Ferroelectric Tunneling Junctions Based on Yttrium Doped Hafnium Dioxide

Hafnium dioxide (HfO₂)-based thin films are considered promising ferroelectric materials for modern semiconductor integration. Various methods have been explored to induce ferroelectricity in hafnium oxide-based thin films, including atomic layer deposition, chemical doping, and solid solution techniques. Among the diverse doping species, yttrium-doped hafnium dioxide (YHO) stands out as a novel candidate due to its robust ferroelectric polarization, reliability, and scalability.<br/><br/>In this study, we are going to utilize the high ferroelectric polarization value of YHO, approximately 50 μC/cm², to showcase ferroelectric polarization modulation of tunneling resistance. We also propose the device structure of ferroelectric tunneling junctions using YHO as the tunneling layer. We fabricate high quality epitaxial YHO thin films using pulsed laser deposition on single crystal SrTiO₃ (110)/(001) (STO) substrates. The crystal orientations of YHO were analyzed using X-ray diffraction, confirming the presence of the ferroelectric orthorhombic (Pca2₁) phase with two structure domains. Ferroelectric tests were carried out on our YHO films by a ferroelectric tester and piezoresponse force microscopy and ferroelectric tester.<br/><br/>Subsequent to the ferroelectric measurement, we utilized conductive atomic force microscopy and piezoresponse force microscopy to measure variations in polarization direction and tunneling resistance. Ultimately, we showcase the high-quality Pt/YHO/La_0.7Sr_0.3MnO₃devices and measure the resistance hysteresis loops. This innovative material holds significant potential for improving the performance and efficiency of ferroelectric tunnel junctions.