Low‐Frequency Electronic Noise in Quasi‐2D van der Waals Antiferromagnetic Semiconductor FePS₃—Signatures of Phase Transitions

Abstract

These layered quasi-2D van der Waals (vdW) compounds have interesting electronic, optical, and magnetic properties that can offer new device functionalities. [7][8][9][10][11][12][13][14][15][16][17][18][19] It has been demonstrated that some MPX 3 thin films are one of the rare few-layer vdW materials, which can have stable intrinsic antiferomagnetism (AF) even at mono-and few layer thicknesses. [20][21][22] The existence of weak vdW bonds between the MPX 3 layers makes them potential candidates for the 2D spintronic devices. The metal element of the MPX 3 materials modifies the bandgap from a medium bandgap of ≈1.3 eV to a wide bandgap of ≈3.5 eV. [1][2][3] The diverse properties of these materials tunable by proper selection and combination of the M and X elements make the MPX 3 materials an interesting platform for fundamental science and practical applications. [1][2][3][4][23][24][25][26][27][28][29][30] Among MPX 3 materials, FePS 3 is particularly promising. Its Ising-type ordering allows it to maintain the bulk-like magnetic behavior down to a single monolayer, which explains its moniker -"magnetic graphene." [31] The cleavage energy of FePSe 3 is slightly higher than that of graphite, while that for all other combinations of the M and X elements is lower than that of graphite. [32] The Néel temperature, T N , for FePS 3 is reported to be around 118 K. [1,2,20] It shows strong magnetic anisotropy. [15,33,34] In the crystal, each Fe atom is ferromagnetically coupled with two of its neighbors but the layer is antiferromagnetically coupled with nearest layers making it a zigzag-AF (z-AF) material. [1] The semiconducting nature of FePS 3 , with the energy bandgap of 1.5 eV, and a possibility of the strain engineering of electron and phonon band-structure create additional means for the control of both electron and spin transport. [9,17,35] The quantized spin waves, i.e., magnons in FePS 3 , have frequencies in the terahertz (THz) frequency range, [36,37] which makes this material interesting for THz magnonic devices. However, the electron and spin transport properties of FePS 3 have not been studied in sufficient details yet to assess the potential of such materials for THz applications.Here, we report the results of investigation of low-frequency current fluctuations, i.e., electronic noise, in thin films of FePS 3. The current-voltage (I-V) and noise characteristics

Charge-Density-Wave Thin-Film Devices Printed with Chemically Exfoliated 1T-TaS2 Ink

“…The temperatures at which the phase transitions happen agree well with the resistance data shown in Figure (b,c). The increase in the low-frequency noise at the phase transition points has been observed for various materials and phase transitions of different types. ,, The noise was shown to increases in the vicinity of the metal–insulator transition, spin-glass transition, , and other various phase transitions. , The exact physical mechanism in each case can vary. In general, one expects that more structural disorder, due to crystal lattice reconstruction or defects, results in a higher level of the low-frequency noise …”

“…The increase in the low-frequency noise at the phase transition points has been observed for various materials and phase transitions of different types. 17,22,49 The noise was shown to increases in the vicinity of the metal−insulator transition, 50 spin-glass transition, 51,52 and other various phase transitions. 53,54 The exact physical mechanism in each case can vary.…”

TiO2/FePS3 S‐Scheme Heterojunction for Greatly Raised Photocatalytic Hydrogen Evolution

“…[11][12][13] The rational design and synthesis of such a photocatalyst require not only the emerging nanosized building blocks with desired features, but also efficient charge dissociation/ transfer boosted by the strong built-in electric field in a favorable junction system.In the past decades, 2D materials have demonstrated great capacity to achieve efficient and cost-effective photocatalysis for various reactions, due to their distinct physicochemical features. [14][15][16][17][18][19][20][21] Recently, an emerging 2D material, FePS 3 (FPS), [22][23][24][25][26][27] has displayed numerous attractive characteristics for catalysis: i) Ultrathin structure facilitating rapid bulkto-surface electron-hole transport; ii) high specific surface area accelerating efficient adsorption/desorption of reactant and product, and benefiting the anchoring of other nanobuilding blocks; iii) exposed under-coordinated edge atoms serving as active sites to advance the reactions; iv) thicknessdependent electronic band structure promoting the regulation of light absorption and redox abilities of charge carriers; v) p-type semiconductor nature favoring the construction of certain junction system with a strong built-in electric field. Albeit the above alluring advantages, [28][29][30] only a few works reported the application of FPS in photocatalysis.…”

Printed Electronic Devices with Inks of TiS3 Quasi-One-Dimensional van der Waals Material

“…One can see that the noise generally follows the 1/f trend, and it increases with the increase in bias voltage as expected. 84,87,90 There are some traces of Lorentzian-type bulges at frequencies above f = 100 Hz. They can indicate the presence of certain defects or impurities with a particularly high concentration that act as the trapping centers for the charge carriers contributing to the current conduction.…”

“…The details of our experimental setup and measurement procedures have been reported elsewhere in the context of other material systems. , The analysis of the noise spectral density, its functional dependence on frequency, electric bias, and temperature can provide a wealth of information on the electron transport, particularly in material systems with high concentrations of defects and impurities, which act at the charge trapping sites. We have successfully used electronic noise spectroscopy for monitoring phase transitions in materials, which reveal strongly correlated phenomena. ,− Typically, at the frequencies f < 100 kHz, materials show the spectral noise density of S ( f ) ∼ 1/ f γ type, with γ ∼ 1. In Figure a,b we present the voltage-referred noise power spectral density, S v , and the normalized current noise power spectral density, S I / I 2 , for the device channel printed with the quasi-1D TiS 3 ink as a function of frequency.…”