Quantum-dot logic circuits layout building blocks for innovative devices, including printable electronics, flexible displays, and medical diagnostics. 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. The innovation assures an economical 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 innovative devices.
For decades, extra high purity silicon has been used for microelectronic manufacturing in a clean-room environment. Several technologies allow manufacturing complex electronic circuits outside a clean room, using available chemical techniques, which is inexpensive. Colloidal semiconductor nanoparticles are one such emerging technology, due to their small size unique properties controlled by quantum mechanics.
A quantum-dot consists of a semiconductor core covered with organic molecules. They combine the advantages of well-understood traditional semiconductors with the chemical versatility of molecular systems. The new types of flexible electronic circuits are realized and that could be printed onto any surfaces as well as plastic, paper, and even human skin.
The fundamental component of electronic circuitry is a transistor that acts as a switch triggered by an applied voltage. Transistors have pairs of n- and p-type devices that control the flow of positive and negative electrical charges, respectively. These complementary transistors are the foundation of CMOS (Complementary Metal Oxide Semiconductor) technology, which enables microprocessors, memory chips, image sensors, and other electronic devices.
The first quantum dot transistors were exhibited about two decades ago. Nevertheless, integrating complementary n- and p-type devices within the same quantum dot layer remained an enduring challenge. Furthermore, most of the attempts in this area have focused on nanocrystals based on lead and cadmium and these elements are highly toxic heavy metals.
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 integration of n- and p-transistors in the same quantum dot layer. As proof of the 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.
Reference : Los Alamos National Laboratory
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