ZnO纳米线阵列的电沉积法制备及表征

December 物理化学学~(Wuli Huaxue Xuebao) Acta P ．一Chim．Sin．，2010，26(12)：3369—3372 3369 [Article] ZnO纳米线阵列的电沉积法制备及 表 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 征 王丹丽 阮永丰 张灵翠 杨红波 (天津大学理学阮 天津 300072) www．whxb．pku．edu．cn 摘要： 利用直流电沉积方法在多孔氧化铝模板的孔洞中生成锌纳米线，在氧气氛围中，于800。C下氧化2 h， 将氧化铝中的锌氧化成氧化锌．本研究利用氧气氛围进行锌的氧化，大大提高了传统方法的氧化锌纳米线的制 备效率．用场发射扫描电子显微镜(FE．SEM)、透射电子显微镜(TEM)和X射线衍射仪(XRD)对其形貌及成分进 行表征和 分析 定性数据统计分析pdf销售业绩分析模板建筑结构震害分析销售进度分析表京东商城竞争战略分析 ，结果表明，氧化铝模板的有序孔洞中填充了大尺寸、均匀连续的多晶态氧化锌纳米线．纳米线具 有约 1000：1的高纵横比，其长度等于氧化铝模板的厚度，直径约为80 nm．光致发光(PL)光谱表明，氧化锌纳米 线在 504 nm处有由于氧空位引起的较强蓝绿光发射．这为进一步研究ZnO／AAO组装体发学性质和开发新型 功能器件提供了基础． 关键词： 阳极氧化铝： 氧化锌； 纳米线阵列； 电沉积： 氧化 中图分类号： 0646； 078； O61 Preparation by Electrodeposition and Characterization of ZnO Nanowire Arrays WANG Dan—Li RUAN Yong—Feng ZHANG Ling—Cui YANG Hong·Bo (SchoolofScience,Tianjin University,Tianjin 300072， R．China) Abstract．． 0rdered zinc(Zn)nanowire arrays embedded jn anodic aIuminum oxide(AA0)templates were prepared by an effective electrodeposition method．Oxygen was used to oxidize the electrodeposited zinc nanowire arrays in the AAO templates．By thermal treatment in an oxygen atmosphere at 800。C for 2 h，the deposited Zn was completely oxidized．The microstructures and opticaI properties of the synthesized zinc oxide(ZnO)nanowire arrays were investigated by field emission scanning electron microscopy (FE—SEM)，transmission electron microscopy(TEM)，X．ray diffraction(XRD)，and photoluminescence(PL) spectrum analytic apparatus．We found that Iarge scale polycrystalline ZnO nanowire arrays were uniformIv assembled in fhe nanochannels of the AAO template．The nanowires have a very high aspecf ratio of about 1 000：1 with the length equaling lhe template thickness and a diameter of about 80 nm．PL measurements of the ZnO／AAO assembly showed a strong green emission at 504 nm．which was attributed tO the oxygen vacancy defects of the ZnO nanowires．These results can be used in further studies of the structural and functional properties of electroluminescence devices based on the ZnO／AAO assembly． Key W ords： Anodic aluminum oxide； Zinc oxide； Nanowire array； EIectr0depOs⋯On： Oxidization The multifunctional material ZnO has been used to make va． ristors，gas sensors，solar cells，and other devices since 1950s ． It has attracted great interest recently in the semiconductor field because ofits large direct bandgap，s~ong exciton binding energy and important application prospects in optoelectronic devices． Most researches have been focused on its nanostructures and Received：August 30，2010；Revised：October 8，2010；Published on Web：October 22 ， 2010． Corresponding author．Email：13．1anyf@tju．edu．cn；Tel：+86-22—27406635． The project was supposed by the Natural Science Foundation ofTianjin，China(07JCZDJC00600，07JCYBJC06000) 天津市自然科学基金(07JCZDJC00600，07JCYBJC06000)资助项 目 ⑥ Editorial office ofActa Physico．Chimica Sinica 3370 Acta P s．一Chim．Sin．201 0 VO1．26 P·type doping ，while few researches have been done on the luminescence of ZnO with non-p—n junction．It is possible to fabricate a new type of ZnO electroluminescence device with non-p一 junction by inserting ZnO into anodic aluminum oxide (AAO)templates ．Based on the properties of AA0 photonic crystals，the lum inescence of ZnO in the device mentioned above would be enhanced-9J_AAO has also been extensively used to synthesize nanometer-size fibril，rods，wires，and tubules through a variety of methodst10-11】 ． Ordered ZnO nanowires play an im， portant role in those applications．ZnO nanowire arrays were synthesized by one—step electrodeposition㈣ in an AAO template． The deposition of Zn(OH)2 introduced by aqueous solution competes with the formation of ZnO㈣ and the Zn(OH)2 can quench the near band emission of ZnOt ．Li et a1．I also suc cessfully prepared ZnO nanowire arrays in an AA0 template through therm ally oxidizing the Zn nanowire arrays in air． However,the thermal oxidation time was very long(about 35 h) and the deposited area was quite smal1．