In-situ investigation on the thermal decomposition of van der Waals MoO3

Highlights: • Thermal stability of van der Waals MoO₃ nanosheet were investigated in-situ. • Three modes of decomposition were observed. • Preferential decomposition along [0 0 1] were observed. • O_s atom is the lest stable oxygen atom in the lattices. The van der Waals α-MoO₃ is one of the most attracted two-dimensional metal oxides in opto-electronics Thermal stability is one of the key properties in device application. Here, the thermal decomposition of individual α-MoO₃ nanosheet was investigated using in-situ microscope and Raman spectroscopy. It's found that the nanosheet decomposes above 400 °C. Three decomposition behaviors, including void decomposition, edge decomposition and layer-by-layer decomposition were found. The O_a atom is the most unstable oxygen atom that causes a preferential decomposition along the [0 0 1] direction. Thermal stress accumulated in the [1 0 0] direction leads to a non-linear temperature dependent Raman shifting.