【作者】 刘硕；

【导师】 张跃；

【作者基本信息】 北京科技大学 ， 材料科学与工程， 2017， 博士

【摘要】 石墨烯具有优异的载流子传输能力和良好的透光性及柔韧性,被认为是构建柔性电子和光电器件的理想材料。利用半导体材料优异的光电转换能力构建石墨烯/半导体的复合结构,是获得高性能光电探测器件的有效途径。本论文控制合成出高质量的石墨烯和ZnO纳米线,采用摩擦静电辅助转移的方法实现了石墨烯的清洁转移,分别构建了石墨烯与单根ZnO纳米线以及石墨烯与ZnO纳米线阵列异质结光电探测器件,系统研究了压电电子学效应对器件性能的调控规律和内在机制。采用化学气相沉积法制备了石墨烯,利用SEM和拉曼光谱研究了生长参数对石墨烯形貌的影响,通过调节生长参数实现了单层、双层和多层的石墨烯的制备。采用化学气相沉积法和水热法分别制备了单根ZnO纳米线和ZnO纳米线阵列,多种表征手段显示两种方法获得的ZnO纳米线均沿[0001]方向生长,结晶性良好。采用摩擦静电辅助转移的方法实现了石墨烯的清洁转移,从而在不需要聚合物辅助的前提下,完成了石墨烯往PET、PI和PTFE等基底上的转移,解决了传统PMMA辅助转移法易产生杂质残留的问题。利用AFM的SKPM功能对转移过程中基底表面带电密度进行了研究,发现表面电荷可以保持超过2 h,保证了转移过程中石墨烯与基底的稳定结合。多种表征手段证实,转移获得的石墨烯结构完整、表面无杂质。在此基础上,研究了石墨烯的电学和力学性能。研究表明,转移后的石墨烯电学性能优异,并且承受基底大角度和多次弯曲后,器件性能依然可以保持,证实了利用摩擦静电辅助转移获得的石墨烯样品适合构建柔性的电子和光电器件。构建了石墨烯/ZnO纳米线异质结光电探测器,对器件在光伏和光栅压两种模式下对紫外光的响应进行了研究。由于石墨烯优异的载流子传输能力和ZnO纳米线对紫外光的有效吸收,器件在两种模式下都表现出优异的紫外光探测能力。在此基础上,研究了压电电子学效应对器件性能的调控规律,发现由于ZnO纳米线在应变下产生的压电电势对界面能带结构的影响,器件的性能可以得到进一步的提升。在光伏工作模式下,由于ZnO纳米线弯曲时产的负压电电势抬升了肖特基势垒的高度,展宽了耗尽层的宽度,增强了内建电场对光剩载流子的分离效率,使得器件在-0.44%的压缩应变下,响应度提高了 1.54倍;而在光栅压工作模式下,由于ZnO纳米线弯曲时产生的正压电电势降低了肖特基势垒的高度,提高了 ZnO中的光生电子向石墨烯中的注入效率,使得器件在0.44%的拉伸应变下,响应度提高了 26%。构建了石墨烯/ZnO纳米线阵列异质结光电探测器,通过表面处理抑制ZnO表面的缺陷密度,获得了良好的肖特基接触,肖特基结的开关比由2提高到了 114,反向漏电流降低到了 nA量级,器件在零偏压和反向偏压下的光电探测性能也随之得到提升。利用压电电子学效应进一步对器件性能进行了优化,发现在-0.349%的压缩应变下,器件的响应度可以提高17%,这归因于ZnO纳米线在压缩应变下负的压电电势对界面能带的显著调控。更多还原

【Abstract】 Due to its outstanding carrier transport ability and remarkable transparence,flexibility and strength,graphene has been considered as a promising material for next generation electronics and optoelectronics.In this regards,combing graphene with other semiconductors who possess prominent photoelectric conversion ability has been a valid way to obtain high-performance photodetector.In this article,high-quality graphene and ZnO nanowire were synthesized,graphene was transferred by a trbioelectricity-aasited method to other substrate and hybrids structures based on graphene and single ZnO nanowires as well as ZnO nanowires array were constructed.Piezoelectronic effect influence on the device performance was systematically investigated.Graphene was synthesized by the CVD method.The influence of growth parameters was investigated by SEM and Raman spectrum.By tuning the growth parameters,single-layer,bi-layer and multi-layer graphene were obtained.Single ZnO nanaowire and ZnO nanowires array were synthesized through CVD and shuire respectively.Characterizations results show that ZnO nanowire obtained by these two methods grow along[0001]direction.Compared with the CVD growth sample,ZnO nanowire synthesized by the hydrothermal growth method posesse more defects but higher uniformity of the growth direction.Using the trbioelectricity-aasited method,graphene was successfully transferred from copper foil to other substrates including PET,PI,PTFE,by the attraction force from the friction induced accumulated charge.Through the SKPM model of AFM,the charge density on the substrate was investigated.It is found the accumulated chage can stay on the substrate for more than 2 h,which is enough for the graphene transfer,due to the typical copper etching process is only 15 min.Characterization results show the structure integrity of transferred graphene is preserved and no residue is observed.To verify the electrical properties of graphene,a hybrid photodectector was constructed by decorating ZnO nanoparticles on graphene.The devie shows good detection ability to UV light and no performance degradation was observed even under bending,confirming the stability of the transferred graphene by the trbioelectricity-aasited method.Graphene/ZnO nanowire hybrid photodectector was successfully constructed.By connecting the different part of the device into test circuit,two detection models were realized,named photovoltage model and photo-gating model.Owing to the outstanding carriers transport ability of graphene and photo absorption ability of ZnO,the device shows good performance in both two models.The modulation of the device performance by piezoelectronic effect was then investigated.It is found the responsivity was improved by 2.54 times under-0.44%compressive strain for the photovoltage model and 26%under 0.44%tensile strain for the photo-gating model.Another Graphene/ZnO hybrid photodectector was constructed by transfer graphene on the ZnO nanowires array for UV detection.Surface passivation by H2O2 was first carried out to improve the contact properties between graphene and ZnO.As a result,the on-off ration was enhanced and the leakage current was decreased.Piezoelectronic effect was then used to improve the device perforamance further.The responsivity was enhanced by 17%under-0.349%compressive strain due to the dramatical modulation of the band structure in the device interface by the ZnO piezopotential.更多还原