APP  >> Vol. 9 No. 8 (August 2019)

    基于CdS薄膜的柔性光探测器研究
    CdS Film-Based Flexible Photodetectors

  • 全文下载: PDF(2338KB) HTML   XML   PP.373-378   DOI: 10.12677/APP.2019.98044  
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作者:  

陈红蕾,盛俊华,彭 锐,叶传瑶,王 敏:合肥工业大年夜学,材料迷信与工程学院,安徽 合肥

关键词:
电子束蒸镀PET衬底CdS薄膜柔性光探测器光电流 Electron Beam Evaporation PET Substrate CdS Films Flexible Photodetector Photocurrent

摘要:

本文采取电子束蒸发镀膜法在PET柔性衬底上制备出基于CdS薄膜的柔性光探测器。PET对高温有敏理性,应用电子束蒸发镀膜办法可以在高温下制备出CdS薄膜。应用XRD、拉曼光谱和AFM对PET上CdS薄膜停止表征,成果注解所制备的薄膜致密性好、性能优良。批量制备器件,在偏压为1 V,光功率为365 nm的紫外光源照射条件下停止光照应性能测试,取得的光电流为0.347 μA,照应度达到17.35 A/W。对器件在不合曲折应变下停止测试。统计测试数据显示CdS薄膜柔性光探测器件在0.08%~0.12%应变下,曲折前后光电流变更较小,注解CdS薄膜柔性光探测器在应变成~0.1%下性能稳定。

CdS film-based flexible photodetectors were fabricated by depositing CdS films on flexible PET substrate in combination with evaporating the Au/Cr electrodes using the shadow mask. PET is sensitive to high temperature and films can be deposited at low temperature by e-beam evaporation method. The as-produced CdS films were characterized by XRD, Raman and AFM, and the results show that the preparation of CdS films with good compactness has been succeeded on PET by e-beam evaporation method. The photoresponse properties were tested under the irradiation of a 365 nm ultraviolet light with power of 1 mW/cm2
under a bias voltage of 1 V. The obtained photocurrent and calculated responsivity are 0.347 μA and 17.35 A/W, respectively. Finally, the devices were tested under bending with different strains for 1 h. The statistics results show that the photocurrents of the CdS film-based flexible photodetectors have little to no change before and after bending under the strain of 0.08% to 0.12%, indicating that the devices have stable performance under the strain of ~0.1%.

1. 引言

近年来,柔性显示、可穿着和可折叠设备愈来愈遭到人们的看重,柔性薄膜光探测器件逐步进入人们的视野,并广泛应用于智能控制、电子设备、航天航空等范畴中 [1] [2] 。CdS是直接带隙的II-VI族化合物半导体材料,能隙宽度为2.42 eV,能隙较宽,接收系数较高,接收系数在104~105 cm−1,在350~500 nm的波长范围内,CdS有较好的接收 [3] [4] [5] ,常作为光探测器的光接收层材料。聚对苯二甲酸乙二纯酯(PET)具有优胜的机械性能、耐化学腐化,在可见光范围内有很高的透过率,是以PET是优胜的柔性衬底材料 [6] ,但PET不耐高温,高温下轻易产生塑性变形 [7] 。电子束蒸发法镀膜温度较低,且操作步调简单,薄膜的质量好,膜厚轻易控制,所以采取电子束蒸发镀膜法在高温下制备CdS薄膜。并应用掩膜板蒸镀电极,修建光探测器阵列。对制备出的柔性器件停止描写构造分析,研究曲折前后光照应性能。

2. 实验

实验采取厚度为50 μm尺寸大年夜小为6 cm × 8 cm的PET (聚对苯二甲酸乙二纯酯)作为衬底,经过丙酮和乙醇各超声清洗5 min,清洗PET外面尘土和杂质,空气枪吹干,用等离子清洗机清洗15 min,去除外面的无机物和残余杂质等,确保PET衬底干净、有亲水性。将清洗好的PET用沟道宽度为40 μm的条带掩膜板贴紧,在电子束蒸发镀膜机的基板上固定好。设置好蒸镀参数,蒸镀100 nm的CdS条带薄膜。将制备好的CdS条带薄膜/PET样品取出,剪下一部分,分别停止XRD,拉曼,AFM测试分析,其他的CdS条带薄膜/PET,条带与相婚配的沟道长度50 μm的电极阵列掩膜板贴合,在CdS条带薄膜/PET上分别蒸镀10 nm Cr和100 nm Au作为电极。制备出的样品自上而下的构造为:电极/CdS条带薄膜/PET,同时具有电极阵列,制备出CdS薄膜柔性光探测器。

3. 实验成果分析

图1是100 nm CdS薄膜/PET衬底的XRD衍射图谱(a)和实验选用的PET衬底的XRD衍射图谱(b)。在CdS的衍射图谱中在23.1˚、26.4˚、43.7˚、47.8˚和52.1˚的地位上有5个衍射峰,个中,26.4˚、43.7˚和52.1˚的峰为立方晶CdS衍射峰,分别关于立方晶的(111)、(220)和(311)晶面。47.8˚对应的为六方晶CdS衍射峰,对应的六方晶面为(103)晶面,23.1˚对应的峰为基底PET的衍射峰。可见电子束蒸发镀膜所得的CdS薄膜为立方晶和六方晶混淆构造。个中立方晶的占比远远多于六方晶,大年夜部分的CdS薄膜的构造为立方晶构造,衍射图谱没有出现明显的杂峰,注解样品纯度较高,没有其他杂质和衍生物。

