROPERTIES OF A 03A3= ⁵¹ [011] TILT BOUNDARY IN GERMANIUM

W. Skrotzki*, ^H. Wendt**, ^C.B. Carter and D.L. Kohlstedt

Department ^of Material Science and Engineering,

Cornell University, Ithaca, NY 14853 - 1501, ^USA

Revue Phys. Appl. ²³ (1988) ^{681 AVRIL 1988,}

Interest in understanding ^the correlation between structure and properties ^of grain

boundaries has recently ^been stimulated by

both the technological importance ^of poly- crystalline ^{Si in the} production ^{of solar}

cells and electronic devices, ^{and the in-} creasing ^{use of} ceramic materials for

high-temperature energy conversion. For the first class of materials, ^{the electri-}

cal activity ^of grain boundaries is a pri-

mary problem; ^for the second class, grain boundary ^{diffusion and} mechanical strength

of grain boundaries determine the sinte-

ring ^{behaviour and the service} lifetime, respectively. ^{In the} present ^{work Ge} bicrystals have been chosen as a model ma-

terial to study ^the relation between structure and mechanical properties ^of grain boundaries.

The grain boundary ^{discribed here is close}

to aL = ⁵¹ boundary with 16.1° tilt about [011]. Analysis by conventional and

high resolution transmission electron

microscopy shows that the structure of this boundary ^{consists of a} linear array of Lomer dislocations spaced ^{1.43 nm} apart. ^The secondary dislocations accommo-

dating the small deviation (~ 0,3°) ^from the £ = ⁵¹ coincidence structure repre- sent irregularities ^{in the} spacing ^{of the} primary dislocations and are found to have

non-primitive DSC-Burgers ^vectors.

Bicrystals with this grain boundary ^{at an} angle ^of 450 with respect ^{to the} specimen

axis have been subjected to creep deforma- tion at 0,95 T. ^{and a stress of} 20 MPa. To detect any macroscopic sliding ^effects along ^the boundary, ^{marker lines almost} perpendicular ^{to the} boundary ^{were scribed}

on the specimen ^{surface. In} addition, ^a

carbon grid ^was evaporated ^{onto the sur-}

face to help protect the marker lines from thermal etching and to record the inhomo-

geneity ^{of the} bicrystal deformation.

Investigations ^{of the} microstructure ^after creep deformation show a subgrain ^struc-

ture which has knit together ^{with the in-} itial large angle grain boundary. ^{With in-} creasing ^{distance from the} grain boundary

the subgrain ^size decreases. This result correlates with the higher ^{strains obser-}

ved in a region ^{near the} grain ^boundary

compared to the rest of the matrix. The

knitting ^{of a} subgrain boundary ^{with the} initial grain boundary leads to the addi- tion of the misorientation of the subgrain boundary ^{to the} misorientation of the

large angle boundary. ^{Since the misorien-} tation of the subgrain boundaries differ,

the density ^and arrangement ^{of the secon-} dary dislocations has to change along ^the boundary ^{from one} grain to another.

Upon entering ^the grain boundary ^matrix dislocations décompose ^into secondary grain boundary dislocations. The decompo- sition product dépends ^{on the} type ^{of Bur-}

gers ^vector. Direct crossover of lattice dislocations through ^the boundary ^has only

be observed for screw dislocations with a/2 [011] Burgers vector. The passing pro-

cess involves a reaction with the grain boundary ^structure.

Bowing ^{out of} grain boundary dislocations indicates their motion in the interface.

Since secondary dislocations _may produce ledges ^{in the} boundary, this dislocation movement can result in a shift of the

grain boundary plane, ^i.e. grain boundary migration. ^The driving force for grain boundary migration ^is proceded by ^{the in-} terfacial tension which tries to achieve mechanical equilibrium ^{at the} triple junc-

tions between the large angle boundary ^and subgrain boundaries. The dislocation mo-

tion is by glide ^{or climb} depending ^{on the} Burgers vector. If the Burgers ^{vector has}

a component normal to the interface dislo- cation motion involves climb. Motion of

components parallel ^{to the interface} pro- duces grain boundary sliding. ^{No offsets}

of the marker lines are detected at magni-

fications up to thousand times. Thus pos- sible sliding ^effects along ^the grain boundary plane ^{are much smaller than} usually ^{observed in métal} bicrystals ^under

similar conditions.

Présent address:

*) ^{Institut für} Géologie ^und Dynamik ^der Lithosphâre, Universitât Gôttingen, ^Gold-

schmidtstr. 3, ^D-3400 Gôttingen, ^FRG

**) ^Siemens AG, Otto-Hahn-Ring ^6,

D- 8000 München, ^FRG

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/rphysap:01988002304068100