Gallium selenide crystals are used in semiconductors, ultra-thin nanomaterials, and other applications due to their unique electronic and optical properties. GaSe crystals are layered and soft, and take days to grow, making it difficult to fully explore their applications and advance future technologies.
To compensate for the time difference, an international research team has developed a method to produce crystals of comparable quality in just 5 minutes.
The study was published on December 26and2021, in the Nano-research newspaper.
In this paper, we propose an ultra-fast crystal growth process with low energy consumption and capable of producing crystals of excellent quality. We also demonstrate that large GaSe crystals – half to one centimeter long – can be obtained in the short period of five minutes..
Yumeng Shi, Study Co-Corresponding Author and Professor, Engineering Technology Research Center for 2D Material Information Function Devices and Systems of Guangdong Province, Shenzhen University
Yumeng Shi is also a professor at the Ministry of Education’s International 2D Materials Collaborative Laboratory for Optoelectronics Science and Technology, Institute of Microscale Optoelectronics, Shenzhen University.
GaSe crystals are typically grown using chemical vapor transport, in which the starting chemical components react with a solution, reconfiguring their constituents into liquid, gas, and solid phases, which settle as crystals when properly separated, usually by temperature.
They can also be grown using the vertical Bridgman technique, which uses the same temperature controls but involves a seed crystal that shares the geometry of the crystal to be grown. As the material is produced, it forms its own crystal formation on the seed.
Although these growing techniques are well established, growing these high-quality, large-scale crystals is often a time-consuming, expensive, and complicated process..
Zhongchang Wang, Study Co-Corresponding Author and Principal Investigator, Atomic Manipulation Group for Quantum Nanotechnology, International Iberian Nanotechnology Laboratory
According to scientists, nucleation is the key to crystal growth. This is the first step in the assembly of molecules into a new structure, like the point at which water begins to freeze.
Traditional processes adopt the strategy of suppressing nucleation by lowering the concentration of the feedstock, which inevitably results in a much lower growth rate.
Jingbo Li, co-corresponding author of the study and professor, Institute of Semiconductors, South China Normal University
Li also noted that increasing the concentration of the raw material increases the growth rate, but decreases the quality of the crystal.
“Growth kinetics change and may result in dendrite crystals or cracks. Therefore, an ultra-fast crystal synthesis process, which suppresses nucleation events without the need to reduce raw material supply, is urgently required.Li remarks.
Scientists have used liquid metal to improve an approach called atmospheric pressure chemical vapor deposition (CVD) to reduce nucleation density – or the number of molecules that self-assemble into different or low-quality crystals – and maintain a high growth rate at the same time. .
This method of synthesis involves a substrate reacting with another chemical under atmospheric pressure. A chemical vapor is produced during the reaction, which is deposited on the substrate. The substrate, in this case, is liquid gallium, which produces a high quality crystal of a suitable size in 5 minutes.
To analyze the crystals, the scientists used the crystals to make a photodetector, which uses light to generate electrical signals, and found that it worked similarly to photodetectors made with slowly growing GaSe crystals.
Shi says, “Our proposed technique could be extended to other low melting point metals, opening a new avenue for potential optoelectronic applications of 2D crystals..”
“Then, we plan to further study the microscopic mechanism of this new method at the atomic level and promote the industrialization of this method. We look forward to cooperation with enterprises to promote single crystal growth processing technology and its resulting single crystal products.“, added Shi.
Other contributors to the study include Zuxin Chen, Quan Chen and Zebing Chai, Institute of Semiconductors, South China Normal University; Bin Wei, School of Materials, Sun Yat-Sen University; Jun Wang, School of Electrical Engineering and Automation, Wuhan University; and Yanping Liu, School of Physics and Electronics, Hunan Key Laboratory for Super-microstructure and Ultrafast Process, Central South University.
Zuxin Chen is also associated with Shenzen University Engineering Technology Research Center for Guangdong Province 2D Material Information Functional Devices and Systems and Iberian International Nanotechnology Laboratory.
The study was financially supported by the National Natural Science Foundation of China, the Postdoctoral Science Foundation, the Key Project of the Department of Education of Guangdong Province, and the Shenzhen Peacock Plan.
Chen, Z. et al., (2021) Ultra-rapid growth of high-quality, large-sized GaSe crystals by a liquid metal promoter. Nano-research. doi.org/10.1007/s12274-021-3987-6.