In a groundbreaking development reported by the US Daily Science on June 21, researchers from the United States have successfully harnessed the quantum tunneling effect using nano-sized insulators made of boron nitride and gold quantum dots. This innovation has led to the creation of transistors that do not rely on traditional semiconductors, potentially ushering in a new era for electronic devices.
For many years, the miniaturization of electronic components has pushed the limits of current technology. Scientists have managed to pack millions of semiconductors onto a single silicon chip. However, according to Ye Yuejin, a physicist at the Michigan Institute of Technology and lead researcher of the study, "the transistor cannot be made any smaller in the next 10 to 20 years." He also pointed out that existing semiconductor materials are inherently limited, leading to significant energy loss in the form of heat.
To overcome these challenges, scientists have explored various materials and designs, but all have been based on traditional semiconductors like silicon. In 2007, Ye took a different approach by aiming to create transistors without any semiconductor material. His idea was to use nano-scale insulators and place nano-metals on top of them. The team chose boron nitride nanotubes (BNNTs) as the base structure.
They then used lasers to create three-nanometer-wide gold quantum dots (QDs) placed on top of the BNNTs, forming what is now known as QDs-BNNTs. According to Ye, "boron nitride nanotubes are the perfect pedestal for gold quantum dots. They are small, controllable, and consistent in diameter. Plus, they are insulating, which helps limit the size of the quantum dots."
Researchers collaborated with scientists at ORNL to energize the quantum dots by applying electrodes at both ends of the BNNTs at room temperature. What happened next was fascinating: electrons moved precisely between the quantum dots, demonstrating the quantum tunneling effect. Ye remarked, "The stability of this device is very good."
Using this setup, Ye’s team built a transistor that had no semiconductor “outline.†When a sufficient voltage is applied, it becomes conductive, and when the voltage drops or is turned off, it returns to an insulating state. Importantly, the device does not suffer from the "leakage" issue common in silicon-based transistors, where electrons escape into the insulator, causing unnecessary heat and energy waste.
John Yaschchacker, a physicist at Michigan Technological University, helped develop a theoretical model for the new transistor. He noted that while other researchers had previously used quantum tunneling to build transistors, those devices only functioned at extremely low temperatures—around 4.2K, close to absolute zero. The new device, however, operates efficiently at room temperature.
The key to Ye’s gold-nanotube device lies in its small size—just 1 micrometer long and 20 nanometers wide. Yaschchacker explained, "The width of the gold island must be on the nanometer scale to control electrons at room temperature. If it's too large, too many electrons can flow through it. In theory, when the electrodes are just a fraction of a micrometer apart, the tunnel can be nearly zero."
Die Casting
Die casting is a metal casting process that involves forcing molten metal under high pressure into a mould cavity. The mould cavity, also known as a die, is typically made of hardened steel and is custom-designed to produce the desired shape of the final product.
The process begins with melting the metal, usually non-ferrous metals such as zinc, aluminum, magnesium, or copper alloys, in a furnace. Once the metal reaches the desired temperature, it is injected into the mold cavity at high pressure using a hydraulic or mechanical press.
The high pressure helps to quickly fill the mold cavity and ensures that the molten metal solidifies rapidly to produce precise and complex shapes with fine surface details. After the metal solidifies, the mold is opened, and the casting is ejected from the die.
Die casting is commonly used to produce a wide range of metal components and products with high dimensional accuracy, excellent surface finish, and tight tolerances. It is widely employed in industries such as automotive, aerospace, electronics, and consumer goods manufacturing.
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