Hybrid SNO Paper Published in APL Materials

Our paper on hybrid molecular beam epitaxy (MBE) of SrNbO3+d thin films, led by Suresh Thapa and Ryan Comes, was recently published in APL Materials! Achieving high-quality synthesis of Nb-cation-containing films is challenging, owing to the refractory nature of this elements. However, using hybrid MBE we show it is possible to stabilize this structure with the addition of a SrHfO3 capping layer, pointing toward new applications for high-mobility electronics.

From the abstract:

4d transition metal oxides have emerged as promising materials for numerous applications including high mobility electronics. SrNbO3 is one such candidate material, serving as a good donor material in interfacial oxide systems and exhibiting high electron mobility in ultrathin films. However, its synthesis is challenging due to the metastable nature of the d1 Nb4+ cation and the limitations in the delivery of refractory Nb. To date, films have been grown primarily by pulsed laser deposition (PLD), but development of a means to grow and stabilize the material via molecular beam epitaxy (MBE) would enable studies of interfacial phenomena and multilayer structures that may be challenging by PLD. To that end, SrNbO3 thin films were grown using hybrid MBE for the first time using a tris(diethalamido)(tert-butylimido) niobium precursor for Nb and an elemental Sr source on GdScO3 substrates. Varying thicknesses of insulating SrHfO3 capping layers were deposited using a hafnium tert-butoxide precursor for Hf on top of SrNbO3 films to preserve the metastable surface. Grown films were transferred in vacuo for X-ray photoelectron spectroscopy to quantify elemental composition, density of states at the Fermi energy, and Nb oxidation state. Ex situ studies by X-ray absorption near edge spectroscopy and scanning transmission electron microscopy illustrate that the SrHfO3 capping plays an important role in preserving crystalline quality of the material and the Nb 4d1 metastable charge state in atmospheric conditions.

To view the manuscript, visit: https://doi.org/10.1063/5.0097699

To download the article directly, click here.