Estimation of suitable condition for observing copper–phthalocyanine crystalline film by transmission electron microscopy

The decay of the electron diffraction intensity of a copper–phthalocyanine crystalline film was quantitatively measured at room temperature by transmission electron microscopy (TEM) as a function of current density and beam diameter. The measurements revealed that the critical dose increases with decreasing current density, decreasing beam diameter and increasing acceleration voltage. Generally, the damage process only depends on the electron dose. However, the temperature rise of the copper–phthalocyanine enhances the damage process. The relationship between damage and acceleration voltage has been measured, and the result shows that an increase in acceleration voltage decreases the damage. The relationship between image contrast and acceleration voltage was also measured using a single-wall carbon nanotube (SWNT) as a radiation-insensitive substitute for the copper–phthalocyanine in order to obtain atomic-level images. The results revealed that image contrast increases with decreasing acceleration voltage. Using these oppositely behaving results, the most suitable voltage for observing copper–phthalocyanine crystalline films was estimated. The results show that low acceleration voltages should be used for imaging to achieve the minimum specimen resolution limit.