Cl. Claypool et al., Tunneling mechanism implications from an STM study of H3C(CH2)(15)HC=C=CH(CH2)(15)CH3 on graphite and C14H29OH on MoS2, J PHYS CH B, 103(34), 1999, pp. 7077-7080
The observations reported herein confirm that the bright spots in high-reso
lution STM images of adsorbed alkanes and alkanols are predominantly due to
the electronic and topographic structure of the molecule, and not predomin
antly due to the substrate. STM images of a monolayer of 17,18-pentatriacon
tadiene, H3C(CH2)(15)-HC=C=CH(CH2)(15)CH3, adsorbed on graphite were obtain
ed to evaluate whether changes in the orientation of the exposed methylene
hydrogen atoms relative to the STM tip produced changes in the observed pat
tern of bright spots in a STM image. STM images of this system showed a pat
tern of bright spots within individual molecules that appears to change on
either side of the allene -C=C=C- functionality. STM images were also obtai
ned for tetradecanol overlayers on graphite and MoS2 surfaces. The angles a
nd distances observed in the images of tetradecanol on MoS2 were nearly ide
ntical to those measured previously in our laboratories for alkanol and alk
ane monolayers on graphite despite that fact that the separation between br
ight spots in an STM image of graphite is 2.46 Angstrom, while the separati
on between bright spots in STM images of MoS2 is 3.16 Angstrom.