Volatile Hexavalent Oxo-amidinate Complexes: Molybdenum and Tungsten Precursors for Atomic Layer Deposition

Aidan R. Mouat, Anil U. Mane, Jeffrey W. Elam, Massimiliano Delferro*, Tobin J. Marks, Peter C. Stair

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

New complexes MoO2(tBuAMD)2 (1) and WO2(tBuAMD)2 (2) (AMD = acetamidinato) are synthesized and fully characterized as precursors for atomic layer deposition (ALD). They contain metal-oxo functionalities not previously utilized in ALD-type growth processes and are fully characterized by 1H and 13C NMR, X-ray diffraction (XRD), Fourier transform infrared, thermogravimetric analysis, single-crystal XRD, and elemental analysis. Guided by quartz-crystal microbalance studies, ALD growth methodologies for both complexes have been developed. Remarkably, these isostructural compounds exhibit dramatic differences in ALD properties. Using 1 and O3, amorphous, ultrathin molybdenum oxynitride (MoON) films are grown on Si(100) wafers. Using 2 and H2O yields amorphous WO3 films on Si(100) wafers that crystallize as WO3 nanowires upon annealing. Although 1/H2O and 2/O3 growth was attempted, effective ALD growth could only be obtained with 1/O3 and 2/H2O, underscoring reactivity differences in these precursors. Film thicknesses, compositions, and optical and electrical parameters are characterized by variable angle spectroscopic ellipsometry, X-ray reflectivity, grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and atomic force microscopy techniques. The hitherto unknown ALD chemistry of group VI metal-oxo compounds lays a foundation for their use in the ALD synthesis of heterogeneous catalysts.

Original languageEnglish (US)
Pages (from-to)1907-1919
Number of pages13
JournalChemistry of Materials
Volume28
Issue number6
DOIs
StatePublished - Mar 22 2016

Funding

The NUANCE Center is supported by the MRSEC program (NSF DMR- 1121262) at the Materials Research Center, the Keck Foundation, the International Institute for Nanotechnology (IIN), the State of Illinois, through the IIN, and Northwestern University. The J. B. Cohen X-ray diffraction facility is supported by the MRSEC program of the National Science Foundation (Grant DMR-1121262) at the Materials Research Center of Northwestern University. Purchase of the NMR instrumentation at the Integrated Molecular Structure Education and Research Center (IMSERC) at Northwestern was supported by the National Science Foundation (Grant CHE- 1048773).

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Materials Chemistry

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