【作者】 于晓明；

【导师】 祁阳；

【作者基本信息】 东北大学 ， 材料物理与化学， 2009， 博士

【摘要】 本文利用化学湿法各向异性刻蚀技术对单晶Si(100)衬底进行表面改型处理；利用化学法—液相沉积技术以及物理法—射频磁控溅射技术在普通Si(100)衬底和经过表面改型处理的Si衬底上制备钛酸锶(STO)薄膜；采用溶胶—凝胶旋涂方法制备Bi-2212超导薄膜。主要研究内容如下：1.单晶Si(100)衬底表面“V”型沟槽结构的获得。使用KOH溶液和刻蚀速率缓和剂异丙醇(IPA)的混合溶液作为刻蚀剂,开创性地使用Ti02作为刻蚀掩模在单晶Si(100)衬底上获得了Si[010]方向平行排列侧壁为Si(110)面的“V”型沟槽结构。通过对不同的刻蚀时间和掩模厚度等刻蚀条件的研究得出：随着刻蚀时间的增加,“V”型沟槽的深度和宽度逐渐增加,掩模也不断被消耗,当掩模消耗殆尽后,已经形成的沟槽结构的顶端开始被腐蚀而导致结构恶化。掩模太厚则容易脱落,太薄则起不到保护衬底的作用。利用30分钟的刻蚀时间和200nm厚的Ti02掩模可以得到侧壁较光滑平整的“V”型沟槽结构。同时,基于各向异性刻蚀的同性刻蚀也可得到“V”型沟槽,但其质量有待提高。本章制备的“V”型沟槽衬底结构是以后工作的基础,为下步薄膜的制备提供了优异的衬底材料。2.采用液相沉淀法(LPD)和射频磁控溅射法制备STO薄膜。在已经获得表面为“V”型沟槽的Si(100)衬底上制备STO薄膜。经过实验和分析得出：衬底表面亲水性是液相沉积法能否进行的基础,对衬底亲水处理10分钟可以得到较好的亲水效果：在较低的沉积温度(40-C),650℃退火4小时后得到光滑平整的薄膜表面形貌,沉积温度升高则表面相貌变差。在溅射法制备STO薄膜的过程中,在衬底温度为300-C的条件下,经过700℃的后退火处理得到了[l00)]方向择优取向的STO过渡层,衬底温度和退火温度的升高及降低均使[l00)]方向择优取向趋势减弱,同时溅射功率和溅射气压的降低有利于薄膜[l00)]择优取向生长。3.溶胶—凝胶旋涂法制备Bi-2212薄膜。薄膜前驱液使用金属硝酸盐作为反应物,EDTA为络合剂,三乙醇胺作为聚合剂。实验结果表明：经过9小时水浴,黏度为55mPa.s的溶胶与衬底结合最好；通过对溶胶干燥工艺的摸索,得出在600℃下迅速干燥的工艺可以解决由于前驱膜聚集而导致的薄膜分块以及成分不均和表面形貌恶化的问题；通过对热处理工艺的探索,得出830℃是Bi-2212相的最佳生成温度,经过5小时的升温和3小时的保温得到了纯度最高的Bi-2212薄膜；通过对涂胶次数的研究,得出在保证Bi-2212相纯度的前提下,旋涂5次的薄膜具有较光滑的表面形貌和较好的超导转变特征。对在Si衬底上生长Bi-2212薄膜的研究中发现：在平的Si(100)衬底上获得了一定程度c轴外延的Bi-2212薄膜,但是杂相较多,由杂质引起的表面形貌不佳的情况需要改善；而在“V”型沟槽衬底上,Bi-2212薄膜呈现一定程度的a,b轴垂直衬底表面生长,该结果需要进一步的实验来确认。更多还原

【Abstract】 In this dissertation, anisotropic wet etching method was used to modify the surface pattern of single Si(100) substrate; Liquid phase deposition and RF magnetron sputtering were adopted to obtain STO film; Spin-coating sol-gel method was employed to prepare Bi-2212 film. The main contents of the dissertation are as follows:1. The fabrication of V-grooves on single Si(100) substrate. In this paper, parallel and continuous V-grooves along the Si[010] direction with sidewalls of Si(110) were formed on Si(100) substrate using KOH/IPA solution as etchant, and the TiO2 film was deposited on the Si(100) as resist mask by RF-magnetron sputtering. The investigation on different etching time and thickness of mask showed that the depth and width of V-grooves decreased gradually with the increase of etching time, and the mask was also consumed continuously. Top of the grooves were corroded and the structure were deteriorated when the mask was exhausted. So the substrate cannot be well protected if the mask was too thin, while the mask tended to fall off from the substrate if the mask was too thick. V-grooves with smooth sidewalls were obtained when the etching time was 30 min and the thickness of TiO2 mask was 200 nm. In the meanwhile, V-grooves could also be obtained using isotropic wet etching method based on anisotropic etching method, while the quality is undesirable. The modified substrate with V-grooves is the base for the preparation of films with different orientation.2. Liquid phase deposition and RF magnetron sputtering were adopted to obtain STO film. STO film was deposited on Si(100) substrates with V-grooves. Results revealed that quality of STO films prepared via LPD depended on the wettability of substrate surface, and the wettability was desirable when the hydrophilic treatment for the substrates was 10 min. Smooth film was obtained when the deposition temperature was 40℃, followed by annealing at 650℃for 4 h, and large grains occurred when increasing the deposition temperature. STO film with [e00)] preferred orientation was obtained when the substrate temperature is 300℃via RF magnetron sputtering, followed by post annealing at 700℃. The increase and decrease of substrate temperature or annealing temperature would deteriorate the preferred orientation, while the decrease of sputtering power and pressure improved the degree of preferred orientation of STO film. 3. Spin-coating sol-gel method was employed to prepare Bi-2212 film. Nitrates were used as the reactor, ethylenediaminetetracetic acid (EDTA) as chelating agent and triethanolamine (TEA) as polymerizing agent. Results revealed that the attachment of sol film and substrate is optimal when the time of water bath is 9h, which the viscosity of sol was 55mPa.s. In the meanwhile, the optimization of drying process showed that the rapid drying at 600℃can decrease both the partition of film brought by the assembling of precursor gel film and the ingredient segregation brought by the different dissolvability of every ingredient.In addition,830℃was the optimal heat treatment temperature to form Bi-2212 single phase, and Bi-2212 thin film with high quality can be obtained when the heating-up time and holding time are 5 h and 3 h, respectively. At last, the times for spin-coating were also investigated, and 5 times was desirable to obtain films with smooth surface and better superconductivity property. The Bi-2212 film was c-axis epitaxial on flat Si(100) substrate, but the impurity should be reduced, and the surface morphology need to be improved. For the film grown on modified substrate, the a, b-axis epitaxial film could be found on sidewall of V-grooves, but the result need to be confirmed.更多还原