Tsinghua team realizes 3D printing technology of nearly 100% functional nano par

The research team of Professor Sun Hongbo and Associate Professor Lin Linhan from the Department of Precision Instruments of Tsinghua University proposed a new technology of nano particle 3D laser assembly based on chemical bonding by using photo generated high-energy carriers to control the surface chemical activity of nano materials.

Based on this technology, the research team demonstrated the complex three-dimensional structures and heterostructures of various nano particles, realized high-precision laser micro nano manufacturing beyond the optical diffraction limit, and provided a new idea for the preparation of micro nano functional devices.

This achievement was published in the journal Science on September 2, entitled "3D Nanoprinting of Semiconductor Quantum Dots by Photo Electron Induced Chemical Bonding".

Research background and achievements

As the source of the emergence and development of high and new technologies in the 21st century, nano science and technology originate from a series of strange new physical and chemical effects caused by the reduction of material size to nano scale, including quantum confinement effect and quantum tunneling effect in semiconductor materials, surface plasmon resonance of metal materials, etc.

The preparation of existing nano devices is mainly based on micro nano manufacturing technologies such as photolithography and electron beam exposure, which is only applicable to a limited variety of nano materials. As a planar preparation process, it is difficult to achieve three-dimensional manufacturing of nano materials. On the other hand, chemical synthesis can be used to achieve the preparation and precise cutting of colorful (different sizes, morphologies, and compositions) nanoparticles, and these nanomaterials have high crystal quality, good surface quality, and superior optical, electrical, and magnetic properties. However, these chemically synthesized nanoparticles lack effective device based preparation technology, which has become the technical bottleneck of their wide application.

In view of the above problems, the research team proposed a new principle of photo induced chemical bonding, realized the laser three-dimensional assembly technology of nanoparticles, and used various nanoparticles as raw materials to assemble three-dimensional nano devices. Taking the semiconductor quantum dot with a core shell structure as an example (as shown in Figure 1), the laser excited quantum dot generates electron hole pairs, drives the tunneling and surface migration of photogenerated holes through energy level matching, promotes the desorption of quantum dot surface ligands and the formation of active chemical sites, thereby inducing the surface chemical bonding of quantum dots, and realizes efficient assembly between quantum dots.

Fig. 1 Schematic diagram of the principle of photoinduced chemical bonding

Based on the above principles, the research team further focused and programmed the laser beam, and achieved the precision molding of the complex three-dimensional structure of nanomaterials.

Figure 2. 3D Nanoprint Structure Morphology of Quantum Dots

Compared with the existing micro nano fabrication technology, this technology has the following distinctive features. High purity of printing materials: compared with the existing laser 3D nano printing technology, this technology breaks through the principle limitation of photopolymerization, does not require any optical bonding components, and realizes 3D printing of nearly 100% functional nano particle components; Strong 3D processing capability: it can realize nano printing of various 3D structures such as complex linear, bending and body structure (Figure 2); High printing resolution: nonlinear light excitation is used to make the printing resolution break through the optical diffraction limit. The density of printing point array exceeds 20000 ppi, and the printing limit resolution reaches 77 nm, and excellent homogeneity is maintained in large-scale array processing; With multi-component printing function: using quantum dots of different sizes as raw materials, this technology also shows the multi-component

heterogeneous composite printing capability (Figure 3).

Figure 3. RGB tri color printing and heteropatterning of quantum dots

In this paper, a quantum dot micro photodetector with high sensitivity and light response based on the above technology is demonstrated. It is worth pointing out that the micro nano manufacturing principle of photoinduced chemical bonding has a wide range of material and structural adaptability. Through energy level design, high-precision micro nano manufacturing of a variety of semiconductor and metal materials can be realized, which opens up a new way to prepare nano devices, and has important application prospects in the fields of on chip optoelectronic device integration, high-performance near eye display, etc.

This research was supported by the National Key R&D Program, the National Natural Science Foundation of China, the Tsinghua Foshan Innovation Fund and the National Key Laboratory of Precision Testing Technology and Instruments.

Source: Sina.com - 3D Science Valley