- Nano Express
- Open Access
Ferromagnetism in ultrathin MoS2 nanosheets: from amorphous to crystalline
© Zhang et al.; licensee Springer. 2014
- Received: 10 July 2014
- Accepted: 16 October 2014
- Published: 22 October 2014
Two-dimensional materials have various applications in the next generation nanodevices because of their easy fabrication and particular properties. In this work, we studied the effects of crystalline order on the magnetic properties of ultrathin MoS2 nanosheets. Results indicate that all the fabricated samples show clear room temperature ferromagnetism. The amorphous sample has the larger saturation magnetization than that of the crystallized samples, where the disordered grain boundary or defects in the nanosheets are considered to be responsible for the long-range magnetic order. These MoS2 nanosheets with versatile functions may have potential applications in spintronics, nanodevices, and photodevices.
- Room Temperature Ferromagnetism
- Crystalline Order
- MoS2 Nanosheets
- Couple Plasma Atomic Emission Spectrometer
Magnetic ordering in materials that do not have partially filled d or f orbitals named defect-induced magnetism (DIM) is a topic of interest in recent years [1–3]. Until now, the DIM phenomenon has been finally observed in a broad spectrum of materials, from several oxides to carbon based materials [4, 5] and to the transition-metal dichalcogenide with the atomic thickness [6, 7].
Recently, as one of the central members in transition metal dichalcogenide compounds, MoS2 with its remarkable electronic properties such as charge density wave transitions in transition metal dichalcogenides make the material interesting from both fundamental and applied research perspectives [8–10]. For example, reports demonstrate strong photoluminescence emergence and anomalous lattice vibrations in single- and few-layered MoS2 films [11, 12]. Results also indicate that the single-layer MoS2 exhibits a high channel mobility (approximately 200 cm2V−1 s−1) and current on/off ratio (1 × 108) when it was used as the channel material in a field-effect transistor . Most recently, it is proposed that the indirect band gap of bulk MoS2 with a magnitude of approximately 1.2 eV transforms gradually to a direct band gap of approximately 1.8 eV in single-layer samples [14, 15], which is in contrast to pristine graphene with a band gap of approximately 0 eV and few-layered h-BN with a band gap of approximately 5.5 eV .
Recently, theoretical studies suggested that, although bulk MoS2 is a diamagnetic material, it becomes ferromagnetic when MoS2 nanoribbons are formed with zigzag edges, defects are induced, or nonmetals such as H, B, C, N, and F are absorbed [17, 18]. In addition, formation of magnetic moments was also reported in MonS2n clusters, nanoparticles, and nanoribbons of MoS2 from first principle studies [19–21]. Experimentally, the interesting ferromagnetism phenomenon in nanosheets of MoS2 had previously been reported and the observed magnetic signal is attributed to the presence of unsaturated edge atoms . The weak ferromagnetism was also obtained in the freestanding nanosheets and in the bulk MoS2 irradiated by proton, which increases the TC up to 895 K [23, 24]. Further, the existence of magnetism in the pristine MoS2 has been reported despite that there are differences depending on the layer thickness .
Although such unexpected ferromagnetic behavior ascribed to edge states and defects in MoS2 has been reported, there are no experimental observations of ferromagnetism in MoS2 with a different degree of crystallization. In this letter, MoS2 nanosheets from amorphous to crystalline were prepared by a hydrothermal method reaction at different temperatures. The structure and magnetic properties were studied. Results indicate that all the samples show clear room ferromagnetism and the ferromagnetism weakened with the crystalline order increasing.
MoS2 nanosheets with different crystalline order were synthesized by the hydrothermal method. Sodium molybdate dihydrate, 1.5 g, and thioacetamide, 2.2 g, were dissolved together in 50 ml of deionized water and stirred for 2 h. Then, the solution was transferred into a Teflon-lined stainless steel autoclave and reacted at different temperatures (180°C, 200°C, 220°C and 240°C) for 24 h. Finally, the products were filtered and washed with water and dried in a vacuum.
