15,520 research outputs found
Controlled Synthesis of Organic/Inorganic van der Waals Solid for Tunable Light-matter Interactions
Van der Waals (vdW) solids, as a new type of artificial materials that
consist of alternating layers bonded by weak interactions, have shed light on
fascinating optoelectronic device concepts. As a result, a large variety of vdW
devices have been engineered via layer-by-layer stacking of two-dimensional
materials, although shadowed by the difficulties of fabrication. Alternatively,
direct growth of vdW solids has proven as a scalable and swift way, highlighted
by the successful synthesis of graphene/h-BN and transition metal
dichalcogenides (TMDs) vertical heterostructures from controlled vapor
deposition. Here, we realize high-quality organic and inorganic vdW solids,
using methylammonium lead halide (CH3NH3PbI3) as the organic part (organic
perovskite) and 2D inorganic monolayers as counterparts. By stacking on various
2D monolayers, the vdW solids behave dramatically different in light emission.
Our studies demonstrate that h-BN monolayer is a great complement to organic
perovskite for preserving its original optical properties. As a result,
organic/h-BN vdW solid arrays are patterned for red light emitting. This work
paves the way for designing unprecedented vdW solids with great potential for a
wide spectrum of applications in optoelectronics
Interface Dipole : Effects on Threshold Voltage and Mobility for both Amorphous and Poly-crystalline Organic Field Effect Transistors
We report a detailed comparison on the role of a self-assembled monolayer
(SAM) of dipolar molecules on the threshold voltage and charge carrier mobility
of organic field-effect transistor (OFET) made of both amorphous and
polycrystalline organic semiconductors. We show that the same relationship
between the threshold voltage and the dipole-induced charges in the SAM holds
when both types of devices are fabricated on strictly identical base
substrates. Charge carrier mobilities, almost constant for amorphous OFET, are
not affected by the dipole in the SAMs, while for polycrystalline OFET
(pentacene) the large variation of charge carrier mobilities is related to
change in the organic film structure (mostly grain size).Comment: Full paper and supporting informatio
Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric.
Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ∼30 cm(2) V(-1) s(-1), on/off ratio of 10(3)-10(4), switching current >100 μA, transconductance >50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays
Organic Single-Crystal Field-Effect Transistors
We present an overview of recent studies of the charge transport in the field
effect transistors on the surface of single crystals of organic
low-molecular-weight materials. We first discuss in detail the technological
progress that has made these investigations possible. Particular attention is
devoted to the growth and characterization of single crystals of organic
materials and to different techniques that have been developed for device
fabrication. We then concentrate on the measurements of the electrical
characteristics. In most cases, these characteristics are highly reproducible
and demonstrate the quality of the single crystal transistors. Particularly
noticeable are the small sub-threshold slope, the non-monotonic temperature
dependence of the mobility, and its weak dependence on the gate voltage. In the
best rubrene transistors, room-temperature values of as high as 15
cm/Vs have been observed. This represents an order-of-magnitude increase
with respect to the highest mobility previously reported for organic thin film
transistors. In addition, the highest-quality single-crystal devices exhibit a
significant anisotropy of the conduction properties with respect to the
crystallographic direction. These observations indicate that the field effect
transistors fabricated on single crystals are suitable for the study of the
\textit{intrinsic} electronic properties of organic molecular semiconductors.
We conclude by indicating some directions in which near-future work should
focus to progress further in this rapidly evolving area of research.Comment: Review article, to appear in special issue of Phys. Stat. Sol. on
organic semiconductor
Tactile sensing chips with POSFET array and integrated interface electronics
This work presents the advanced version of novel POSFET (Piezoelectric Oxide Semiconductor Field Effect Transistor) devices based tactile sensing chip. The new version of the tactile sensing chip presented here comprises of a 4 x 4 array of POSFET touch sensing devices and integrated interface electronics (i.e. multiplexers, high compliance current sinks and voltage output buffers). The chip also includes four temperature diodes for the measurement of contact temperature. Various components on the chip have been characterized systematically and the overall operation of the tactile sensing system has been evaluated. With new design the POSFET devices have improved performance (i.e. linear response in the dynamic contact forces range of 0.01–3N and sensitivity (without amplification) of 102.4 mV/N), which is more than twice the performance of their previous implementations. The integrated interface electronics result in reduced interconnections which otherwise would be needed to connect the POSFET array with off-chip interface electronic circuitry. This research paves the way for CMOS (Complementary Metal Oxide Semiconductor) implementation of full on-chip tactile sensing systems based on POSFETs
Sensing with FETs - once, now and future
In this paper a short overview is given of the several FET-based sensor devices and the operational principle of the ISFET is summarized. Some of the shortcomings of the FET sensors were circumvented by an alternative operational mode, resulting in a device capable of acid/base concentration determination by coulometric titrant generation as well as in an original pH-static enzyme sensor. A more recent example is presented in which the ISFET is used for the on-line monitoring of fermentation processes. Future research is directed towards direct covalent coupling of organic monolayers on the silicon itself. In addition, the field-effect can be applied to the so-called semiconducting nanowire devices, ultimately making single molecule detection of charged species possible
Hole mobility in organic single crystals measured by a "flip-crystal" field-effect technique
We report on single crystal high mobility organic field-effect transistors
(OFETs) prepared on prefabricated substrates using a "flip-crystal" approach.
This method minimizes crystal handling and avoids direct processing of the
crystal that may degrade the FET electrical characteristics. A chemical
treatment process for the substrate ensures a reproducible device quality. With
limited purification of the starting materials, hole mobilities of 10.7, 1.3,
and 1.4 cm^2/Vs have been measured on rubrene, tetracene, and pentacene single
crystals, respectively. Four-terminal measurements allow for the extraction of
the "intrinsic" transistor channel resistance and the parasitic series contact
resistances. The technique employed in this study shows potential as a general
method for studying charge transport in field-accumulated carrier channels near
the surface of organic single crystals.Comment: 26 pages, 7 figure
Disorder engineering and conductivity dome in ReS2 with electrolyte gating
Atomically thin rhenium disulphide (ReS2) is a member of the transition metal
dichalcogenide (TMDC) family of materials characterized by weak interlayer
coupling and a distorted 1T structure. Here, we report on the electrical
transport study of mono- and multilayer ReS2 with polymer electrolyte gating.
We find that the conductivity of monolayer ReS2 is completely suppressed at
high carrier densities, an unusual feature unique to monolayers, making ReS2
the first example of such a material. While thicker flakes of ReS2 also exhibit
a conductivity dome and an insulator-metal-insulator sequence, they do not show
a complete conductivity suppression at high doping densities. Using dual-gated
devices, we can distinguish the gate-induced doping from the electrostatic
disorder induced by the polymer electrolyte itself. Theoretical calculations
and a transport model indicate that the observed conductivity suppression can
be explained by a combination of a narrow conduction band and Anderson
localization due to electrolyte-induced disorder.Comment: Submitted versio
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