Effects of Coating Materials on Field Emission Scanning Electron Microscopy Images

Taking non-conductive mesoporous SiO2 (SBA-15) with nano pore structure as the research material,the effects of three kinds of common electrical conductive coatings (Au,Pt and Cr coatings) on the field emission scanning electron microscopy (FE-SEM) images were studied.The results show that the charging phenomenon of the FE-SEM images could be reduced by all these three kinds of coatings.However,the morphology of the nano-size pores totally disappeared after coating Au film.When the Pt film was deposited on the sample surface,SBA-15 still kept the mesoporous structure but the pore size became smaller.Meanwhile,the pore and wall sizes of SBA-15 were close to the original morphology even though the Cr film was deposited on the sample.The grain sizes of the conducting coatings were the key factor of affecting the morphologies.The sizes of most of Au particles were over 5 nm,and sizes of most of Pt particles were about 2 nm.So the 4 nm pores of SBA-15 would be obscured by them.The sizes of Cr particles were only 1 nm and most of Cr particles were amorphous.Therefore,the real structure of SBA-15 could be shown even after the Cr film with several nano thickness was deposited.