ACS Nano ACS Nano Tungsten oxide mediated quasi-van der Waals Epitaxy of WS2 on Sapphire Cohen Assael Mohapatra Pranab K. Hettler Simon Universidad de Zaragoza Patsha Avinash Narayanachari K. V. L. V. Shekhter Pini Cavin John Rondinelli James M. Bedzyk Michael Dieguez Oswaldo Arenal Raul Ismach Ariel 2023 research-article