Interplay between boron doping and epitaxial relationships in VO 2 films grown by laser ablation

• Published in: Thin solid films 2023-03, Vol.768
• Main Authors: Bailly, Aude, Bouvier, Pierre, Grenier, Stéphane, Hajlaoui, Thameur, Gaudin, Michael, Ramos, Aline Y., Chaker, Mohamed, Laversenne, Laetitia
• Format: Article
• Language: English
• Subjects: Condensed Matter; Materials Science; Physics
• ISSN: 0040-6090
• DOI: 10.1016/j.tsf.2023.139729

In this contribution, the effect of boron doping on the functional and structural properties of VO2 thin films is investigated. Temperature-dependent measurements were performed on pure and boron-doped (0.5 and 1.3 at.%) VO2 films grown on Al2O3(0001) by Reactive Pulsed Laser Deposition. Increasing the boron concentration leads to a noticeable decrease of the transition temperature (by ∼12°C), accompanied by a significant modification of the hysteresis loop shapes. The phase transition occurs at ca. 73 °C in the undoped film, while it drops down to ca. 60 °C in the film containing the highest boron amount. The undoped sample exhibits the best resistivity contrast (about 4 orders of magnitude) with a relatively narrow hysteresis cycle (∼ 6 °C). The most doped sample has a broad and significantly reduced resistivity contrast (less than 3 orders of magnitude). Raman spectroscopy and high-resolution X-ray diffraction were performed to elucidate the nature of the involved phases and their structure. A correlation was found between increasing the boron concentration and the formation of two peculiar in-plane epitaxial relationships; the VO2 films evolving from one to the other. We also evidenced the presence of the transient M2 phase in the most doped sample.