Optical Properties Of Two Dimensional Semiconductors

Two dimensional materials (2D) have become a huge research focus in recent history due to the interesting properties and phenomena that occur with reduced dimensionality. Additionally, the reduced size of these materials, the plethora of different properties available in the 2D arsenal, and the ability to relatively easily combine different 2D materials makes them extremely promising for nanodevices and future computing architectures. Here, we investigate the optical properties of two different 2D semiconductors, germanane and transition metal dichalcogenides (TMDs).

Learn about the most recent advances in 2D materials with this comprehensive and accessible text. Providing all the necessary materials science and physics background, leading experts discuss the fundamental properties of a wide range of 2D materials, and their potential applications in electronic, optoelectronic and photonic devices. Several important classes of materials are covered, from more established ones such as graphene, hexagonal boron nitride, and transition metal dichalcogenides, to new and emerging materials such as black phosphorus, silicene, and germanene. Readers will gain an in-depth understanding of the electronic structure and optical, thermal, mechanical, vibrational, spin and plasmonic properties of each material, as well as the different techniques that can be used for their synthesis. Presenting a unified perspective on 2D materials, this is an excellent resource for graduate students, researchers and practitioners working in nanotechnology, nanoelectronics, nanophotonics, condensed matter physics, and chemistry.

In-depth overview of two-dimensional semiconductors from theoretical studies, properties to emerging applications! Two-dimensional (2D) materials have attracted enormous attention due to their exotic properties deriving from their ultrathin dimensions. 2D materials, such as graphene, transition metal dichalcogenides, transition metal oxides, black phosphorus and boron nitride, exhibit versatile optical, electronic, catalytic and mechanical properties, thus can be used in a wide range of applications, including electronics, optoelectronics and optical applications. Two-Dimensional Semiconductors: Synthesis, Physical Properties and Applications provides an in-depth view of 2D semiconductors from theoretical studies, properties to applications, taking into account the current state of research and development. It introduces various preparation methods and describes in detail the physical properties of 2D semiconductors including 2D alloys and heterostructures. The covered applications include, but are not limited to, field-effect transistors, spintronics, solar cells, photodetectors, light-emitting diode, sensors and bioelectronics. Highly topical: 2D materials are a rapidly advancing field that attracts increasing attention Concise overview: covers theoretical studies, preparation methods, physical properties, potential applications, the challenges and opportunities Application oriented: focuses on 2D semiconductors that can be used in various applications such as field-effect transistors, solar cells, sensors and bioelectronics Highly relevant: newcomers as well as experienced researchers in the field of 2D materials will benefit from this book Two-Dimensional Semiconductors: Synthesis, Physical Properties and Applications is written for materials scientists, semiconductor and solid state physicists, electrical engineers, and readers working in the semiconductor industry.

This volume contains the Proceedings of the NATO Advanced Research Workshop on "Growth and Optical Properties of Wide Gap II-VI Low Dimensional Semiconductors", held from 2 - 6 August 1988 in Regensburg, Federal Republic of Germany, under the auspices of the NATO International Scientific Exchange Programme. Semiconducting compounds formed by combining an element from column II of the periodic table with an element from column VI (so called II-VI Semiconductors) have long promised many optoelectronic devices operating in the visible region of the spectrum. However, these materials have encountered numerous problems including: large number of defects and difficulties in obtaining p- and n-type doping. Advances in new methods of material preparation may hold the key to unlocking the unfulfilled promises. During the workshop a full session was taken up covering the prospects for wide-gap II-VI Semiconductor devices, particularly light emitting ones. The growth of bulk materials was reviewed with the view of considering II-VI substrates for the novel epitaxial techniques such as MOCVD, MBE, ALE, MOMBE and ALE-MBE. The controlled introduction of impurities during non-equilibrium growth to provide control of the doping type and conductivity was emphasized.

