BIT’s progress in controlling crystalline structure of 2D materials

News Resource: School of Chemistry and Chemical Engineering

Editor: News Agency of BIT

Translator: Liu Lanjun, News Agency of BIT


Recently, Professor Zhou Jiadong from School of Physics of BIT, in collaboration with Associate Researcher Duan Junxi, achieved a breakthrough in the synthesis of 2D intercalated V3S5 crystal materials. Leveraging a binary metal precursor co-reaction mechanism and chemical vapor deposition method, they managed to control the synthesis within the system of two-dimensional vanadium-based intercalated chalcogenide compounds. Further research was conducted to investigate the related properties of these synthesized materials. Their significant research findings have been published in the prestigious international journal Advanced Functional Materials.

Research on the atomic structure engineering of 2D transition metal chalcogenides (TMCs) provides a promising platform to achieve attractive fascinating propertiesincluding superconductivity, interlayer excitons, magnetism and charge-density waves (CDWs). The intercalation method is considered a powerful approach to manipulate the atomic structures of 2D TMCs while introducing novel physical properties. Notably,2D intercalated TMCs such as Cr1+xTe2,Nb1+xS2,TaxS(Se)y,and VxSy have been synthesized. VxSy compounds, in particular, exhibit  various physical properties, making them promising candidates for spintronic devices. For example, the V5S8 crystal was precisely prepared by chemical vapor transport(CVT) method and exhibits antiferromagnetic property with Néel temperature of 32 K. The self-intercalated V9S16 and V5S8+x nanosheets, synthesized by the molecular beam epitaxy method, exhibited a CDW transition. Additionally, the VS2-VS hetero-dimentional superlattice, produced by the chemical vapor deposition (CVD) method, showcases room-temperature in-plane Hall effect. All these studies illustrate that intercalating differently ordered V atoms into the interlayer gap of VS2 can achieve exotic properties. However, the controllable synthesis of novel 2D self-intercalated VxSy compounds directly via CVD still remains a challenge.

Based on this, we have proposed a binary metal precursor co-reaction growth mechanism executed through the chemical vapor deposition method. By regulating the vapor pressure of the vanadium source during the growth process, we’ve successfully synthesize 2D self-intercalated V3S5 crystal .Firstly, the metallic V3S5 crystal exhibits phase transition at around 20 K. Secondly, due to the inherent electro-electric interaction of V3S5, an increase in resistance and unsaturated negative magnetoresistance were observed in the two-dimensional V3S5 crystal at low temperatures. This work not only promotes our understanding of the growth mechanism of vanadium based chalcogenides, but also provides new insights for the synthesis of other self intercalated transition metal chalcogenides.


Fig1. Synthesis and characterization of V3S5 crystal.

(a, b) The atomic structure of V3S5 .

(c) Synthesis mechanism of two-dimensional V3S5 crystal.

         (d) Optical morphology of two-dimensional V3S5.

(e) AFM diagram of V3S5.

(f) V3S5 thickness dependent Raman spectroscopy.

(g) 2D V3S5 XPS spectroscopy.


Fig 2. 2D V3S5 controllable growth.

(a-c) V3S5 optical morphology grown on 520 ˚ C (a), 550 ˚ C (b) and 580 ˚ C (c).

(d) The average thickness distribution of V3S5 under different growth temperatures.

(e-g) V3S5 grew on optical morphology at different growth times at 1 min (e), 5 min (f), and 10 min (g).

(h) The relationship between the average size of two-dimensional V3S5 and growth time.

(i-k) The optical morphology of V3S5 grown at different argon flow rates was observed at 80 sccm (i), 100 sccm (j), and 120 sccm (k).

(l) The relationship between the average thickness of V3S5 and the Ar flow rate.


Fig 3. SHG signal of V3S5 under 1064 nm laser.

(a)SHG test schematic diagram.

(b)The relationship between laser power and SHG intensity;

(c)Second order nonlinear coefficient fitting diagram;

(d) The polarization angle variation relationship of SHG intensity along the parallel and vertical directions of V3S5.


Fig 4. STEM characterization of two-dimensional V3S5.

(a)TEM images of V3S5 crystal and TEM-EDS mapping of S (b) and V (c) elements.

(d) STEM-HAADF image of V3S5 crystal.

(e) V3S5 crystal electron diffraction pattern.

(f) Cross section STEM-HAADF image of V3S5 crystal.


Fig5. Electrical properties of two-dimensional V3S5 crystal.

(a)The curve of resistance changing with temperature.

(b)The curve of resistance changing with temperature under different magnetic fields.

(c)Changes in magnetic resistance at different temperatures.

(d)The variation of Hall resistance Rxy with magnetic field at different temperatures.

(e, f) Changes in carrier density and mobility with temperature.

BIT is the primary institution associate withthis work, doctoral student Wang Ping from the School of Physics, is the first author. Professor Zhou Jiadong and Associate Researcher Duan Junxi from the School of Physics are co corresponding authors . This work has received support from the National Natural Science Foundation and the Beijing University of Technology Foundation project.

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