High Thermoelectric Performance Achieved in GeTe–Bi2Te3 Pseudo‐Binary via Van der Waals Gap‐Induced Hierarchical Ferroelectric Domain Structure

GeTe is an interesting material presenting both spontaneous polarization (ferroelectrics) and outstanding electrical conductivity (ideal for thermoelectrics). Pristine GeTe exhibits classic 71° and 109° submicron ferroelectric domains, and near unity thermoelectric figure of merit ZT at 773 K. In this work, it is demonstrated that Bi₂Te₃ alloying in GeTe lattice can introduce vast Ge vacancies which can further evolve into nanoscale van der Waals gaps upon proper heat treatment, and that these vacancy gaps can induce 180° nanoscale ferroelectric domain boundaries. These microstructures eventually become a hierarchical ferroelectric domain structure, with size varying from submicron to nanoscale and polarization from 71°, 109° to 180°. The establishment of hierarchical ferroelectric domain structure, together with the nanoscale Ge vacancy van der Waals gaps, has profound effects on the electrical and thermal transport properties, resulting in a striking peak thermoelectric ZT ≈ 2.4 at 773 K. These findings might provide an alternative conception for thermoelectric optimization via microstructure modulation.     

SBT铁电薄膜及其脉冲准分子激光制备

采用脉冲准分子激光沉积法在Ｐｔ／Ｔｉ／ＳｉＯ２／Ｓｉ衬底上成功地制备了ＳＢＴ铁电薄膜，发现存在一个最佳沉积衬底温度约为４５０℃。在该温度下沉积的ＳＢＴ薄膜具有较饱和的方形电滞回线，其剩余极化Ｐｒ和矫顽电场Ｅｃ分别为８．４μＣ／ｃｍ２和５７ｋＶ／ｃｍ。     

一种感光栅GaN基高电子迁移率晶体管紫外探测器

利用GaN基高电子迁移率晶体管(HEMT)的栅控特性和铁电体的光伏效应机制,制备了一种新型(光敏感层/HEMT)光探测器件。主要研究了复合薄膜和溅射气氛对光敏感薄膜的光伏性能以及对新型感光栅极探测器的光探测能力的影响。结果表明,PZT/ZnO复合薄膜的量子效率峰值达到14.55%;有氧氛围下制备的PZT薄膜剩余极化强度达到52.31μC/cm²;沉积PZT/ZnO复合薄膜的探测器在紫外光照下相比于暗场下的源漏饱和电流最多增加12.64mA。可见,所制备的新型探测器对紫外光具有优良的探测能力,为光探测的研究提供了新的方向。     

基于压电力显微镜的铌酸锂电畴稳定性研究

研究了Z切700 nm厚的单晶铌酸锂(LiNbO₃)薄膜电畴的调控方法。利用X射线衍射仪(XRD)和原子力显微镜(AFM)对单晶LiNbO₃薄膜的晶向和形貌进行了表征,并通过外加电场对单晶LiNbO₃薄膜电畴进行调控。研究结果表明,该LiNbO₃薄膜具有单一的(006)衍射峰,表面光滑、粗糙度低(均方根粗糙度小于1 nm)。通过外加电场和预设电畴图案对LiNbO₃电畴进行精准调控,并测试了电畴稳定性。测试结果显示,调控后的电畴在温度为25~150℃内处于稳定状态,且在30 d内保持稳定,未发生弛豫现象。该研究为LiNbO₃电畴工程器件的研发和应用提供了重要的技术支撑。     

无压烧结制备0.88PMN-0.12PT高度透明铁电陶瓷的显微结构研究

用传统的无压烧结工艺制备出稀土元素La掺杂的高度透明纯钙钛矿相0.88Pb(Mg1/3Nb2/3)O3-0.12Pb Ti O3(简称0.88PMN-0.12PT)铁电陶瓷。当陶瓷样品厚度为0.8 mm时,在1550 nm处透光率达67%,接近其理论极限。电滞回线测量结果表明该组分透明陶瓷为典型的弛豫铁电体。显微结构观察结果表明陶瓷非常致密,晶粒排列规则,晶界结合强度高,多呈穿晶断裂,晶界干净,且厚度2 nm。     

Preparation of (Pb0.88La0.12)TiO3 thin films for dynamic random access memory by low pressure-metalorganic chemical vapor deposition

La-modified lead titanate (PLT) thin films were prepared by hot-wall type low pressure-metalorganic chemical vapor deposition method. Pb(dpm)₂, La(dpm)₃, and titanium tetraisopropoxide were used as source materials. The films were deposited at 500°C under the low pressure of 1000 mTorr and then annealed at 650°C for 10 min in oxygen ambient. Sputter-deposited platinum electrodes and 180 nm thick PLT thin films were employed to form MIM capacitors with the best combination of high charge storage density (26.7 μC/cm² at 3V) and low leakage current density (1.5 × 10^-7 A/cm² at 3V). The measured dielectric constant and dielectric loss were 1000∼1200 and 0.06∼0.07 at zero bias and 100 kHz, respectively.     

热分解法制备钛酸铅镧薄膜及其电性能研究

本文研究了用金属有机物热发解法制备ＰＬＴ８薄膜的工艺过程和基片对薄膜结构的影响，并且给出了铁电性能的测量结果。     

新型铁电玻璃陶瓷的研究进展

综述了铌酸盐、钛酸盐、铋层钙钛矿结构三种类型的铁电玻璃陶瓷的性能及应用,分析比较了熔融法、烧结法、sol-gel法和激光诱导法四种制备方法的优缺点,基于铁电玻璃陶瓷材料研究和应用现状,探讨了此类材料的研究方向与发展前景。     

退火处理对0.5PZN-0.5PZT陶瓷弛豫性的影响

采用常规陶瓷工艺制备了Pb(Zn_(1/3)Nb_(2/3))_(0.5)(Zr_(0.5)Ti_(0.5))_(0.5)O_3 (0.5PZN-0.5PZT)铁电陶瓷,并在氧气氛下进行退火.运用XRD、直流电导率和介电温度谱测试氧气氛退火前后陶瓷相结构与电性能的变化,并对弛豫性与微结构的关系进行探讨.结果表明,氧气氛退火可有效补偿体系中的氧空位,降低四方相含量,材料的弛豫性显著增强.     

Ferroelectricity-modulated resistive switching in Pt/Si:HfO2/HfO2-x/Pt memory

It is investigated for the effect of a ferroelectric Si:HfO₂ thin film on the resistive switching in a stacked Pt/Si:HfO₂/highly-oxygen-deficient HfO_2-x/Pt structure. Improved resistance performance was observed. It was concluded that the observed resistive switching behavior was related to the modulation of the width and height of a depletion barrier in the HfO_2-x layer, which was caused by the Si:HfO₂ ferroelectric polarization field effect. Reliable switching reproducibility and long data retention were observed in these memory cells, suggesting their great potential in non-volatile memories applications with full compatibility and simplicity.