Low temperature microscope technology can be traced back to the last century including the time of light microscope, and its history is over a hundred years. In the field of electron microscopy, low temperature techniques such as the freeze-fracture replica, freeze-sectioning, freeze-substitution, etc. were tested up to early 1960s. According to the progress of the rapid-freezing method, the freeze-substitution and freeze-etching replica methods have provided great successful results.The low temperature scanning electron microscope (LTSEM) was also tested by Echlin et al. in 1970, and thereafter, a number of LTSEM constructions were attempted. These LTSEMs are generally classified into two groups: the type with fracturing and coating facilities directly attached to the SEM column, and the group having a separated preparation chamber and a transfer device. The LTSEM so far constructed were reviewed comprehensively in greater detail. Some such instruments were designed taking account of stringent requirements of low temperature techniques. These systems, however, seemed to be too comprehensive, involving complex procedures as compared withe their resolutions. In comparison with the conspicuous results obtained by other low temperature techniques, the LTSEM can be regarded as still in the stage prior to practical application from the viewpoint of the high resolution. In consideration of these circumstances, the present paper aims at providing a new LTSEM to realize simple operation retaining the advantage of the ultrastructural preservation by the rapid-freezing and the high resolution by introducing the high-excitation objective lens.
Fabrication and characterization of solid-state nanopores using a field emission scanning electron microscope
