Induced Crystallization Behavior Of Silicon At Different Cooling Rates

Silicon is one of the elements with large reserves on the earth.Because of its good photovoltaic conversion characteristics,solar cells prepared with it have the advantages of high photoelectric conversion efficiency and high-cost performance.Therefore,polycrystalline silicon still has broad development prospects for a popular photovoltaic material for related research in the photovoltaic industry.This article briefly summarizes the nature and research significance of silicon,the growth technology of silicon crystal industry,and introduces molecular dynamics methods and microstructure characterization methods in detail.Emphasis is placed on simulating the silicon-induced crystallization process under different conditions in order to deeply explore the silicon-induced crystallization process and the evolution of the microstructure under different crystal planes and different cooling rates.This paper adopts the Stillinger-Weber potential function suitable for describing the solidification process of silicon and uses molecular dynamics method to simulate the silicon-induced crystallization process under different crystal planes and different cooling rates.The results obtained are carefully analyzed and characterized by means of radial distribution function,atomic average energy,bond angle distribution function,Voronoi polyhedron index,dislocation extraction algorithm and three-dimensional visualization.In the process of silicon induced crystallization with different crystal planes,the final state is all in crystalline state at low cooling rate.With the increase of cooling rate,the induced crystallization systems of three planes are all in the state of coexistence of crystalline and amorphous states.At the same cooling rate,the(1 0 0)crystal plane is the fastest,the(1 10)crystal plane is the second,and the(1 1 1)crystal plane is the slowest among the moving rates of the solid-liquid interface.The solid-liquid interface between the(1 0 0)crystal plane and the(1 1 0)crystal plane moves forward in a plane as a whole,showing an atomic-level sawtooth microscopically,while the solid-liquid interface of the(1 1 1)crystal plane is easy to appear concavity on the interface,which will hinder the normal progress of crystallization.In the induced crystallization of(1 0 0)and(1 1 0)crystal planes,only the cubic diamond structure appeared.However,two kinds of structures,cubic diamond structure and hexagonal diamond structure,are formed in the process of induced crystallization,and there is no obvious relationship between the atom number of the hexagonal diamond structure and the cooling rate.The atoms of the cubic diamond structure and the hexagonal diamond structure are in a competitive relationship,and the number of atoms in the cubic diamond structure is larger.The cooling rate has a significant effect on the induced crystallization rate of silicon.The crystallization rate under the same cooling rate is(1 0 0)crystal plane >(1 1 0)crystal plane >(1 1 1)crystal plane.Among the three crystal planes,the(1 1 1)crystal plane is the most sensitive to changes in the cooling rate,followed by(1 1 0),and the least sensitive is the(1 0 0)crystal plane.In the induced crystallization process of silicon at different cooling rates,there are fewer atomic defects formed on(1 0 0)crystal plane and(1 1 0)crystal plane,but more atomic defects formed on(1 1 1)crystal plane.Among the three crystal planes,dislocations are formed at all cooling rates in(1 1 1)crystal plane,and the relationship between the number of dislocations and the cooling rate is weakly correlated.The majority of dislocation types are1/6 <1 1 2> partial dislocations.There is only a few 1/2 < 1 1 0> perfect dislocation.On the whole,the probability of dislocation formation in the system is(1 1 1)crystal plane >(1 1 0)crystal plane >(1 0 0)crystal plane.Therefore,(1 0 0)crystal plane and(1 1 0)crystal plane are more suitable for silicon induced crystallization than(1 1 1)crystal plane,which is more suitable for forming high quality silicon crystal.