Scanning tunneling microscopy investigations of metal dichalcogenide materials. Final report, 1 November 1989-30 June 1993

Technical Report · Mon Oct 25 00:00:00 EDT 1993

OSTI ID:5429189

Lieber, C M

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, Ni(x)Mo(l-x)S2, MoS(2-x)Se(x) and MoS(2-x)Te(x) 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.

• Research Organization: Columbia Univ., New York, NY (United States). Dept. of Chemistry
• OSTI ID: 5429189
• Report Number(s): AD-A-272910/1/XAB; CNN: AFOSR-90-0029
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DOPED MATERIALS
LUBRICATING PROPERTIES
WEAR
MOLYBDENUM SULFIDES
NIOBIUM SELENIDES
NICKEL
PROGRESS REPORT
SELENIUM
TELLURIUM
TRIBOLOGY
CHALCOGENIDES
DOCUMENT TYPES
ELEMENTS
MATERIALS
METALS
MOLYBDENUM COMPOUNDS
NIOBIUM COMPOUNDS
PHYSICAL PROPERTIES
REFRACTORY METAL COMPOUNDS
SELENIDES
SELENIUM COMPOUNDS
SEMIMETALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
360603* - Materials- Properties