Raivat Singhania

Transition metal dichalcogenides (TMDC), such as MoTe2, are a promising new class of materials with wide ranging applications in the computing, optics, and photovoltaic industries. The deposition quality of these films has a drastic effect on overall film properties, and therefore device performance. In particular, achieving uniform and reproducible nucleation is important for creation of single monolayer films.  However, islanding often occurs during film growth in which isolated regions of the film form initially, creating a discontinuous film and/or non-uniform film thickness, both of which are undesirable. We have investigated the uniformity and thickness control of molybdenum oxide films that are deposited via atomic layer deposition (ALD) and are precursors to MoTe2 TMDCs. High-sensitivity low energy ion spectroscopy (HS-LEIS) was used to assess surface coverage and islanding of a variety of film MoOx films ranging in thickness from 0.2 nm to over 7 nm. HS-LEIS is used for this purpose due to its ability to selectively detect and differentiate between atoms in the outermost atomic layer and subsurface atoms. Absence of a signal from the substrate indicated that uniform nucleation and coverage of the surface with MoOx occurred at film thicknesses of approximately 0.5 nm. Ongoing research is focused on using Monte-Carlo simulations to predict LEIS spectra, which would allow for more quantitative analysis of nucleation and film growth. Quantitative analysis of nucleation and film growth is of great importance for next generation electronics that rely on layers that are only one or several atomic layers in thickness.