蓝青铜K0.3MoO3单晶Peierls相变研究

测量了蓝青铜K_0.3MoO₃单晶Ｒ-Ｔ曲线，发现曲线在２８０Ｋ左右有异常变化，计算得到１８０Ｋ以下的半导体能隙为１３２０Ｋ（０.１１ｅＶ）．液氮温度下测量了晶体的非线性导电性，得到电场阈值为０.1２９Ｖ／ｃｍ．样品ＤＳＣ研究表明，样品在２４０Ｋ处经历一新的Ｐｅｉｅｒｌｓ相变，且为一级相变，据此对相变的微观性质进行了定量计算．１８０Ｋ附近Δｃ_p-Ｔ曲线表明，１８０Ｋ处的相变为一个二级相变加一个一级相变 关键词：     

TixSb2Te Thin Films for Phase Change Memory Applications

Sb2 Te films with different Ti contents （TixSb2 Te） are derived via the target-attachment method by using the magnetron sputtering technique. The effects of the Ti content on the phase change characteristics and the microstructures are investigated by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy and atom force microcopy. Resistance-temperature measurements are carried out to reveal the enhanced crystallization temperature of TixSb2 Te films, indicating a better thermal stability in such films. Both the activation energy and the temperature for 10 y data retention increase with increasing the concentration of Ti. It indicates that the crystallization of the amorphous Sb2 Te film could be suppressed by the introduction of Ti. The improvement of crystallization temperature and the thermal stability of the amorphous Sb2 Te film results from the introduction of Ti in Sb- Te bond that decreases the binding energy of Sb 4d and Te 4d.     

铁电磁体Pb(Fe1/2Nb1/2)O3相变特征

借助与示差扫描量热法、磁化率测量、电子自旋共振、铁电与介电性质测量及电子衍射系统地研究了Pb(Fe_1/2Nb_1/2)O₃(PFN)的电、磁性质和相变特征．结果表明发生在380K附近的顺电－铁电转变和发生在145K附近的顺磁 反铁磁转变分别为一级相变和二级相变或弱一级相变．在室温下,PFN的剩余极化与矫顽场分别为11.5μC/cm²和3.04kV/cm.介电测量表明PFN的顺电-铁电相变为弥散型相变．其弥散指数为1.62.电子衍射表明Fe³⁺与Nb⁵⁺离子在B位置上是无序分布的,正是这种与无序分布相关联的成分涨落导致铁电相变的弥散性. 关键词：     

Optical study of Ba(Mn_xTi_(1-x)O_3) thin films by spectroscopic ellipsometry

Stoichiometric Ba(Mn_xTi_(1-x)O_3) (BMT)thin films with various values of x were deposited on Si(111)substrates by the sol-gel technique.The influence of Mn content on the optical properties was studied by spectroscopic ellipsometry(SE)in the UV–Vis–NIR region.By fitting the measured ellipsometric parameter(Ψand)with a four-phase model(air/BMT+voids/BMT/Si(111)),the key optical constants of the thin films have been obtained.It was found that the refractive index n and the extinction coefficient k increase with increasing Mn content due to the increase in the packing density.Furthermore,a strong dependence of the optical band gap Egon Mn/Ti ratios in the deposited films was observed,and it was inferred that the energy level of conduction bands decreases with increasing Mn content.     

Bipolar resistance switching in the fully transparent BaSnO_3-based memory device

The fully transparent indium-tin-oxide/BaSnO3/F-doped SnO2 devices that show a stable bipolar resistance switching effect are successfully fabricated. In addition to the transmittance being above 87% for visible light, an initial forming process is unnecessary for the production of transparent memory. Fittings to the current-voltage curves reveal the interfacial conduction in the devices. The first-principles calculation indicates that the oxygen vacancies in cubic BaSnO3 will form the defective energy level below the bottom of conduction band. The field-induced resistance change can be explained based on the change of the interracial Schottky barrier, due to the migration of oxygen vacancies in the vicinity of the interface. This work presents a candidate material BaSnO3 for the application of resistive random access memory to transparent electronics.     

The charge storage characteristics of ZrO2 nanocrystallite-based charge trap nonvolatile memory

ZrO2 nanocrystallite-based charge trap flash memory capacitors incorporating a(ZrO2)0.6(SiO2)0.4 pseudobinary high-k oxide film as the charge trapping layer were prepared and investigated.The precipitation reaction in the charge trapping layer,forming ZrO2 nanocrystallites during rapid thermal annealing,was investigated by transmission electron microscopy and X-ray diffraction.It was observed that a ZrO2 nanocrystallite-based memory capacitor after post-annealing at 850℃ for 60s exhibits a maximum memory window of about 6.8V,good endurance and a low charge loss of ～25% over a period of 10 years(determined by extrapolating the charge loss curve measured experimentally),even at 85℃.Such 850℃-annealed memory capacitors appear to be candidates for future nonvolatile flash memory device applications.     

Performance improvement of charge trap flash memory by using a composition-modulated high-k trapping layer

A composition-modulated （HfO2）x（Al2O3）1-x charge trapping layer is proposed for charge trap flash memory by controlling the A1 atom content to form a peak and valley shaped band gap. It is found that the memory device using the composition-modulated （HfO2）x（Al2O3）l-x as the charge trapping layer exhibits a larger memory window of 11.5 V, improves data retention even at high temperature, and enhances the program/erase speed. Improvements of the memory characteristics are attributed to the special band-gap structure resulting from the composition-modulated trapping layer. Therefore, the composition-modulated charge trapping layer may be useful in future nonvolatile flash memory device application.     

蓝青铜K_(0－3)MoO_3单晶Peierls相变研究

测量了蓝青铜Ｋ０３ＭｏＯ３单晶ＲＴ曲线，发现曲线在２８０Ｋ左右有异常变化，计算得到１８０Ｋ以下的半导体能隙为１３２０Ｋ（０１１ｅＶ）．液氮温度下测量了晶体的非线性导电性，得到电场阈值为０１２９Ｖ／ｃｍ．样品ＤＳＣ研究表明，样品在２４０Ｋ处经历一新的Ｐｅｉｅｒｌｓ相变，且为一级相变，据此对相变的微观性质进行了定量计算．１８０Ｋ附近ΔｃｐＴ曲线表明，１８０Ｋ处的相变为一个二级相变加一个一级相变     

Li+离子掺杂Gd2O3：Sm3+纳米晶的发光增强

采用燃烧法制备了Gd₂O₃:Sm³⁺和Li⁺离子掺杂的Gd₂O₃:Sm³⁺纳米晶,根据X射线衍射图谱确定所得纳米样品为纯立方相。在室温下,用275 nm和980 nm激发光激发各样品时,可分别观测到Sm³⁺离子的强荧光发射和上转换特征发射,其主发射峰分别位于560,602,650 nm处,分别对应着Sm³⁺离子的⁴G_5/2→⁶H_5/2,⁴G_5/2→⁶H_7/2和⁴G_5/2→⁶H_9/2的电子跃迁,其中以⁴G_5/2→⁶H_7/2跃迁的光谱强度最大。实验表明Li⁺离子的掺入使得Sm³⁺离子的荧光发射强度显著增加。通过对样品的XRD、TEM和激发光谱、发射光谱的研究,分析了引起样品荧光强度变化的原因。