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Chinese Academy of Sciences develops low-dimensional semiconductor technology: nano-brush “draws” various chips

The Chinese Academy of Sciences announced today that domestic scholars have developed a simple method for fabricating low-dimensional semiconductor devices – using a “nano-brush” to outline future optoelectronic devices, which can “draw” various required chips.

With the development of technology, people’s requirements for semiconductor technology are getting higher and higher, but the difficulty of semiconductor manufacturing is getting bigger and bigger, and the process below 10nm is extremely expensive, which requires other technologies.

The Chinese Academy of Sciences said that in the foreseeable future, more Electronic components need to be integrated in a smaller area. In response to this demand, low-dimensional materials with a thickness of only 0.3 to several nanometers (tens of thousands of hair diameters) have emerged.

Such materials can be compared to ultra-thin paper, only much thinner than paper, and can be used to fabricate nanometer-thick electronic devices.

From materials to devices, the existing preparation process needs to go through a very complicated and complicated process, which is extremely unfavorable for the rapid screening of low-dimensional materials suitable for the preparation of electronic devices.

Recently, researchers from the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences have developed a simple method for fabricating low-dimensional semiconductor devices – using a “nano-brush” to outline future optoelectronic devices.

Because 2D materials are like thin sheets of paper, their properties are easily affected by the environment. Using this feature, the researchers covered a layer of ferroelectric thin film on the surface of the two-dimensional material, and used a nanoprobe to apply a voltage to scan the surface of the ferroelectric material, and to achieve accurate properties of the two-dimensional material by changing the properties of the ferroelectric material at the corresponding position manipulation.

After designing the function of the device, researchers only need to use their imagination and use the nano-probe “brush” to draw various electronic device patterns on the “canvas” of the ferroelectric thin film. properties, the desired device can be fabricated.

In the actual experimental operation, the “brush” is the nano-probe of the atomic force microscope, and its function is equivalent to the gate electrode of a traditional transistor, which can be used to apply positive or negative voltages.

But unlike the traditional gate electrode, the tip of the atomic force microscope can be moved arbitrarily, like a “walking brush”, which can accurately “draw” nanoscale devices in horizontal space.

In this process, researchers can easily build various electronic and photonic devices, such as memories, photodetectors, photovoltaic cells, and more, by controlling the positive and negative voltages applied to the needle tip.

The picture below is a heart-shaped pattern written with the tip of a probe, which fully reflects the arbitrariness of graphic editing.

Moreover, after a device is written, it can be re-scanned by applying different voltages with the needle tip, and it can also be written into a new functional device, just like writing on paper and then rewriting it with an eraser, that is, the same device can be repeated over and over again. Use and realize different functions.

Just like a robot, refresh the control program and you can do different things.

The researchers took this probe-scanning technique a step further and applied it to quasi-nonvolatile memory.

Quasi-non-volatile memory refers to a type of memory that can simultaneously write data faster and save data for a longer time. It makes sense to develop this type of storage technology, for example, it can prolong the retention time of data when we shut down the computer or shut down the computer suddenly and unexpectedly.

In addition, this device preparation technology can also be used to design “electrical writing, optical reading” memory. The optical disc we use daily is a typical “optical reading” storage medium.

Since the type of low-dimensional semiconductor carriers will change under the action of the tip scanning electric field, the luminescence intensity will also change significantly.

Therefore, combined with the characteristics of arbitrary editing of scanned graphics, researchers can design a periodically changing array.

Each area of ​​these array patterns is controlled by the needle tip to control its carrier type, thereby controlling the luminous intensity of the low-dimensional material, and then a photo of the fluorescence intensity can be directly obtained by taking a photo with a camera.

The information of each storage unit is “clear at a glance” in this photo, dark cells can be used to represent “0” in the storage state, and bright cells can be used to represent “1”, similar to a new type of storage “CD” “.

Researchers can simply and directly obtain the information of each storage unit by taking fluorescence pictures.

Using this technology, the theoretical storage density can reach several T-Byte/in2 by means of voltage readout.

This research was completed by the Shanghai Institute of Technical Physics, Chinese Academy of Sciences in cooperation with Fudan University, East China Normal University, Nanjing University, and the Institute of Microelectronics, Chinese Academy of Sciences.

The research results have been published in “Nature-Electronics” on January 24, 2020, with the title of “Programmable transition metal dichalcogenide homojunctions controlled by nonvolatile ferroelectric domains”.

Author: Xian Rui