不同晶粒尺寸Mg掺杂(Ba0.6Sr0.4)0.925K0.075TiO3薄膜的直流场介电性能研究

采用溶胶凝胶工艺,在Pt/Ti/SiO2/Si衬底制备了Mg掺杂(Ba0.6Sr0.4)0.925K0.075TiO3(BSKT)薄膜.X射线衍射(XRD)和扫描电镜(SEM)分析测定了物相微结构和薄膜表面形貌,研究了Mg掺杂含量对BSKT晶粒尺寸和直流场介电调谐性能的影响,讨论了直流场介电损耗谱演变的原因.结果表明,Mg掺杂BSKT使薄膜表面粗糙度、晶粒尺寸、介电常量、介电损耗和调谐量都降低;在室温1MHz下,BSKT薄膜有最大的调谐量73.6%;6%(摩尔分数)Mg掺杂BSKT薄膜有最低的介电损耗为0.0088;发现直流场下薄膜的介电损耗谱演变一方面可能与薄膜的晶粒尺寸有关,另一方面也可能与测试温度有关.     

Ce掺杂ZnO压敏薄膜的微观结构与电学性能研究

通过溶胶-凝胶法制备了一种稀土Ce掺杂的ZnO-Bi2O3压敏薄膜,对薄膜进行了XRD、AFM、介电与压敏性能的表征。结果表明,Ce掺杂不会影响ZnO-Bi2O3压敏薄膜的晶体结构,但是会减小ZnO-Bi2O3压敏薄膜的晶粒尺寸。Ce掺杂会降低ZnO-Bi2O3压敏薄膜的漏电流,减小材料的介电损耗,提升ZnO-Bi2O3压敏薄膜的非线性性能。当Ce掺杂量达到0.3%(摩尔分数)时,ZnO-Bi2O3压敏薄膜的压敏电压达到了175V/mm,漏电流降低至502μA。     

La2O3掺杂对BST/MgO复合陶瓷显微结构和性能的影响

采用固相反应法制备了未掺杂和La2O3掺杂(0.5%、1%、2%(摩尔分数))的Ba0.55Sr0.45TiO3/MgO复合陶瓷材料,并研究了它们的显微结构和各种介电性能.研究结果表明,La2O3除一部分会进入BST晶格獭代Ba或Sr的位置外,还会有一部分与MgO等形成无定形态物质滞留在晶界,起到抑制BST晶粒生长的作用.BST/MgO复合陶瓷的居里温度随La2O3掺杂量的增大而降低,居里温度的降低导致了介电常数的减小.适量的La2O3掺杂提高了复合陶瓷的调谐性,而且La2O3掺杂明显降低了复合陶瓷的微波介电损耗.0.5%(摩尔分数)La2O3掺杂的BST/MgO复合陶瓷具有最佳的综合介电性能,其在10kHz下的调谐性为6.9%(2kV/mm),3.99GHz时的介电常数和介电损耗分别为87.5和3.35×10-3,基本可以满足铁电移相器的使用要求.     

钴掺杂改性TiO_2的制备及其光催化性能研究

选用六水合硝酸钴((Co(NO3)2·6H2O)为掺杂剂,以钛酸四丁酯(TBOT)为原料,利用水热法制备出钴掺杂改性的TiO_2光催化剂,并利用XRD、SEM、EDS等方法对样品进行表征,研究了Co/TiO_2催化剂的结构、形貌和组成及其对甲基橙的光催化降解性能。结果表明,通过水热法制备的纯TiO_2及Co/TiO_2均为金红石相结构,掺杂Co2+并未改变TiO_2的晶体结构,Co/TiO_2为单分散相的球型,分布较均匀。Co/TiO_2对甲基橙的降解能力相比纯TiO_2有显著提高,当Co2+的掺杂量为1%(mol,摩尔百分含量)时,降解效果最好,最高降解率可达到97.4%。     

铬掺杂钛酸锶钡陶瓷的介电调谐性能

研究了Cr掺杂对钛酸锶钡(Ba0.6Sr0.4TiO3,BST)陶瓷的介电及其可调性能的影响.结果表明,少量的Cr可进入BST品格形成固溶体,并促进晶粒生长.当Cr掺杂量(摩尔分数)低于1.0%时,陶瓷的介电损耗急剧降低,调谐率明显提高,综合性能显著改善,其中Cr掺杂0.6%的BST陶瓷具有最佳的综合性能,其在1MHz下的介电损耗为0.0005,品质因子(FoM)达到500,而未掺杂样品的FoM值仅为60.Cr掺杂陶瓷损耗的急剧降低可归因于Cr3 离子的还原和Cr3 、Cr2 受主行为中和了氧空位的施主行为.     

