沉积预制层衬底温度对CIGS薄膜结构特性的影响

Influence of substrate temperature of deposited precursor layer on structural properties of CIGS thin films

采用三步共蒸发工艺在玻璃衬底上制备CIGS薄膜,研究沉积预制层的衬底温度对CIGS薄膜结构特性的影响。薄膜的厚度、组份、晶相结构、表观形貌和电学特性分别由台阶仪、X射线荧光光谱(XRF)、X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)和霍耳效应测量仪来表征。沉积预制层的衬底温度较低(如300℃和360℃)时,预制层中Ga含量较低,容易形成In2Se3相;而衬底温度较高(如400℃)时,预制层中Ga含量较高,容易形成(In,Ga)2Se3相;原因是Ga2Se3的形成焓(-462.4kJ/mol)比In2Se3的(-360kJ/mol)低,没有In2Se3稳定;In2Se3相比Ga2Se3相更容易稳定存在,尤其是在低温下;当温度较高时,Ga2Se3相也容易存在,与In2Se3一起形成(In,Ga)2Se3固溶体。而且,衬底温度较高(如400℃)时,沉积的CIGS薄膜中的Ga含量比其它两种衬底温度下沉积的薄膜都高,薄膜粗糙度较小,迁移率和载流子浓度都比较大,电阻率较小。

In this article,CIGS thin films were deposited on glass substrates by three-stage co-evaporation technique, and the influence of substrate temperature of deposited precursor layer on structural properties of CIGS thin films is researched. The thickness, the composition, the crystal structure, the morphology and the electical properties of the films were measured by step meter, X-ray diffraction （XRD）, scanning electron microscope （SEM） and Hall meter respectively. Ga content in precursor layers is lower,and InzSe3 phase is more easily formed for lower substrate temperatures （for 300 ℃ and 360 ℃）. Ga con- tent in precursor layers is higher, and （In, Ga）2 Se3 phase is more easily formed for higher substrate tem- perature （for 400 ℃ ）. The reason is that formation enthalpy of Ga2 Se3 （--462.4 kJ/mol） is lower than that of In2 Se3 （--360 kJ/mol）, and In2 Se3 phase is stabler than Gaz Se3 phase under low temperature es- pecially. When substrate temperatures are higher,GazSe3 phase is easy to be formed,and is made up of （In,Ga）2 Se3 and Inz Se3 phases. Furthermore,Ga content in CIGS thin films deposited under higher sub- strate temperature （for 400℃ ） is higher than that under lower temperature, and the coarseness and re- sistivity of CIGS films are lowe1：,while the mobility and the carrier density of CIGS films are higher.