In situ measurement of electrical conductivity of alumina under electron irradiation in a high voltage electron microscope

Role of specimen thickness on the electrical conductivity of single crystalline alumina under electron irradiation

“…The RIC promptly increases to a higher value than that without irradiation by about three orders of magnitude due to electronic excitation. 15 Even though the experimental conditions were similar to that of Hodgson, no bulk and surface degradation were observed in the specimens, other than only a decrease of both the conductivity with total dpa of 9.4ϫ10 Ϫ5 (5.0ϫ10 9 Gy), in contrast to the abrupt increase in the surface conductivity at 3.3ϫ10 Ϫ5 dpa in our previous study where the RIED experiment was 7.7ϫ10 Ϫ5 dpa. [3][4][5][6]15 Increases of RIC with increasing specimen thickness are found here.…”

“…15 Even though the experimental conditions were similar to that of Hodgson, no bulk and surface degradation were observed in the specimens, other than only a decrease of both the conductivity with total dpa of 9.4ϫ10 Ϫ5 (5.0ϫ10 9 Gy), in contrast to the abrupt increase in the surface conductivity at 3.3ϫ10 Ϫ5 dpa in our previous study where the RIED experiment was 7.7ϫ10 Ϫ5 dpa. [3][4][5][6]15 Increases of RIC with increasing specimen thickness are found here. We also checked for errors in the calculated conductivity which might have been caused by surface conduction using Kesternich et al's method 17 and found no error in the bulk conductivity.…”

“…The value of RIC in our previous study of 270-mthick alumina after a few seconds reach stability of the beam current was 7.2ϫ10 Ϫ6 S/m whereas the respective values for 125-, 332-, and 545-m-thick alumina are 5.3ϫ10 Ϫ6 , 9.7 ϫ10 Ϫ6 , and 4.5ϫ10 Ϫ5 S/m, respectively, so the value of RIC of 270-m-thick alumina is between the 125-and 332m-thick specimens. 15 It indicates that RIC is strongly dependent on the specimen thickness rather than either the applied electric field or the type of electrode materials provided ͑the ionizing dose rate is the same͒. This dependence of RIC will be discussed below.…”

“…On the other hand, RIED became controversial when other groups failed to find RIED in alumina with 1-2 MeV electrons, with 28 MeV He ϩ ions and with fast neutrons. [12][13][14][15][16][17][18][19] Jung et al, 20 Kesternich et al, 17,21 and Kinoshita et al 13,15 found RIED-like behavior in alumina that was not a bulk effect, could be explained by surface contamination or internal fracture of the insulator. Hodgson 10 has found the production of point defects during irradiation by optical spectroscopy which influences the observed microstructural changes.…”

Effect of Cr2O3 and NiO dopants in α-Al2O3 on its electrical conductivity under electron irradiation

“…[3,4], however, it does not specify what nature of impurities affect the RIC in a-Al 2 O 3 . In addition, few systematic studies have been done for the effect of impurities on the RIC in a-Al 2 O 3 , although many studies have been carried out under different radiation fields [5][6][7][8][9][10][11][12][13][14][15]. Thus it has not been determined that what nature of impurities effectively suppresses RIC.…”