【作者】 胡秋发；

【导师】 周耐根；

【作者基本信息】 南昌大学 ， 材料物理与化学， 2014， 硕士

【摘要】 a-Si:H/c-Si异质结太阳电池既利用了薄膜制造工艺的优势，同时又发挥了晶体硅和非晶硅的材料性能特点，具有实现高效低成本硅太阳电池的发展前景。本文尝试应用分子动力学模拟研究a-Si:H/c-Si薄膜生长，主要模拟考察了生长温度、基团入射动能、入射频率对在Si(001)面及Si(111)面上a-Si:H薄膜生长及其结构的影响，并采用Voronoi多面体结构分析方法分析了的它们的原子结构，得到以下结论：（1）对不同衬底温度下a-Si:H/c-Si(001)及a-Si:H/c-Si(111)薄膜生长模拟研究发现：随温度的升高，在两种衬底表面上生长的a-Si:H薄膜表面都是越光滑，内部越致密，同时SiH含量、H含量和悬挂键密度均下降。不同的是在Si(111)面生长的薄膜表面粗糙度随温度降低的线性关系更明显，且在同温下其内部致密度比Si(001)面生长的薄膜较小。并进一步分析讨论了造成这些结果的原因。（2）对不同入射动能下a-Si:H/c-Si(001)及a-Si:H/c-Si(111)薄膜生长模拟研究发现：随着入射动能增大，在两种衬底表面上生长的a-Si:H薄膜表面越光滑，内部结构越致密，H含量和悬挂键密度均下降，且它们变化的速率都先快后慢，SiH含量则是先降后升，不同的是，在Si(001)表面生长时，SiH含量变化对应的入射动能分界点为0.65eV，而Si(111)为0.16eV。同时进一步分析讨论之。（3）在不同入射频率下a-Si:H/c-Si(001)及a-Si:H/c-Si(111)薄膜生长模拟研究得到：薄膜形貌及内部紧密程度与入射频率的关系不大，SiH含量、H含量和悬挂键密度均变化不大，其原因是入射频率对SiH3基团的吸附率、到达表面后的运动和成膜后原子的晶化率等都没有明显的影响。（4）氢化非晶硅薄膜中近邻Voronoi多面体拓扑结构十分复杂，按多面体指数法难以有效统计。但其度量性质研究发现：低温下生长薄膜结构要比高温下更复杂；且随着温度的升高，出现孔洞结构的几率要更小，Voronoi多面体越接近球形结构，其歪扭程度更低。（5）运用最近邻Voronoi多面体分析表明，随着温度的升高，在Si(001)面及Si(111)面生长的a-Si:H薄膜中最近邻原子间形成的四面体<4,0,0,0>局域结构含量增加，反映出最近邻原子局域结构趋于四面体化；在Si(001)面入射动能小于0.04eV及在Si(111)面入射动能小于0.16eV时，随着入射动能的增大在两个面生长的薄膜局域结构趋向于四面体化排列，而高于该能量后再增大入射动能对薄膜结构局域四面体化排列改变影响不大。（6）运用次近邻Voronoi多面体分析表明，随着温度升高，入射动能的增加，在Si(001)面及Si(111)面生长的a-Si:H薄膜其低配位多面体<0,4,4,0>、<1,3,3,1>、<0,4,4,1>、<0,3,6,0>及<0,4,4,2>等含量降低，而高配位下的<0,3,6,3>、<0,2,8,2>、<0,4,4,4>及<0,3,6,4>多面体含量增加，这四种次近邻Voronoi多面体的含量增加反应了薄膜中硅原子次近邻原子间的局域类晶体结构排布增强。更多还原

【Abstract】 a-Si:H/c-Si heterojunction solar cell takes not only the advantage of thin-filmmanufacturing technology, but also the advantages of both crystalline silicon andamorphous silicon. It has the potential prospect to be a high-efficiency and low-costsilicon solar cell. This paper attempts to apply molecular dynamics method tosimulate the growth of a-Si:H/c-Si thin film. The effects of substrate temperature,incident kinetic energy, incident frequency and growth plane of substrate on the thea-Si:H film structural characteristics were investiaged. The Voronoi polyhedralstructure analysis method was applied to analyze the arrangement of atoms. Theresults are as follows:(1) The studies of a-Si:H/c-Si(001) and a-Si:H/c-Si(111) thin film growth underdifferent substrate temperature shows that: as the substrate temperature increased, thesurface roughness decreased and the inherent density increased, the contents of H,SiH and dangling bonds decreased for the a-Si:H thin films growth on both Si (001)and Si (111) substrate. The difference was that the relationship between the surfaceroughness and temperature of Si (111) substrate was closer linearity than that of Si(001) substrate. And the inherent density of the film growth on Si (111) substrateshowed more porous than that of Si (001) substrate. And further the reaons of theseresults were analyzed and discussed.(2) The studies of a-Si:H/c-Si(001) and a-Si:H/c-Si(111) thin film growth underdifferent incident kinetic energy shows that: as the incident kinetic energy increased,the change trends are similar for the films both growth on Si (001) substrate and Si(111) substrate, i.e. the surface roughness decreased, the inherent density increased,the contents of H and dangling bonds decreased, and their rate of change was fast firstand then slow. The difference between the two substrates was the critical energy forthe variety of SiH content,0.64eV for Si(001) and0.16eV for Si (111). And furtherthe reaons of these results were analyzed and discussed.(3) The studies of a-Si:H/c-Si(001) and a-Si:H/c-Si(111) thin film growth underdifferent incident frequency shows that: the surface morphology and inherent density of a-Si:H films were not associated with incident frequency, the contents of SiH, Hand dangling bond density. The reasons of them were that the incident frequency hadlittle effect on the SiH3radical adsorption rate, the radical surface diffusion and thecrystallization rate of the film.(4) The neighbor Voronoi polyhedra topology structure of hydrogenatedamorphous silicon thin films were too complicated to count the polyhedron indexeffectively. But the metric properties of Voronoi polyhedra shows that: the structureof thin films which growth at low temperature were more complicated than at hightemperature; As the substrate temperature increased, the probability of hole structurein the films would decrease, and the Voronoi polyhedral would be less distorted, beclose to spherical structure.(5) By using the nearest neighbor Voronoi polyhedron analysis method, we foundthat: As the substrate temperature increased, the content of <4,0,0,0> polyhedral,which represented local tetrahedron structure, increased in a-Si:H films growth bothon Si(001) substrate and on Si(111) substrate; When the energy was less than0.04eVof Si(001) or0.16eV of Si(111) substrate, the increase of incident kinetic energywould result in the increase of the local tetrahedron structure. After those criticalenergy, the increase of incident kinetic energy was not associated with the localtetrahedral arrangement.(6) By using the second-nearest neighbor Voronoi polyhedron analysis method,we found that: As the substrate temperature and incident kinetic energy increased, thecontents of low coordination polyhedra, such as <0,4,4,0>,<1,3,3,1>,<0,4,4,1>,<0,3,6,0> and <0,4,4,2>, decreased. While the contents of high coordinationpolyhedra, such as <0,3,6,3>,<0,2,8,2>,<0,4,4,4> and <0,3,6,4>, increased. Thecontents of the four types of second-nearest neighbor Voronoi polyhedra increasedindicated that the atomic paracrystalline structure arrangement of second-nearestneighbor silicon atoms in a-Si:H films gradually enhanced.更多还原