Development and application of intermittent electron irradiation technique with a high voltage electron microscope

Abstract

Abstract. 2014 For the purpose to observe and analyze the transient phenomena after the start of irradiation and the relaxation phenomena after the cessation of irradiation, techniques for intermittent electron irradiation are developed with a high voltage electron microscope, utilizing the STEM function installed in H-1250ST. One of the two methods developed is to make move the electron beam along a circle passing the area of interest in each cycle, which has an advantageous feature of invariant accumulated irradiation time regardless of the frequency. In another method, the electron beam goes back and forth between two positions, in which there is a free choice of the combination of the on-and off-time of electron beam. Dynamical control of electron beam position is made with two deflection coils placed at a right angle, which are driven by a computer loaded with two-phase-signal oscillator through D/A converter. Examples of applications are quoted on the relaxation effect of accumulated point defects on the nucleation and growth of interstitial clusters introduced in metals by electron irradiation.

Effect of pulse irradiation on the evolution of damage structure

“…The growth rate at low frequency was close to 0.97, as shown by arrow A for the continuous beam irradiation of 0.0167 dpa/s (0.1dpa ×1/6), and that at high frequency was to 1.9 for continuous beam irradiation of 0.1 dpa/s as shown by arrow B. The open circles in the figure denote the data collected by Arai et al [5]. The absolute values are not compared directly because they depend on ZSI_I, ZSI_I2, ZSI_V and ZSI_V2, but the frequency dependence of the growth rate is simulated well.…”

“…3 illustrates the case of Al irradiated at 453 K with a damage rate in pulse duration, H, of 0.1dpa/s and τ/T = 1/6. These conditions were the same as those in the electron irradiation experiment conducted by Arai et al [5]. Increasing the pulse frequency resulted in an increase in the loop growth rate.…”

“…Hence, if the pulse duration L is shorter than time L2, the pulse train will fulfill the conditions for the interstitial migration efficiency to be dominant. The interstitial dominant conditions during irradiation were demonstrated experimentally by Arai et al [5]. They utilized the scanning ability of high voltage electron microscopy for the generation and observation of irradiation induced defect clusters.…”

Progress in environmental high-voltage transmission electron microscopy for nanomaterials

“…It is worth mentioning that STEM provided advantages for accurate control of an nm-sized probe on a sample plane. This could be useful for reduction and studies of irradiation damages using flip-flop and rotational motions of an electron probe [82].…”