Ferroelectricity in Y:HfO2 thin films grown on transparent FTO/glass substrates through a multi-step deposition-annealing process

Abstract

Optically transparent ferroelectric memories are essential for the advancement of next-generation electronic devices. Hafnium Oxide (HfO2) – based ferroelectric thin films that are highly compatible with complementary metal-oxide-semiconductor (CMOS) technology have been extensively studied for use in non-volatile memory devices. However, fabricating transparent ferroelectrics typically requires the deposition of orthorhombic phase HfO2 on inherently amorphous transparent substrates like glass, which is highly challenging. Here, transparent Yttrium-doped HfO2 (HYO) thin films were grown on fluorine-doped SnO2 (FTO)/glass substrates using a multi-step deposition and annealing technique. By optimizing the number of layers and annealing temperatures, transparent ferroelectric HYO capacitors with transmission exceeding 70 % in the visible spectrum were developed. Capacitors with 10 layers displayed robust ferroelectric properties, while those with 6, 8, and 12 HYO layers showed significant leakage. Analysis of current density-electric field plots indicates that leakage current mechanisms in the capacitors varies with the number of HYO layers. The number of layers in the multi-step deposition and annealing process is crucial in achieving the desired ferroelectric characteristics in HYO films deposited on FTO/glass substrates. The study paves the way to fabricate transparent capacitors for the integration of HfO2-based FE materials in next-generation smart electronic devices. © 2024 Elsevier B.V.