Explanation

Also known as laser thermal decomposition and laser chemical decomposition, it is a method of using laser as energy to promote chemical vapor phase reactions. Laser thermal decomposition refers to the process that the laser focuses on the backing materials and makes the reactant gas in the region occur similar to the general thermal decomposition chemical vapor deposition (CVD) process by raising the temperature in the local region. The difference is that the heat source at this time is laser light energy. In order to achieve laser thermal decomposition, it is necessary to choose a wavelength suitable for laser absorption, so that the substrate has a high absorption coefficient, and the main reaction gas should be transparent. Laser chemical decomposition refers to the process of decomposing reactant gases into simpler molecules or atoms when they absorb single or multiple photons. Laser has the characteristics of good monochromaticity and high power density. By selecting the wavelength of the absorption photon to match the excitation wavelength of the reaction gas, the gas can be heated to the spontaneous reaction temperature in a very short time, and the chemical reaction can be promoted. Compared with other vapor synthesis methods, laser chemical vapor deposition has the following advantages: 1 The reactants are directly heated by absorbing photons, without the need for high-temperature walls, resulting in higher purity products. 2. The reaction area is limited in a small heating space, and the temperature gradient is steep, which helps to strictly control the nucleation, growth rate and exposure time of particles, so that ultrafine powder with narrow particle size distribution can be synthesized. 3. The reaction conditions can be strictly controlled to ensure that gas molecules passing through the reaction area have almost the same time and temperature history.

Classification