Metalorganic chemical vapor deposition of rare-earth sulfides

Sebastian Beer, Ruhr University Bochum, Bochum, Germany
Stefan Cwik, Ruhr University Bochum, Bochum, Germany
Anjana Devi, Ruhr University Bochum, Bochum, Germany

Rare-earth sulfides (RES) are gaining significant attention in the research community as they are highly interesting for a broad field of applications such as photovoltaics, thermoelectrics or spintronics owing to their interesting functional properties. Reports on research related to RES in thin film form have been limited and especially their growth via vapor phase deposition such as metalorganic chemical vapor deposition (MOCVD) has hardly been explored although this technique has a huge potential for large scale applications. The lack of suitable RE precursors has been the main cause for the slow progress made in this field. Our focus was to develop an MOCVD process for Nd2S3 which is a highly interesting material system possessing a band gap between 1.9 eV and 2.5 eV for α and γ-Nd2S3 phases respectively. For photovoltaics, γ-Nd2S3 is considered as an alternative and promising photoabsorber material for novel lead/cadmium free solar cells. For the first time we were able to establish a novel MOCVD process for neodymium sesquisulfide (Nd2S3) thin films in the range of 400 °C to 600 °C. The film characteristics were investigated via X-ray diffraction, atomic force microscopy, scanning electron microscopy, Rutherford backscattering spectrometry/nuclear reaction analysis and X-ray photoelectron spectroscopy. Furthermore, UV/Vis and photoluminescence measurements were performed and the results demonstrated the potential of Nd2S3 in optoelectronics.

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