The Preparation Of ZnO/SnS Nano Heterojunction Arrays And Photoelectric Characteristics Research

With the both characteristics of new-type ZnO and SnS semiconductor materials, weintegrated n-type ZnO nanowire arrays with p-type SnS semiconductor material fordevelopment of new solar cell, UV photodetector, LED devices and new type sensors. Thealigned ZnO naowire arrays was prepared by hydrothermal method, and the p-type SnSsemiconductor material was fabricated by thermal evaporation and electroplating process,respectively. In this thesis, the one-dimensional nano-scale ZnO/SnS core-shell heterojunctionarrays were synthesized and the characteristics were analyzed by XRD, SEM, PL spectrum,IV measurement and photoelectric effect test, respectively. The main research contents are asfollows:(1)Aligned ZnO NW arrays were directly prepared on zinc foil substrates reacting inaqueous ammonia. All of the reacting processes were performed in a sealed Teflon reactionkettle. The ZnO NW array samples with different appearance and microstructure wereprepared, and the effects of solution concentration, pressure and growth time on themicrostructure of ZnO NW arrays has been studied, respectively. The preferred growthorientation, microstructure and morphology of synthesized NWs were characterized. Thecorresponding relationships of shapes and reaction conditions to synthesized ZnO NW arrayswere analyzed. And the growth processes of various ZnO NW arrays were studied.(2)With two methods of vacuum thermal evaporation and electroplating process, p-typeSnS thin films and nano p-type SnS coating layer were deposited on the Si substracts and thesurface of aligned ZnO NW, respectively. So the core-shell nano heterojunction arrays ofn-ZnO/p-SnS were constructed. And the as-prepared ZnO/SnS core-shell heterojunctionarrays were analyzed by XRD, SEM, PL spectrum analytic methods, respectively. Meanwhile,comparative analysis of synthesized samples under different testing conditions is carried out.By changing the experimental parameters, such as voltage, solution concentration andreaction time, etc., the influence of experimental parameters on the crystallization of SnScoating layer was studied. And by changing the reaction temperature, vacuum pressure, thedistance between the sample holder and the evaporation source, etc., so the effect ofexperimental conditions to the material performance of SnS coating layer was analyzed. Itshould be noted that the as-prepared SnS coating layer with electrodeposition method wasbetter than the other preparation methods. The optimal prepared condition for SnS coating layer growth is the concentration of the reaction solution is5mmol, the reactive time is10s and the electroplating voltage is0.2V. in the end, the effect of annealing processes to theZnO/SnS heterojunction samples prepared with electrodeposition method was discussed.After the samples were annealed treatment at200℃for1h, the crystallinity of the ZnO/SnSheterojunctions was improved clearly. And the growth defects were reduced significantly, theIV contact characteristics of PN heterojunction as the optical and electrical properties werealso enhanced.(3)Thirdly, the photoelectric characteristics of the prepared n-ZnO/p-SnS core-shellnano-heterojunctions were studied. The results showed that the larger the diameter of ZnOnanowires, the smaller of the internal resistance in the ZnO/SnS nano pn junction, so thebetter of the IV contact characteristics in the n-ZnO/p-SnS core-shell nano-heterojunctions.Conversely, the smaller the diameter of the ZnO nanowires, the larger the internal resistanceand contact barrier in the n-ZnO/p-SnS PN junction as the specific surface area of ZnO NWsare increased. The results given that the contact characteristics of ZnO/SnS nanoheterojunction arrays synthesized by electrodeposition method are better then the samples’ones prepared with thermal evaporation method. Meanwhile, the photocurrent of the nanoheterojunction arrays increases gradually as the decrease of the diameter of ZnO nanowires.Under the same deposition conditions, if the electrodeposition solution concentration is toohigh or too low, it will all cause the SnS coating layer thickness spent thick or too thin. It willaffect the contact characteristics and photoelectric conversion characteristics of n-ZnO/p-SnScore-shell nano-heterojunction arrays. It was found that5mmo SnCl22H2O solutionconcentration in electroplating process is optimum preparing conditions, and photoelectricperformance of nano heterojunction arrays is best.