Charge Contrast: Some ESEM Observations of A New/Old Phenomenon

Abstract

Over the past few years there have been occasional reports of unusual secondary electron contrasts in certain nonmetallic materials using conventional (CSEM-Johansen et al, 1997), low voltage (LV-SEM-Harker et al, 1993; Harker et al, 1994) and environmental scanning electron microscopy (ESEM-Griffin, 1997; T. Hardt, personal communication) which have documented novel contrast mechanisms whose origins are not yet well understood. Indeed, similar observations were made over 20 years ago in certain uncoated materials (such as SiC) using conventional SEM (Sawyer and Page, 1978). Aspects of these charge contrast imaging (CCI) phenomena are further documented here in a series of ESEM experiments on polished cross sections of uncoated travertine calcite. What is “old” is the fact that these contrasts have been reported on several occasions. What is “new” is the observation that these unusual contrasts are more readily studied and, in some cases, have been found in a wider range of materials using ESEM.