Production and Characterization of MoSe 2 Nanotubes by Electron Irradiation
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Production and characterization of MoSe2 nanotubes by electron irradiation D. H. Galván, R. Rangel1 and E. Adem2 Centro de Ciencias de la Materia Condensada-UNAM, Apartado Postal 2681, C. P. 22800, Ensenada, B. C., México. 1 Escuela de Ingeniería Química, Universidad Michoacana de S. N. H., Edificio"K", Ciudad Universitaria, C. P. 58060, Morelia, Michoacán, México. 2 Instituto de Física-UNAM, Apartado Postal 20-364, 01000 México, D. F., México. ABSTRACT In this work, we report the production of MoSe2 (molybdenum diselenide) nanotubes formed by irradiating the samples with high doses of electron irradiation. The irradiation was performed on a 2 MeV Van de Graaff accelerator at the following conditions: voltage 1.3 MeV, current 5µA current, dose rate 25 kGy/min, and total dosage 1 MGy. We observed well-defined nanotubes of several nm long and few nm wide, which suppose to be hollow and capped at one end. As the level of irradiation was increased to 1 MGy, elongated onion-like structures were observed.
INTRODUCTION Carbon nanotubes were discovered by Iijima [1] in 1991, which prompted numerous studies because of their superior mechanical property [2] and unique electronic behavior [3]. For example nanotubes are expected to have a high strength-to-weight ratio [4] which is advantageous in advanced composites to be used in high performance materials such as aircraft frames. The small dimensions of the tubes shows promise for use as gas adsorption medium [5,6], a field emitter for use in flat-panel display [7], nanoscale electronic devices [8], and lately they have been used as microscope probes [9]. In 1992, Ugarte [10] reported that electron irradiation of carbon soot produced onion-like structures. Ugarte obtained such structures under a high flux of electrons in a transmission electron microscope (TEM). The graphite structure is also showed by metal dichalcogenides, represented by MX2 ( M = Mo, W, Nb, etc., whilst X = S, Se, Te, etc.). In our case MoSe2, which its layered structure is depicted in Fig. 1. Still all the members of these family might present similar behavior and possible formation of nanotubes and onion-like structures, only MoS2 and WS2 compounds and few variation of them, have been extensively synthesized up to now. Lately, Galván et el. reported nanotube formation on MoTe2 [11], WSe2 [12] and NbSe2 [13]. EXPERIMENTAL METHOD In this work we report the formation of nanotube structures in MoSe2 (molybdenum selenide) also known as Drysdallite. The initial samples were obtained from commercial
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powders ( Alfa-Aesar 99.9 % pure ) of MoSe2. Afterwards, the material was irradiated with electrons on a 2 MeV Van de Graff accelerator (High Voltage Engineering Corporation). The irradiation conditions were the following: 1.3 MeV voltage, 5 µA current, dose rate 25 kGy/min, total dosage 1 Mgy. The dosimeter used was radiochromic films (FWT-60) from Far West Technology. X-ray analyses were performed in a Philips XRD/X'PERT system using Cu Kα radiation at 40 KV voltage and 45 mA current. For Transmision Ele
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