We report on the transport and low-frequency noise measurements of MoS2 thin-film transistors with "thin" (2-3 atomic layers) and "thick" (15-18 atomic layers) channels. The back-gated transistors made with the relatively thick MoS2 channels have advantages of the higher electron mobility and lower noise level. The normalized noise spectral density of the low-frequency 1/f noise in "thick" MoS2 transistors is of the same level as that in graphene. The MoS2 transistors with the atomically thin channels have substantially higher noise levels. It was established that, unlike in graphene devices, the noise characteristics of MoS2 transistors with "thick" channels (15-18 atomic planes) could be described by the McWhorter model. Our results indicate that the channel thickness optimization is crucial for practical applications of MoS2 thin-film transistors.
High Mobility Ambipolar MoS2 Field-Effect Transistors: Substrate and Dielectric Effects
我们在二氧化硅和聚甲基丙烯酸甲酯（PMMA）衬底上制作了二硫化钼场效应晶体管，并在四探针配置中测量了载流子迁移率。对于SiO2上的多层MoS 2，迁移率为30-60 cm 2/Vs，与厚度（15-90 nm）相对无关，并且大多数器件表现出单极n型行为。相比之下，PMMA上的多层MoS 2显示出随厚度增加的迁移率，在厚度约50 nm处高达470 cm 2/Vs（电子）和480 cm 2/Vs（空穴）。迁移率对厚度的依赖性指向在增加迁移率中的块状MoS 2的长程介电效应。
Statistical Study of Deep Sub-Micron Dual-Gated Field-Effect Transistors on Monolayer CVD Molybdenum Disulfide Films
具有1.8 eV直接带隙的单层二硫化钼（MoS 2）是一种有前途的二维材料，在下一代纳米电子应用中有可能超过石墨烯。本文采用化学气相沉积（CVD）方法在Si/SiO_2衬底上制备单层MoS_2薄膜，并对基于双栅MoS_2场效应晶体管的器件性能进行了全面的研究。超过100个设备进行了研究，以获得在CVD二硫化钼的设备性能的统计描述。我们检查和缩小规模的晶体管的沟道长度为100 nm，并实现了创纪录的高漏电流62.5 mA/mm的CVD单层二硫化钼膜以往报道。我们进一步提取了低功函数金属Ti在单层CVD MoS 2上的本征接触电阻，其期望值为175 Ω.mm，通过适当的选通可以显著降低到10 Ω.mm。最后，得到了不同沟道长度下载流子的场效应迁移率（μFE）。考虑到接触电阻的影响，单层CVD MoS 2薄膜的平均和最大本征μFE分别为13.0和21.6 cm 2/Vs。
Competing interactions produce finite-size textures in myriad condensed matter systems, typically forming elongated stripe or round bubble domains. Transitions between stripe and bubble phases, driven by field or temperature, are expected to be reversible in nature. Here we report on the distinct character of the analogous transition for nanoscale spin textures in chiral Co/Pt-based multilayer films, known to host Néel skyrmions, using microscopy, magnetometry, and micromagnetic simulations. Upon increasing field, individual stripes fission into multiple skyrmions, and this transition exhibits…
Magnetic skyrmions form in chiral multilayers from the shrinking or fission of elongated stripe textures. Here we report an experimental and theoretical study of the temperature dependence of this stripe-to-skyrmion transition in Co/Pt-based multilayers. Field-reversal magnetometry and Lorentz microscopy experiments over 100 - 350 K establish the increased efficacy of stripe-to-skyrmion fission at higher temperatures - driven primarily by the thermal evolution of key magnetic interactions - thereby enhancing skyrmion density. Atomistic calculations elucidate that the energy barrier to fission …
Transconductance as a Probe of Valley Thermodynamics in Multilayer WSe$_2$
Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS)（物质·材料纳米结构研究センター（MANA），国立物質研究所（NIMS））；Department of Nanotechnology for Sustainable Energy, Kwansei Gakuin University（关西学院大学持続可能エネルギーナノテクノロジー学科）
We experimentally demonstrate the formation of room-temperature skyrmions with radii of about 25\,nm in easy-plane anisotropy multilayers with interfacial Dzyaloshinskii-Moriya interaction (DMI). We detect the formation of individual magnetic skyrmions by magnetic force microscopy and find that the skyrmions are stable in out-of-plane fields up to about 200 mT. We determine the interlayer exchange coupling as well as the strength of the interfacial DMI. Additionally, we investigate the dynamic microwave spin excitations by broadband magnetic resonance spectroscopy. From the uniform Kittel mode…
We present a theoretical study of the onset of electric polarization close to a surface in magnetic materials and in thin films and multilayers. We consider two different paths that lead to the onset of multiferroic behavior at the boundary in materials that are bulk collinear ferromagnets or antiferromagnets. These two paths are distinguished by the presence or absence of a surface induced Dzyaloshinskii-Moriya interaction which can be taken into account through Lifshitz invariants in the free energy of the system. Experimental consequences are discussed in the light of the developed theory.
Universal dependence on the channel conductivity of the competing weak localization and antilocalization in amorphous InGaZnO$_4$ thin-film transistors
We report a study of the magnetization reversals and skyrmion configurations in two systems - Pt/Co/MgO and Ir/Fe/Co/Pt multilayers, where magnetic skyrmions are stabilized by a combination of dipolar and Dzyaloshinskii-Moriya interactions (DMI). First Order Reversal Curve (FORC) diagrams of low-DMI Pt/Co/MgO and high-DMI Ir/Fe/Co/Pt exhibit stark differences, which are identified by micromagnetic simulations to be indicative of hybrid and pure Néel skyrmions, respectively. Tracking the evolution of FORC features in multilayers with dipolar interactions and DMI, we find that the negative FORC …
Pseudo-potential Band Structure Calculation of InSb Ultra-thin Films and its application to assess the n-Metal-Oxide-Semiconductor Transistor Performance