X-ray diffraction (XRD, X'Pert PRO PHILIPS with Cu Kα radiation) was employed to study the crystal structure. The morphology of the samples was obtained by using the high-resolution transmission electron microscopy (HRTEM, TecnaiTM G2 F30, FEI, Hillsboro, OR, USA). X-ray photoelectron spectroscopy (XPS, Kratos Axis Ultra, Manchester, UK) was utilized to determine the bonding characteristics of the samples. The composition was confirmed by an inductively coupled plasma atomic emission spectrometer (ICP, ER/S). The measurements of magnetic properties were made using the Quantum Design MPMS magnetometer based on superconducting quantum interference device (SQUID).
ICP results for the MoS 2 nanosheets
Element content (ppm)
The ultrathin MoS2 nanosheets with different crystalline order were fabricated, and their magnetic properties were studied. Results indicate that all the fabricated samples show clear room ferromagnetism and the amorphous sample has larger saturation magnetization owing to having more disordered grain boundary or defects. This unusual ferromagnetism may open perspectives for its application in spintronics devices.
This work is supported by the NSFC (Grant No. 51202101, 11474137), the Specialized Research Fund for the Doctoral Program of Higher Education (20120211120005), the National Science Foundation for Fostering Talents in Basic Research of the National Natural Science Foundation of China, the Open Project of Key Laboratory for Magnetism, and the Magnetic Materials of the Ministry of Education of Lanzhou University (LZUMMM2014015).
- Wu H, Stroppa A, Sakong S, Picozzi S, Scheffler M, Kratzer P: Magnetism in C- or N-doped MgO and ZnO: a density-functional study of impurity pairs. Phys Rev Lett 2010, 105: 267203.View ArticleGoogle Scholar
- Slipukhina I, Mavropoulos P, Blügel S, Ležaić M: Ferromagnetic spin coupling of 2p impurities in band insulators stabilized by an intersite Coulomb interaction: nitrogen-doped MgO. Phys Rev Lett 2011, 107: 137203.View ArticleGoogle Scholar
- Esquinazi P, Hergert W, Spemann D, Setzer A, Ernst A: Defect-induced magnetism in solids. IEEE Trans Magn 2013, 49: 4668.View ArticleGoogle Scholar
- Xu Q, Schmidt H, Zhou S, Potzger K, Helm M, Hochmuth H, Lorenz M, Setzer A, Esquinazi P, Meinecke C, Grundmann M: Room temperature ferromagnetism in ZnO films due to defects. Appl Phys Lett 2008, 92: 082508. 10.1063/1.2885730View ArticleGoogle Scholar
- Yazyev OV, Helm L: Defect-induced magnetism in graphene. Phys Rev B 2007, 75: 125408.View ArticleGoogle Scholar
- Zhang X, Zhang J, Zhao J, Pan B, Kong M, Chen J, Xie Y: Half-metallic ferromagnetism in synthetic Co9Se8 nanosheets with atomic thickness. J Am Chem Soc 2012, 134: 11908. 10.1021/ja3046603View ArticleGoogle Scholar
- Gao DQ, Xue QX, Mao XZ, Wang WX, Xu Q, Xue DS: Ferromagnetism in ultrathin VS 2 nanosheets. J Mater Chem C 2013, 1: 5909. 10.1039/c3tc31233jView ArticleGoogle Scholar
- Popov I, Seifert G, Tomanek D: Designing electrical contacts to MoS2 monolayers: a computational study. Phys Rev Lett 2012, 108: 156802.View ArticleGoogle Scholar
- Yin ZY, Li H, Li H, Jiang L, Shi YM, Sun YH, Lu G, Zhang Q, Chen XD, Zhang H: Single-layer MoS2 phototransistors. ACS Nano 2012, 6: 74. 10.1021/nn2024557View ArticleGoogle Scholar