Figure 1. (a) XRD of 100 nm thick CdS thin film on PET substrate, (b) XRD of PET substrate

图1. (a)PET基底上的100 nm厚CdS薄膜的XRD图,(b) PET衬底的XRD图

图2是100 nm CdS薄膜/PET衬底图2(a)和PET衬底图2(b)的拉曼光谱。可见在去除衬底PET的特点峰后,可明显的不雅察到CdS拉曼光谱的两个纵光子声学特点峰 [8] ,分别位于301.4 cm−1和601.6 cm−1处,特点峰明显且清楚,解释其结晶性好,膜的质量高。

Figure 2. (a) Raman analysis of 100 nm thick CdS films on PET substrate, (b) Raman analysis of PET substrate

图2. (a) PET基底上的100 nm厚CdS薄膜拉曼光谱,(b) PET衬底的拉曼光谱

图3为原子力显微镜对PET衬底上100 nm CdS薄膜停止不雅察并拟合所取得的2D图象图3(a)和3D图象图3(b),经过过程外面粗糙度计算,Rq = 1.32 nm,Ra = 1.05 nm,可见蒸镀在PET上的CdS薄膜稳定且外面崛起幅度小,生成的薄膜粒径大年夜小均匀,具有优胜的结晶性和致密性。

Figure 3. (a) 2D and (b) 3D AFM images of 100 nm thick CdS thin filmonPET substrate

图3. PET基底上100 nm厚CdS薄膜的(a) 2D和(b) 3DAFM图

CdS薄膜柔性光探测器件在偏压为1 V,光功率为1 mW/cm2的波长为365 nm的紫外光源照射条件下停止光探测性能测试。光照应度(Rλ)是光电探测器基本性能的参数之一。计算公式:Rλ = ∆I/PS [9] ,个中∆I (光电流)是光源照射下的电流与暗电流之差,P是照射光源的功率。S是薄膜受光照的有效区域面积。光暗电导比 = Iph/Idark [10] ,比值越大年夜,说冥器件照应性能越好。图4是制备好的CdS薄膜柔性光探测器件在不合曲折应变条件(0%,0.08%,0.12%,0.16%,0.2%)下,曲折1小时后的归一化电流–时间周期图。在10 s时加光源照射,CdS薄膜接收光子能量,取得能量的电子跃迁到导带上,构成电子空穴对,进步电导率,使电流敏捷上升并稳定。在20 s时撤去光源后,电子和空穴恢复复合,电流以较快的速度降低 [11] ,反复4组加光–撤光操作取得周期图。未曲折时∆I = 0.347 μA,Rλ = 17.35 A/W,光暗电导比≈1.04。测试取得的Rλ比白等人制备的CdS薄膜器件探测的照应度赶过2个量级 [12] ,解释电子束蒸发镀膜法取得的薄膜质量高,均匀性好。拉伸曲折产生应变(ε)由公式ε = (t/2R) × 100%计算所得,t是样品PET厚度,R是曲折时曲率半径。在应变成0.08%下曲折1小时后,∆I = 0.334 μA,曲折后光电流与未曲折年光电流的百分比为96%,注解器件在曲折前后光电流变更较小。从图4中可以看出,CdS薄膜柔性光探测器件在0.08%、0.12%、0.16%曲折应变下,光电流根本没有变更。当曲折应变成0.2%时,光电流变小,但光照应周期仍稳定。光电流降低的缘由是,硫化镉薄膜在曲折过程当中,受应力感化会产生渺小裂纹,但随着曲折应变的增长,裂纹逐步增多,影响载流子的传输,薄膜电阻变大年夜,使得光电流降低。

Figure 4. I-tcurve of CdS film-based flexible photodetector after bending for 1 h with different strains

图4. CdS薄膜柔性光探测器在不合应变下曲折前后的电流–时间曲线

图5是经过过程掩膜板批量制备好的CdS薄膜柔性光探测器件,分别0.08%、0.12%、0.16%、0.2%的曲折应变,曲折1小时,每组应变条件下10个器件曲折后光电流与未曲折光电流的百分比统计图。从统计图中可以看出:在0.08%曲折应变时,器件曲折后光电流是未曲折时的96%。曲折应变0.12%、0.16%下,器件曲折后光电流仍能达到未曲折时的83%以上。应变在0.2%时,器件曲折后光电流是未曲折时的63.8%。测试成果注解该器件在~0.1%应变下曲折前后光照应性能稳定,随着应变增长,器件光照应性能愈来愈不稳定,但仍能正常任务。

Figure 5. Statistics of the normalized photocurrent of CdS film-based flexible photodetectors under bending for 1 h with different strains

图5. CdS薄膜柔性光探测器在不合应变下曲折前后的电流-时间曲线

4. 结论

本文经过过程电子束蒸发镀膜法,高温下在PET衬底上成功制备出CdS薄膜光探测器阵列,且对CdS薄膜柔性光探测器停止了研究。电子束蒸发镀膜法处理了PET不耐高温的成绩,制备出的CdS薄膜致密均匀。其光照应测试注解CdS薄膜柔性光探测器阵列光照应度高,在~0.1%应变下曲折前后光照应性能稳定。该制备办法简单,可批量临盆,本钱昂贵。

基金项目

国度天然迷信基金面上项目(21473047)。

NOTES

*通信作者。

文章援用:
陈红蕾, 盛俊华, 彭锐, 叶传瑶, 王敏. 基于CdS薄膜的柔性光探测器研究[J]. 应用物理, 2019, 9(8): 373-378. https://doi.org/10.12677/APP.2019.98044

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