磁控溅射法制备的CdS:Al薄膜的性质研究

doi:10.15541/jim20160357

摘要/Abstract

摘要：

采用Al和CdS双靶共溅射的方法, 调控Al和CdS源的沉积速率, 制备出不同Al掺杂浓度的CdS:Al薄膜。通过XRD、SEM、AFM、紫外-可见透射光谱分析、常温霍尔测试对CdS: Al薄膜的结构、形貌、光学和电学性质进行表征。XRD结果表明, 不同Al掺杂浓度的CdS:Al薄膜均为六方纤锌矿结构的多晶薄膜, 并且在(002)方向择优生长。SEM和AFM结果表明, CdS:Al薄膜的表面均匀致密, 表面粗糙度随着Al掺杂浓度的增加略有增加。紫外-可见透射光谱分析表明, CdS:Al薄膜禁带宽度在2.42~2.46 eV 之间, 随着Al掺杂浓度的增加而略微减小。常温霍尔测试结果证明, 掺Al对CdS薄膜的电学性质影响显著, 掺Al原子浓度3.8%以上的CdS薄膜, 载流子浓度增加了3个数量级, 电阻率下降了3个数量级。掺Al后的CdS薄膜n型更强, 有利于与CdTe形成更强的内建场, 从而提高太阳电池效率。用溅射方法制备的CdS:Al薄膜的性质适合用作CdTe薄膜太阳电池的窗口层。

关键词: CdS:Al薄膜, 射频磁控溅射, CdTe太阳电池

Abstract:

CdS:Al thin films with different doping concentrations were deposited by controlling deposition rate of CdS and Al targets in co-sputtering process. The morphological, structural, optical, and electrical properties of as-prepared CdS:Al films were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), UV-visible absorption spectrum, and room temperature Hall-system. XRD patterns indicates that all the CdS:Al films are polycrystalline films with hexagonal wurtzite structure and have a preferential orientation in (002) direction. The uniform and compact films can effectively be formed on insulating substrates. It is worth noting that the average grain size increases with Al doping concentration. On the other hand, the surface root-mean-square (RMS) roughness also shows slightly increase. UV-visible transmittance spectra show that the band gap of CdS:Al film decreases slightly in the range of 2.42-2.46 eV with increasing Al doping concentration. The Hall measurements indicate that the effect of Al doping concentration on electrical property of CdS films is apparent. In comparison with the un-doped CdS thin films, the carrier concentration of CdS:Al films increases by three orders of magnitude when the Al concentration is higher than 3.8%, while the resistivity of which decreases by three orders of magnitude. The doping level of CdS films is improved by doping with Al atoms to enhance the built-in electric field, which may realize high open voltage (V_oc) for CdTe thin film solar cells. The properties of CdS:Al film prepared by co-sputtering are suitable as a window layer of CdTe thin film solar cells.

Key words: CdS:Al films, RF magnetron sputtering, CdTe solar cells

中图分类号:

TQ174

王佛根, 陈蕴璐, 任胜强, 张家远, 武莉莉, 冯良桓. 磁控溅射法制备的CdS:Al薄膜的性质研究[J]. 无机材料学报, 2017, 32(4): 413-417.

WANG Fo-Gen, CHEN Yun-Lu, REN Sheng-Qiang, ZHANG Jia-Yuan, WU Li-Li, FENG Liang-Huan. Properties of CdS:Al Films Deposited by Magnetron Sputtering[J]. Journal of Inorganic Materials, 2017, 32(4): 413-417.

图/表 9

表1 不同Al掺杂浓度的CdS薄膜的目标和实际原子浓度

Table 1 Target and actual atomic concentrations of CdS:Al films

Target concentration of Al atoms(X₀)	Actual concentration of Al atoms(X₁)	Deviation (X₁-X₀)
1.0%	1.5%	0.5%
3.0%	3.8%	0.8%
4.6%	5.2%	0.6%
6.0%	6.3%	0.3%
7.0%	7.4%	0.4%

图1 未掺杂和不同Al掺杂浓度的CdS薄膜的XRD图谱

Fig. 1 XRD patterns of un-doped and Al-doped CdS films

图2 未掺杂和不同Al掺杂浓度的CdS薄膜的表面SEM照片

Fig. 2 SEM surface images of un-doped and Al-doped CdS films

图3 未掺杂和不同Al掺杂浓度CdS薄膜的晶粒尺寸分布图

Fig. 3 Distribution of average grain size of undoped and Al doped CdS films

图4 未掺杂和不同Al掺杂浓度的CdS薄膜的粗糙度

Fig. 4 Roughness of un-doped and Al-doped CdS films

图5 未掺杂和不同Al掺杂浓度的CdS薄膜的紫外-可见透过谱

Fig. 5 UV-visible absorption spectra of undoped and Al doped CdS films

图6 CdS:Al薄膜的禁带宽度与掺杂浓度的关系

Fig. 6 Relationship between energy band gap of CdS:Al film and Al doping concentration

