Exploiting the properties of two-dimensional crystals requires a mass production method able to produce heterostructures of arbitrary complexity on any substrate. Solution processing of graphene allows simple and low-cost techniques such as inkjet printing to be used for device fabrication. However, the available printable formulations are still far from ideal as they are either based on toxic solvents, have low concentration, or require time-consuming and expensive processing. In addition, none is suitable for thin-film heterostructure fabrication due to the re-mixing of different two-dimensional crystals leading to uncontrolled interfaces and poor device performance. Here, we show a general approach to achieve inkjet-printable, water-based, two-dimensional crystal formulations, which also provide optimal film formation for multi-stack fabrication. We show examples of all-inkjet-printed heterostructures, such as large-area arrays of photosensors on plastic and paper and programmable logic memory devices. Finally, in vitro dose-escalation cytotoxicity assays confirm the biocompatibility of the inks, extending their possible use to biomedical applications.

Articles you may be interested indc modulation in field-effect transistors operating under microwave irradiation for quantum readout J. Appl. Phys. 98, 044505 (2005); 10.1063/1.2007852 Microwave operation and modulation of a transistor laser Appl. Phys. Lett. 86, 131114 (2005); 10.1063/1.1889243Effect of signal modulated optical illumination on the Schrödinger wave function in a quantum well in a modulation doped field effect transistor and related device characteristics Resonant tunneling field-effect transistor based on wave function shape modulation in quantum wiresWe present a theoretical study of semiconductor T -structures which may exhibit transistor action based on quantum interference. The electron transmission through a semiconductor quantum wire can be controlled by an external gate voltage that modifies the penetration of the electron wavefunction in a lateral stub, affecting in this way its interference pattern. The structures are modeled as ideal two-dimensional electron waveguides and a tight-binding Green's function technique is used to compute the electron transmission and reflecti.on coefficients. The calculations show that relatively small changes in the stub length can induce strong variations in the electron transmission across the structure. Operation in the fundamental transverse mode appears to be important for applications. We also show that a bound state of purely geometrical origin nucleates at the intersection between waveguide and stub. The performance of the device can be improved by inserting additional stubs of slightly different lengths. Taking into account the applicable scaling rules, we give estimates of the experimental parameters that optimize the transmission characteristics and speed of operation ofthe proposed transistor. 3892

A theoretical study of quantum interference phenomena in a T-shaped semiconductor structure is presented. Transmission and reflection coefficients are computed by use of a tight-binding Green function technique. As expected, the results resemble the well-known solutions for the electromagnetic field in waveguides with the main difference that the penetration of the wave function of the electrons can be controlled by external voltages. We conclude that transistor action based on quantum interference should be observable in such structures, and we present general results for the functional dependences of the transmission coefficient which corresponds to a transconductance.

We show that shot noise in a resonant-tunneling diode biased in the negative differential resistance regions of the I-V characteristic is enhanced with respect to "full" shot noise. We provide experimental results showing a Fano factor of up to 6.6, and show that it is a dramatic effect caused by electronelectron interaction through the Coulomb force, enhanced by the particular shape of the density of states in the well. We also present numerical results from the proposed theory, which are in agreement with the experiment, demonstrating that the model accounts for physics relevant to the phenomenon.[S0031-9007(97)05143-0] PACS numbers: 73.40.Gk, 72.70. + m, 73.20.Dx Deviations from the purely poissonian shot noise (the so-called "full" shot noise) in mesoscopic devices and resonant tunneling structures have been the subject of growing interest in the last decade [1][2][3][4][5][6][7][8][9][10][11]. The main reason is that noise is a very sensitive probe of electron-electron interaction [12], because of both the Pauli principle and the Coulomb force, and provides information but obtainable from dc and ac characterization; furthermore, noise depends strongly on the details of device structure, so that the capability of modeling it in nanoscale devices implies and requires a deep understanding of the collective transport mechanisms of electrons.Almost all published theoretical and experimental studies have focused on the suppression of shot noise due to negative correlation between current pulses caused by single electrons traversing the device. Such correlation may be introduced by Pauli exclusion, which limits the density of electrons in phase space, and/or by Coulomb repulsion, depending on the details of the structure and on the dominant transport mechanism [6-8], and make the pulse distribution subpoissonian, leading to suppressed shot noise.In particular, for the case of resonant tunneling structures, several theoretical and experimental studies have appeared in the literature [2][3][4][5][6][7][8][9][10][11], assessing that the power spectral density of the noise current S in such devices may be suppressed down to half the "full" shot noise value S full 2qI, i.e., that associated with a purely poissonian process.In this Letter, we propose a theoretical model and show experimental evidence of the opposite behavior, that is, of enhanced shot noise with respect to S full , which is to be expected in resonant tunneling structures biased in the negative differential resistance region of the I-V characteristic. An attempt to model such phenomenon has been presented in Ref. [13].We shall show that in such a condition Coulomb interaction and the shape of the density of states in the well introduce positive correlation between consecutive current pulses, leading to a superpoissonian pulse distribution, which implies a superpoissonian shot noise.First, we shall show an intuitive physical picture of the phenomenon, then we shall express it in terms of a model for transport and noise in generic resonant tunneling stru...

A well-defined insulating layer is of primary importance in the fabrication of passive (e.g. capacitors) and active (e.g. transistors) components in integrated circuits. One of the most widely known 2-Dimensional (2D) dielectric materials is hexagonal boron nitride (hBN).Solution-based techniques are cost-effective and allow simple methods to be used for device fabrication. In particular, inkjet printing is a low-cost, non-contact approach, which also allows for device design flexibility, produces no material wastage and offers compatibility with almost any surface of interest, including flexible substrates.In this work we use water-based and biocompatible graphene and hBN inks to fabricate all-2D material and inkjet-printed capacitors. We demonstrate an areal capacitance of 2.0 ± 0.3 nF cm -2 for a dielectric thickness of ~3 µm and negligible leakage currents, averaged across more than 100 devices. This gives rise to a derived dielectric constant of 6.1 ± 1.7. The inkjet printed hBN dielectric has a breakdown field of 1.9 ± 0.3 MV cm -1 . Fully printed capacitors with sub-µm hBN layer thicknesses have also been demonstrated. The capacitors are then exploited in two fully printed demonstrators: a resistor-capacitor (RC) low-pass filter and a graphene-based field effect transistor.