1. Online supplementary Figure S1
Fig. S1. Bright-field TEM images obtained under (a) g=(11-1), (b) g=(-11-1), (c) g=(-200) and (d) g=(0-22).

2. Online supplementary Figure S2
Fig. S2. Sequential snapshots of thickening of the deformation twins, extracted from the supplemental movie 3. (a)-(c) Dark-field TEM images of the deformation twin growing to various thickness, insert in (a) is the corresponding SAED patterns and all the dark-field TEM images are taken by using the (111)T spot.

3. Online supplementary Figure S3
Fig. S3. TEM images of the middle of the tensile test sample close to failure (a) twins on the primary and conjugate planes, (b) bright-field TEM image of the twins and (c) dark-field image showing twins on one planes, and (d) corresponding SAED patterns showing twin characteristics