石墨炔修饰的ZnO薄膜紫外探测器

ZnO Ultraviolet Photodetector Modified with Graphdiyne

制备了石墨炔修饰的金属-半导体-金属结构的ZnO紫外探测器,研究了不同旋涂次数的石墨炔修饰对探测器性能的影响。实验结果表明,石墨炔修饰的探测器比未修饰器件的光电流提高4倍,暗电流降低2个数量级,同时探测器的响应度和探测率也明显提高,其中旋涂2次的石墨炔修饰的器件特性为最优。在10 V偏压下,旋涂2次的石墨炔修饰的探测器响应度高达1759 A·W^(-1),探测率高达4.23×10^(15) Jones,这是迄今为止报导过的溶胶-凝胶法制备的ZnO紫外探测器的最高值。经过对探测器各项性能的测试分析可知,石墨炔修饰的ZnO探测器性能的提高归因于石墨炔良好的空穴传输特性。暗环境下ZnO与石墨炔界面处形成p-n结,使探测器的暗电流大幅降低;光照条件下光生空穴在石墨炔中聚集,减少了电子空穴对的复合,有效提高了器件的光电流。由于石墨炔修饰减少了ZnO表面的氧分子吸附和解吸附过程,器件的响应速度也明显加快。

ZnO is an ideal material for ultraviolet(UV)detection due to its wide direct-bandgap,high exciton binding energy,and high internal photoconductive gain.However,ZnO UV detectors have the disadvantages of slow response speed and low detectivity.Graphdiyne(GD)is a novel carbonaceous allotrope,and possesses excellent electronic performance in air.In this study,the metal-semiconductor-metal(MSM)structured lateral ZnO UV detectors were prepared,and GD was employed to modify the ZnO surface.The effects of GD deposited 1–3 times(viz.1T,2T,and 3T GD)on the performance of ZnO ultraviolet detector were carefully investigated.The results show that the dark current of the bare ZnO detector is 24μA under a bias of 10 V,while that of the graphdiyne-modified detector is^0.34μA(about two orders of magnitude reduction).The dark current remains almost the same for the 1T,2T and 3T GD films.The photocurrents of 1–3T GD-modified detectors were 0.21,0.32,0.27 mA,respectively.The device modified with 2T GD displays the highest photocurrent,which is significantly enhanced in comparison to the unmodified device(0.08 mA)under a 365-nm UV radiation of 100μW·cm?2.Meanwhile,the responsivity and detectivity are improved remarkably.Under a bias of 10 V,the 2T-GD-modified detector displays high responsivity of 1759 A·W?1 and detectivity of 4.23×1015 Jones.The detectivity is thus far the highest for ZnO UV detectors prepared by the sol-gel method.The improved performance of the GD-modified detector is attributed to the p-n junction formed between the GD and the ZnO film.At dark,the p-n junction is formed between the ZnO film and the GD,which greatly decreases the dark current of the detector.Under UV illumination,photogenerated holes accumulate in the GD,reducing electron-hole recombination;thus,the photocurrent is significantly increased.Furthermore,desorption and absorption of oxygen on the ZnO surface are much reduced due to the GD attached on the ZnO surface,thus improving the response speed of the detector.However,the intensive distribution of GD slightly hinders the UV absorption of ZnO thin films,reducing the responsivity of the detector.Careful optimization shows that the use of 2T GD gives the best output,and the corresponding ZnO UV detector exhibits very good performance.Overall,this study demonstrates that using GD can effectively improve the performance of ZnO UV detector.