Two-dimensional (2D) materials have recently caught much attention due to their exceptional properties and their potential applications in opto-electronics. Graphene, transition metal dichalcogenides (TMDs), and black phosphorus (b-P) are some of the main candidates from the 2D material family that show great promise in their ability to have properties such as high mobility, anisotropy, desirable band gap, and many more. Here, we'll discuss some of the history of these 2D semiconductors and some of the properties that make them unique and interesting. This will be focusing on the electrical and opto-electrical properties of 2D semiconductors in measurements conducted during my graduate research studies. Some of these measurements include 2-terminal and 4-terminal contact configurations, photoconductivity, transport, photoluminescence, and Raman spectroscopy. The 2D semiconductors used in these experiments are post-graphene such as TMDs, post transition metals, and b-P. The photoconductivity was measured on few-layered WSe$_{2}$ field-effect transistors (FETs) using both 2-terminal and 4-terminal configurations under 532~nm laser source. For an incident laser power of 248 nW, we extracted 18 A/W and $\sim$4000\% for the two-terminal responsivity (R) and an external quantum efficiency (EQE) respectively, when a bias voltage $V_{ds}$ = 1 V and a gate voltage $V_{bg}$ = 10 V were applied to the sample. R and EQE saw an increase by 370\% to $\sim$85 A/W and $\sim$20000\% respectively, when using a four-terminal configuration. The photogating effect was observed in our few-layered (3-4 layers) ReS$_{2}$ FETs in which varying the incident optical power shifted the FETs' threshold voltage. The photogating effect produced a significant gain in the electrical response of the FETs to incident light as measured by R and EQE. We obtained a maximum R of 45 A/W corresponding to an EQE of $\sim$10500\% in a 4-terminal measurement of the photoconductivity in the ON-state. We attribute both the photogating and the observed gain to the influence of charge traps. We also presented a detailed study on the Raman spectra and on the temperature dependence of the electrical transport properties of arsenic-doped black phosphorus (b-AsP) with an As fraction of x = 0.25. Field-effect transistors fabricated from few-layered b-AsP exfoliated onto Si/SiO$_{2}$ substrates exhibited hole-doped like conduction with a room temperature ON/OFF current ratio of $\sim$10$^{3}$ and an intrinsic field-effect mobility approaching $\sim$300 cm$^{2}$V$^{-1}$s$^{-1}$ at 300 K which increases up to 600 cm$^{2}$V$^{-1}$s$^{-1}$ at 100 K when measured via a 4-terminal method. The ON to OFF current ratio is observed to increase up to 10$^{5}$ at 4 K. Similarly to pristine b-P, its transport properties revealed a high anisotropy between armchair and zig-zag directions. Photoluminescence (PL) and transport measurements were conducted on vanadium-doped InSe FETs using 2-terminal configuration under 532 nm and 785 nm excitation. Low temperature measurements were also studied ranging from 295 K to $\sim$13 K in a cryostat. Transport measurements showed little to no current when drain-source and back-gate voltages were applied and under low temperature. Low temperature PL showed blue-shifted peaks at T $>$ 50 K and red-shifted peaks at T $

2D Materials for Nanophotonics presents a detailed overview of the applications of 2D materials for nanophotonics, covering the photonic properties of a range of 2D materials including graphene, 2D phosphorene and MXenes, and discussing applications in lighting and energy storage. This comprehensive reference is ideal for readers seeking a detailed and critical analysis of how 2D materials are being used for a range of photonic and optical applications. Outlines the major photonic properties in a variety of 2D materials Demonstrates major applications in lighting and energy storage Explores the challenges of using 2D materials in photonics

This volume contains the Proceedings of the NATO Advanced Research Workshop on "Optical Properties of Narrow-Gap Low-Dimensional Structures", held from July 29th to August 1st, 1986, in St. Andrews, Scotland, under the auspices of the NATO International Scientific Exchange Program. The workshop was not limited to optical properties of narrow-gap semiconductor structures (Part III). Sessions on, for example, the growth methods and characterization of III-V, II-VI, and IV-VI materials, discussed in Part II, were an integral part of the workshop. Considering the small masses of the carriers in narrow-gap low dimensional structures (LOS), in Part I the enhanced band mixing and magnetic field effects are explored in the context of the envelope function approximation. Optical nonlinearities and energy relaxation phenomena applied to the well-known systems of HgCdTe and GaAs/GaAIAs, respectively, are reviewed with comments on their extension to narrow gap LOS. The relevance of optical observations in quantum transport studies is illustrated in Part IV. A review of devices based on epitaxial narrow-gap materials defines a frame of reference for future ones based on two-dimensional narrow-gap semiconductors; in addition, an analysis of the physics of quantum well lasers provides a guide to relevant parameters for narrow-gap laser devices for the infrared (Part V). The roles and potentials of special techniques are explored in Part VI, with emphasis on hydrostatic pressure techniques, since this has a pronounced effect in small-mass, narrow-gap, non-parabolic structures.

For the most part of this work, we study the effects of focused ion beam implantation in InGaAs/GaAs quantum well structures.