溶胶—凝胶法制备掺钇氧化锌薄膜及其性能研究
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摘要
ZnO是一种新型的Ⅱ-Ⅵ族宽禁带化合物半导体材料,不仅光电性能优异、化学稳定性好、热稳定性高,且易于掺杂形成性能更为优异的材料,因而在太阳能电池、液晶显示器、短波长发光器件等领域具有广阔的应用前景。
ZnO薄膜的制备技术有多种,相比较而言,溶胶-凝胶(sol-gel)法具有成膜均匀性好、与衬底附着力强、易于原子级掺杂及工艺简单等优点。本论文采用溶胶-凝胶法,用旋转涂覆技术在玻璃基底上进行了掺钇氧化锌(YZO)薄膜的制备、掺杂等相关内容研究。主要研究了陈化时间、掺杂浓度、预处理温度、退火温度以及镀膜层数对薄膜的结晶状况、表面形貌、电阻率和透光率等的影响,探讨了溶胶-凝胶法制备YZO薄膜过程中,YZO薄膜的晶体结构与透射率、禁带宽度及导电性能之间的关系。研究结果如下:
(1)差热分析结果表明钇掺杂对ZnO薄膜的形成过程没有影响,且不存在与钇元素相关的相变,即掺入的钇大部分进入晶格。
(2)晶体结构分析表明:所制备的YZO薄膜呈六角纤锌矿结构,且表现出(002)晶面的取向性生长。其中YZO薄膜最佳的制备条件是:Y掺杂浓度为0.5at%、陈化时间为72h、预处理温度为300℃、退火温度为500℃、涂覆5层,其(002)晶面的衍射峰最强、半高宽最小,即结晶性和c轴择优取向性最好。而Y掺杂浓度的增加将使得晶粒粒径减小,薄膜的结晶性能下降。
(3)AFM分析表明YZO薄膜表面均匀致密,陈化时间的延长有利于薄膜的取向生长,同时粗糙度增大。
(4)透射光谱表明:所制备的YZO薄膜在可见光波段的透射率均超过85%,由最佳条件制备的薄膜其透光率最高,达到90%,这与XRD结果相一致,说明结构与性能之间存在对应关系。
(5)从YZO薄膜(αhv)~2～hv的曲线看各种参数对薄膜的光学禁带宽度都有影响,其中掺杂浓度对禁带宽度的影响最大,其次是退火温度、镀膜层数。
(6)电阻率测试结果显示随着掺杂浓度的增加,薄膜电阻率先减小后增大,掺杂浓度为1at%的薄膜其电阻率最低,为3.37×10~2Ω.cm。
ZnO is a novelⅡ-Ⅵfamily wide bandgap compound semiconductor with outstanding electro-optical performance、higher chemical/thermal stability and be prone to dope other elements forming material with more outstanding performance. So ZnO has wide applications in many fields such as solar cells、liqiud crystal display(LCD) and shortwave luminescence parts of apparatus.
A variety of thin film deposition techniques are employed to deposit zinc oxide films.Sol-gel technique offers many advantages for the fabrication of coatings, including excellent equality、strong adhesion to substrate、easy to dope at atomy level and simple technics.In this paper we study the preparation and properties of yttrium-doped ZnO thin films which have been deposited on common glass by spin coationg technique using sol-gel method.The effect of aging time、dopant concentration、pretreatment temperature、annealing temperature、layers of film plating on the crystal quality,morphology,electrical and optical properties of ZnO thin films are investigated.The relations between the structure、transmission、bandgap at the process of preparation YZO thin films by sol-gel method was researched.The results show that:
(1) The forming process of thin films undoped and doped is similar from the result of TG-DTA,and don't exist changes with yttrium element related.So the majority of doped yttrium enters the crystal lattice.
(2) The results of XRD shows that the YZO thin films assume hexagonal wurtzite structure.The crystal equality and preferential c-axis oriented are the best, the(002) peak is strongest,the FWHM is least when the optimized growing parameters are:72h(aging time)、300℃(pretreatment temperature)、500℃(annealing temperature) and 5 layers.The crystal quality and the grain size of YZO thin films decrease and the FWHM increases with the increase of dopant concentration.
(3) The analysis of AFM indicates that the YZO thin films are even and compact. The extended aging time is propitious to the preferential c-axis oriented growth and increase the coarseness of thin films.
(4) The transmission spectrum of all thin films suggests that the average transmittance in the visible range(380nm-760nm) is beyond 85%.The transmittance can reach 90%when best condition.This result is coincident with the result of XRD.
(5) Each parameter influences the bandgap of thin films from the(ahv) ~2～hv curve.The primary factor is dopant concentration,the secondary factors are annealing temperature and layers of film plating.
