ZnS、ZnS:Mn纳米材料的制备及其光电器件性能研究

【作者】 王彩凤；

【导师】 李清山； 王继锁；

【作者基本信息】 曲阜师范大学 ， 光学， 2017， 博士

【摘要】 ZnS是II-VI族一种非常重要的半导体材料,具有较好的光学和电学性能,在光电子器件、发光二极管、传感器、探测器和化工等领域应用广泛。对ZnS进行Mn掺杂得到的ZnS:Mn晶体材料的光学性能也十分优异。尤其是不同纳米结构的ZnS,由于量子限制效应,常会表现出不同于体材料的新颖特殊的光电性能。本文首先在Si上利用脉冲激光沉积（PLD）法和水热法分别生长了ZnS、ZnS:Mn薄膜及其纳米结构材料,研究了不同生长条件对ZnS、ZnS:Mn的结构、形貌和光学特性的影响。然后又以GaN为衬底生长了ZnS:Mn薄膜及其纳米颗粒,通过合理调节薄膜的生长参数和后退火处理条件,可以使ZnS:Mn/GaN复合体系发出白光。另外,为了提高白光发射质量,在中间插入一层ZnO薄膜或Zn O纳米棒,得到了发射白光性能较好的ZnS:Mn/ZnO/GaN复合膜体系及其核壳结构的纳米棒阵列,并初步研究了ZnS:Mn/ZnO/GaN核壳阵列器件的电致发光特性。最后在石英衬底上生长了ZAZ（ZnS/Au/ZnS、ZnS/Au/ZnO）三层膜,研究了三层膜的光学和电学性能。具体内容如下:1、以Si（100）为衬底,利用PLD技术在不同制备条件下生长了ZnS、ZnS:Mn薄膜。采用XRD、AFM、SEM及PL技术,分别研究了ZnS、ZnS:Mn薄膜的结构、形貌和发光特性。结果发现,制备得到的ZnS薄膜是多晶,在425nm和445nm左右有两个发光峰。当衬底温度从室温到400℃时,生长的ZnS:Mn也是多晶,当衬底温度升高到500℃和600℃时,生长的ZnS:Mn薄膜近似单晶,在28.5°附近有一个较强的衍射峰,归属于立方β-ZnS薄膜的（111）晶向。当衬底和退火温度升高时,衍射峰都变强,说明ZnS:Mn薄膜的结晶质量得到改善。另外,ZnS:Mn的光致发光特性受温度的影响也较大。590nm左右归因于Mn2+4T1?6A1发射的橙红光随温度升高而逐渐增强,同时峰位发生蓝移。2、在不同条件下,利用水热法在Si（100）上制备了ZnS纳米结构。发现用Zn（NO3）2·6H2O作为Zn源、SC（NH2）2作为S源得到的ZnS球状颗粒的发光性能较好。基于此,我们研究了溶液浓度、生长温度、有无种子层对ZnS球状颗粒的晶体结构和发光性质的影响。结果发现,在不同制备条件下,所有样品的发光谱都覆盖了400⁷00nm的可见光区域,由中心位于520nm的绿色发光峰和570nm的肩峰组成。当溶液浓度为0.03 mol/L,生长温度为140℃时,ZnS球状颗粒的发光最强。然而,对于在ZnS种子层上生长的ZnS纳米颗粒,中心发光峰位蓝移到500nm左右,发光强度减小。另外,以四水合乙酸锰Mn（CH3COOH）2·4H2O作为掺杂的Mn源,还制备了ZnS:Mn纳米结构,对其发光特性受Mn掺杂浓度的影响进行了研究。SEM显示其表面形貌也为球形颗粒,和纯净ZnS相比,掺入Mn之后,平均粒径减小。当掺杂浓度变大时,衍射峰有移向小角度现象。随着Mn的掺杂浓度从0.5%增加到2%,580nm左右与Mn相关的4T1-6A1发射强度增大,超过2%时,发光强度反而降低。3、利用PLD技术在GaN衬底上制备了ZnS:Mn薄膜,对ZnS:Mn/GaN复合体系发光特性受衬底温度和退火温度的影响进行了研究。结果发现,ZnS:Mn/GaN复合体系的PL谱包括600nm左右的橙红色发光峰和440nm附近的蓝色发光峰,适当调整蓝光和红光发射强度的比例,ZnS:Mn/GaN复合体系可以发射出白光。但要想得到质量较高的白光发射,根据红绿蓝三基色叠加的原理,必须使复合体系中的绿光发射出来,为此,利用ZnO可以发射550nm的深能级发射的有利条件,在GaN和ZnS:Mn之间插入ZnO薄膜或ZnO纳米棒,得到ZnS:Mn/ZnO/GaN复合膜体系及其核壳阵列结构。使得ZnS:Mn/ZnO/GaN的发光覆盖了从紫外到红光的整个区域（350⁷00nm）,色坐标分别为（0.3103,0.3063）和（0.3347,0.318）,非常接近标准白光区域（0.33,0.33）。这说明制备得到的ZnS:Mn/ZnO/GaN核壳结构阵列器件可以发射出较强的白光。另外,用水热法在GaN衬底上生长了ZnS:Mn纳米颗粒,详细研究了其结构和光致发光特性。研究发现,ZnS:Mn/GaN纳米颗粒结构的PL谱由三个发光峰构成,分别是来源于GaN的440nm蓝光,归因于ZnS带隙中的S空位能级电子（中性施主）与Zn空位能级空穴（中性受主）的复合引起的500nm附近绿光,以及来源于Mn离子的4T1-6A1跃迁产生的580nm的橙黄光。通过CIE分析,其发光色坐标为（0.3319,0.3196）,也接近于白光发射。另外,还初步研究了ZnS:Mn/ZnO/GaN核壳结构的纳米棒阵列器件的电致发光特性,发现在正向电压下,EL谱由415nm左右的蓝紫光和610nm附近的橙红光组成,且随着激励电压的增大,发光增强。EL谱的色坐标都和标准白光非常接近。通过拟合分峰处理发现EL谱实际上由400、430、570和630nm这四个发光带构成。对于该异质结器件的具体发光机制及其实用性还需要进一步探索。4、利用PLD技术在透明石英上生长了ZnS/Au/ZnS三层膜结构,详细研究了金属Au层厚度、ZnS层厚度、衬底温度和退火温度等因素对ZnS/Au/ZnS光电性质的影响。结果发现,Au层膜厚对三层薄膜的载流子浓度和面电阻影响最大。当Au层和ZnS层厚度分别为10nm和60nm时,薄膜的品质因数最高为3.34×10-3Ω^-1,此时三层薄膜在400⁸00nm的平均透过率为81%,面电阻为36.4Ω/sq,载流子浓度为1.91×1021cm-3。通过研究衬底温度和退火温度对ZnS/Au/ZnS三层薄膜光电性能的影响发现,室温下制备得到的三层薄膜光电性能最优,而在适当的温度下退火可以提高其光电性能。当200℃退火后,三层薄膜的品质因数为5.48×10-3Ω^-1,透过率为82.7%,面电阻为27.3Ω/sq。另外,还初步研究了ZnS/Au/ZnO复合薄膜的光电性能。更多还原

