The Piezoresponse in WO[sub.3] Thin Films Due to N[sub.2]-Filled Nanovoids Enrichment by Atom Probe Tomography

• Published in: Materials Vol. 16; no. 4
• Main Authors: Pineda-Domínguez, Pamela M, Boll, Torben, Nogan, John, Heilmaier, Ma, Hurtado-Macías, Abel, Ramos, Manuel
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.02.2023
• Subjects: Dielectric films; Electric fields; Thin films; Germany
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16041387

Tungsten trioxide (WO[sub.3]) is a versatile n-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 d[sub.33] = 35 pmV[sup.−1] on WO[sub.3] thin films ~200 nm deposited using RF-sputtering onto alumina (Al[sub.2]O[sub.3]) substrate with post-deposit annealing treatment of 400 °C in a 3% H[sub.2]/N[sub.2]-forming gas environment. X-ray diffraction (XRD) confirms a mixture of orthorhombic and tetragonal phases of WO[sub.3] with domains with different polarization orientations and hysteresis behavior as observed by piezoresponse force microscopy (PFM). Furthermore, using atom probe tomography (APT), the microstructure reveals the formation of N[sub.2]-filled nanovoids that acts as strain centers producing a local deformation of the WO[sub.3] lattice into a non-centrosymmetric structure, which is related to piezoresponse observations.