低损耗掺杂BST薄膜的射频磁控溅射沉积及其阻抗特性研究

利用射频磁控溅射法和快速热退火处理,在高电阻Si基片上制备了具有较低介电损耗的MgO掺杂Ba_(0.25)Sr_(0.75)TiO_3(BST)铁电薄膜。通过XRD和SEM,分别对BST铁电薄膜的微结构和表面形貌进行了分析。利用铁电分析仪和低频阻抗分析仪分别测试了BST薄膜样品的铁电特性和介电性能。研究表明,MgO掺杂的BST薄膜的介电损耗要低于纯的BST薄膜,并且在掺杂浓度为5%(摩尔分数)时,获得最佳的实验结果。在室温和250 Hz的条件下,测得700℃退火的BST铁电薄膜样品的矫顽电场强度(E_C)和剩余极化强(P_r)分别为1.15 V/cm和4.06μC/cm~2,介电常数和介电损耗因子分别为370和0.005。     

Co/ATO复合薄膜的结构与电磁光特性

以低成本的无机盐 SnCl₂·2H₂O、SbCl₃和Co(NO₃)₂·9H₂O 为原料,采用溶胶-凝胶法与浸渍提拉技术成功地制备出Co掺杂的ATO(Sb掺杂SnO₂)复合薄膜。利用XRD、SEM、四探针电阻仪、紫外-可见光分光光度计及振动样品磁强计(VSM)等测试方法对Co/ATO复合薄膜的结构与物性进行了表征与评价。结果表明：少量的Co 掺杂ATO复合薄膜仍保持四方金红石结构,复合薄膜中的晶粒分布均匀,其晶粒尺寸分布为4～7 nm;随着Co含量的增加,Co/ATO复合薄膜的电阻率呈现出先降低后提高,且当Co含量为0.5 mol %时,Co/ ATO复合薄膜的电阻率最低为5. 6×10- 3Ω·cm;在400～700 nm可见光范围内,平均透过率达到90 %以上,其光学带隙在3.9～4.0eV之间,且随着Co含量的增加,可见光透过率和光学带隙呈下降趋势;Co含量为3.0 mol%的ATO复合薄膜具有室温铁磁性,其矫顽力约为100Oe,磁性根源主要归结为磁性原子与基体载流子相互作用的结果。     

Co掺杂量对ZnO薄膜结构及光学特性的影响

采用脉冲激光沉积法(PLD)在SiO2村底上成功制备了具有c轴择优生长特性的Zn1-xCoxO(x=0.05、0.1、0.2、0.3)系列薄膜.通过X射线衍射和能谱仪研究了Co掺杂量对薄膜晶体结构和成分的影响;同时利用光致发光谱(PL)和透过率研究了薄膜的光学特性.结果表明,当掺杂浓度为10%时,薄膜生长最好,c轴择优生长最为显著;Co元素的掺入改变了薄膜的紫外、绿光和蓝光发射,分析认为主要是Co元素的掺入量改变了薄膜的禁带宽度、氧错位缺陷浓度和锌填隙缺陷的浓度;Co元素掺杂浓度为5%时,薄膜的透过率超过90%.此外,探讨了不同波段光发射的可能机理.     

稀土及过渡金属掺杂TiO_2的制备及光催化性能研究

选用六水合硝酸镧(La(NO_3)_3·6H_2O)及六水合硝酸钴(Co(NO_3)_2·6H_2O)为掺杂剂,以钛酸四丁酯(TBOT)为原料,采用水热法制备了稀土La及过渡金属Co共掺杂的二氧化钛(TiO_2)复合光催化剂,并通过XRD、SEM、EDS、FT-IR表征手段对样品进行了分析。以甲基橙为模型污染物,研究La及Co共掺杂量对复合光催化剂活性的影响。结果表明:通过水热法制备的催化剂为球型结构的金红石相,掺杂La和Co并未改变TiO_2的晶体结构;(La/Co)/TiO_2复合材料对甲基橙的降解能力相比纯TiO_2有显著提高,当La及Co的共掺杂量为1%(mol,摩尔含量)时,降解效果最好,最高降解率可达到98.2%。     

