2D Diluted Multiferroic Semiconductors upon Intercalation

Abstract

Recently, coexistence of FE and other ferrocity in several 2D systems has been theoretically proposed. [3][4][5][6][7][8][9][10][11][12][13][14] 2D materials such as graphene, [15] phosphorene [16] and MoS 2 [17] with atomicthickness and high electron-mobility may render a high density for integration and high speed for operation. Especially, a recent study demonstrated that highly uniform, solution-processable, phasepure MoS 2 nanosheets can be prepared by electrochemical intercalation, rendering scalable fabrication of large-area 2D transistor array. [18] Their epitaxial growth on substrate also allows of lattice mismatch at the van der Waals interface, facilitating their combination with semiconductor circuits. For traditional FeRAM and MRAM, their combinations with semiconductor circuits remain to be a challenge. Most robust FM materials are metallic, while traditional FE like pervoskites are wide-gap insulators with poor electron-mobility, and their epitaxial growth on silicon is hindered by the issue of lattice mismatch. FM semiconductors may be obtained by doping 3d transitionmetal (TM) ions in III-V compounds (diluted magnetic semiconductors), [19,20] while diluted FE semiconductors have not been realized by similar doping. It would be highly desirable if FE/multiferroicity can be induced by doping a semiconductor in certain domains, which can be directly integrated in the wafer like n/p doping channels. [21,22] In this work we propose a general approach to obtain diluted FE/multiferroic 2D semiconductors by TM doping. Our first-principles designs are based on previous experimental synthesis of intercalated metal dichalcogenides TX 2 such as M x MoS 2 (M = Ni, Cu, Ag, Cd), [23] (Ni, Cr) 0.33 TS 2 (T = Nb, Ta), [24,25] and Cu x Bi 2 Se 3 , [26][27][28][29][30] holding various "guest" species of atomic thickness in their interlayer space. The adopted methods include traditionally melt growth and chemical interaction method as well as electrochemical intercalation method developed recently, [28] which can efficaciously regulate the concentration of metal ions into layered. Those successful syntheses may be also attributed to the intercalated metal ions such as Ni, Cu, and Ag relatively with much lower cohesive energy in their bulk metals compared with other 3d metals such as Ti or V. A vertical switchable polarization together with a magnetic moment can be induced upon the intercalation of those TM ions. As a result, those 2D high-mobility semiconductors can be endowed with multiferroicity via such doping, and the magnetism can be tuned upon FE switching, rendering efficient "electric writing + magnetic reading" for high-density data storage.The direct combination of high-mobility semiconductors and efficient multiferroic memories within the same material is desirable for integration of multifunctional electronics but remains a challenge. Stimulated by recent progress on intercalation of layered materials, first-principles evidence of 2D room-temperature multiferroicity in a series of doped metal dichalcogen...

Constructing Stable and Potentially High-Performance Hybrid Organic-Inorganic Perovskites with “Unstable” Cations

“…With the reorientations of these polar cations in (H 5 O 2 )SnI 3 as marked by the circles shown in Figure 3(c), where the blue arrows denote the polarization direction of cations and the whole crystal, a ferroelectric polarization of 22.7 μC/cm 2 would emerge, much higher than the previously predicted polarization value of MAPbI 3 [24]. Theoretically, ferroelectricity may benefit pho-tovoltaics because high photovoltage can be induced by polarization, while photogenerated electrons and holes can be separated by a built-in electric field [25,26]. Moreover, combination of a high-mobility narrow-bandgap semiconductor and nonvolatile memory is also desirable [27,28].…”

“…To achieve higher photovoltaic performance (e.g., a Shockley-Queisser efficiency of~25%), direct bandgaps within the optimal range of 0.9-1.6 eV are desired. Here, (H 5 O 2 )PbBr 3 seems to be an ideal candidate as it possesses a modest bandgap and low Δ E. Note that the photovoltaic performance of most current HOIPs is still poor in the infrared region [26], while the low bandgap HOIPs like (H 5 O 2 )SnI 3 may fill the gap. The computed optical absorption spectrum (see Figure 3(b)) suggests even stronger absorption compared with MAPbI 3 [23], rendering (H 5 O 2 )SnI 3 a promising candidate as an efficient solar absorber.…”

Intercalated phases of transition metal dichalcogenides

“…Firstprinciple calculations predict that the intercalation of transition metal ions such as Ni, Cu, Ag, Cd into TMDs (e.g., MoS 2 , Bi 2 Se 3 , or CrS 2 ) can generate both ferromagnetism and ferroelectricity, and that these could be stable in the ambient. 42,158 In the initial intercalation state of AB-stacked Cr-intercalated MoS 2 , Cr ion is tetrahedrally coordinated with one bond to the upper layer and three bonds to the lower layer; this causes the vertical distance between Cr ion and the top layer to be longer than the distance of Cr ion to the bottom layer. The polarization direction is downward at the initial state.…”

“…32 In 1986, the first monolayer MoS 2 suspension was reported through intercalation with lithium followed by reaction with water. 33 Intercalation modifies the properties of TMD by a myriad of effects, including charge doping, [34][35][36] expansion of c axis lattice constants, [37][38][39][40] orbital hybridization, [41][42][43] and phonon scattering. 37,44,45 A wide range of properties could be promoted or tuned, from electrical conductivity, 46,47 optical modes, 48,49 magnetic order, 43,50 thermoelectricity, 45,51 catalytic activities, 52,53 to energy storage and conversion performances.…”

Structure Engineering of 2D Materials toward Magnetism Modulation

“…This method not only introduced magnetism into 2D nonmagnetic materials, but also promoted the development of a magnetassisted transfer technique for preparing large-area 2D material films. In addition, O-intercalated graphene/Ni (111), [55] transition metal-intercalated MoS 2 or other TMDs, [56] lithium or magnesium ion-intercalated FeO 2 [42] were also theoretically predicted to introduce magnetism into 2D materials respectively.…”