Molybdenum trioxide (MoO3) is a material with special properties that make it an ideal candidate for applications in on-chip optoelectronic and photonic devices. This compound, which in its stable form is known as α-MoO3, is made up of layers of octahedron-shaped nanocrystals and has special optical properties, such as birefringence, which consists of separating any ray of light that passes through it into two distinct beams of light, which are highly valued in the manufacture of photonic components. However, until now it has been a challenge to develop thin films of α-MoO3 with sufficient crystalline quality and the desired orientation of the nanoplatelets that compose them, which prevented taking full advantage of its properties in technological applications.

In this work, the team’s researchers have managed to develop a manufacturing technique that allows the creation of ultra-thin films made up of a dense network of α-MoO3 nanoplatelets, with excellent uniformity (all the nanoplatelets have the same size) and with control of the crystallographic orientation. These films, thanks to their properties in the visible spectrum of light, open up new possibilities for the integration of this material in multilayer chip devices in the field of nanophotonics.

The process of obtaining the α-MoO3 nanoplatelet film began with the exfoliation of disordered α-MoO3 crystals in chosen solvents to obtain loose ultrathin nanoplatelets. These nanoplatelets were then stripped and deposited on previously treated substrates using the group’s pulsed laser deposition method, which formed a dense and uniformly distributed network. A thermal annealing technique was then used to improve the crystalline quality and adhesion of the nanoplatelets to the substrate.
The research team plans to carry out further work along this line to achieve the formation of a multilayer structure in the future, which will also have applications in the design of future integrated optical and optoelectronic devices.
Molybdenum (Mo) in nature is an element with a concentration of 1.5 ppm in the continental crust and 10 ppm in the oceanic crust, where it is more abundant. This element appears as a by-product of copper and silver mining. However, molybdenum is more common than other elements currently used in device manufacturing, so it is considered a sustainable material.

Article: E. Nieto-Pinero, S. Negrete-Aragón, I. Muñoz Ochando, M. Vondráček, B. Galiana, R.J. Pelaéz, B. Maté, S. López-Andrés, R. Serna “Building nanoplatelet α-MoO3 films: A high quality crystal anisotropic 2D material for integration”. Applied Surface Science Volume 6721 Article number 160871

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