(6) The resistivity of thin films decreases first then increases with the increase of dopant concentration.The minimum resistivity is 3.37×10~2Ω.cm with dopant concentration 1at%.
ZnO薄膜的制备技术有多种,相比较而言,溶胶-凝胶(sol-gel)法具有成膜均匀性好、与衬底附着力强、易于原子级掺杂及工艺简单等优点。本论文采用溶胶-凝胶法,用旋转涂覆技术在玻璃基底上进行了掺钇氧化锌(YZO)薄膜的制备、掺杂等相关内容研究。主要研究了陈化时间、掺杂浓度、预处理温度、退火温度以及镀膜层数对薄膜的结晶状况、表面形貌、电阻率和透光率等的影响,探讨了溶胶-凝胶法制备YZO薄膜过程中,YZO薄膜的晶体结构与透射率、禁带宽度及导电性能之间的关系。研究结果如下:
(1)差热分析结果表明钇掺杂对ZnO薄膜的形成过程没有影响,且不存在与钇元素相关的相变,即掺入的钇大部分进入晶格。
(2)晶体结构分析表明:所制备的YZO薄膜呈六角纤锌矿结构,且表现出(002)晶面的取向性生长。其中YZO薄膜最佳的制备条件是:Y掺杂浓度为0.5at%、陈化时间为72h、预处理温度为300℃、退火温度为500℃、涂覆5层,其(002)晶面的衍射峰最强、半高宽最小,即结晶性和c轴择优取向性最好。而Y掺杂浓度的增加将使得晶粒粒径减小,薄膜的结晶性能下降。
(3)AFM分析表明YZO薄膜表面均匀致密,陈化时间的延长有利于薄膜的取向生长,同时粗糙度增大。
(4)透射光谱表明:所制备的YZO薄膜在可见光波段的透射率均超过85%,由最佳条件制备的薄膜其透光率最高,达到90%,这与XRD结果相一致,说明结构与性能之间存在对应关系。
(5)从YZO薄膜(αhv)~2～hv的曲线看各种参数对薄膜的光学禁带宽度都有影响,其中掺杂浓度对禁带宽度的影响最大,其次是退火温度、镀膜层数。
(6)电阻率测试结果显示随着掺杂浓度的增加,薄膜电阻率先减小后增大,掺杂浓度为1at%的薄膜其电阻率最低,为3.37×10~2Ω.cm。
ZnO is a novelⅡ-Ⅵfamily wide bandgap compound semiconductor with outstanding electro-optical performance、higher chemical/thermal stability and be prone to dope other elements forming material with more outstanding performance. So ZnO has wide applications in many fields such as solar cells、liqiud crystal display(LCD) and shortwave luminescence parts of apparatus.
A variety of thin film deposition techniques are employed to deposit zinc oxide films.Sol-gel technique offers many advantages for the fabrication of coatings, including excellent equality、strong adhesion to substrate、easy to dope at atomy level and simple technics.In this paper we study the preparation and properties of yttrium-doped ZnO thin films which have been deposited on common glass by spin coationg technique using sol-gel method.The effect of aging time、dopant concentration、pretreatment temperature、annealing temperature、layers of film plating on the crystal quality,morphology,electrical and optical properties of ZnO thin films are investigated.The relations between the structure、transmission、bandgap at the process of preparation YZO thin films by sol-gel method was researched.The results show that:
(1) The forming process of thin films undoped and doped is similar from the result of TG-DTA,and don't exist changes with yttrium element related.So the majority of doped yttrium enters the crystal lattice.
(2) The results of XRD shows that the YZO thin films assume hexagonal wurtzite structure.The crystal equality and preferential c-axis oriented are the best, the(002) peak is strongest,the FWHM is least when the optimized growing parameters are:72h(aging time)、300℃(pretreatment temperature)、500℃(annealing temperature) and 5 layers.The crystal quality and the grain size of YZO thin films decrease and the FWHM increases with the increase of dopant concentration.
(3) The analysis of AFM indicates that the YZO thin films are even and compact. The extended aging time is propitious to the preferential c-axis oriented growth and increase the coarseness of thin films.
(4) The transmission spectrum of all thin films suggests that the average transmittance in the visible range(380nm-760nm) is beyond 85%.The transmittance can reach 90%when best condition.This result is coincident with the result of XRD.
(5) Each parameter influences the bandgap of thin films from the(ahv) ~2～hv curve.The primary factor is dopant concentration,the secondary factors are annealing temperature and layers of film plating.
(6) The resistivity of thin films decreases first then increases with the increase of dopant concentration.The minimum resistivity is 3.37×10~2Ω.cm with dopant concentration 1at%.
引文
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