In addition to graphene, two-dimensional materials you don't know are also useful.

Mobile phones and tablets can be rolled up like newspapers, and the screen integrated in contact lenses can directly read information ... These scenes that sound like science fiction are becoming more and more real under the impetus of new two-dimensional materials.

Two-dimensional material is a new type of crystal material with the thickness of one or several atomic layers. At present, it has developed into a complete material system, covering various types from conductors, semiconductors and superconductors to insulators, ferroelectrics, ferromagnets and antiferromagnets. High-quality two-dimensional materials play an important role in exploring new physical phenomena and further expanding their applications in microelectronics and optoelectronics.

The two-dimensional materials team led by Zhang Guangyu, deputy director of Songshan Lake Materials Laboratory, has carried out a series of work around the research, preparation and application of two-dimensional materials and achieved international leading research results.

Nowadays, "graphene" has become a well-known "star material", and products such as graphene batteries are gradually applied in the commercial field. As early as 2004, the research team of Professor Andre Geim from the University of Manchester in the United Kingdom successfully separated graphene, a graphite material with a single atomic layer, which triggered a research upsurge of two-dimensional materials, and the relevant researchers won the 20 10 Nobel Prize in physics.

In recent years, driven by miniaturization and flexibility of semiconductor devices, two-dimensional materials show unique advantages because of their excellent optical, electrical and mechanical properties (such as high sensitivity, ultra-high transparency and semiconductor characteristics).

"The special properties of two-dimensional materials give them a wide range of application prospects. First of all, in terms of physical properties, two-dimensional materials are only one atomic layer thick, which makes such materials have ultra-high transparency and good flexibility. " Zhang Guangyu introduced that an important application direction of two-dimensional materials in the future is flexible and transparent electronic devices.

"There are no dangling bonds on the surface of two-dimensional materials, and the lattice matching degree is not high in the process of epitaxial growth and preparation. It belongs to van der Waals epitaxy, and there are basically no restrictions on materials and processes." Zhang Guangyu said.

The appearance of two-dimensional materials provides a new way to break through the performance limitations of traditional semiconductor devices and a new idea to realize various functional applications.

More than 1500 flexible MoS2 field effect transistor devices can be integrated in an area smaller than the size of a nail. In September 2020, the team led by Zhang Guangyu published the paper "Large-area Flexible Transparent Electronic Devices Based on Single-layer MOSFET" in the electronic journal Nature electronics.

The team used the epitaxial growth of four-inch high-quality, highly oriented single-layer molybdenum disulfide film, combined with traditional micromachining technology, optimized insulation layer and contact resistance, and prepared large-area flexible transparent molybdenum disulfide field effect transistors and various logic devices. The device shows excellent characteristics: the transistor device density can reach 15 18/cm2, and the yield is as high as 97%, which is the highest index in the reported results and is at the international leading level; A single device also shows good electrical performance and flexibility.

Zhang Guangyu pointed out, "At present, mature semiconductor processes mostly use 8-inch or 12-inch silicon wafers. The larger the size, the more integrated chips and the lower the cost. Therefore, it is the same idea to realize the preparation of large-size molybdenum disulfide wafers, but the larger the size, the higher the technical requirements. "

There are still some problems in the preparation of large-area high-quality molybdenum disulfide films, such as small grain size, many grain boundaries and random orientation. In order to solve this problem, Zhang Guangyu team used a self-designed multi-source chemical vapor deposition system to epitaxially prepare a four-inch high-quality continuous single-layer molybdenum disulfide wafer on sapphire substrate through vertical growth and multi-point nucleation.

He described the principle like this: "It's like spraying water on the wall with a watering can. The first generation of equipment has only one nozzle, and the spraying area is relatively small; The second generation equipment uses three nozzles to spray together, which expands the spraying area by three times; The third generation equipment uses six sources to spray together. In this case, the sprayed area is larger and more uniform. "

"Two-dimensional semiconductor materials have many excellent characteristics, which can make up for the shortcomings of semiconductor materials such as silicon in application, give full play to the advantages of the materials themselves, and realize some new and more suitable application scenarios. Such as flexible wearable devices, ultra-sensitive detectors, etc. " He said that secondary materials are not omnipotent, but have special application scenarios suitable for them, and these characteristics should be used to develop their corresponding products.

At the beginning of 20 19, the two-dimensional materials team of Songshan Lake Materials Laboratory started construction. He said that the two-dimensional materials team mainly focuses on materials research with promising application prospects. Two-dimensional materials have to go through an essential process to be truly applied to real life, including verifying the feasibility of two-dimensional materials in principle and technology, optimizing various process parameters and improving the performance of devices in all aspects.

As a new team, two-dimensional materials team building is one of the most important tasks. At present, there are less than ten fixed members of the team, all of whom have different research backgrounds. "There are both materials and devices; There are not only processing and device preparation, but also characterization and measurement ... "Zhang Guangyu said that team work requires members to cooperate with each other, so that research work can be carried out with higher quality and efficiency.

With the construction of Songshan Lake Materials Laboratory on the right track, more and more outstanding overseas researchers choose to join the laboratory to carry out their own scientific research work here. Two young scientific research backbones in the team were recruited and introduced by Zhang Guangyu when he went to Europe to preach. In his view, this is a good sign. "As a new scientific research institution in Guangdong Province, Songshan Lake Materials Laboratory has relatively sufficient resources in all aspects and has strong attraction. At the same time, Dongguan also provides a stage for scientific research talents to do things with peace of mind and concentrate on scientific research. "