Then, the critical dose for different Bragg planes was measured, from low-index planes to high-index planes, at an electron dose rate of 1 e -Å -2 s -1 and an accelerating voltage of 300 kV, as shown in fig. . It indicates that the critical dose of high index planes, such as {400} and {431}, is lower compared to the critical dose of low index planes, such as {110}, {200}, {211} and {222}.