1,266 research outputs found
Graphene field-effect transistors based on boron nitride gate dielectrics
Graphene field-effect transistors are fabricated utilizing single-crystal
hexagonal boron nitride (h-BN), an insulating isomorph of graphene, as the gate
dielectric. The devices exhibit mobility values exceeding 10,000 cm2/V-sec and
current saturation down to 500 nm channel lengths with intrinsic
transconductance values above 400 mS/mm. The work demonstrates the favorable
properties of using h-BN as a gate dielectric for graphene FETs.Comment: 4 pages, 8 figure
All CVD Boron Nitride Encapsulated Graphene FETs with CMOS Compatible Metal Edge Contacts
We report on the fabrication and characterization of field effect transistors
(FETs) based on chemical vapor deposited (CVD) graphene encapsulated between
few layer CVD boron nitride (BN) sheets with complementary metal oxide
semiconductor (CMOS) compatible nickel edge contacts. Non-contact Tera-hertz
time domain spectroscopy (THz-TDS) of large-area BN/graphene/BN (BN/G/BN)
stacks reveals average sheet conductivity >1 mS/sq and average mobility of 2500
cm/Vs. Improved output conductance is observed in direct current (DC)
measurements under ambient conditions, indicating potential for radio-frequency
(RF) applications. Moreover, we report a maximum voltage gain of 6 dB from a
low frequency signal amplifier circuit. RF characterization of the GFETs yields
an f x L product of 2.64 GHzm and an f x L
product of 5.88 GHzm. This study presents for the first time THz-TDS usage
in combination with other characterization methods for device performance
assessment on BN/G/BN stacks. The results serve as a step towards scalable, all
CVD 2D material-based FETs for CMOS compatible future nanoelectronic circuit
architectures.Comment: 6 page
Mechanical properties of freely suspended atomically thin dielectric layers of mica
We have studied the elastic deformation of freely suspended atomically thin
sheets of muscovite mica, a widely used electrical insulator in its bulk form.
Using an atomic force microscope, we carried out bending test experiments to
determine the Young's modulus and the initial pre-tension of mica nanosheets
with thicknesses ranging from 14 layers down to just one bilayer. We found that
their Young's modulus is high (190 GPa), in agreement with the bulk value,
which indicates that the exfoliation procedure employed to fabricate these
nanolayers does not introduce a noticeable amount of defects. Additionally,
ultrathin mica shows low pre-strain and can withstand reversible deformations
up to tens of nanometers without breaking. The low pre-tension and high Young's
modulus and breaking force found in these ultrathin mica layers demonstrates
their prospective use as a complement for graphene in applications requiring
flexible insulating materials or as reinforcement in nanocomposites.Comment: 9 pages, 5 figures, selected as cover of Nano Research, Volume 5,
Number 8 (2012
Inelastic Phonon Scattering in Graphene FETs
Inelastic phonon scattering in graphene field-effect transistors (FETs) is
studied by numerically solving the Boltzmann transport equation in three
dimensional real and phase spaces (x, kx, ky). A kink behavior due to ambipolar
transport agreeing with experiments is observed. While low field behavior has
previously been mostly attributed to elastic impurity scattering in earlier
studies, it is found in the study that even low field mobility is affected by
inelastic phonon scattering in recent graphene FET experiments reporting high
mobilities . As the FET is biased in the saturation regime, the average carrier
injection velocity at the source end of the device is found to remain almost
constant with regard to the applied gate voltage over a wide voltage range,
which results in significantly improved transistor linearity compared to what a
simpler model would predict. Physical mechanisms for good linearity are
explained, showing the potential of graphene FETs for analogue electronics
applications
Dielectric Breakdown in Chemical Vapor Deposited Hexagonal Boron Nitride
