Solution Combustion Processed High Entropy Oxide Dielectrics for Microelectronic Applications

Abstract

An investigation of dielectric constant on the sintered high entropy oxide capacitor composed of Co, Cu, Mg, Zn, Ni (i.e., (CoCuMgZnNi)O), Ce, La, Pr, Sm, Y (i.e., (CeLaPrSmY)O) and Co, Cr, Fe, Mn, Ni (i.e., (CoCrFeMnNi)O) developed using solution combustion synthesis is performed. Stabilization of phase in high entropy oxide is extremely important as it directly influences the properties. In order to explore phase stabilization, in-depth studies of thermal, structural, morphological, and compositional analyses are carried out. The precursors of (CoCuMgZnNi)O were found to combust at 270 ºC and 400 ºC was considered to be the formation temperature. The (CoCuMgZnNi)O fully stabilized at 1000 ºC shows a single-phase, fcc rocksalt structure with an Fm-3m space group. (CoCuMgZnNi)O displays one of its parent oxide Mg-O structural properties. Dielectric measurements at room temperature showed high constant (κ) with magnitudes ~1.9 × 103, 4.7× 101, and 0.9 × 101 at 100, 1 k, and 100 kHz. In addition, a low-temperature formation of (CeLaPrSmY)O was evidenced at 500 °C and fully stabilized at 1000 ºC with a single-phase, fcc fluorite structure with an Fm-3m space group. The (CeLaPrSmY)O displays one of its parent oxide Ce-O structural properties. Dielectric measurements at room temperature showed dielectric constant (κ) ≈ 29 – 5.7 from 100 Hz - 1 MHz. Simultaneously, the precursors of (CoCrFeMnNi)O undergo combustion at a low temperature below 250 °C. Upon crystallization at 500 °C, no secondary impurity oxides were detected and phase-stabilized to a spinel structure (Fd-3m). The spinel (CoCrFeMnNi)O exhibited high dielectric constant, with values approximately 1.2 × 103, 7.3× 102, and 3.1 × 101 at 100, 1 k and 100 kHz. The optimized processing parameters are further implemented on depositing (CoCrFeMnNi)O dielectric thin film followed by a thin film transistor. The spinel (CoCrFeMnNi)O thin film exhibited high dielectric constant and low leakage current density, with values approximately 3 × 101, measured at 1 kHz and ~ 10-8 A.cm-2. The (CoMnNiFeCr)O thin film was integrated into thin film transistors with a molybdenum disulfide channel. The transistor operated at low voltage (< 5V) and showeda field effect mobility of 8.8 cm2 V-1 s-1, an on-off ratio of approximately 105, a threshold voltage of -1.5 V, and a subthreshold swing of 0.38 V.dec-1.