Author
A D Yoffe
Bio: A D Yoffe is an academic researcher. The author has contributed to research in topics: Hall effect & Conductivity. The author has an hindex of 7, co-authored 8 publications receiving 794 citations.
Papers
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TL;DR: In this paper, the effects of intercalation of the layer type transition metal dichalcogenides by a variety of organic molecules, alkali metals, or 3D transition metals are discussed.
Abstract: Intercalation of the layer type transition metal dichalcogenides by a variety of organic molecules, alkali metals, or ‘3d’ transition metals, provides a powerful way to finely tune the electron occupation of the relatively narrow ‘d’ bands met in these solids These transition metal dichalcogenides are highly anisotropic solids, sometimes referred to as ‘two-dimensional’ solids, and the intercalant molecules which are electron donors enter between the layers This can result in profound changes in the electronic properties of the host lattice, and these changes can be understood in terms of charge transfer and increased interlayer separation The phenomena discussed include optical properties, transport properties, super-conductivity, order-disorder phenomena and phase changes, staging, magnetic properties, metal-insulator transitions, Anderson localization, and fast-ion conduction Some possible practical applications are also considered
597 citations
TL;DR: In this paper, the resistivity, Hall effect and magnetic susceptibility have been measured as a function of temperature for the first row transition metal intercalates of niobium disulphide, M 1/3NbS2 (M = Mn, Fe, Co, Ni), where the intercalate ions form an ordered superlattice.
Abstract: The resistivity, Hall effect and magnetic susceptibility have been measured as a function of temperature for the first row transition metal intercalates of niobium disulphide, M1/3NbS2 (M = Mn, Fe, Co, Ni), where the intercalate ions form an ordered superlattice. Metallic behaviour, associated with conduction in the niobium d bands, is observed, and sharp anomalies are seen at the temperatures at which the localized moments on the intercalate ions order. The Mn inter calation complex orders ferromagnetically, the Fe, Co and Ni complexes anti-ferromagnetically. The splittings of the intercalate d levels by the crystal field are proposed and possible magnetic interactions are discussed.
111 citations
TL;DR: In this paper, room-temperature measurements of the in-plane resistivity and Hall coefficient of TiSe2 and TiS2 as a function of pressure are presented, and the authors interpret the changing p-d band overlap in terms of a changing p − d band overlap, which is consistent with the semimetallic picture for this material.
Abstract: Presents room-temperature measurements of the in-plane resistivity (j,Eperpendicular to c) and Hall coefficient (jperpendicular to c,B/sub //c/) of TiSe2 and TiS2 as a function of pressure. With pressure both the resistivity and Hall coefficient decrease rapidly in TiSe2; this the authors interpret in terms of a changing p-d band overlap, and is consistent with the semimetallic picture for this material. In contrast, the Hall coefficient of TiS2 is completely independent of pressure, indicating that the carriers present do not arise from this p-d band overlap, but rather from partial occupation of the band as a result of slight Ti excess. Thus the extrinsic semiconductor picture for TiS2 is favoured by the authors.
65 citations
TL;DR: In this paper, the two charge density wave (CDW) transitions in 4Hb TaS2 have been followed under pressure, and the two transition temperatures were lowered when pressure was applied; the 315K atmospheric pressure transition associated with CDW formation in the octahedral layers was suppressed by 35 kbar, the 22K transition in the trigonal prismatic layers were suppressed at 8.5 kbar.
Abstract: The two charge density wave (CDW) transitions in 4Hb TaS2 have been followed under pressure. The two transition temperatures were lowered when pressure was applied; the 315K atmospheric pressure transition associated with CDW formation in the octahedral layers was suppressed by 35 kbar, the 22K transition associated with CDW formation in the trigonal prismatic layers was suppressed at 8.5 kbar. The fall in the 22K transition correlates with the rise in superconducting transition temperature. The behaviour of the resistivity at the CDW transitions is discussed and charge transfer from the octahedral layers to the trigonal prismatic layers is proposed. The effect of pressure on CDW formation in trigonal prismatic material is related to its superconducting behaviour under pressure through the microscopic CDW theory of Chan and Heine (1973).
34 citations
TL;DR: In this article, the Hall coefficient and conductivity of TiS2 have been measured and it has been shown that the strong temperature dependence of the conductivity is matched by a strong pressure dependence that is consistent with electron-phonon scattering.
Abstract: Measurements of the pressure dependence of the Hall coefficient and conductivity of TiS2 indicate that TiS2 is an extrinsic semiconductor. The strong temperature dependence of the conductivity is matched by a strong pressure dependence that is consistent with electron-phonon scattering. In contrast, TiSe2 is a semimetal, with a strongly pressure dependent p-d band overlap. The transition temperature of the structural phase transition in TiSe2 falls at -1.2K kbar-1.
