A carbon nanotube (CNT) was used as a tip for a noncontact-mode atomic force microscope (NC-AFM). A CNT tip was attached to an Au/Si tip by a well-controlled procedure in a scanning-electron-microscope (SEM) chamber. The NC-AFM with the CNT tip produced highly reproducible images of right-handed helical turns of linear deoxyribonucleic acid (DNA) with a spacing of 3.5 ±1.0 nm. The full-width at half-maximum (FWHM) of the cross section of DNA measured was 3.1 ±0.6 nm.
We investigate the difference in atomic resolution images between the Si(100)2×1 reconstructed surface with a dangling bond and the Si(100)2×1:H monohydride surface without a dangling bond using noncontact atomic force microscopy. On the Si(100)2×1 surface, the distance between bright spots is 3.2 ±0.1 Å, which is larger than that between silicon atoms. On the Si(100)2×1:H surface, the distance between bright spots is 3.5 ±0.1 Å, which is in good agreement with that between hydrogen atoms. For the first time, individual hydrogen atoms are resolved. This means that the distance between measured bright spots forming dimers is increased by the hydrogen termination.
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