TY - JOUR
AU1 - Shindo,, Daisuke
AU2 - Suzuki,, Satoshi
AU3 - Sato,, Kuniaki
AU4 - Akase,, Zentaro
AU5 - Murakami,, Yasukazu
AU6 - Yamazaki,, Kazuya
AU7 - Ikeda,, Yuuta
AU8 - Fukuda,, Tomohisa
AB - Abstract The charging effect due to electron irradiation in an electron microscope has been studied so far with incident electrons. Here we report on a new specimen holder to control the charging effect by using electrons emitted from an irradiation port in the holder while maintaining a constant intensity of the incident electron beam. Details of the charging effect, such as electric field variation, are expected to be investigated by electron holography. The new specimen holder was developed by modifying a double-probe piezodriving specimen holder to introduce an electron irradiation port in one of its two arms. As a result, the new modified specimen holder consists of a piezodriving probe and an electron irradiation port, both of which can be controlled in three dimensions, using piezoelectric elements and micrometers. We demonstrate that variations in the charging effect for epoxy resin and surface contamination can be observed by electron holography. piezodriving probe, specimen holder, charging effect, electron irradiation For dynamic observations in a transmission electron microscope (TEM), a piezodriving probe [1–5] and an environmental cell [6,7] have been developed, and in situ experiments have been performed extensively utilizing these specimen holders. Some of the authors of this paper have developed a double-probe piezodriving holder [8] utilized for conductivity measurements and electron holography analysis of an electric field under the electric shielding condition. Recently, a multifunctional TEM-specimen holder containing a laser irradiation port in one of its two arms in addition to the piezodriving probe has been developed [9]. This specimen holder was demonstrated to be useful for studying various photoinduced phenomena. For example, an electron holography study with this multifunctional TEM-specimen holder was carried out to investigate the change in the electric field due to the discharging effect of laser irradiation on organic photoconductors [9,10]. To control the charging effect due to the electron irradiation, in this study, we developed a new specimen holder, which incorporates an irradiation port for thermal electrons. A photograph of the top portion of the new multifunctional TEM-specimen holder is shown in Fig. 1a. The double-probe piezodriving holder was modified to introduce an electron irradiation port in its left arm (arm 1). For converging the electron beam emitted from a filament of a commercial light bulb, a reduction lens (electrostatic lens) was inserted at the top of the electron irradiation port. Figure 1b shows a schematic illustration of the new specimen holder. The electron irradiation port equipped with the filament and the probe can be manipulated independently in three dimensions by controlling the motions of arms 1 and 2. However, the electron irradiation port could be moved in a limited range mainly for adjusting the electron illumination conditions. These two arms are driven by micrometers and piezoelectric elements, which are located in the tail portion of the holder [8,9]. Three manual micrometers are used to effect coarse movement of the electron irradiation port and the probe, while three piezoelectric elements are used to effect fine movement. The geometrical configuration of a specimen, the reduction lens and the filament with the thermal electrons (indicated by a red arrow) are shown in Fig. 1b. Fig. 1. Open in new tabDownload slide (a) Photograph of the top portion of the new specimen holder equipped with a piezodriving probe and an electron irradiation port. (b) Schematic illustration of the specimen holder. Fig. 1. Open in new tabDownload slide (a) Photograph of the top portion of the new specimen holder equipped with a piezodriving probe and an electron irradiation port. (b) Schematic illustration of the specimen holder. Figure 2 shows the electrical circuit of the specimen holder with the electron irradiation port. In Fig. 2, Vfilament, Vacc and Vreduction lens are the filament voltage, the accelerating voltage for thermal electrons and the voltage for the reduction lens, respectively. Figure 3 indicates the probe current measured at the specimen position with a filament voltage Vfilament of 5.6 V as a function of the reduction lens voltage for three accelerating voltages, Vacc, of 20, 85 and 100 V. Modifying the reduction lens voltage makes the convergence of electrons emitted from the filament controllable. The electric current was measured at the specimen position with a detector consisting of a Pt sphere 1 mm in diameter. It is seen that with increasing accelerating voltage, the probe current increases, while the current tends to decrease with increasing reduction lens voltage. Fig. 2. Open in new tabDownload slide Electric circuit of the specimen holder with the electron irradiation port. Vfilament, Vacc and Vreduction lens represent the filament voltage, the accelerating voltage for thermal electrons and the voltage for the reduction lens, respectively. Fig. 2. Open in new tabDownload slide Electric circuit of the specimen holder with the electron irradiation port. Vfilament, Vacc and Vreduction lens represent the filament voltage, the accelerating voltage for thermal electrons and the voltage for the reduction lens, respectively. Fig. 3. Open in new tabDownload slide Probe current measured at the specimen position as a function of reduction lens voltage with accelerating voltages of 20, 85 and 100 V. Fig. 3. Open in new tabDownload slide Probe current measured at the specimen position as a function of reduction lens voltage with accelerating voltages of 20, 85 and 100 V. For investigating the