【Abstract】 ZnS is a kind of important Ⅱ-Ⅵ group compound semiconductor material,having good optical and electrical properties,and it has been widely used in optoelectronic devices,light-emitting diodes,sensors,detectors,solar cells and chemical engineering,etc.ZnS:Mn crystals show excellent optical properties by doping Mn in ZnS.Especially,the different nanostructures of ZnS often exhibit special photoelectric performances which are different from its bulk material due to quantum confinement effect.ZnS,ZnS:Mn films and their nanostructures were prepared on Si substrate using pulsed laser deposition technique and hydrothermal method respectively,and the influence of different growth conditions on the structure,morphology and optical properties were studied.Then,ZnS:Mn films and its nanoparticles were deposited on GaN substrates,and ZnS:Mn/GaN composite system can emit white light by reasonably adjust the growth parameters and post-annealing treatment conditions of the films.In addition,in order to improve the quality of white light emission,ZnO thin films or ZnO nanorods were inserted as the middle layer,then ZnS:Mn/ZnO/GaN composite system and its core-shell nanorods array which have good white light emission performance were obtained.The electroluminescent characteristics of ZnS:Mn/ZnO/Ga N core-shell nanorods array device were preliminary studied.Finally,ZAZ（ZnS/Au/ZnS、ZnS/Au/ZnO）transparent conductive tri-layer films were prepared on transparent quartz substrates,and their photoelectric properties were studied in detail.Specific contents are as follows:1.ZnS and ZnS:Mn films were grown on Si（100）substrates using PLD technology under different experimental conditions.By utilizing X-ray diffraction（XRD）,atomic force microscope（AFM）and photoluminescence（PL）technology,the structure,morphology and luminescence properties of ZnS and ZnS:Mn films were studied.The results show that,the prepared ZnS is polycrystalline film,and its PL peak located at 425 nm and 445 nm.When the substrate temperature increases from room temperature to 400 ℃,the obtained ZnS:Mn is also polycrystalline film,however,when the substrate temperature increases up to 500 ℃ and 600 ℃,the obtained ZnS:Mn is single crystal film,and there is only one strong diffraction peak near 28.5°,which is belong to cubic β-ZnS（111）orientation.With the increase ofsubstrate temperature,the diffraction peak gradually becomes strong and sharp,which indicates that the film quality is gradually getting better.With the increase of annealing temperature,the crystallization quality of ZnS:Mn films is improved.At the same time,we also found that the substrate temperature and annealing temperature had a great influence on the photoluminescence properties of ZnS:Mn thin films.With the increase of temperature,the PL intensity of orange-red light around 590 nm which is ascribed to 4T1-6A1 emission of Mn2+ gradually increases,along with the blueshift of the peak.2.ZnS nanostructures were grown on Si（100）substrate using hydrothermal synthesis method under different experimental conditions.It is found that,the luminous performance of ZnS spherical nanoparticles is best which were obtained using Zn（NO3）2·6H2O as Zn source,thiourea（SC（NH2）2）as S source.Based on this,the influences of solution concentration,growth temperature and seed layer on the crystal structure and luminescence properties of ZnS spherical nanoparticles were studied.The results show that,under different preparation conditions,all the spectrum of the samples is a 400⁷00nm wide band,which is composed of green emission band centered near 520 nm and a shoulder peak around 570 nm.When the concentration of solution is 0.03 mol/L and the growth temperature is 140℃,the luminous intensity of ZnS spherical nanoparticles is the largest.However,for the ZnS nanoparticles grown on ZnS seed layer,the emission peak position blue shifts to about 500 nm,and the PL intensity decreases.In addition,ZnS:Mn nanostructures were prepared using Mn（CH3COOH）2·4H2O as the doping source,and studied the effects of Mn doping concentration on its structure and luminescent properties.SEM results showed that the surface morphology is also spherical particles.Compared with pure ZnS,the average particle size