一维纳米硅材料的制备与性能研究

【作者】 牛俊杰；

【导师】 杨德仁； 沙健；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2005， 博士

【摘要】 近年来,一维纳米半导体材料由于其特殊的物理性质被人们广泛地研究。而作为现代微电子产业基础的硅材料,其一维纳米尺寸(纳米硅线、管)的材料制备和性能研究更是引起了人们的兴趣。 本论文通过CVD、热蒸发等方法,制备了有序化自组装纳米硅丝阵列、不同直径纳米硅丝、纳米硅管等一维纳米材料。并且通过SEM、FESEM、TEM、HRTEM、SAED、XRD等测试手段,对纳米硅材料进行了形貌和结构分析;此外,还通过Raman散射、FTIR红外分析、PL荧光光谱分析等仪器,对纳米硅丝的光学性能进行了分析。本论文主要结论如下所述: 自组装阵列化纳米硅丝:论文采用NCA氧化铝模板,并结合CVD技术,成功制备出了高度阵列化排列的纳米硅丝。通过结构分析,这些整齐排列的纳米硅丝晶体质量良好,其生长方向主要为Si(111)晶向。纳米硅丝的直径可以通过调节NCA纳米孔的直径大小来调节,一般为10-100nm之间;其长度可以通过调整不同的模板厚度以及生长时间来改变。同时论文研究了对低温生长的原生纳米硅丝在高温下长时间退火,得到了结晶理想的纳米硅丝结构。 硫化物辅助法生长纳米硅丝:论文提出利用硫化物辅助制备纳米硅丝的新方法。该方法通过高温热蒸发硫单质或者硫化物,用硅片作为衬底反应而成。其特点是纳米硅丝的硅源不是来自硅烷或者硅氧化物,而是来自硅衬底本身。该方法制备简单,并且硫在其生长过程其起到辅助作用,但最后生成气体消失,不会对硅丝造成污染,并且硅源直接来自于衬底本身,减少了制备流程。结合纳米硅丝的生长过程,论文提出了一种硫化物辅助生长机理。 CVD和NCA氧化铝模板技术制备多晶纳米硅管:论文利用CVD和NCA氧化铝模板技术,制备出纳米硅管。尽管人们对纳米硅管进行过理论上的分析,但是由于其结构上的限制,在实验中很难被合成出来。论文利用VLS机理,加上氧化模板中纳米孔的限制作用,在CVD系统中成功地合成出了纳米硅管结构。通过EDX能谱测试,该结构主要为Si和少量氧组成;其直径大约为50-100nm,这与NCA模板纳米孔的直径有关;通过HRTEM观察,其晶体结构为部分结晶,一般为多晶和非晶相结合的结构。 纳米硅丝的一级Raman散射、付立叶红外(FTIR)及荧光光谱(PL)研究:论文研究了纳米硅丝的光学性质,结合考虑温度效应的声子限域模型,对纳米硅丝的一级RamanT0散射峰进行了理论计算,并与实验结果进行了对比。研究发现,考虑温度效应的纳米硅丝一级RamanT0峰与实验吻合的比较一致。据此认为,纳米硅丝的Raman峰与体硅相比的偏移,主要由激光发热引起纳米硅丝内部温度升高,以致其混乱度增加,导致其峰位发生红移:同时发现,对于直径为~30nm和~100nm纳米硅丝的Raman峰位却没更多还原

【Abstract】 Recently, one-dimensional nano-materilas especially semiconductors are being studied for their potential physical properties. Because silicon is an important material in present microelectronics, the interest in synthesis and characteristic of one-dimensional nano-silicon (nanowires(SiNWs), silicon nanotubes(SiNTs)) is also raised.In this paper, we synthesized some one-dimensional nano-materials including the silicon nanowires with orderly array, different diameters and silicon nanotubes via methods of CVD, thermal evaporation, etc. The morphology and structure were inspected and analyzed by SEM, FESEM, TEM, HRTEM, SAED, XRD, etc. Furthermore, the optic properties of the SiNWs were analyzed through Raman spectrum, FTIR, PL spectrum, etc. The main results in the paper are listed below:The array-orderly SiNWs: We got the array-orderly SiNWs by using the NCA template and CVD techniques. The as-grown SiNWs have a high crystal quality, and the growth direction is mainly the Si(111). Furthermore, the diameters are among 10-100nm, which can be adjusted by changing the size of the nano-hole in NCA; The length can be controlled by changing the growth time and the thickness of the NCA. Furthermore, we annealed the original sample of SiNWs which is fabricated at low temperature at high point with long time. After annealing, the defects were eliminated and the crystal quality was improved.The synthesis SiNWs by sulfide-assisted method: This is a novel fabrication of SiNWs. The SiNWs was got on the silicon substrate through thermal evaporation sulfur of sulfide. The specialty is that the silicon is not from silane or other silicon oxide, but silicon substrate. Not only the fabrication process is simple, the sulfur assists the form of SiNWs but disappears by format of sulfur dioxide. According to the facts, a sulfide-assisted mechanism was suggested.Fabrication of poly-crystal silicon nanotubes (SiNTs) by CVD and NCA template techniques: The silicon nanotubes have been studied extensively because their special geometry structure and semiconductor property. However, the SiNTs were very difficult to synthesize in experiment due to their special structure. We successfully synthesized the SiNTs by using CVD and NCA template techniques according to the VLS mechanism and limitation of the nano-hole in the template. The nanotubes were composed of silicon and small oxygen by the EDX spectrum. And the diameters were among 50-100nm, which were related to the size of NCA. From the HRTEM, we knew that the nanotubes were partlycrystal with poly and non-crystal structure.The first-order Raman scattering, FTIR and PL spectra of SiNWs: The disordered mode including temperature effect was used to analyze the first-order Raman scattering (TO) in SiNWs. The first-order Raman scattering (TO) in SiNWs was calculated according to the phonon confinement mode including temperature. From the comparison, the position and peak width of the first-order Raman scattering with temperature agreed with those of the experimental results. Therefore, we considered that the heating effect by laser induced the high temperature at the sample and induced the red shift. Furthermore, that the positions of the first-order Raman scattering in SiNWs with ~30nm and ~100nm displayed no obvious shift showed the phonon confinement effect due to the small size did not play a key reason in the Raman shift. Furthermore, we also found the crystal quality of the SiNWs was weakly improved after long-time exposure by laser.According to the FTIR spectra of SiNWs, we analyzed the structure of the Si-0 in SiNWs under different growth conditions by using disorder mode. The intensity of the peak related to the silicon lattice would increase with the crystal quality enhanced; Furthermore, the intensity of the peak related to the oxide would decrease with the thickness of the oxide shell on SiNWs decreased. We also found the position of the peak related to the oxide (mainly was 1080cm"1 ) was similar with that of oxide film on silicon wafer.Furthermore, from the results of the PL spectra of the SiNWs, we think that the peak of 550nm maybe relate to the oxygen; while the 600nm maybe relate to the nature of silicon including the defects.更多还原