Precursors' order effect on the properties of sulfurized Cu2ZnSnS4 thin films
Precursors' order effect on the properties of sulfurized Cu2ZnSnS4 thin films
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DOI：
10.1088/0268-1242/24/10/105013
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发表时间：
2009-10
影响因子：
1.9
通讯作者：
P. Fernandes;P. Salomé;A. F. da Cunha
中科院分区：
文献类型：
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作者：
P. Fernandes;P. Salomé;A. F. da Cunha
一种直流磁控溅射的方法来生长高品质的Cu 2 ZnSnS 4（CZTS）薄膜，用作太阳能电池的吸收层，正在开发中。这种方法结合了金属前体的直流溅射与S蒸汽中的硫化以及生长后的KCN处理，以去除可能不需要的Cu 2 −xS相。在这项工作中，我们报告的结果，改变前体的沉积顺序上的最终CZTS薄膜的形态和结构特性的影响的研究。KCN处理对光学性质的影响也通过漫反射测量进行了分析。使用触针轮廓术、SEM/EDS分析、XRD和拉曼光谱对生长的各个阶段进行了形态、成分和结构分析。漫反射率的研究已经完成，以估计的CZTS膜的带隙能量。我们测试了铜前体的两种不同沉积顺序，即Mo/Zn/Cu/Sn和Mo/Zn/Sn/Cu。触针轮廓测定法分析显示，在KCN处理之前和之后，分别在300-550 nm和230-250 nm的范围内具有高的平均表面粗糙度。所有的XRD谱显示在28.45°处沿沿着（1 1 2）的择优生长取向。拉曼光谱在338 cm-1和287 cm-1处显示出归因于Cu 2 ZnSnS 4的主峰。这些测量也证实了KCN处理在去除Cu 2-xS相方面的有效性。从漫反射测量的分析，两种前体序列的带隙能量估计接近1.43eV。KCN处理的薄膜显示出更好的定义的吸收边，但是，带隙值没有显着的影响。热点探针测量证实了CZTS具有p型半导体行为，C-V分析用于估计多数载流子密度，给出的值为3.3 × 1018 cm−3。
A dc magnetron sputtering-based method to grow high-quality Cu2ZnSnS4 (CZTS) thin films, to be used as an absorber layer in solar cells, is being developed. This method combines dc sputtering of metallic precursors with sulfurization in S vapour and with post-growth KCN treatment for removal of possible undesired Cu2−xS phases. In this work, we report the results of a study of the effects of changing the precursors' deposition order on the final CZTS films' morphological and structural properties. The effect of KCN treatment on the optical properties was also analysed through diffuse reflectance measurements. Morphological, compositional and structural analyses of the various stages of the growth have been performed using stylus profilometry, SEM/EDS analysis, XRD and Raman Spectroscopy. Diffuse reflectance studies have been done in order to estimate the band gap energy of the CZTS films. We tested two different deposition orders for the copper precursor, namely Mo/Zn/Cu/Sn and Mo/Zn/Sn/Cu. The stylus profilometry analysis shows high average surface roughness in the ranges 300–550 nm and 230–250 nm before and after KCN treatment, respectively. All XRD spectra show preferential growth orientation along (1 1 2) at 28.45°. Raman spectroscopy shows main peaks at 338 cm−1 and 287 cm−1 which are attributed to Cu2ZnSnS4. These measurements also confirm the effectiveness of KCN treatment in removing Cu2-xS phases. From the analysis of the diffuse reflectance measurements the band gap energy for both precursors' sequences is estimated to be close to 1.43 eV. The KCN-treated films show a better defined absorption edge; however, the band gap values are not significantly affected. Hot point probe measurements confirmed that CZTS had p-type semiconductor behaviour and C–V analysis was used to estimate the majority carrier density giving a value of 3.3 × 1018 cm−3.