不同铝掺杂量ZnO薄膜性能的研究

以铝掺杂质量分数为1%、2%、3%的Zn/Al合金为靶材,采用直流反应磁控溅射技术在玻璃衬底上制备了不同铝含量ZnO:Al(AZO)透明导电薄膜。研究了衬底温度对AZO薄膜电学性能的影响;同时,研究铝掺杂量不同、电阻率相同的AZO薄膜的载流子浓度与迁移率的关系。结果表明:随着Al掺杂量的增加,薄膜最佳性能(透过率90%,电阻率6×10-4Ω·cm左右)时的衬底温度值会降低;电阻率相同的样品,1%铝掺杂的薄膜迁移率和透光率均高于2%铝掺杂薄膜的。     

Study on dielectric and tunable properties of Cr-doped Ba<Subscript>0</Subscript><Subscript>.6</Subscript>Sr<Subscript>0.4</Subscript>TiO<Subscript>3</Subscript> thin films by rf sputtering

Ba_0.6Sr_0.4TiO₃ dielectric thin films doped by Cr(0, 1, 2.5, 5, 10 mol%) (BSTC) were prepared by radio frequency magnetron sputtering on Pt/Ti/SiO₂/Si substrates. The structure and morphology of the BSTC thin films were studied by atomic force microscopy and X-ray diffraction. The effect of Cr doping on the dielectric properties of BST thin films were analyzed. The results show that the dielectric loss of Cr doping BST thin films is lower than that undoped, and the tunability increased with Cr doping. The thin film doped with 5 mol% Cr has the best dielectric properties. The tunability, loss and figure of merit (FOM) at 1 MHz were 38.9%, 0.0183, and 21.3, respectively.     

钛酸锶钡薄膜C-V曲线不对称现象研究

采用射频（RF）磁控溅射在Pt／Ti／SiO2／Si（100）衬底上制备了Ba0.6Sr0.4TiO3（BST）薄膜。通过研究BST薄膜的电容-偏压（C-V）特性曲线发现,溅射过程中的离子注入引起底电极／铁电薄膜界面处产生了过渡层,从而导致C-V曲线不对称。最后我们通过改进溅射工艺对这一机理进行了实验验证。     

Improvement in dielectric and tunable properties of Fe-doped Ba0.6Sr0.4TiO3 thin films grown by pulsed-laser deposition

Fe-doped Ba(0.6)Sr(0.4)TiO3 (BST) thin films were prepared on Pt/Si substrates by the pulsed-laser deposition method. The concentrations of Fe dopants vary from 0.1 mol% to 1.0 mol%. Our results indicate that a certain amount of Fe dopants can decrease the dielectric loss of BST thin films without causing the significant reduction of the tunability. The leakage current of BST thin films also was reduced by the addition of Fe dopants. BST thin films doped with 0.3 mol% Fe ions show a minimum dielectric loss of 0.88% at 10(6) Hz, which is 1.7% for the undoped BST films. Moreover, the 0.3 mol% Fe-doped BST films reveal a maximum figure of merit (FOM) of 51, indicating the improved comprehensive dielectric and tunable properties.     

溅射工艺参数对Ba0.5Sr0.5TiO3薄膜沉积速率和介电性能的影响

铁电/介电BST(BaxSr1-xTiO3)薄膜在微电子学、集成光学和光电子学等新技术领域有广泛的应用前景.用射频磁控溅射方法制备了厚约700 nm的Ba0.5Sr0.5TiO3薄膜,采用Al/BST/ITO结构研究了溅射功率、溅射气压、O2/(Ar O2)比和基片温度对上述BST薄膜沉积速率和介电性能的影响,并根据这些结果分析了较优的工艺条件,同时用XRD、XPS和SEM研究了薄膜的晶相、组成和显微结构.     

Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.     

（Ba0.6Sr0．4）Ti1-xZnxO3薄膜的介电调谐性能

利用溶胶-凝胶法在Pt／TiO2/SiO2/Si衬底上制备了（Ba0．6Sr0．4）Ti1-xZnxO3（BSTZ）薄膜,用X射线衍射和扫描电镜分析测定了BSTZ的微结构和薄膜的表面形貌,研究Zn掺杂量对其介电调谐性能的影响,结果表明,随Zn含量的增加BSTZ物相无明显变化,其介电常数、调谐量先增加后降低,但介电损耗却先降低后增加。在室温1MHz下,1．5m01％Zn掺杂BSTZ薄膜有最大的调谐量54．26％;2．5mol％Zn掺杂BSTZ薄膜有最低的介电损耗0．0148和最大的优值因子30．3。     