Insulating films are essential in multiple electronic devices because they can provide essential functionalities, such as capacitance effects and electrical fields. Two-dimensional (2D) layered materials have superb electronic, physical, chemical, thermal, and optical properties, and they can be effectively used to provide additional performances, such as flexibility and transparency. 2D layered insulators are called to be essential in future electronic devices, but their reliability, degradation kinetics, and dielectric breakdown (BD) process are still not understood. In this work, the dielectric breakdown process of multilayer hexagonal boron nitride (h-BN) is analyzed on the nanoscale and on the device level, and the experimental results are studied via theoretical models. It is found that under electrical stress, local charge accumulation and charge trapping/detrapping are the onset mechanisms for dielectric BD formation. By means of conductive atomic force microscopy, the BD event was triggered at several locations on the surface of different dielectrics (SiO2, HfO2, Al2O3, multilayer h-BN, and monolayer h-BN); BD-induced hillocks rapidly appeared on the surface of all of them when the BD was reached, except in monolayer h-BN. The high thermal conductivity of h-BN combined with the one-atom-thick nature are genuine factors contributing to heat dissipation at the BD spot, which avoids self-accelerated and thermally driven catastrophic BD. These results point to monolayer h-BN as a sublime dielectric in terms of reliability, which may have important implications in future digital electronic devices.Fil: Jiang, Lanlan. Soochow University; ChinaFil: Shi, Yuanyuan. Soochow University; China. University of Stanford; Estados UnidosFil: Hui, Fei. Soochow University; China. Massachusetts Institute of Technology; Estados UnidosFil: Tang, Kechao. University of Stanford; Estados UnidosFil: Wu, Qian. Soochow University; ChinaFil: Pan, Chengbin. Soochow University; ChinaFil: Jing, Xu. Soochow University; China. University of Texas at Austin; Estados UnidosFil: Uppal, Hasan. University of Manchester; Reino UnidoFil: Palumbo, FĂ©lix Roberto Mario. ComisiĂłn Nacional de EnergĂa AtĂłmica; Argentina. Universidad TecnolĂłgica Nacional; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Lu, Guangyuan. Chinese Academy of Sciences; RepĂşblica de ChinaFil: Wu, Tianru. Chinese Academy of Sciences; RepĂşblica de ChinaFil: Wang, Haomin. Chinese Academy of Sciences; RepĂşblica de ChinaFil: Villena, Marco A.. Soochow University; ChinaFil: Xie, Xiaoming. Chinese Academy of Sciences; RepĂşblica de China. ShanghaiTech University; ChinaFil: McIntyre, Paul C.. University of Stanford; Estados UnidosFil: Lanza, Mario. Soochow University; Chin
Insulators for 2D nanoelectronics: the gap to bridge
Nanoelectronic devices based on 2D materials are far from delivering their full theoretical performance potential due to the lack of scalable insulators. Amorphous oxides that work well in silicon technology have ill-defined interfaces with 2D materials and numerous defects, while 2D hexagonal boron nitride does not meet required dielectric specifications. The list of suitable alternative insulators is currently very limited. Thus, a radically different mindset with respect to suitable insulators for 2D technologies may be required. We review possible solution scenarios like the creation of clean interfaces, production of native oxides from 2D semiconductors and more intensive studies on crystalline insulators
MoS2 Dual-Gate MOSFET with Atomic-Layer-Deposited Al2O3 as Top-Gate Dielectric
We demonstrate atomic-layer-deposited (ALD) high-k dielectric integration on
two-dimensional (2D) layer-structured molybdenum disulfide (MoS2) crystals and
MoS2 dual-gate n-channel MOSFETs with ALD Al2O3 as top-gate dielectric. Our C-V
study of MOSFET structures shows good interface between 2D MoS2 crystal and ALD
Al2O3. Maximum drain currents using back-gates and top-gates are measured to be
7.07mA/mm and 6.42mA/mm at Vds=2V with a channel width of 3 {\mu}m, a channel
length of 9 {\mu}m, and a top-gate length of 3 {\mu}m. We achieve the highest
field-effect mobility of electrons using back-gate control to be 517 cm^2/Vs.
The highest current on/off ratio is over 10^8.Comment: submitted to IEEE Electron Device Letter
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