Synthesis and formation mechanisms of BaZrO3 thin films prepared on ZrN-coated substrates by a low temperature hydrothermal-galvanic couple method

Barium zirconate (BaZrO3; BZO) films exhibiting superior physical and chemical properties were synthesized over ZrN-coated Si substrates by a low temperature hydrothermal-galvanic couple method. Firstly, ZrN thin films were deposited onto Si by unbalanced magnetron sputtering. Subsequently, the ZrN-coated Si substrates were soaked in 0.5 M Ba(OH)2 mixed with various molar concentrations of NaOH at 90 °C for different reaction times by aid of a galvanic couple setup. Although no external power sources were applied, pronounced galvanic currents were detected during the synthesis and revealed a very different plateau behavior. X-ray diffraction patterns show that cubic crystalline BZO films were formed on ZrN/Si in highly alkaline solutions for sufficient reaction time. Amorphous nano-layered oxides were present at lower-pH solutions. Aided by galvanic effects, more OH− ions in the solution and longer reaction time would facilitate formation of a dense crystalline BZO. Reaction routes and formation mechanisms of the BZO films have been proposed.