An In Situ Study of Precursor Decomposition via Refractive Index Sensing in p-Type Transparent Copper Chromium Oxide

Oxide semiconductors are penetrating into a wide range of energy, environmental, and electronic applications, possessing a potential to outrun currently employed semiconductors. However, an insufficient development of p-type oxides is a major obstacle against complete oxide electronics. Quite often oxide deposition is performed by the spray pyrolysis method, inexpensive to implement and therefore accessible to a large number of laboratories. Although, the complex growth chemistry and a lack of in situ monitoring during the synthesis process can complicate the growth optimization of multicomponent oxides. Here we present a concept of plasmonic, optical sensing that has been applied to spray pyrolysis oxide film growth monitoring for the first time. The proposed method utilizes a polarization based refractive index sensing platform using Au nanodimers as transducing elements. As a proof of concept, the changes in the refractive index of the grown film were extracted from individual Cu(acac)(2) and Cr(acac)(3) precursors in real time to reveal their thermal decomposition processes. Obtained activation energies give insight into the physical origin of the narrow temperature window for the synthesis of high performing p-type transparent conducting copper chromium oxide CuxCrO2. The versatility of the proposed method makes it effective in the growth rate monitoring of various oxides, exploring new candidate materials and optimizing the synthesis conditions for acquisition of high performing oxides synthesized by a high throughput cost-effective method.

Automated summary

Oxide semiconductors have the potential to surpass currently employed semiconductors, but the insufficient development of p-type oxides is a major obstacle. This study introduces an optical sensing method for monitoring oxide film growth during spray pyrolysis. By extracting the changes in refractive index in real time, the thermal decomposition processes can be understood and synthesis conditions can be optimized.