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You searched for +publisher:"EPFL" +contributor:("Kis, Andras"). Showing records 1 – 2 of 2 total matches.

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EPFL

1. Lembke, Dominik Sebastian. Contacts and Environmental Effects in Two-Dimensional MoS2 Field-Effect Transistors.

Degree: 2014, EPFL

Two-dimensional (2D) semiconductors such as single- and few-layer molybdenum disulphide(MoS2) are promising building blocks for prospect flexible, transparent and low power electronics. Due to an electronic bandgap of the order of ~1.8 eV and atomic-scale tenuity of 6.5 Å, field-effect transistors (FETs) based on single-layer MoS2 exhibit high current Ion/Ioff-ratios and low power dissipation. Encapsulating single-layerMoS2 within a dielectric layer protects it from exposure to ambient air and improves device performance. By investigating the performance limits of such devices we demonstrate that they can reproducibly sustain several 100 µA/µm, saturate at high bias and exhibit break down current densities 50× larger than Cu. In addition, we investigate high-frequency operation of high-performance MoS2 FETs based on one- to few-layers. They exhibit current-, power- and voltage-gain in the GHz-range. Improving our understanding of contacts formed between metals and 2D semiconductors is important for the advancement of this technology because Schottky barriers impede device performances. The common assumption when modeling these contacts is that the thermionic emission model for a three-dimensional system is valid also in 2D. Here, we show that the understanding of 2D semiconductor/metal junctions can be improved by considering imageforce barrier-lowering and neglecting band bending at the interface. With this modifications, we can reproduce the output characteristics of 2D MoS2 FETs with excellent accuracy. The model is applicable over the whole range of investigated parameters such as temperature, doping and applied bias. While single-layer MoS2 attracted interest due to its broken inversion symmetry and spin/valley coupling, few-layer MoS2 is considered a more viable option for technological applications where its higher mobility and lower contact resistance offer an advantage. However, so far it remains unclear whether few-layers are intrinsically superior or if the difference is due to environmental effects. Here, we provide a systematic comparison of the field-effect mobility in single-, double- and trilayer MoS2 after thorough in-situ annealing. It shows that a single-layer exhibits the highest mobilities, while it is most sensitive to ambient air. In conclusion, this thesis offers important contributions towards the understanding of the performance limits, Schottky barrier height and field-effect mobility in encapsulated and bare 2D MoS2. The presented results support the feasibility of novel flexible, transparent and low power electronics based on this material. Advisors/Committee Members: Kis, Andras.

Subjects/Keywords: nanoelectronics; two-dimensional (2D) material; field-effect transistor (FET); transition metal dichalcogenide (TMDC); Molybdenum disulphide (MoS2); dielectric; mobility; Schottky barrier; saturation; breakdown

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Lembke, D. S. (2014). Contacts and Environmental Effects in Two-Dimensional MoS2 Field-Effect Transistors. (Thesis). EPFL. Retrieved from http://infoscience.epfl.ch/record/203795

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Lembke, Dominik Sebastian. “Contacts and Environmental Effects in Two-Dimensional MoS2 Field-Effect Transistors.” 2014. Thesis, EPFL. Accessed August 22, 2019. http://infoscience.epfl.ch/record/203795.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Lembke, Dominik Sebastian. “Contacts and Environmental Effects in Two-Dimensional MoS2 Field-Effect Transistors.” 2014. Web. 22 Aug 2019.

