The electrocrystallization process refers to the whole process from the emergence of free atoms of cations in the cathode discharge to form crystalline nuclei, to the formation of crystals and the formation of a metal layer on the surface of the cathode. In the electrocrystallization process, the growth mode and process of the new crystal nucleus, and the surface state of the base metal will have a great impact on the structure (Such as the thickness of the deposited layer, the size of the crystal grain, the morphology of the texture, etc.) and performance of the deposited layer. The supporting electrolyte generally refers to an electrolyte that can increase the conductivity of the solution, and does not participate in the reaction itself. The inert supporting electrolyte can be an inorganic salt, an inorganic acid or a buffer. In the process of electrocrystallization, the supporting electrolyte system has a great influence on the nucleation and growth of crystal grains. Different ions have different effects on the electrodeposition process of metals, such as affecting the precipitation rate of the metal, the location of the precipitation, and the crystallization method of the metal. Electrocrystallization is an important method for preparing semiconductor materials. The choice of electrocrystallization supporting electrolyte is very important. The electrolyte should be a solution with high stability, good solubility and wide electrochemical window. Many semiconductor thin film materials (Si, Ge, Te, Se, etc.) need to be prepared by electrocrystallization in a supporting electrolyte. The common structure of this type of electrolyte is ammonium salt. Therefore, this type of electrolyte can be widely used in the preparation of semiconductor materials.
Applications:
- Preparation of semiconductor materials: There are many methods for preparing semiconductor materials, such as chemical or physical vapor deposition (CVD, PVD), pulsed laser deposition (PLD), molecular beam epitaxy (MBE), etc. Electrocrystallization technology is particularly suitable for preparing semiconductor materials, especially for preparing nano-semiconductor materials. It is a low-temperature technology that can effectively control the grain size. The electrochemical window of an aqueous solution as an electrolyte is narrow, and electrocrystallization is difficult. Organic solvents can get smooth and uniform deposits, but the thickness is difficult to control. Ionic liquids have the advantages of wide electrochemical window, large conductivity, relatively low viscosity, and good chloride solubility required for electrocrystalline semiconductors, and are relatively excellent electrocrystallization supporting electrolytes. The method can not only prepare Si, Ge, Te, Se and other semiconductor materials, but also can prepare Si, Ge nanowires, obtain higher electron transmission speed, and be applied in the field of field effect transistor solar cells and nano-magnetic materials. In addition, photonic crystals are a new type of optical material whose dielectric constant changes periodically in space. The method can prepare Ge photonic crystals and realize potential applications in the fields of all-optical storage and optical switching.
Reference
- Hiroyuki Anzai, Madoka Tokumoto, Gunzi Saito. Effect of the Solvent Used for Electrocrystallization of Organic Metals [J]. Molecular Crystala and Liquid Crystals, 1985, 125(1), 385-392.