159 research outputs found
Atomic-Layer-Deposited Al2O3 on Bi2Te3 for Topological Insulator Field-Effect Transistors
We report dual-gate modulation of topological insulator field-effect
transistors (TI FETs) made on Bi2Te3 thin flakes with integration of
atomic-layer-deposited (ALD) Al2O3 high-k dielectric. Atomic force microscopy
study shows that ALD Al2O3 is uniformly grown on this layer-structured channel
material. Electrical characterization reveals that the right selection of ALD
precursors and the related surface chemistry play a critical role in device
performance of Bi2Te3 based TI FETs. We realize both top-gate and bottom-gate
control on these devices, and the highest modulation rate of 76.1% is achieved
by using simultaneous dual gate control.Comment: 4 pages, 3 figure
Electron spin magnetism of zigzag graphene nanoribbon edge states
The electron spin states of zigzag graphene nanoribbon (ZGNR) edge play a pivotal role in the applications of graphene nanoribbons. However, the exact arrangements of the electron spins remain unclear to date. In this report, the electronic spin states of the ZGNR edge have been elucidated through a combination of quantum chemical investigation and previous electron spin resonance experiment observations. An alternating alpha and beta spin configuration of the unpaired electrons along the ZGNR edge is established in ambient condition without any external magnetic field, and the origin of the spin magnetism of the ZGNR edge is revealed. It paves a pathway for the understanding and design of graphene based electronic and spintronic devices. (C) 2014 AIP Publishing LLC
Synthesis and Characterization of 2D Atomic Layers
As electronic devices have continued to become smaller, a pressing need has developed for new technologies in order to surpass current size constraints. As such, 2-dimensional materials have become a topic of great interest in experimental device research. Monolayer black phosphorus, or phosphorene, is one such 2D material which shows significant potential as a p-type semiconductor. Phosphorene exhibits a number of unique and desirable electrical properties such as a layer-dependent band gap, high carrier mobility, and anisotropic conductivity. An investigation into optimal growth of black phosphorus, the precursor material to phosphorene, as well as characterization of phosphorene-based devices will be performed
MoS2 Nanoribbon Transistors: Transition from Depletion-mode to Enhancement-mode by Channel Width Trimming
We study the channel width scaling of back-gated MoS2
metal-oxide-semiconductor field-effect transistors (MOSFETs) from 2 {\mu}m down
to 60 nm. We reveal that the channel conductance scales linearly with channel
width, indicating no evident edge damage for MoS2 nanoribbons with widths down
to 60 nm as defined by plasma dry etching. However, these transistors show a
strong positive threshold voltage (VT) shift with narrow channel widths of less
than 200 nm. Our results also show that transistors with thinner channel
thicknesses have larger VT shifts associated with width scaling. Devices
fabricated on a 6 nm thick MoS2 crystal underwent the transition from
depletion-mode to enhancement-mode.Comment: 3 pages, 3 figures, to appear in IEEE Electron Device Letter
Continuous-wave and Transient Characteristics of Phosphorene Microwave Transistors
Few-layer phosphorene MOSFETs with 0.3-um-long gate and 15-nm-thick Al2O3
gate insulator was found to exhibit a forward-current cutoff frequency of 2 GHz
and a maximum oscillation frequency of 8 GHz after de-embedding for the
parasitic capacitance associated mainly with the relatively large probe pads.
The gate lag and drain lag of the transistor was found to be on the order of 1
us or less, which is consistent with the lack of hysteresis, carrier freeze-out
or persistent photoconductivity in DC characteristics. These results confirm
that the phosphorene MOSFET can be a viable microwave transistor for both
small-signal and large-signal applications.Comment: Accepted for oral presentation at IMS 201
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