Tunable Rectifier Research Articles

Dynamic Variation of Rectification Observed in Supramolecular Mixed Mercaptoalkanoic Acid.

Functionality in molecular electronics relies on inclusion of molecular orbital energy level within a transmission window. This can be achieved by designing the active molecule with accessible energy levels or by widening the window. While many studies have adopted the first approach, the latter is challenging because defects in the active molecular component cause low breakdown voltages. Here, it is shown that control over the packing structure of monolayer via supramolecular mixing transforms an inert molecule into a highly tunable rectifier. Binary mixed monolayer composed of alkanethiolates with and without carboxylic acid head group as a proof of concept is formed via a surface-exchange reaction. The monolayer withstands high voltages up to |4.5 V| and shows a dynamic rectification-external bias relationship in magnitude and polarity. Sub-highest occupied molecular orbital (HOMO) levels activated by the widened transmission window account for these observations. This work demonstrates that simple supramolecular mixing can imbue new electrical properties in electro-inactive organic molecules.

An Anti‐Ambipolar Cryo‐Phototransistor

AbstractNovel anti‐ambipolar transistors (AATs) are gate tunable rectifiers with a marked potential for multi‐valued logic circuits. In this work, the optoelectronic applications of AATs in cryogenic conditions are studied, of which the AAT devices consist of vertically stacked p‐SnS and n‐ MoSe2 nanoflakes to form a type‐II staggered band alignment. An electrostatically tunable p‐SnS/n‐MoSe2 cryo‐phototransistor is presented with unique anti‐ambipolar characteristics and cryogenic‐enhanced optoelectronic performance. The cryo‐phototransistor exhibits a sharp and highly symmetric anti‐ambipolar transfer curve at 77 K with the peak‐to‐valley ratio of 103 operating under a low bias voltage of 1 V. The high cooling‐enhanced charge mobilities in the cryo‐phototransistor grant this AAT device remarkable photodetection capabilities. At 77 K, the p‐SnS/n‐MoSe2 cryo‐phototransistor, holding a broad photoresponse in the spectral range of 250−900 nm, demonstrates its high responsivity of 2 × 104 A W−1 and detectivity of 7.5 × 1013 Jones with the excitation at 532 nm. The high‐performance p‐SnS/n‐MoSe2 low‐dimensional phototransistor with low operating voltages at 77−150 K is eligible for optoelectronic applications in cryogenic environments. Furthermore, the cryo‐characteristics of this heterostructure can be further extended to design the mul‐tivalued logic circuits operated in cryogenic conditions.

Molecular Rectifiers with a Very High Rectification Ratio Enabled by Oxidative Damage in Double-Stranded DNA

In this work, we report a novel strategy to construct highly efficient molecular diodes using oxidatively damaged DNA molecules. Being exposed to several endogenous and exogenous events, DNA suffers from constant oxidative damage, leading to the oxidation of guanine to 8-oxoguanine (8oxoG). Here, we study the charge migration properties of native and oxidatively damaged DNA using a multiscale multiconfigurational methodology comprising molecular dynamics, density functional theory, and kinetic Monte Carlo simulations. We perform a comprehensive study to understand the effect of different concentrations and locations of 8oxoG in a dsDNA sequence on its charge-transport properties and find tunable rectifier properties having potential applications in molecular electronics such as molecular switches and molecular rectifiers. We also discover the negative differential resistance properties of the fully oxidized Drew-Dickerson sequence. The presence of 8oxoG guanine leads to the trapping of charge, thus operating as a charge sink, which reveals how oxidized guanine saves the rest of the genome from further oxidative damage.

A Multifunctional Device Based on Graphene/Silicon Heterojunction

Heterojunction devices based on two-dimensional materials have been widely studied in the fields of electronics and optoelectronics. As the complexity of the chip system increases, the ability to realize multi-function in a single device is increasingly in demand. Here, we propose a multifunctional device based on graphene/silicon heterojunction, which can operate in photodetection mode or tunable rectifier mode. The heterojunction barrier is tunable by the external electric field. The photodetection range covers ultraviolet to visible, and the responsivity can reach 51 A/W and 495 A/W at 266 nm and 532 nm while keeping the off-state current at a low level of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> A. With the control of the external electric field, the device can also function as a tunable rectifier to achieve three states: positive-pass, off, and negative-pass, which can be applied in signal processing and logic circuit. The multifunctional integrated device has potential in future optoelectronic logic applications while reducing the cost and the device footprint.

Half adder capabilities of a coupled quantum dot device

In this paper we demonstrate two realizations of a half adder based on a voltage-rectifying mechanism involving two Coulomb-coupled quantum dots. First, we examine the ranges of operation of the half adder’s individual elements, the AND and XOR gates, for a single rectifying device. It allows a switching between the two gates by a control voltage and thus enables a clocked half adder operation. The logic gates are shown to be reliably operative in a broad noise amplitude range with negligible error probabilities. Subsequently, we study the implementation of the half adder in a combined double-device consisting of two individually tunable rectifiers. We show that this double device allows a simultaneous operation of both relevant gates at once. The presented devices draw their power solely from electronic fluctuations and are therefore an advancement in the field of energy efficient and autonomous electronics.

Rectifying acoustic phonons

We propose an acoustic phonon rectifier, utilizing an array of triangular holes drilled in an elastically isotropic material. It is numerically confirmed that rectification of acoustic phonons occurs even in the frequency region with corresponding wavelength comparable to the dimensions of the scatterers. There is a threshold frequency, above which the rectification occurs. The threshold frequency depends on structural periodicity, which enables to realize a tunable rectifier.

Threshold-voltage tuning characteristics of all-organic electrochemical vertical rectifiers on flexible substrates

A printed all-organic electrochemical vertical tunable rectifier is demonstrated using a conducting polymer as the active material on a flexible plastic substrate. Solution processable poly(3,4-ethylenedioxythiophene) combined with poly(styrene sulfonic acid) (PEDOT:PSS) was coated on polyester film; the rectifier channel was patterned on the PEDOT:PSS film through directly writing technique without the need for masks, patterns, or dies. A vertically layered electrochemical cell was structured via printing and laminating processes to reduce driving voltages. The resulting rectifier is a three-terminal device; the functionality of threshold voltage tuning is realized by adjusting the potential difference within the electrochemical cell. The driving voltages are reduced significantly compared to rectifiers with lateral device architecture. In a single device, the threshold voltage is tunable between 0.16 and 1.0 V while a bias voltage is swept from 0.9 to 1.7 V.

Circuit design techniques for very low-voltage analog functional blocks using triple-tail cells

Novel circuit design techniques for very low-voltage analog functional blocks using triple-tail cells are presented. A triple-tail cell is operable on very low voltage because it possesses a very simple circuit structure, and it operates as a gain controllable differential amplifier and a tunable rectifier. It is very suitable for analog functional blocks, such as operational transconductance amplifiers (OTA's), four-quadrant analog multipliers, logarithmic intermediate-frequency (IF) amplifiers, and automatic gain control (AGC) amplifiers, to be realized using triple-tail cells with a small circuit scale. Therefore, a triple-tail cell is the most essential circuit for very low-voltage operation in signal processing. Furthermore, very low-voltage operation at a 1 V supply voltage and the fundamental characteristics of the basic circuits consisting of triple-tail cells, such a transconductance controllable OTA, four-quadrant analog multipliers, a logarithmic IF amplifier, and an AGC amplifier, were verified with transistor-arrays and discrete components on a breadboard.