Abstract
Considering that two-dimensional (2D) molybdenum trioxide has acquired more attention in the last few years, it is relevant to speed up thickness identification of this material. We provide two fast and non-destructive methods to evaluate the thickness of MoO3 flakes on SiO2/Si substrates. First, by means of quantitative analysis of the apparent color of the flakes in optical microscopy images, one can make a first approximation of the thickness with an uncertainty of ±3 nm. The second method is based on the fit of optical contrast spectra, acquired with micro-reflectance measurements, to a Fresnel law-based model that provides an accurate measurement of the flake thickness with ±2 nm of uncertainty.
Highlights
Since the isolation of graphene by mechanical exfoliation in 2004 [1], the catalog of different 2D materials with complementary properties keeps growing [2,3,4,5,6,7,8,9]
It has been used in thin films to enhance the injection of holes in organic light-emitting diodes as a buffer layer [17,18], in organic photovoltaics [19], perovskite solar cells [20] and silicon solar cells [21], it can be used in gas sensors [15,22,23]
The direct comparison between the Atomic Force Microscopy (AFM) and the optical images allows us to build up a color-chart correlating the apparent color of the MoO3 flakes deposited on top of the 297 nm SiO2/Si substrate with their corresponding thickness with an uncertainty of ±3 nm
Summary
Since the isolation of graphene by mechanical exfoliation in 2004 [1], the catalog of different 2D materials with complementary properties keeps growing [2,3,4,5,6,7,8,9]. Molybdenum trioxide (MoO3) in its α-phase is a van der Waals material with a monolayer thickness of ~0.7 nm [11,12] and a direct bandgap of approximately 3 eV [13,14,15], suitable for such applications [16] It has been used in thin films to enhance the injection of holes in organic light-emitting diodes as a buffer layer [17,18], in organic photovoltaics [19], perovskite solar cells [20] and silicon solar cells [21], it can be used in gas sensors [15,22,23]. This material displays an in-plane anisotropy of the crystal structure in its layered phase (α-MoO3) [16,35,36,37,38], which can be exploited to fabricate novel optical and optoelectronic devices [39,40,41], and anisotropic phonon polariton propagation along the MoO3 surface has been observed [42]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
