Teplotní závislost úbytku hmoty u pryskyřice Epon

Temperature dependent mass loss of Epon resin sections

abstrakt

en

A scanning transmission electron microscope (STEM) is a useful device combining features of scanning and transmission electron microscopes [1]. Nowadays, low voltage STEM – here we mean a transmission mode in a SEM [2] that uses, in respect to a commercial STEM, much lower voltages – is increasingly used also for imaging of ultrathin sections. However, many TEM operators consider STEM as a significant source of radiation damage for observation of ultrathin sections. Two main features caused by beam damages are the mass loss and the contamination. Both types of damages depend on the used electron energy and the electron dose applied to the sample. In general, the mass loss depends on the sample composition and the contamination results mainly from the poor vacuum in the specimen chamber of the SEM and cleanness of the sample surface. One of possibilities to limit the damage is imaging at a reduced temperature. We focus on quantitative investigations of the mass loss of embedding media ultrathin sections at room temperature and at -130°C. Our preliminary results show that the mass loss at 30 keV can be reduced with using of low temperature of the sample at relatively low doses as seen in Fig. 1. Interesting is nearly same mass loss after irradiation of dose 3000 e-/nm2. We assume that this is due to the gradual heating of the sample placed on the grid, and its poor thermal conductivity.

A scanning transmission electron microscope (STEM) is a useful device combining features of scanning and transmission electron microscopes [1]. Nowadays, low voltage STEM – here we mean a transmission mode in a SEM [2] that uses, in respect to a commercial STEM, much lower voltages – is increasingly used also for imaging of ultrathin sections. However, many TEM operators consider STEM as a significant source of radiation damage for observation of ultrathin sections. Two main features caused by beam damages are the mass loss and the contamination. Both types of damages depend on the used electron energy and the electron dose applied to the sample. In general, the mass loss depends on the sample composition and the contamination results mainly from the poor vacuum in the specimen chamber of the SEM and cleanness of the sample surface. One of possibilities to limit the damage is imaging at a reduced temperature. We focus on quantitative investigations of the mass loss of embedding media ultrathin sections at room temperature and at -130°C. Our preliminary results show that the mass loss at 30 keV can be reduced with using of low temperature of the sample at relatively low doses as seen in Fig. 1. Interesting is nearly same mass loss after irradiation of dose 3000 e-/nm2. We assume that this is due to the gradual heating of the sample placed on the grid, and its poor thermal conductivity.

mass loss; Epon; beam damage

03.05.2016

Praha

56–57

2