Quantum-dot transistors create a printable electronics

Researchers at Los Alamos National Laboratory and their collaborators from the University of California, Irvine have created fundamental electronic building blocks out of tiny structures known as quantum dots and used them to assemble functional logic circuits.

Photo
By depositing gold (Au) and Indium (In) contacts, researchers create two crucial types of quantum dot transistors on the same substrate, opening the door to a host of innovative electronics.
Source: Los Alamos National Laboratory

The innovation promises a cheaper and manufacturing-friendly approach to complex electronic devices that can be fabricated in a chemistry laboratory via simple, solution-based techniques, and offer long-sought components for a host of innovative devices. “Potential applications of the new approach to electronic devices based on non-toxic quantum dots include printable circuits, flexible displays, lab-on-a-chip diagnostics, wearable devices, medical testing, smart implants, and biometrics,” said Victor Klimov, a physicist specializing in semiconductor nanocrystals at Los Alamos.

For decades, microelectronics has relied on extra-high purity silicon processed in a specially created clean-room environment. Recently, silicon-based microelectronics has been challenged by several alternative technologies that allow for fabricating complex electronic circuits outside a clean room, via inexpensive, readily accessible chemical techniques. Colloidal semiconductor nanoparticles made with chemistry methods in much less stringent environments are one such emerging technology. Due to their small size and unique properties directly controlled by quantum mechanics, these particles are dubbed quantum dots.

A colloidal quantum dot consists of a semiconductor core covered with organic molecules. As a result of this hybrid nature, they combine the advantages of well-understood traditional semiconductors with the chemical versatility of molecular systems. These properties are attractive for realizing new types of flexible electronic circuits that could be printed onto virtually any surface including plastic, paper, and even human skin. This capability could benefit numerous areas including consumer electronics, security, digital signage and medical diagnostics.

A key element of electronic circuitry is a transistor that acts as a switch of electrical current activated by applied voltage. Usually transistors come in pairs of n- and p-type devices that control flows of negative and positive electrical charges, respectively. Such pairs of complementary transistors are the cornerstone of the modern CMOS (complementary metal oxide semiconductor) technology, which enables microprocessors, memory chips, image sensors and other electronic devices.

The first quantum dot transistors were demonstrated almost two decades ago. However, integrating complementary n- and p-type devices within the same quantum dot layer remained a long-standing challenge. In addition, most of the efforts in this area have focused on nanocrystals based on lead and cadmium. These elements are highly toxic heavy metals, which greatly limits practical utility of the demonstrated devices.

The researchers have demonstrated that by using copper indium selenide (CuInSe2) quantum dots devoid of heavy metals they were able to address both the problem of toxicity and simultaneously achieve straightforward integration of n- and p-transistors in the same quantum dot layer. As a proof of practical utility of the developed approach, they created functional circuits that performed logical operations.

The innovation that Klimov and colleagues are presenting in their new paper allows them to define p- and n-type transistors by applying two different types of metal contacts (gold and indium, respectively). They completed the devices by depositing a common quantum dot layer on top of the pre-patterned contacts. “This approach permits straightforward integration of an arbitrary number of complementary p- and n-type transistors into the same quantum dot layer prepared as a continuous, un-patterned film via standard spin-coating,” said Klimov.

The research was published in Nature Communications.

Subscribe to our newsletter

Related articles

Using smartwatch to control insulin production

Using smartwatch to control insulin production

Researchers have developed a gene switch that can be operated with the green LED light emitted by commercial smartwatches.

Wearables can help predict blood test results

Wearables can help predict blood test results

Smartwatches and other wearable devices may be used to sense illness, dehydration and even changes to the red blood cell count.

Tiny injectable chips use ultrasound for monitoring

Tiny injectable chips use ultrasound for monitoring

Engineers have developed the smallest single-chip system that is a complete functioning electronic circuit - and implantable chip visible only in a microscope.

Sensor warns of impending COVID-19 cytokine storm

Sensor warns of impending COVID-19 cytokine storm

Scientists report preliminary results on a sweat sensor that acts as an early warning system for an impending cytokine storm, which could help doctors more effectively treat patients.

Wearables and the promising future of personalised diagnostics

Wearables and the promising future of personalised diagnostics

Researchers have proposed that wearable devices could be used to develop a network of health data about a patient, allowing for early diagnosis of COVID-19, even when the patient is asymptomatic.

Tattoo made of gold nanoparticles for diagnostics

Tattoo made of gold nanoparticles for diagnostics

Scientists have developed a novel type of implantable sensor which can be operated in the body for several months to transmit information on vital values and concentrations of substances or drugs in the body.

Sticker detects cystic fibrosis in newborn's sweat

Sticker detects cystic fibrosis in newborn's sweat

Researchers have developed a novel skin-mounted sticker that absorbs sweat and then changes color to provide an accurate, easy-to-read diagnosis of cystic fibrosis within minutes.

New class of quantum dots primed for imaging

New class of quantum dots primed for imaging

A new class of quantum dots opens a range of practical applications, including medical imaging and diagnostics and quantum communication.

Microneedle patch delivers drugs and procures testing samples

Microneedle patch delivers drugs and procures testing samples

Researchers have developed a biobattery-powered device capable of both delivering large molecule pharmaceuticals across the skin barrier and extracting interstitial fluid for diagnostic purposes.

Popular articles

Subscribe to Newsletter