图7 CdS:Al薄膜的电阻率与掺杂浓度的关系图

Fig. 7 Relationship between resistance of CdS:Al film and Al doping concentration

图8 CdS:Al薄膜的迁移率以及载流子浓度与掺杂浓度的关系图

Fig. 8 Migration rate and carrier concentration of CdS:Al films prepared with different Al doping concentrations

参考文献 20

[1]	MOUTINHO H R, ALBIN D, YAN Y, et al.Deposition and properties of CBD and CSS CdS thin films for solar cell application . Thin Solid Films, 2003, 436(2): 175-180.
[2]	BONNET D.Manufacturing of CSS CdTe solar cells. Thin Solid Films, 2000, 361(7): 547-552.
[3]	DUAN X F, LIEBER C M.General synthesis of compound semiconductor nanowires. Adv. Mater., 2000, 12(4): 298-301.
[4]	JUN Y W, LEE S M, KANG N J, et al.Controlled synthesis of multi-armed CdS nanorod architectures using monosurfactant system. Am. Chem. Soc., 2001, 123( 21): 5150-5153.
[5]	LEE JAE-HYEONG, LEE DONG-JIN.Effects of CdCl2 treatment on the properties of CdS films prepared by r.f. magnetron sputtering. Thin Solid Films, 2007, 5(15): 6055-6059.
[6]	NAIR P K, NAIR M T S, GARCÍA V M, et al. Semiconductor thin films by chemical bath deposition for solar energy related applications. Solar Energy Materials & Solar Cells, 1998, 52(3/4): 313-344.
[7]	WU X J, ZHANG J Y, ZHANG Z Z, et, al. Effect of Fe dopling on the optical properties of GdS. Chinese Journal of Luminescence, 2008, 29(1): 144-148.
[8]	BONILLA S, DALCHIELE E A.Electrochemical deposition and characterization of CdTe polycrystalline thin films. Thin Solid Films, 1991, 204(2): 397-403.
[9]	KOBAYASHI M, NAKAMURA S, KITAMURA K, et al.Luminescence properties of CdS quantum dots on ZnSe. Journal of Vacuum Science & Technology, 1999, 17(17): 2005-2008.
[10]	SAKAI H, TAMARU T, SUMOMOGI T, et al.Crystal direction of CdS thin film produced by laser ablation. Japanese Journal of Applied Physics, 1998, 37(7A): 4149-4153.
[11]	FELDMEIER E M, FUCHS A, SCHAFFNER J, et al.Comparison between the structural, morphological and optical properties of CdS layers prepared by close space sublimation and RF magnetron sputtering for CdTe solar cells. Thin Solid Films, 2011, 519(21): 7596-7599.
[12]	FEREKIDES C S. High efficiency CSS CdTe solar cells. Thin Solid Films, 2000, 361-362(99): 520-526.
[13]	MIREMADI B K, COLBOW K, HARIMA Y.A CdS photoconductivity gas sensor as an analytical tool for detection and analysis of hazardous gases in the environment. Rev Sci Instrum. Review of Scientific Instruments, 1997, 68(68): 3898-3903.
[14]	KOBAYASHI M, KITAMURA K, UMEYA H, et al.Growth of CdS self-organized quantum dots by molecular beam epitaxy and application to light emitting diode structures. Journal of Vacuum Science Technology B Microelectronics & Nanometer Structures, 2000, 18(3): 1684-1687.
[15]	WILSON J I B, WOODS J. The electrical properties of evaporated films of cadmium sulphide. Journal of Physics & Chemistry of Solids, 1973, 34(2): 171-181.
[16]	DENG Y, YANG J, YANG R, et al. Cu-doped CdS and its application in CdTe thin film solar cell. AIP Advances, 2016, 6(1): 015203-1-10.
[17]	HOSSAIN M S, ISLAM M A, HUDA Q, et al.Growth optimization of ZnxCd1-xS thin films by radio frequency magnetron co-sputtering for solar cell applications. Thin Solid Films, 2013, 548(12): 202-209.
[18]	ATAY F, BILGIN V, AKYUZ I, et al.The effect of In doping on some physical properties of CdS films. Materials Science in Semiconductor Processing, 2003, 6(4): 197-203.
[19]	PATIL B N, NAIK D B, SHRIVASTAVA V S.Synthesis and characterization of al doped CdS thin films grown by chemical bath deposition method and its application to remove dye by photocatalytic treatment. Chalcogenide Letters, 2011, 8(2): 117-121.
[20]	XU H, WU L, WANG W, et al.The Influence of hydrogen on the properties of zinc sulfide thin films deposited by magnetron sputtering. International Journal of Photoenergy, 2014, 2014(1): 1-6.