SYNCHROTRON WHITE BEAM X-RAY TOPOGRAPHY OF SILICON CARBIDE POLYTYPES

Examples of edge topographs

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J26

A new Long Period Polytype (LPP) 152H/456R previously unseen which is shown by the closely spaced magnified reflections in the topograph. A description of the polytype content of the 1370 mm thick crystal J26 .

J52 - Click on the topograph to see an indexed enlargement - American Club Sandwich

An enlargement from an edge topograph of the three most common polytypes 6H, 4H, 15R found in coalescence in SiC along with defect bands and one-dimensionally disordered (1DD) layers. The main {314l} row is shown centrally while the {5270} reflection to the middle left contains bands of high defect density which often indicate the presence of 1DD layers. The 4H polytype is located in the middle of the row while the 15R reflection is closest and situated asymmetrically about the zero layer line. The two parts of the 6H polytype appear separated by a gap.

Polytype Model : 6H + 4H + 6H + 1DD + 6H + 1DD + 6H + 1DD + 15R

Polytype Next Nearest Neighbour Relationships and Sandwich models

A survey of polytype neighbourism in SiC from a survey of 135 crystals showing: the sample number, polytype classification, a depth profile of polytype content, overall sample thickness (in microns), Long Period Polytypes / one-dimensionally disordered layers and defect bands. The various non degenerate polytype configurations observed in the survey have been termed a "sandwich".

Abbreviations: ACS-American Club Sandwich OS-Open Sandwich AS-Asymmetric Sandwich SP-Single Polytype SS-Simple Sandwich DP-Double Polytype MP-Multiple Polytype

SiC polytypes
crystal J no Sandwich type Polytype model crystal size mm plate # 1DD layers mm Thesis Topograph LPP repeat Notes / Model Defect band boundaries
1 ACS 6H+1DD+6H+LPP+1DD+LP 760 187 20,50
24H, 78H Gasilova/Mitchell ALL


2 ACS 15R+1DD+15R+1DD+6H 790 188 10,20 Yes
ALL


3 OS 6H+1DD 570 189 70






4 AS 4H+1DD+6H 320 190 40






5 SP 6H 800 191







6 SS 6H+1DD+6H 940 192,364,365,366 40 Yes
ALL


7 SP 6H 1180 185,186







8 ACS 6H+LPP+4H+1DD+4H 390 471 ?,12.5






9 SP 6H 420 472,494







10 DP 15R+6H 400 193







11 ACS 15R+1DD+6H+1DD+6H+1DD+6H 2010 194, 476 80,110,40


ALL


12 AS 6H+4H+1DD+6H+15R+15R+6H 3625 81 40

ALL


13 ACS 6H+1DD+4H+1DD+6H 2280 83 20,60 Yes
  Radiat. Phys. Chem. Fig 6. ALL


14 ACS 15R+1DD+15R+1DD+6H+1DD+4H+6H 1250 86 15,70,30 Yes
 4H/15R Indexed
 ALL


15 ACS 6H+4H+1DD+6H+1DD+6H+1DD+6H 1180 87,88 60,5,5 Yes Missing piece ? ALL


16 SS 6H+1DD+6H 80 98 5






17 OP 6H+1DD 780 91 30






18 ACS 6H+1DD+6H+1DD+6H 2280 409,410 10,7.5


ALL


19 ACS 4H+1DD+4H+1DD+4H+1DD+15R+6H+15R 1275 100 20,20,40


ALL


20 AS 6H+4H+1DD+4H+6H 1470 101 20 Yes
ALL


21 AS 6H+4H+1DD+6H 1120 102 50


ALL


22 ACS 6H+1DD+6H+1DD+6H 2740 103 12.5,7.5


ALL


23 ACS 6H+1DD+6H+15R+1DD+15R 2100 104 90,10


ALL


24 AS 4H+6H+4H+1DD+6H 800 105 80 Yes
ALL


25 ACS 6H+1DD+6H+1DD+15R 400 106 20,20


ALL


26 ACS 6H+1DD+6H+LPP+6H 1370 107 12 Yes 152H/456R   Phil. Mag. Lett. Fig 2 ALL


27 MP 6H+4H+6H\15R(overgrowth) 120 130







28 AS 6H+15R+1DD+4H 1050 174 70


ALL


29 AS 6H+4H+1DD+6H 1020 195 90 Yes
ALL


30 SP 6H 1935 196







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