Vancouver:

Lembke DS. Contacts and Environmental Effects in Two-Dimensional MoS2 Field-Effect Transistors. [Internet] [Thesis]. EPFL; 2014. [cited 2019 Aug 22]. Available from: http://infoscience.epfl.ch/record/203795.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Lembke DS. Contacts and Environmental Effects in Two-Dimensional MoS2 Field-Effect Transistors. [Thesis]. EPFL; 2014. Available from: http://infoscience.epfl.ch/record/203795

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


EPFL

2. Bertolazzi, Simone. Charge-transport properties of monolayer MoS2 at the interface with dielectric materials.

Degree: 2015, EPFL

Two-dimensional (2D) semiconductors, consisting of single-sheets of layered transition metal dichalcogenides (TMD), are attracting enormous interest from both fundamental science and technology. Monolayer molybdenum disulfide (MoS2), a typical example from this class of materials, is currently under intense research investigation because its direct band gap, atomic-scale thickness and mechanical flexibility could enable a wide range of novel technological applications, such as low-power flexible/transparent electronics, displays and wearable sensors. Critical to all these applications are the material mechanical strength, the mobility of charge-carriers in the 2D semiconductor and its interaction with the surrounding environment. This thesis describes experimental research conducted on these critical aspects and shows a proof-of-concept device application based on heterostructures of MoS2 and graphene. The main goal of the research was to assess experimentally the potential of monolayer MoS2 for application in flexible electronics. The thesis is based on three papers. The first paper describes the measurements of the in-plane stiffness and breaking strength of free-standing membranes of monolayer MoS2. Nanoindentation experiments were performed with the tip of an atomic force microscope (AFM) to extract the material's Young's modulus (E ~ 270 GPa) and breaking strength (σmax ~ 23 GPa). Breaking occurred at maximum internal strain εint ~ 11%, which indicates that monolayer MoS2 is suitable for integration on flexible plastic substrates. The second paper represents the core work of this thesis. It explores the charge transport properties of monolayer MoS2 supported by different dielectric substrates, such as thin polymer films of parylene, atomically flat sapphire and 2D sheets of hexagonal boron nitride (h-BN). It was found that substrate surface corrugations do not represent a major limit to charge-carrier mobility in monolayer MoS2, which seems at this stage dominated by impurities and material's defects. Field-effect transistors with mobility ~ 100 cm2/Vs and on/off current ratio Ion/Ioff > 105 were successfully integrated on parylene substrates, whose root-mean-square roughness Rq can be more than two times larger than the thickness of the transistor channel itself. Because parylene is also a flexible material, this work showed a viable method for the realization of high-mobility and high performance flexible devices based on 2D semiconductors. Finally, the third paper describes a flash-memory cell fabricated using monolayer MoS2/graphene heterostructures and dielectric layers of HfO2 grown by atomic layer deposition (ALD). The architecture of the device resembles that of a floating-gate transistor. Monolayer MoS2 acts as the transistor channel, graphene electrodes are used to collect and inject the charge carriers, and a piece of multilayer graphene serves as ultrathin charge trapping layer. In this paper, it was shown that graphene contacts to monolayer MoS2 result in ohmic-like current-voltage… Advisors/Committee Members: Kis, Andras.

Subjects/Keywords: Two-dimensional (2D) materials; transition metal dichalcogenides; molybdenum disulfide (MoS2); field-effect transistors; mechanical properties; dielectrics; flash memory

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Bertolazzi, S. (2015). Charge-transport properties of monolayer MoS2 at the interface with dielectric materials. (Thesis). EPFL. Retrieved from http://infoscience.epfl.ch/record/207620

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Bertolazzi, Simone. “Charge-transport properties of monolayer MoS2 at the interface with dielectric materials.” 2015. Thesis, EPFL. Accessed August 22, 2019. http://infoscience.epfl.ch/record/207620.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Bertolazzi, Simone. “Charge-transport properties of monolayer MoS2 at the interface with dielectric materials.” 2015. Web. 22 Aug 2019.

Vancouver:

Bertolazzi S. Charge-transport properties of monolayer MoS2 at the interface with dielectric materials. [Internet] [Thesis]. EPFL; 2015. [cited 2019 Aug 22]. Available from: http://infoscience.epfl.ch/record/207620.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Bertolazzi S. Charge-transport properties of monolayer MoS2 at the interface with dielectric materials. [Thesis]. EPFL; 2015. Available from: http://infoscience.epfl.ch/record/207620

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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