utility of this multifunctional TEM-specimen holder, an insulating material, i.e. epoxy resin, shielded with an Mo plate on the top was used. A photograph of the specimen taken from the back is shown in Fig. 4. Figure 5a shows an electron hologram that was acquired from the vacuum area near the edge of the Mo plate. Note that the epoxy region was shielded by the Mo plates with a total thickness of 100 μm in this experimental setup, in order to avoid irradiation by the incident electrons. There is a small contamination at the position indicated as ‘C’ with a black arrow. Figure 5b–h shows reconstructed phase images indicating the electric potential distribution around the specimen edge with a change in the filament voltage. Vacc and Vreduction lens were set at 100 and 0 V, respectively. At the initial stage, with the filament voltage Vfilament being 0, the contamination was found to be positively charged, while no charging effect was observed in the epoxy resin, since it was shielded. This results from the emission of secondary electrons with most of the high-energy incident electrons (300 keV) transmitting the contamination. On the other hand, when the filament voltage Vfilament was increased up to 4.5 V, the electric potential around the contamination position gradually changed to negative. The relative changes in the electric potential on the line A–B in Fig. 5b–e are indicated in Fig. 6. The electric potentials are normalized at position B. This change is considered to result from electron-buildup due to the low energy of electrons emitted from the electron port. There are also charging effects in other areas due to the epoxy resin where no charging effects were seen at the initial condition. On the other hand, when the filament voltage Vfilament decreased, the negative charging effect gradually decreased and finally changed to a positive charging condition, as observed in the initial condition. This reversible charging effect clearly demonstrates the stability of the multifunctional TEM-specimen holder developed in this study. Further applications using this multifunctional TEM-specimen holder are in progress. Detailed results of the analysis will be published elsewhere. Fig. 4. Open in new tabDownload slide Photograph of epoxy resin shielded with a Mo plate taken from the back. Fig. 4. Open in new tabDownload slide Photograph of epoxy resin shielded with a Mo plate taken from the back. Fig. 5. Open in new tabDownload slide (a) Electron hologram observed around the specimen (epoxy resin) edge. (b)–(h) Reconstructed phase images showing the electric potential distribution around the specimen edge with changing filament voltage. The arrows indicate the position of a small contamination at the specimen edge. See text for details. Fig. 5. Open in new tabDownload slide (a) Electron hologram observed around the specimen (epoxy resin) edge. (b)–(h) Reconstructed phase images showing the electric potential distribution around the specimen edge with changing filament voltage. The arrows indicate the position of a small contamination at the specimen edge. See text for details. Fig. 6. Open in new tabDownload slide Relative change of the electric potential along the line A–B in Fig. 5b–e. The electric potential is normalized at position B. Fig. 6. Open in new tabDownload slide Relative change of the electric potential along the line A–B in Fig. 5b–e. The electric potential is normalized at position B. In conclusion, a new multifunctional TEM-specimen holder equipped with a piezodriving probe and an electron irradiation port was developed. Reversible charging–discharging with epoxy resin shielded by an Mo plate was clearly observed by electron holography. It is expected that the holder developed in this work will be utilized for the study of various electron-induced charging phenomena by electron holography. Funding This work was partly supported by Post-Silicon Materials and Devices Research Alliance for Special Education and Research Expenses and by Grants-in-Aid for Scientific Research (S) (19106002) from JSPS. Acknowledgements The authors are grateful to Dr. Y. Kondo (JEOL Co. Ltd.) for his collaboration. References 1 Ohnishi H , Kondo Y , Takayanagi K . Quantized conductance through individual rows of suspended gold atoms , Nature , 1998 , vol. 395 (pg. 780 - 783 ) Google Scholar Crossref Search ADS WorldCat 2 Kizuka T , Yamada K , Deguchi S , Naruse M , Tanaka N . 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Simultaneous measurements of conductivity and magnetism by using microprobes and electron holography , Appl. Phys. Lett. , 2006 , vol. 88 (pg. 223103-1 - 223103-3 ) OpenURL Placeholder Text WorldCat 9 Shindo D , Takahashi K , Murakami Y , Yamazaki K , Deguchi S , Suga H , Kondo Y . Development of a multifunctional TEM specimen holder equipped with a piezodriving probe and a laser irradiation port , J. Electron Microsc. , 2009 , vol. 58 (pg. 245 - 249 ) Google Scholar Crossref Search ADS WorldCat 10 Takahashi K , Murakami Y , Shindo D . Charging and discharging phenomena in organic photoconductors observed using electron holography , Key Engineering Materials , 2012 , vol. 508 (pg. 315 - 322 ) Google Scholar Crossref Search ADS WorldCat Author notes 4 Present address: Seiko Instruments Inc., Matsudo 270-2222, Japan. © The Author 2013. Published by Oxford University Press [on behalf of The Japanese Society of Microscopy]. All rights reserved. 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TI - Multifunctional TEM-specimen holder equipped with a piezodriving probe and an electron irradiation port
JF - Microscopy
DO - 10.1093/jmicro/dft021
DA - 2013-08-01
UR - https://www.deepdyve.com/lp/oxford-university-press/multifunctional-tem-specimen-holder-equipped-with-a-piezodriving-probe-hc3f6Mpmry
SP - 487
EP - 490
VL - 62
IS - 4
DP - DeepDyve
ER -