Destructive role of oxygen in growth of molybdenum disulfide determined by secondary ion mass spectrometry

Abstract

The application of secondary ion mass spectrometry (SIMS) in investigation and comparison of molybdenum disulfide (MoS₂) films grown on SiO₂, Al₂O₃ and BN substrates is presented. SIMS measurements of the MoS₂/substrate interface reveals oxygen out-diffusion from the substrates containing oxygen and the formation of an amorphous MoOS layer in addition to MoS₂. The total area of MoS₂ domains covering the substrate is directly related to the type of substrate. For SiO₂, small triangular domains of MoS₂ separated by amorphous MoOS material are observed. For Al₂O₃, the sizes of the MoS₂ domains are drastically improved due to the higher stability of sapphire. For a BN substrate, SIMS measurements reveal a uniform MoS₂ coverage over the whole 2-inch wafer. These results show the destructive role of oxygen released from substrates such as SiO₂ or Al₂O₃ during the growth process of MoS₂. The fast and cheap growth process on a non-oxide substrate allows large wafer-scale uniform molybdenum disulfide material to be obtained, which is promising for device fabrication.