Chemical Vapor Deposition of NbS₂ from a Chloride Source with H₂ Flow: Orientation Control of Ultrathin Crystals Directly Grown on SiO₂/Si Substrate and Charge Density Wave Transition

Abstract

This paper reports the growth and characterization of c-axis-oriented NbS 2 thin films on SiO 2 /Si substrate by ambient pressure chemical vapor deposition (CVD) using a generic metal chloride source.We found that NbS 2 nanosheets can be grown directly on the SiO 2 /Si substrate with the aid of hydrogen gas mixed in the carrier gas. Detailed examination of the growth parameters was made possible using a separateflow CVD apparatus. It appears that the major cause of the misorientation is the off-stoichiometry with surplus Nb. The quality of the films was evaluated by X-ray diffraction and Raman spectroscopy as well as resistivity measurements at low temperatures. They showed a resistivity minimum at the same temperature of the charge density wave (CDW) transition for a bulk single crystal of 3R-NbS 2 .

Optical probing charge density wave and lattice vibration in metallic 2D materials

“…As a result, the nucleation of MoS2 is more likely to occur on the SiO2/Si substrate. However, the analogous growth time dependence we observed has been found in NbS2 flakes on the same substrate[112]. At the beginning of the synthesis, nucleation sites are first absorbed onto the SiO2/Si substrate.…”

2D Metallic Transitional Metal Dichalcogenides for Electrochemical Hydrogen Evolution

“…As mentioned earlier, the feeding rate of precursors and the reaction temperature are crucial factors in the CVD growth of MTMDCs. Group‐5 metal chlorides featured with low sublimation points have been proved as effective precursors for synthesizing 2D MTMDC nanosheets . Nevertheless, such group‐5 metal chlorides are easily hydrolyzed into oxides or harmful hydrogen chlorides, thus hard to be used as stable precursors.…”

Recent progress in the controlled synthesis of 2D metallic transition metal dichalcogenides

“…The MCl n precursors with high chemical activities can be evaporated at a relatively high rate, thus facilitating the growth of MTMDCs. Accordingly, a plenty of 2D MTMDCs have been synthesized by such CVD strategy, such as VS 2 [36,37], VSe 2 [21,43,66], TaS 2 [25], TaSe 2 [24], and NbS 2 [39][40][41]. Notably, the obtained 2D MTMDCs on SiO 2 /Si usually presented a vertical growth behavior, with as-grown nanosheets vertically oriented on the substrate surface ( figure 5(b)).…”

“…However, a comprehensive review about the most recent progress on the preparations of 2D MTMDCs is still lacking. In this topic review, we will summarize the recent advances regarding the synthetic routes of 2D MTMDC materials (VS 2 , VSe 2 , TaS 2 , TaSe 2 , NbS 2 , NbSe 2 , etc) [23][24][25][36][37][38][39][40][41][42][43], including mechanical/chemical exfoliations, CVT, and MBE. More significantly, we will introduce the state-of-the-art CVD routes used to realize the large-scale growth of 2D MTMDCs, by using different transition metal-based feedstocks including transition metal chlorides (MCl n ) and transition metal oxidations (MO n ) mixed with alkali halides (AH, where A=Na or K, and H=Cl, Br or I).…”