arXiv subjects

Ariel Ismach

Publications and source records attributed to Ariel Ismach.

6 recordsLinked to original sources

arXiv2023

Edge-based 2D alpha-In2Se3-MoS2 ferroelectric field effect device

Heterostructures based on two dimensional (2D) materials offer the possibility to achieve synergistic functionalities which otherwise remain secluded by their individual counterparts. Herein ferroelectric polarization switching in alpha-In2Se3 has been utilized to engineer multilevel non-volatile conduction states in partially overlapping alpha-In2Se3-MoS2 based ferroelectric semiconducting field effect device. In particular, we demonstrate how the intercoupled ferroelectric nature of alpha-In2Se3 allows to non-volatilely switch between n-i and n-i-n type junction configurations based on a novel edge state actuation mechanism, paving the way for sub-nanometric scale non-volatile device miniaturization. Furthermore the induced asymmetric polarization enables enhanced photogenerated carriers separation resulting in extremely high photoresponse of 1275 AW-1 in the visible range and strong non-volatile modulation of the bright A- and B- excitonic emission channels in the overlaying MoS2 monolayer. Our results show significant potential to harness the switchable polarization in partially overlapping alpha-In2Se3-MoS2 based FeFETs to engineer multimodal non-volatile nanoscale electronic and optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2020

Large-Scale and Robust Multifunctional Vertically-Aligned MoS$_2$ Photo-Memristors

Memristive devices have drawn considerable research attention due to their potential applications in non-volatile memory and neuromorphic computing. The combination of resistive switching devices with light-responsive materials is considered a novel way to integrate optical information with electrical circuitry. On the other hand, 2D materials have attracted substantial consideration thank to their unique crystal structure, as reflected in their chemical and physical properties. Although not the major focus, van der Waals solids were proven to be potential candidates in memristive devices. In this scheme, the majority of the resistive switching devices were implemented on planar flakes, obtained by mechanical exfoliation. Here we utilize a facile and robust methodology to grow large-scale vertically aligned MoS$_2$ (VA-MoS$_2$) films on standard silicon substrates. Memristive devices with the structure silver/VA-MoS$_2$/Si are shown to have low set-ON voltages (<0.5V), large-retention times ($>2\times10^4$ s) and high thermal stability (up to 350 $^\circ$C). The proposed memristive device also exhibits long term potentiation / depression (LTP/LTD) and photo-active memory states. The large-scale fabrication, together with the low operating voltages, high thermal stability, light-responsive behaviour and long-term potentiation/depression, makes this approach very appealing for real-life non-volatile memory applications.

physics.app-ph↗

arXiv2020

Growth-Etch Metal-Organic Chemical Vapor Deposition Approach of WS2 Atomic-Layers

Metal organic chemical vapor deposition (MOCVD) is one of the main methodologies used for thin film fabrication in the semiconductor industry today and is considered one of the most promising routes to achieve large-scale and high-quality 2D transition metal dichalcogenides (TMDCs). However, if not taken special measures, MOCVD suffers from some serious drawbacks, such as small domain size and carbon contamination, resulting in poor optical and crystal quality, which may inhibit its implementation for the large-scale fabrication of atomic-thin semiconductors. Here we present a Growth-Etch MOCVD (GE-MOCVD) methodology, in which a small amount of water vapor is introduced during the growth, while the precursors are delivered in pulses. The evolution of the growth as a function of the amount of water vapor, the number and type of cycles and the gas composition is described. We show a significant domain size increase is achieved relative to our conventional process. The improved crystal quality of WS2 (and WSe2) domains was demonstrated by means of Raman spectroscopy, photoluminescence (PL) spectroscopy and HRTEM studies. Moreover, time-resolved PL studies show very long exciton lifetimes, comparable to those observed in mechanically exfoliated flakes. Thus, the GE-MOCVD approach presented here may facilitate their integration into a wide range of applications.

physics.app-ph↗

arXiv2014

Mesoscale Imperfections in MoS2 Atomic Layers Grown by Vapor Transport Technique

The success of isolating small flakes of atomically thin layers through mechanical exfoliation has triggered enormous research interest in graphene and other two-dimensional materials. For device applications, however, controlled large-area synthesis of highly crystalline monolayers with a low density of electronically active defects is imperative. Here, we demonstrate the electrical imaging of dendritic ad-layers and grain boundaries in monolayer molybdenum disulfide (MoS2) grown by vapor transport technique using microwave impedance microscopy. The micrometer-sized precipitates in our films, which appear as a second layer of MoS2 in conventional height and optical measurements, show 2 orders of magnitude higher conductivity than that of the single layer. The zigzag grain boundaries, on the other hand, are shown to be more resistive than the crystalline grains, consistent with previous studies. Our ability to map the local electrical properties in a rapid and nondestructive manner is highly desirable for optimizing the growth process of large-scale MoS2 atomic layers.

cond-mat.mtrl-sci↗

arXiv2013

Non-destructive and Rapid Evaluation of CVD Graphene by Dark Field Optical Microscopy

Non-destructive and rapid evaluation of graphene directly on the growth substrate (Cu foils) by dark field (DF) optical microscopy is demonstrated. Without any additional treatment, graphene on Cu foils with various coverages can be quickly identified by DF imaging immediately after chemical vapor deposition growth with contrast comparable to scanning electron microscopy. The improved contrast of DF imaging compared to bright field optical imaging was found to be due to Rayleigh scattering of light by the copper steps beneath graphene. Indeed, graphene adlayers are readily distinguished, due to the different height of copper steps beneath graphene regions of different thickness.

cond-mat.mtrl-sci↗

arXiv2012

Fermi velocity engineering in graphene by substrate modification

The Fermi velocity is one of the key concepts in the study of a material, as it bears information on a variety of fundamental properties. Upon increasing demand on the device applications, graphene is viewed as a prototypical system for engineering Fermi velocity. Indeed, several efforts have succeeded in modifying Fermi velocity by varying charge carrier concentration. Here we present a powerful but simple new way to engineer Fermi velocity while holding the charge carrier concentration constant. We find that when the environment embedding graphene is modified, the Fermi velocity of graphene is (i) inversely proportional to its dielectric constant, reaching ~2.5$\times10^6$ m/s, the highest value for graphene on any substrate studied so far and (ii) clearly distinguished from an ordinary Fermi liquid. The method demonstrated here provides a new route toward Fermi velocity engineering in a variety of two-dimensional electron systems including topological insulators.

cond-mat.mes-hall↗