Because ofthe absence of suitable pretreatment of the AAO template，the challenge is to fabricate uniform ZnO nanowire arrays with large deposited area． Those drawbacks of the current methods to prepare ZnO／AAO assembly would limit its applications in electroluminescence devices． Inthispaper,amore efficientmethodwasdevelopedtoprepare large scale uniform ZnO nanowires．The oxidizing time was greatly decreased from 35 to 2 h and the deposited area of ZnO nanowire arrays was increased．Field emission scanning electron microscopy(FE—SEM)，transmission electron microscopy(TEM)， X—ray diffraction(XRD)，and photolum inescence(PL)techniques were employed for sample characterization． 1 Experimental The AAO was fabricated by a two—step anodization process ． Briefly,ahighpurity(99．999％)aluminum platewas annealed at 550℃ in air．After being electro—polished．the A1 plate was an- odized in 0．3 mo1．L oxalic acid(>99．5％，analytical reagent， (AR))solution under constant voltage of 40 V at room tempera ture for 10 h．After removal of the anodic alum ina layer,the textured A1 was anodized again under the same condition as the step one．and then the Al layer was removed in a saturated CuC12 (>99％，AR)solution．A subsequent etching treatment was carried out in 5％(w)phosphoric acid(>85％，AR)solution at 30℃ for 30 min to remove the barrier layer and enlarge the pore diameter． The thickness ofthe resultedAAO template is about 100岫 and the pore diameter is about 80 am． Ordered ZnO nanowire arrays embedded in AAO templates were fabricated by electro—depositing Zn followed by oxidation of the deposited Zn．A standard three．electrode electrochemical eell was used for the electric deposition．with a saturated calomel electrode as the reference electrode．a Pt sheet about 3 cm in area served as the count electrode．A Pt layer was placed by magnetron sputtering method onto one side ofthe AAO template used as the working electrode．Before mounting into the electrochemi cal cell， the AAO was immersed in an electrolyte solution under ultrasonic agitation for 1 0 min to remove the contaminants on the template surface and to improve the intemal surface wettability．The treatment iS critical to obtain homogeneous nan owires in the whole growing area．The deposition experiment was carried out in a solution containing 80 g·L『。znS()4·7H20(>99．5％，AR)and 2O g-L H3B03(>99．5％，AR)at room temperature for about 30 min．The voltage range was between 1．25 V and 1-3O V andthe time used was betw een 20 min and 30 min．The higher voltage was applied，the less deposition time was needed．After electro- depositing，the Zn nanowire arrays were embedded in the AAO． The subsequent step was to mechanically polish the Pt electrode， which was on the surface ofAAO．It is essential for Zn nanowire arrays to be oxidized sufficiently and efficiently．Through a therm al treatm ent in oxygen atmosphere at 800℃ for 2 h，the deposited Zn was oxidized completely．The deposited Zn／AAO assembly was black with metallic luster．After oxidation，a white ZnO| O assembly was obtained For FE—SEM study,the samples were quenched in liquid nitrogen for 1 min to obtain a regular cross section．For TEM observation．ZnO nanowires with the AAO template were dissolved in 1 mo卜L- NaOH solution to remove the AAO template and some dissociative ZnO nanowires were gotten． 2 Results and diScussi0n The surface morphology and the structure of the AA0 were observed by field emission scanning electron microscopy fFE—SEM NANOSEM 430，FEI，USA)．As shown in Fig．1A， the AAO has a highly oriented porous structure of uniform Fig．1 FE—SEM images ofAAO template (A)top view,(B)cross section view No．1 2 WANG Dan—Li et a1．：Preparation by Electrodeposition and Characterization of ZnO Nanowire Arrays 3371 Fig．2 FE—SEM images of(A)ZnO nanowire array embedded inAAO and(B)a single nanowire out ofthe channel ofAAO， (C)TEM image of ZnO nanowires TheinsetinfigureA showsthe enlargedimage ofZnO nanowire arrays． 1400 1200 — 1000 800 罂 600 400 200 0 20 40 60 80 20／(。) 350 300 250 盂 200 150 三 1O0 50 0 20 40 60 80 20／(。) Fig．