Phase Formations and Electrical Properties of Various (Bi, La)4Ti3O12 Thin Films by Chemical Solution Deposition

The phase formation and electrical properties of (Bi, La)₄Ti₃O₁₂ (BLT) thin film and V-, Sm-doped BLT thin films prepared by the chemical solution deposition method on Pt/TiO₂/SiO₂/Si substrates have been investigated. It was observed that the microstructure and electrical properties of BLT thin films dramatically varied with V- and Sm-doping. The crystallinity and grain size of BLT thin films were definitely increased by V- and Sm-doping into BLT films, which resulted in the enhancement of remanent polarization in doped BLT films. The remanent polarization (Pr) of Sm-doped BLT films annealed for 3 min by an RTA system was about 9 C/cm². The V- and Sm-doped BLT films also exhibited good fatigue characteristics under bipolar stressing to 10¹⁰ cycles.     

Redistribution of indium implanted in silicon due to thermal treatment and swift heavy ion irradiation

Silicon layers of 150 nm thickness supersaturated with indium up to ≈5 at% were prepared by multiple energy ion implantation. A redistribution of the implanted impurities caused by post-implantation annealing and following irradiation with swift Bi ions has been observed by means of Rutherford backscattering spectrometry in channelling configuration (RBS/C). It is demonstrated by TEM that the thermal decomposition of the supersaturated Si〈In〉 solution is accompanied by polycrystalline recrystallisation of amorphous silicon, precipitation of the second phase (In) both within the implanted layer and on the surface, as well as by impurity redistribution. The main features of the structure transformation under the influence of the Bi ion irradiation are discussed.     

The Distribution of the Energy Gap and Josephson IcRn Product in Bi2Sr2CaCu2O8+x by Tunneling Spectroscopy

We present direct measurements of the density of states by tunneling spectroscopy on slightly overdoped Bi₂Sr₂CaCu₂O_8+x (Bi2212) single crystals at low temperature using break-junction and point-contact techniques. We find that (i) the variation of the gap magnitude, , between 20 and 36 meV is likely to be intrinsic to Bi2212, and (ii) there is a correlation between the maximum value of the Josephson I _c R _n product and the gap magnitude: I _c R _n decreases with the increase of . The maximum I _c R _n value of 26 mV is observed at = 20.5 meV. For = 36.5 meV, the maximum measured value of I _c R _n is 7.3 mV. We conclude that (i) the distribution of the Josephson I _c R _n product as a function of gap magnitude cannot be explained by the presence of a single energy gap in Bi2212, and (ii) the coherence energy scale in Bi2212 has the maximum Josephson strength.     

Memory characteristics of Au/PZT/BIT/p-Si ferroelectric diode

A ferroelectric memory diode consisting of Au/PZT/BIT/p-Si multilayer configuration has been fabricated by pulsed laser deposition (PLD) technique. The ferroelectric properties and the memory characteristics are investigated. The P-E curve of the PZT/BIT/p-Si films system had an asymmetry saturated hysteresis loop with P, = 15 μC/cm2 and Ec = 48 kV/cm, and the decay in remanent polarization was only 10% after 109 switching cycles, meanwhile the increase in coercive field was 12% . The C-V hysteresis loop and the I-V curve showed a memory effect derived from the ferroelectric polarization of PZT/BIT films, and the current density was 6.7 × 10-8 A/cm2 at a voltage of + 4V. Our diode had nonvolatile and nondestructive memory readout operation. There was a read current disparity of 0.05 μA for logic "1" and logic "0" at a read voltage of + 2V, and the stored logical value ("1" or "0") could be read out in 30 min.     