- Li H, Yin ZY, He QY, Li H, Huang X, Lu G, Fam DWH, Tok AIY, Zhang Q, Zhang H: Fabrication of single- and multilayer MoS2 film-based field-effect transistors for sensing NO at room temperature. Small 2012, 8: 63. 10.1002/smll.201101016View ArticleGoogle Scholar
- Splendiani A, Sun L, Zhang Y, Li T, Kim J, Chim C, Galli G, Wang F: Emerging photoluminescence in monolayer MoS2. Nano Lett 2010, 10(4):1271. 10.1021/nl903868wView ArticleGoogle Scholar
- Lee C, Yan H, Brus LE, Heinz LE, Hone TF, Hone J, Ryu S: Anomalous lattice vibrations of single- and few-layer MoS2. ACS Nano 2010, 4: 2695. 10.1021/nn1003937View ArticleGoogle Scholar
- Radisavljevic B, Radenovic A, Brivio J, Giacometti V, Kis A: Single-layer MoS2 transistors. Nat Nanotechnol 2011, 6: 147. 10.1038/nnano.2010.279View ArticleGoogle Scholar
- Mak KF, Lee C, Hone J, Shan J, Heinz TF: Atomically thin MoS2: a new direct-gap semiconductor. Phys Rev Lett 2010, 105: 136805.View ArticleGoogle Scholar
- Schwierz F: Nanoelectronics: flat transistors get off the ground. Nat Nanotechnol 2011, 6: 135. 10.1038/nnano.2011.26View ArticleGoogle Scholar
- Radisavljevic B, Radenovic A, Brivio J, Giacometti V, Kis A: Sketched oxide single-electron transistor. Nat Nanotechnol 2011, 6: 343. 10.1038/nnano.2011.56View ArticleGoogle Scholar
- Ataca C, Sahin H, Aktürk E, Ciraci S: Mechanical and electronic properties of MoS2 nanoribbons and their defects. J Phys Chem C 2011, 115: 3934. 10.1021/jp1115146View ArticleGoogle Scholar
- Ataca C, Ciraci S: Functionalization of single-layer MoS2 honeycomb structures. J Phys Chem C 2011, 115: 13303. 10.1021/jp2000442View ArticleGoogle Scholar
- Shidpoura R, Manteghian M: A density functional study of strong local magnetism creation on MoS2 nanoribbon by sulfur vacancy. Nanoscale 2010, 2: 1429. 10.1039/b9nr00368aView ArticleGoogle Scholar
- Pan H, Zhang YW: Edge-dependent structural, electronic and magnetic properties of MoS 2 nanoribbons. J Mater Chem 2012, 22: 7280. 10.1039/c2jm15906fView ArticleGoogle Scholar
- Li YF, Zhou Z, Zhang SB, Chen ZF: MoS2 nanoribbons: high stability and unusual electronic and magnetic properties. J Am Chem Soc 2008, 130: 16739. 10.1021/ja805545xView ArticleGoogle Scholar
- Zhang J, Soon JM, Loh KP, Yin JH, Ding J, Sullivian MB, Wu P: Magnetic molybdenum disulfide nanosheet films. Nano Lett 2007, 7: 2370. 10.1021/nl071016rView ArticleGoogle Scholar
- Gao D, Si M, Li J, Zhang J, Zhang Z, Yang Z, Xue D: Ferromagnetism in freestanding MoS2 nanosheets. Nanoscale Res Lett 2013, 8: 129. 10.1186/1556-276X-8-129View ArticleGoogle Scholar
- Mathew S, Gopinadhan K, Chan TK, Yu XJ, Zhan D, Cao L, Rusydi A, Breese MBH, Dhar S, Shen ZX, Venkatesan T, Thong JTL: Magnetism in MoS2 induced by proton irradiation. Appl Phys Lett 2012, 101: 102103. 10.1063/1.4750237View ArticleGoogle Scholar
- Tongay S, Vrnoosfaderani SS, Applethon BR, Wu J, Hebard AF: Magnetic properties of MoS 2: existence of ferromagnetism. Appl Phys Lett 2012, 101: 123105. 10.1063/1.4753797View ArticleGoogle Scholar
- Mao X, Xu Y, Xue Q, Wang W, Gao D: Ferromagnetism in exfoliated tungsten disulfide nanosheets. Nanoscale Res Lett 2013, 8: 430. 10.1186/1556-276X-8-430View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.