3 XRD patterns of the Zn nanowire embedded in AAO before(A)and after(B)calcination at 800℃ for 2 h pore sizes，which could be organized in a precise hexagonal structure．The average pore diameter of the AAO obtained is about 80 nm．while the interpore distance is about 120 nm． Fig．1 B shows the FE—SEM image from cross section view of the AAO．It displays that the pore channels are nearly in paral— lel and the internal surface is smooth． Typical FE—SEM images of a ZnO| 0 assembly are shown in Fig．2A．It is observed clearly that the long Zn0 nanowires uniformly embedded in AAO are of perlect straight— ness and continuity．The upper right inset is an enlarged magni— fication image of the ZnO nanowire arrays．It can be seen that 也e surface of the nanowires is smooth．The average diameter Of the ZnO nanowires is about 80 nm．almost equals to the pore sizes of the template used．The nanowires are with very high aspect ratio of about 1000：l，with the length of about 100 gm，which equaling to template thickness．As can be noticed in Fig．2B，a single nanowire is out of the chann el of AAO．It was form ed when the sample was split for a cross section examina— tion．Our data confirmed that the ZnO nanowires were tom— pacted by the eleetrodeposition method． To further confirm our experiment results，Zn0 nanowires were also observed by transmission electron microscopy(TEM TECNAI G F 20．PHILIPS)．Fig．2C displays a result observed by the TEM ．1Two setlarate ZnO nanowires are shown in Fig．2C，and it is noticed that these nanowires are very straight． the diameter of these nanowires is about 80 nm．almost equals to the diameter of the nanochannels． The crystalline struclure was determined by XRD with Cu radiation using a Rigaku X．ray diffractometer,as shown in Fig．3．Fig．3A shows the XRD pattem of as—deposited Z~AAO assembly．There was no any other leature 1ine i11 the sample but those of deposited Zn．Fig_3B shows the XRD pattem of the sample ann ealed in oxygen atmosphere at 800 ℃ for 2 h． No Zn feature Iines can be seen in Fig．3B．while ZnO phase was detected．It indicates that the Zn nanowires imbedded in AAO chann els can be completely oxidized in 2 h under oxy— gen atmosphere condition．However,the same oxidation pro— tess would take 35 h in air．It shortens the preparation time of ^／nm Fig．4 Photoluminescence(PL)spectrum of ZnO nanowires The inset is the PL spectrum ofa blankAAO template． 一 瘁～^ jIsca1 I] 3372 Acta P s．一Chim．Sin．201 0 VO1．26 Zn0l 0 assemblies enormously by the electrodeposition method．Furtherm ore．the XRD patterns indicate that the ZnO nanowires are of polycrystalline structures without preferred orientation．We also found that there was A1203 feature detect． ed neither in Fig．3A nor in Fig_3B．which is because anodic alu— minum oxide is amorphous unti1 heated up to 824℃ ” ． Photoluminescence(PL212，SPEX)measurements were per— formed to study the luminescence property of ZnO nanowires． A strong emission band was observed at 504 am，which was at tributed to the oxygen vacancy defects of Zn0㈣．as shown in Fig．4．A blue emission band at 430 am was observed．Compar． ing the PL spectrum of a blank AAO template(the inset in Fig．41 with that of the ZnO／AAO assembly,we conclude that the broad emission band around 430 nm originates from the AAO template． 3 COnclusions In conclusion．1arge scale unifornl ZnO nanowire a~ays based on hexagonally arranged AAO was fabricated by an ef- fe：ctive electrodeposition method．Their FE．SEM images show that the ZnO nanowire arrays are long，continuous，and un i— form．XRD patterns indicate that Zn nanowires in AAO can be oxidized completely in 2 h at 800℃ in oxygen atmosphere． The ZnO| O assembly has a strong green emission band at 504 niYl and a blue emission band at 430 nm．The green emis— sion is attributed to oxygen defects and the blue emission origi— hates from O The above conclusions suggest that the ZnO| AA0 assembly could be useful for the preparation of ZnO elec— troluminescence devices． References 1 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