decreases after Mn is doped.As the doping concentration increases,the diffraction peak shifts to the small angle.As Mn doping concentration increases from0.5% to 2%,the PL intensity of 4T1-6A1 emission from Mn around 580 nm increases.However,when more than 2%,the luminous intensity decreases.3.ZnS:Mn films were prepared on GaN substrates using PLD technique and the effects of substrate temperature and annealing temperature on luminescence properties of ZnS:Mn/GaN composite systems were studied.The results found that,the PL spectrum of ZnS:Mn/GaN includes orange red light peaked around 600 nm and blue light centered at 440 nm.ZnS:Mn/GaN composite systems can emit white light by appropriatly adjusting the proportion of blue light and red light emission intensity.However,in order to obtain high quality white light emission,the green light should be emitted out from the composites,according to the three primary colors（red,green and blue）superposition principle.Therefore,utilizing the favorable condition that ZnO can emit deep level emission around 550 nm,ZnO thin films or ZnO nanorods were inserted between GaN substrate and ZnS:Mn films,then ZnS:Mn/ZnO/GaN composite system and its core-shell nanorods array device were obtained.The PL spectra of ZnS:Mn/ZnO/GaN cover from ultraviolet to red light（350⁷00nm）in the entire area of the visible light region.The color coordinates are（0.3103,0.3063）and（0.3347,0.318）respectively,very close to the standard white light area（0.33,0.33）.This indicates that the prepared ZnS:Mn/ZnO/GaN core-shell nanorods array device can emit intensive white light.In addition,ZnS:Mn nanoparticles were prepared on GaN substrates using hydrothermal systheis method,and its structure and PL properties were studied in detail.The studies show that,the PL spectrum of ZnS:Mn/GaN nanoparticles consists of three emission bands,that is,the blue light at440 nm emitting from GaN,the green light near 500 nm which is attributed to the recombination of electrons from the energy level of S vacancies（neutral donor）with the holes from the energy level of Zn vacancies（neutral acceptor）with the band gap,and orange light at 580 nm which origins from 4T1-6A1 transition of Mn ions.Through the analysis,the CIE coordinates of its luminous is（0.3319,0.3196）,close to white light emission.In addition,the electroluminescent（EL）characteristics of ZnS:Mn/ZnO/Ga N core-shell nanorods array device were preliminary studied.It is found that,under the forward voltage,the EL spectrum is composed of blue-violet emission around 415 nm and orange light at 610 nm.With the increase of excitation voltage,the luminous intensity gradually increased.The color coordinates of EL spectra are very close to the white area.Through the fitting multi-peak processing,the EL spectrum is composed of 400,430,570 and 630 nm.The specific luminescence mechanism of the heterojunction devices and its availability needs further research.4.ZnS/Au/ZnS transparent conductive tri-layer films were prepared on transparent quartz substrates using PLD technique.The influences of Au thickness,ZnS thickness,substrate temperature and annealing temperature on photoelectric performance of ZnS/Au/ZnS tri-layer films were studied in detail.The results show that,the carrier concentration and sheet resistance of the tri-layer films are mainly depends on the thickness of Au layer.When the thickness of Au layer and ZnS layer are 10 nm and 60 nm respectively,the tri-layer film has the highest quality factor of 3.34×10-3 Ω^-1,and the average transmittance is 81% in the visible light area,sheet resistance is 36.4 Ω/sq,carrier concentration is 1.91×1021cm-3.By studying the effects of substrate temperature and annealing temperature on the photoelectric performances of ZnS/Au/ZnS tri-layer composite films,it is found that,the tri-layer films prepared at room temperature has the best photoelectric performances.When it is annealed at proper temperatures,its photoelectric properties can be improved.When the annealing temperature is 200℃,the quality factor of tri-layer films is 5.48×10-3Ω^-1,and the average transmittance is 82.7%,sheet resistance is 27.3Ω/sq.In addition,the photoelectric characteristics of ZnS/Au/ZnO composite films were preliminary studied.更多还原