Accession Number:

ADA272910

Title:

Scanning Tunneling Microscopy Investigations of Metal Dichalcogenide Materials

Descriptive Note:

Final rept. 1 Nov 89-30 Jun 93,

Corporate Author:

COLUMBIA UNIV NEW YORK DEPT OF CHEMISTRY

Personal Author(s):

Report Date:

1993-10-25

Pagination or Media Count:

45.0

Abstract:

Scanning tunneling microscopy STM and atomic force microscopy AFM have been used to characterize the atomic level structure of electronic properties, reactivity and wear of metal dichalcogenide materials that are or have potential as solid state lubricants. Single crystals Of MoS2, NixMol-x S2, MoS2-xSex and MoS2-xTex have been prepared to determine how chemical modifications affect the local structure and electronic properties of this lubricant. STM images of Ni-doped MoS2 show localized electronic states due to the Ni atoms, while images of Se- and Te-doped materials indicate that anion substitution is electronically delocalized. AFM studies of Te-doped MoS2 show, however, that the tellurium dopants form atomic scale structural protrusions that may reduce sliding friction. AFM has also been used to characterize nanometer scale wear and oxidation on MoS2 and NbSe2 surfaces. In atmosphere at room-temperature AFM studies showed that NbSe2 wears approximately three times faster than MoS2. Furthermore, oxidation studies demonstrated that NbSe2 was significantly more reactive than MoS2 with molecular oxygen. These results indicate that the intrinsic stability of the MoS2 surface make it an effective lubricant, AFM was also used to elucidate the growth of MoO3 on the surface Of MoS2 during oxidation, and to study wear properties of these MoO3 crystallites. The AFM tip was used to define lines with 10 nm resolution in MoO3 and to manipulate distinct MoO3 structures on the MoS2 surface. In addition, metal- substitution in TaS2 has been studied systematically using STM and theoretical methods.

Subject Categories:

  • Inorganic Chemistry
  • Lubricants and Hydraulic Fluids
  • Atomic and Molecular Physics and Spectroscopy
  • Optics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE