【作者】 周雄图；

【导师】 石旺舟；

【作者基本信息】 华东师范大学 ， 凝聚态物理， 2007， 硕士

【摘要】 掺铈钇铁石榴石磁光薄膜,由于具有巨法拉第效应,在高性能非互易波导型器件、集成光学型光隔离器等方面得到广泛的应用。掺杂可改善ZnO薄膜的光电性能而成为目前研究的热点,尤其在有机柔性衬底上生长的ZnO基薄膜具有可卷曲、重量轻等独特的优点,在电子报纸、大视角柔性显示器等领域的应用而引起人们极大的研究兴趣。本文利用脉冲激光沉积(Plused Laser Deposition PLD)技术,选取CelY2Fe5O12和Hf掺杂ZnO(HfxZn1-xO)两种多元氧化物薄膜为研究对象,分别研究了制备工艺、热处理参数、不同掺杂量对两种薄膜结构、磁性能和光、电学性能的影响,获得了如下主要结果:1、利用PLD方法分别在GGG(111)和Si(100)衬底上沉积了CelY2Fe5O12薄膜,对不同衬底上薄膜结构和磁性能分析结果显示:衬底温度为800℃时,可在GGG衬底上制备出具有良好YIG(444)取向的CelY2Fe5O12薄膜,薄膜为顺磁性;而在Si衬底上沉积的CelY2Fe5O12薄膜为非晶结构,经700℃空气中热处理后,薄膜转变为多晶结构,并显示出较强的铁磁性。2、研究了退火温度和Si02过渡层对Si(100)衬底上CelY2Fe5O12薄膜结构和磁性能的影响,结果表明:当退火温度为700℃时,薄膜为接近单一相的Ce1Y2Fe5O12多晶结构,随着退火温度的升高,薄膜出现相分离反应,先是Ce元素以CeO2的形式析出,然后Y3Fe5O12继续分解产生Fe2O3,使得薄膜的饱和磁化强度先增加后减小,且与薄膜中存在的氧空位相关联;比较Si和SiO2/Si衬底上沉积的CelY2Fe5O12薄膜得出, SiO2过渡层由于能够有效抑制薄膜中氧空位的产生,从而提高薄膜的饱和磁化强度。3、通过PLD方法,分别在Si(100)和柔性PET衬底上生长了不同Hf含量掺杂的HfxZn1_xO薄膜,对其微结构和光学性能进行了研究。结果表明,在两种衬底上都可以实现Hf4+离子在ZnO薄膜中的有效掺杂,薄膜具有较高的透射率,荧光光谱显示364nm和380nm两紫外荧光峰共存现象。对于Si衬底上的HfxZnl-xO薄膜,在H晗量为0≤x≤15 mol%范围,薄膜始终保持为单相ZnO的六角纤锌矿结构,且具有高度c轴择优取向。而对于PET衬底上的HfXZn1-xO薄膜,当H晗量大于5 mol%时,薄膜开始向非晶结构转变。不同Hf掺杂量对HfxZnl-XO薄膜的结构和性能的影响表现为:随Hf含量的增加,ZnO薄膜的晶格常数增加,晶粒减小,荧光强度显著增强,薄膜带隙宽度变大,但荧光峰位置基本不变,分析表明荧光峰可能起源于Hf杂质能级和价带间的跃迁。4、5Pa氧压条件下沉积了一系列低Hf含量(Hf含量为0≤x≤2 mol%)HfxZn1-xO薄膜,对其透明导电性能的研究表明,薄膜具有较高的透射率,随掺杂量增大,薄膜方块电阻先减小后增大。当Hf含量0.5 mol%时,薄膜方块电阻可下降到16 Ω/□(电阻率约为1.2×10-3Ω.cm),而其透射率则仍高于85%。更多还原

【Abstract】 Ce-substituted yttrium iron garnet (Ce_xY_3-xFesO₁₂ Ce:YIG) thin films have been widely used in many fields such as high performance non-reciprocal wave-guide devices and integrated optical devices for its large magneto-optic effect and low propagation loss. Doped ZnO has been under an extensive research since appropriate impurity doping can further improve the properties of ZnO. ZnO-based films deposited on flexible polymer substrates have recently gained tremendous interests because they are light and flexible to be easily deformed, and can be used for certain applications, such as smart cards, electronic paper and flexible display where flexibility and lightweight are needed. Pulsed laser deposition is one of the most potential deposition technologies, especially for multi-element oxides thin films who desire film stoichiometry and lower substrate temperature.In this dissertation, The Ce₁Fe₅O₁₂ thin films and Hf-doped ZnO thin films with different Hf contents (Hf_xZn_1-xO) were deposited on various substrates using pulsed laser deposition. The influences of deposition parameters, post-annealing and doping concenstrations on the structure, magnetic, electrical and optical properties of these two multi-element thin films were investigated. The main results are as follows:1. Ce₁Y₂Fe₅O₁₂ films were prepared on GGG （111） and Si （100） substrates respectively using PLD, the microstructures and magnetic properties of films were studied. It was found that crystalline Ce₁Y₂Fe₅O₁₂ films with YIG （444） preferred orientation can be obtained under an optimum condition with pulse frequency of 5 Hz and substrate temperature of 800℃, the films show mostly paramagnetic. Crystalline Ce₁Y₂Fe₅O₁₂ thin films can not be achieved directly on Si substrates; the as-depositited films show amorphous structure and weak magnetion. After a post-annealing under temperature of 700℃, one can found that the films on Si become polycrystalline and show strong ferromagnetic with easy axis of magnetization lying in the plane of the film.2. The effects of annealing temperature and SiO₂ buffer layer on the microstructure and magnetion of Ce₁Y₂Fe₅O₁₂ thin films on Si were studied. The results show that two steps of phase segregation occur with the post-annealing temperature increasing: at first, Ce₁Y₂Fe₅O₁₂ is decomposed into YIG and non-magnetic CeO₂ when annealed at 800 ℃; then YIG continues to be decomposed forming Fe₂O₃ when the temperature is increased up to 900 ℃. Consequently, the saturation magnetization of Ce₁Y₂Fe5O₁₂ films decreases first and then increases with the post-annealing temperature going up, which indicates that the saturation magnetization of Ce₁Y₂Fe₅O₁₂ films is mainly related to the microstructure. A SiO₂ buffer layer is found to be able to improve the magnetic properties of Ce₁Y₂Fe₅O₁₂ films by reducing the oxygen vacances existing in the films.3. Hf_xZn_1-xO films with different Hf concentrations were deposited on Si （100） and PET substrates respectively by PLD, the microstructures and optical properties of films were studied, the results show that Hf ions can be effectively doped into ZnO even on the flexible PET substrates via PLD. All the as-deposited Hf_xZn_1-xO films on Si with Hf contents 0≤x≤15 at % crystallize in a ZnO hexagonal wurtzite structure with a highly preferred c-axis orientation. However, for the films prepared on PET, the films with Hf contents more than 5 at % begin to show amorphous structure. All the films show a hingh transtrmittance; two ultraviolet peaks centered at about 364 and 380 nm co-exist as observed in the fluorescent spectra. The influences of Hf doping concentrations on the films were also studied, one can find that with increasing Hf contents, the lattice constants of Hf_xZn_1-xO films increase, the morphology of the films deteriorates and the intensity of fluorescent peaks enhances remarkably. At the same time, energy gaps increase while the positions of ultraviolet peaks remain unchanged. A possible mechanism of increased luminescence was then discussed.4. The transparent and conductive properities of Hf_xZn_1-xO films deposited under O₂ pressure of 5 Pa and with Hf contents 0≤x≤2 at % were studied. It is found that the films also show a hingh transtrmittance, the conductivity of films decreases first and then increases with increasing Hf contents. The films with Hf contents x=0.5 at % has a minimum of sheet resistance of 16 Ω/□ (With resistivity about 1.2 ×10^-3 Ω·cm), while the transtrmittance maintain at about 85 %.更多还原