33 citations
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TL;DR: This work reviews the historical development of Transition metal dichalcogenides, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.
Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.
13,348 citations
TL;DR: The unique characteristics of incident-light control, prompt photoswitching, and good photoresponsivity from the MoS(2) phototransistor pave an avenue to develop the single-layer semiconducting materials for multifunctional optoelectronic device applications in the future.
Abstract: A new phototransistor based on the mechanically exfoliated single-layer MoS2 nanosheet is fabricated, and its light-induced electric properties are investigated in detail. Photocurrent generated from the phototransistor is solely determined by the illuminated optical power at a constant drain or gate voltage. The switching behavior of photocurrent generation and annihilation can be completely finished within ca. 50 ms, and it shows good stability. Especially, the single-layer MoS2 phototransistor exhibits a better photoresponsivity as compared with the graphene-based device. The unique characteristics of incident-light control, prompt photoswitching, and good photoresponsivity from the MoS2 phototransistor pave an avenue to develop the single-layer semiconducting materials for multifunctional optoelectronic device applications in the future.
3,033 citations
Pennsylvania State University1, Oak Ridge National Laboratory2, Rensselaer Polytechnic Institute3, University of Central Florida4, Yale University5, Purdue University6, Carnegie Mellon University7, Massachusetts Institute of Technology8, University of California, Berkeley9, Lawrence Berkeley National Laboratory10, Rice University11, Chinese Academy of Sciences12, University of Texas at Austin13, University of California, Santa Barbara14
TL;DR: Insight is provided into the theoretical modeling and understanding of the van der Waals forces that hold together the 2D layers in bulk solids, as well as their excitonic properties and growth morphologies.
Abstract: The isolation of graphene in 2004 from graphite was a defining moment for the “birth” of a field: two-dimensional (2D) materials In recent years, there has been a rapidly increasing number of papers focusing on non-graphene layered materials, including transition-metal dichalcogenides (TMDs), because of the new properties and applications that emerge upon 2D confinement Here, we review significant recent advances and important new developments in 2D materials “beyond graphene” We provide insight into the theoretical modeling and understanding of the van der Waals (vdW) forces that hold together the 2D layers in bulk solids, as well as their excitonic properties and growth morphologies Additionally, we highlight recent breakthroughs in TMD synthesis and characterization and discuss the newest families of 2D materials, including monoelement 2D materials (ie, silicene, phosphorene, etc) and transition metal carbide- and carbon nitride-based MXenes We then discuss the doping and functionalization of 2
2,036 citations
TL;DR: The potential of MXenes for the photocatalytic degradation of organic pollutants in water, such as dye waste, is addressed, along with their promise as catalysts for ammonium synthesis from nitrogen.
Abstract: Transition metal carbides and nitrides (MXenes), a family of two-dimensional (2D) inorganic compounds, are materials composed of a few atomic layers of transition metal carbides, nitrides, or carbonitrides. Ti3C2, the first 2D layered MXene, was isolated in 2011. This material, which is a layered bulk material analogous to graphite, was derived from its 3D phase, Ti3AlC2 MAX. Since then, material scientists have either determined or predicted the stable phases of >200 different MXenes based on combinations of various transition metals such as Ti, Mo, V, Cr, and their alloys with C and N. Extensive experimental and theoretical studies have shown their exciting potential for energy conversion and electrochemical storage. To this end, we comprehensively summarize the current advances in MXene research. We begin by reviewing the structure types and morphologies and their fabrication routes. The review then discusses the mechanical, electrical, optical, and electrochemical properties of MXenes. The focus then turns to their exciting potential in energy storage and conversion. Energy storage applications include electrodes in rechargeable lithium- and sodium-ion batteries, lithium-sulfur batteries, and supercapacitors. In terms of energy conversion, photocatalytic fuel production, such as hydrogen evolution from water splitting, and carbon dioxide reduction are presented. The potential of MXenes for the photocatalytic degradation of organic pollutants in water, such as dye waste, is also addressed, along with their promise as catalysts for ammonium synthesis from nitrogen. Finally, their application potential is summarized.
1,201 citations
TL;DR: This book aims to provide a history of Tibet and its people from 1989 to 2002, a period chosen in order to explore its roots as well as specific cases up to and including the year in which descriptions of Tibetans in the region began to circulate.
Abstract: Ronan J. Smith , Paul J. King , Mustafa Lotya , Christian Wirtz , Umar Khan , Sukanta De , Arlene O’Neill , Georg S. Duesberg , Jaime C. Grunlan , Gregory Moriarty , Jun Chen , Jiazhao Wang , Andrew I. Minett , Valeria Nicolosi , and Jonathan N. Coleman *
1,037 citations