We investigate the ability of different carrier gases to control defects and secondary nucleation in atmospheric pressure chemical vapor deposition (APCVD) growth of MoS 2 on Si/SiO 2 substrates. We observe that a reducing environment using H 2 gas is more favorable for achieving uniform two-dimensional (2D) growth. Compared to the growth in an inert environment, secondary nucleation on primary MoS 2 domains grown using H 2 as the carrier gas (H−MoS 2 ) is drastically reduced. We employ a phase-field model to understand the role of enhanced surface diffusion in H−MoS 2 , due to passivation of defects and dangling bonds, promoting compact secondary domain formation as opposed to dendritic secondary domains under an inert environment. Using X-ray photoelectron spectroscopy, we show that the Mo(VI) oxidation state (corresponding to MoO 3 ), which is prominent for MoS 2 grown under an inert atmosphere, is highly suppressed in H−MoS 2 , leading to more pristine MoS 2 . This explains the superior electrical performance of H−MoS 2 compared to those grown with other carrier gases. Our results offer a facile route to explore different growth environments to realize large-area true 2D films.

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Nanoscale transport using the kinesin–microtubule system has been successfully used in applications ranging from self-assembly, to biosensing, to biocomputation. Realization of such applications necessitates robust microtubule motility particularly in the presence of complex sample matrices that can affect the interactions of the motors with the surface and the transport function. In the present work, we explored how the chemical nature and nanoscale topology of various surfaces affected kinesin–microtubule transport. Specifically, we characterized microtubule motility on three distinct interfaces: (i) surfaces modified with self-assembled monolayers (SAMs) displaying three different terminal groups, (ii) SAM-modified surfaces with adsorbed fetal bovine serum (FBS) proteins, and (iii) surfaces where the FBS layer was silicified to preserve an underlying surface topology. The composition and topology of each surface was confirmed with a number of techniques including X-ray photoelectron spectroscopy (XPS), water contact angle, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The majority of surfaces, with the exception of those with the hydrophobic SAM, supported gliding motility consistent with the glass control. Differences in the displacement, velocity, and trajectory of the leading tip of the microtubule were observed in relation to the specific surface chemistry and, to a lesser extent, the nanoscale topology of the different substrates. Overall, this work broadens our understanding of how surface functionality and topology affect kinesin-based transport and provides valuable insights regarding future development of biosensing and probing applications that rely on biomolecular transport.

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