The Piezoresponse in WO Thin Films Due to N-Filled Nanovoids Enrichment by Atom Probe Tomography.

Tungsten trioxide (WO) is a versatile -type semiconductor with outstanding chromogenic properties highly used to fabricate sensors and electrochromic devices. We present a comprehensive experimental study related to piezoresponse with piezoelectric coefficient = 35 pmV on WO thin films ~200 nm deposited using RF-sputtering onto alumina (AlO) substrate with post-deposit annealing treatment of 400 °C in a 3% H/N-forming gas environment. X-ray diffraction (XRD) confirms a mixture of orthorhombic and tetragonal phases of WO with domains with different polarization orientations and hysteresis behavior as observed by piezoresponse force microscopy (PFM).