9:30 AM - 9:45 AM
▲ [15a-A404-3] Nucleation and Growth of MoS2 Crystals on GaN and 4H-SiC Substates Using Ammonium Tetrathiomolybdate Precursor
Keywords:crystals, MoS2, lattice mismatch
1. INTRODUCTION: Transition metal dichalcogenides (TMDCs) layered materials have recently attracted significant interest owing to its excellent optoelectronics properties for device applications. Various studies have shown that the MoS2 is a promising layered material for optoelectronics and visible light photocatalytic application.
2. EXPERIMENTAL DETAILS:The synthesis of MoS2 layer on SiC surface was performed as per the following steps. Firstly, the Ammonium Tetrathiomolybdate [(NH4)2MoS4] was dissolved in N, N-Dimethylformamide super hydrated solution (DMF) (1mg/1ml or approximately 0.1 wt. % solution) and later it was sonicated for 10 min. This solution was then spin-coated onto the surface of GaN and SiC substrate at 2000 rpm for 60 sec. Later the substrate was kept in quartz tube of length 80 cm, along with sulphur powder in two different temperature furnaces, separately. Sulphur evaporated in LTF (Low temperature furnace) at 220° Celsius reacts with the (NH4)2MoS4 to form MoS2 layers on the GaN and SiC, respectively, in HTF (high temperature furnace) which is heated to 750° Celsius.
3. RESULTS AND DISCUSSION: The lattice mismatch between the MoS2 and GaN substrate is 0.8% and with 4H-SiC is around -2.9%. It signifies possible growth of oriented MoS2 crystals with GaN and disoriented with that of SiC. Figure 1a shows the Raman spectra of the MoS2/4H-SiC heterostructure sample. The characteristic E2g and A1g peaks corresponding to MoS2 layer were observed with a peak difference of 24 cm-1, along with the GaN and SiC characteristic peak of the two different substrates, respectively.
4. CONCLUSION: In conclusion, we have demonstrated growth of optically active MoS2 crystals on lattice matched GaN and 4H-SiC substrate using ammonium tetrathiomolybdate precursor in a CVD process. The nucleated triangular MoS2 crystals shows epitaxial growth on GaN and misorientation due to a lattice mismatch on SiC.
2. EXPERIMENTAL DETAILS:The synthesis of MoS2 layer on SiC surface was performed as per the following steps. Firstly, the Ammonium Tetrathiomolybdate [(NH4)2MoS4] was dissolved in N, N-Dimethylformamide super hydrated solution (DMF) (1mg/1ml or approximately 0.1 wt. % solution) and later it was sonicated for 10 min. This solution was then spin-coated onto the surface of GaN and SiC substrate at 2000 rpm for 60 sec. Later the substrate was kept in quartz tube of length 80 cm, along with sulphur powder in two different temperature furnaces, separately. Sulphur evaporated in LTF (Low temperature furnace) at 220° Celsius reacts with the (NH4)2MoS4 to form MoS2 layers on the GaN and SiC, respectively, in HTF (high temperature furnace) which is heated to 750° Celsius.
3. RESULTS AND DISCUSSION: The lattice mismatch between the MoS2 and GaN substrate is 0.8% and with 4H-SiC is around -2.9%. It signifies possible growth of oriented MoS2 crystals with GaN and disoriented with that of SiC. Figure 1a shows the Raman spectra of the MoS2/4H-SiC heterostructure sample. The characteristic E2g and A1g peaks corresponding to MoS2 layer were observed with a peak difference of 24 cm-1, along with the GaN and SiC characteristic peak of the two different substrates, respectively.
4. CONCLUSION: In conclusion, we have demonstrated growth of optically active MoS2 crystals on lattice matched GaN and 4H-SiC substrate using ammonium tetrathiomolybdate precursor in a CVD process. The nucleated triangular MoS2 crystals shows epitaxial growth on GaN and misorientation due to a lattice mismatch on SiC.