脉冲激光沉积Ba0.5Sr0.5TiO3、Pb0.5Ba0.5TiO3和Pb0.5Sr0.5TiO3薄膜及其介电性质

采用脉冲激光沉积法,在Pt／Ti／SiO2／Si基底上分剐制备厚度为350nm的Ba0.5Sr0.5TiO3(BST)、Pb0.5Ba0.5TiO3(PBT)和Pb0.5Sr0.5TiO3(PST)薄膜并研究了它们的介电性质。XRD显示,在相同的制备条件下三者具有不同的择优取向,PST具有(110)择优取向,PBT具有(111)择优取向,而BST则是混合取向。SEM显示三者样品表面均匀致密,颗粒尺寸大约在50nm至150nm之间。PST与BST、PBT相比有更高的介电常数,在频率为10kHz时,分别为874、334和355,而损耗都较低,分别为0．0378、0．0316和0．0423,同时PST漏电流也是最小的。测量薄膜的C-V特性扣铁电性能表明室温下BST呈现的是顺电相,PST和PBT则呈铁电相。本文也测量了薄膜在不同频率下的介电温度特性,BST、PBT和PST均表现出频率弥散现象,即随着频率的降低．居里温度降低而介电常数会升高。并测得BST和PST的居里温度分剐为-75和150℃。而PBT的居里温度在250℃以上。本文研究表明：与BST相比较,PBT的介电常数与之相近,漏电流较大;而PST具有高介电常数,较小的漏电流和较大的电容-电压调谐度,在相关半导体器件中的应用将有很大的潜力。     

Gd掺杂对PZT薄膜介电性能及极化行为的影响

采用sol-gel法在Pt/Ti/SiO₂/Si衬底上制备出高度(100)择优取向的Gd掺杂PZT薄膜(简写为PGZT); 介电测试结果表明, 1mol%Gd掺杂的PZT薄膜介电常数最大, 2mol%Gd掺杂PZT薄膜与未掺杂薄膜的介电常数相差不大, Gd掺入量>2mol%时, 薄膜的介电常数下降; 薄膜的不可逆极化值呈现与介电常数相同的变化趋势, 而可逆极化值变化较小. 在弱电场下(低于矫顽场E_c), 用瑞利定律分析薄膜介电常数随电场强度的变化规律, 1mol%Gd掺杂的薄膜瑞利系数α最大, 说明薄膜中缺陷的浓度最低. 1mol%Gd掺杂的薄膜介电和铁电性能的改善与Gd³⁺在PZT晶格中的占位情况有关.     

溶胶-凝胶法制备锌掺杂Sr_3Co_2Fe_(24)O_(41) Z型铁氧体及其性能

利用柠檬酸溶胶-凝胶法合成了锌掺杂Sr_3(Zn_xCo_(1-x))_2Fe_(24)O_(41),(x=0～0.8)的Z型铁氧体.测试其结构、磁性能、电磁性能与吸波特性.实验结果表明,适量掺杂Zn~(2+)有利于磁性能及吸波性能的改善,在x=0.2时比饱和磁化强度最大,可达51.36 A·m~2·kg~(-1);吸波性能优良,最大吸收量为35.12dB;合成最佳温度为1200℃烧结2小时.     

Enhanced dielectric properties of Mn doped Ba0.6Sr0.4TiO3 thin films fabricated by pulsed laser deposition

Pure and 2 mol% Mn doped Ba_0.6Sr_0.4TiO₃ (BST) thin films have been deposited on La_0.67Sr_0.33MnO₃ (LSMO) coated single-crystal (001) oriented LaAlO₃ substrates using pulsed-laser deposition technique. The bilayer films of BST and LSMO were epitaxially grown in pure single-oriented perovskite phases for both samples, and an enhanced crystallization effect in the BST film was obtained by the addition of Mn, which were confirmed by X-ray diffraction (XRD) and in situ reflective high energy electron diffraction (RHEED) analyses. The dielectric properties of the BST thin films were measured at 100 kHz and 300 K with a parallel-plate capacitor configuration. The results have revealed that an appropriate concentration acceptor doping is very effective to increase dielectric tunability, and to reduce loss tangent and leakage current of BST thin films. The figure-of-merit (FOM) factor value increases from 11 (undoped) to 40 (Mn doped) under an applied electric field of 200 kV/cm. The leakage current density of the BST thin films at a negative bias field of 200 kV/cm decreases from 2.5 × 10^− 4 A/cm² to 1.1 × 10^− 6 A/cm² by Mn doping. Furthermore, a scanning-tip microwave near-field microscope has been employed to study the local microwave dielectric properties of the BST thin films at 2.48 GHz. The Mn doped BST film is more homogeneous, demonstrating its more potential applications in tunable microwave devices.