Parallel synthesis and physical properties of thickness graded LaCoO3

Functional properties of oxide films largely depend upon its thickness. In conventional one-by-one thin film deposition approach, uniform deposition with single thickness is fabricated. Here, we have employed the concepts of combinatorial chemistry in pulsed laser deposition (C-PLD) system for the deposition of LaCoO3 compound. The combinatorial PLD allows one to obtain large variations of thickness onto one substrate in a single experiment. LaCoO3 is chosen to demonstrate the thickness dependent optical properties. Across 9 mm of substrate, more than 30 nm systematic thickness variations were achieved on a 10 mm quartz plate. Controlled mask motion with synchronised laser pulses were introduced to fabricate continuously varying film thickness across the substrate. Structural and surface properties were examined by X-ray diffraction, Raman spectroscopy and AFM respectively. Systematic variations in the electrical resistance and optical band gap were observed with film thickness. Using this unique approach, large number of samples with controlled variation in thickness can be fabricated in single experiment and can be optimized quickly for semiconductors which can be used for tuning the physical properties in RRAMs and solar cells.