Synthesis of the Bi-2222 Compounds of Bi–Sr–Ln(Zr)–Cu–O (Ln = Sm,Eu, Gd,and Dy)

Bi-based superconducting compounds with the 2222 structure has been already synthesized in the Bi₂Sr₂- (Ln_1−x Ce _x )₂Cu₂O_10+y (Ln = Sm, Eu, and Gd) systems. One of the characteristics of these compounds is the existence of the fluorite-like (Ln_1−x Ce _x )₂O₂ block between two CuO₅ pyramids in the crystal structure. The tetravalent ions of Ce⁴⁺ are reported to be necessary to stabilize the 2222 structure. Recently, we have discovered that the Bi-2222 phase could be composed in the Bi₂Sr₂(Ln_2−x Zr _x )Cu₂O _z (Ln = Sm, Eu, Gd, and Dy) systems, where Zr⁴⁺ is used as a new tetravalent ion stabilizing the 2222 structure in stead of Ce⁴⁺. In the new system, nearly single 2222 phase samples have been obtained at the nominal composition of x=0.5 (Ln = Sm, Eu, and Gd) and in the range of 0.1≤x≤0.3 (Ln = Dy). Among them, the sample with Ln = Gd has the smallest resistivity at 273 K. But it is a semiconductor, and the conduction process at low temperatures is assumed to be followed by a two-dimensional VRH. The experimental results for the Gd samples with a partial substitution of Pb for Bi in the Bi₂Sr₂(Gd_2−x Zr _x )Cu₂O _z system are also reported.     

Sol-gel法制备Bi3.15Nd0.85Ti3O12铁电薄膜的性能研究

用sol-gel法成功制备了Bi3.15Nd0.85Ti3O12铁电薄膜,XRD结果表明制备的BNT薄膜具有(117)和(00l)的混合取向,FE-SEM显示薄膜表面光滑致密,颗粒均匀.剩余极化Pr和矫顽场Ec分别为29.5μC/cm2和100kV/cm,经过109次循环后几乎无疲劳.     

超声波-水热法合成Bi2Te3纳米管

以水为反应介质，NaBH4为还原剂，合成了BizTe3纳米管及纳米微粒。溶液首先在超声波发生器中预处理1h，然后置于150℃，水热反应釜中继续反应48h。XRD分析表明：合成产物主要物相为Bi2Te3；SEM观察可见产物中有纳米管生成，纳米管直径约为50-100nm，管壁厚约8-10nm，长度在500nm以上。EDS分析表明：纳米管成份为Bi2Te3。Bi2Te3纳米管可能的生长机制为纳米薄片-卷曲-闭合-纳米管。     

Co3O4/Bi2O3纳米粒子气相光催化降解甲苯的研究

采用微乳法及化学沉淀法制备了复合氧化物Co3O4/Bi2O3纳米粒子，结果表明，微乳法制备的复合氧化物Co3O4/Bi2O3粒子光催化活性更好；活性的提高程度与n（Co）：n（Bi）有关，其最佳配比为0．02：1；随着焙烧温度的增加，光催化活性提高，750℃焙烧的样品催化活性最好。以甲苯为目标反应物，考察了光照强度、甲苯的初始浓度、气相氧浓度、水蒸气含量对甲苯光催化降解反应速率的影响。     

A model of preferential (100) crystal orientation of Si grains grown by aluminium-induced layer-exchange process

The aluminium-induced layer-exchange process allows to grow thin large-grained polycrystalline Si films on foreign substrates. A characteristic feature of these films is the preferential (100) orientation of Si grains, favourable for subsequent epitaxial thickening at low temperatures. In this work, a model based on the preferential nucleation is proposed, which elucidates a possible origin of the preferential (100) orientation and its sensitivity to the preparation and process conditions. The probability of Si nuclei to have respective orientation is attributed to the nucleation barrier, i.e. the critical value of the change of the Gibbs energy during nucleation. The preferential orientation is formed statistically by the nuclei having the lowest nucleation barriers.     

铁电薄膜钛酸铋掺杂改善铁电性及疲劳特性的研究

分析了对铁电薄膜Bi4Ti3O12进行A位、B位掺杂时，Bi4Ti3O12铁电性及疲劳特性的改善及相应的理论解释，并指出Bi4Ti3O12值得进一步深入研究的领域。