氧化铟锡(ITO)薄膜溅射生长及光电性能调控

Growth and the Tunable Optical and Electrical of Sputtered ITO Films

目的选取影响氧化铟锡(ITO)薄膜生长关键的3种参数,即薄膜生长的氧气流量、薄膜厚度和热处理退火,系统研究其对ITO薄膜光学和电学性能的影响规律。方法采用直流溅射法,在氩气和氧气混合气氛中溅射陶瓷靶材制备ITO薄膜样品。利用真空热处理技术对所制备的ITO薄膜进行真空退火处理。通过表面轮廓仪测试厚度、X-射线衍射仪(XRD)表征结构、X-射线光电子能谱仪(XPS)分析元素含量、分光光度计测试透过率和四探针测试薄膜方块电阻,分别评价薄膜厚度、光学性能和电学性能,并对比研究热处理对薄膜结构和光电性能的影响规律。结果电阻率随氧气流量的增加呈现出先缓慢后急剧升高的规律,在氩气和氧气流量比为150∶8时,可得到400 nm厚、电阻率为8.0×10^(-4)Ω·cm的ITO薄膜。厚度增加可降低薄膜电阻率,氧气流量的增加可明显改善薄膜透光性。通过真空热处理可提高室温沉积ITO薄膜的结晶性能,较大程度地降低电阻率。在真空热处理条件下增大薄膜厚度可降低薄膜电阻率,氧气流量增加不利于ITO薄膜电阻率的降低。在氩气和氧气流量为150∶6条件下制备的ITO薄膜,经500℃真空热处理后电阻率可达到最低值(2.7×10^(-4)Ω·cm)。结论通过调控氧气流量和厚度来优化ITO薄膜的结构和氧空位含量,低温下利用磁控溅射法可制备光电性能优异的ITO薄膜;真空热处理可提高薄膜结晶性能,通过氧气流量、厚度和热处理温度3种参数调控可获得最低电阻率的晶态ITO薄膜(2.7×10^(-4)Ω·cm),满足科技和工程领域的需求。

Sn-doped indium oxide(ITO)film,due to the both distinctively transparent and conductive properties,is one of the most widely used transparent and conductive films,which has also been universally employed in various kinds of advanced opt-electron devices.In view of the advantages including facile preparation processes,superior performance and scalability,sputtering technique has been regarded as the optimal method for ITO film fabrication.The three critical parameters,namely oxygen flow rate,thickness and annealing process,were chosen to study the effects on the structure and optical-electrical properties of ITO films.In this work,ITO films were prepared by direct-current(DC)sputtering technology with argon(Ar)and oxygen(O_(2))mixed gases and ceramic ITO target.ITO films were also annealed under vacuum condition.The thickness was measured by contact profilometry(Taylor-Hobson Talystep).The film structure was detected by X-ray diffraction(XRD,Philips X´Pert).The element content was characterized by X-ray photoelectron spectroscopy(XPS).The UV/visible spectra were obtained using a spectrophotometer(Cary 5000,Varian,USA)with a wavelength from 800 nm to 300 nm.The sheet resistance of the ITO film was measured with a four-point co-linear probe method at room temperature.Afterwards,the comparable studies of ITO films obtained in the presence and absence of annealing process were also conducted,particularly the effects on the optical and electrical properties of ITO films.The electric resistivity of as-deposited ITO film slightly increases with the rise of oxygen flow rate,and increases dramatically with continuously increased oxygen flow rate.The resistivity of ITO film with 400 nm thickness reaches 8.0×10^(‒4)Ω·cm with the ratio of Ar∶O_(2)at 150∶8.The increase of thickness promotes to the low resistivity.Larger oxygen flow rate could directly promote the transparency of the ITO films.The annealing process under vacuum condition could increase the crystallinity of ITO film deposited at room temperature,giving rise to the low resistivity.Similarly,the annealed ITO film with large thickness obtains the low resistivity,and higher oxygen flow rate could also increase the resistivity.The ITO film shows the minimum resistivity of 2.7×10^(‒4)Ω·cm when the ratio of Ar∶O_(2)is 150∶6 and annealing temperature fixes at 500℃under the vacuum condition.By tuning the ways of oxygen content and thickness to optimize the structure and oxygen vacancy content of ITO film,the sputtered ITO films with superior optical and electrical properties could be obtained at room temperature.The annealing process could improve the crystallinity of ITO film.The ITO film with the minimum resistivity of 2.7×10^(‒4)Ω·cm can be obtained through adjusting the three critical parameters,the crystalline ITO film with the lowest resistivity can meet the requirements from the scientific and engineering areas.