Simple Cubic (sc) Body-Centered Cubic (bcc) Face-Centered Cubic (fcc) Sodium Chloride (NaCl) Cesium Chloride (CsCl) ZincBlend (ZnS) Diamond (C) (Silicon and Germanium have the Diamond structure)
ANGLE
100
110
010
001
101
0.00
45.0
90.0
011
60.0
111
54.7
35.3
211
35.2
30.0
65.9
311
25.2
31.4
72.4
511
15.8
78.9
711
11.4
37.6
81.9
Purpose and Function
1. Orientation for automatic equipment
2. Indicate type and orientation of crystal.
Primary flat – The flat of longest length located in the circumference of the wafer. The primary flat has a specific crystal orientation relative to the wafer surface; major flat.
Secondary flat – Indicates the crystal orientation and doping of the wafer. The location of this flat varies.
For more information on cleaving or semiconductor substrates in general, see this link