Real Space Observation of Double-Helix DNA Structure Using a Low Temperature Scanning Tunneling Microscopy

Reproducible, reliable and high resolution low temperature scanning tunneling microscopy (LT-STM) images of plasmid DNA (deoxyribonucleic acid) (2739 bp), deposited on a well-defined Cu(111) substrate using pulse injection method under ultra-high vacuum (UHV) condition, have been obtained by using a novel sample preparation technique. These particular low temperature LT-UHV-STM images have revealed the double-helix structures of the DNA that have not been resolved earlier.