Calculation of the intrinsic dead layers thicknesses from Au/Ba0.5Sr0.5TiO3/Pt thin film capacitors

Ferroelectric Ba_0.5Sr_0.5TiO₃ (BST) films were prepared on Pt/Ti/SiO₂/Si substrates by the sol-gel process. The films were spin-coated at 2000 rpm for 30 secs and then pyrolysed for 5 mins at the temperature of 350^∘C. This coating procedure was repeated for 3, 4, 5 and 6 times to obtain BST films with different thicknesses. After coating the films with the desired repetition times, the films were finally annealed in a conventional furnace at temperatures ranging from 600^∘C to 800^∘C with a 50^∘C interval in between. The films obtained with an annealing procedure of 750^∘C were polycrystalline with the presence of an impurity BaCO₃ phase. The capacitance and leakage current were measured and used to extract information on the metal-BST interface. With the series capacitance model and modified Schottky emission equation, the thickness of the dead layers for Au/BST and Pt/BST interfaces were calculated to be less than 6 nm and 5 nm, respectively.     

LEAKAGE CURRENT CHARACTERISTICS OF Pt/Ba0.6Sr0.4TiO3/Pt THIN-FILM CAPACITORS

ABSTRACT

Leakage current characteristics of Pt/Ba_0.6Sr_0.4TiO₃/Pt ferroelectric thin-film capacitors were investigated at the temperature range from 273 K to 393 K. It is implied that there are two conduction regions in the capacitors, i.e. ohmic behavior at low voltage (< 0.4 V) and Poole-Frenkel or Schottky emission mechanism at high voltage (> 1.8 V). The depletion layer widths calculated from Poole-Frenkel model and Schottky emission model are 36.9 nm～ 61.5 nm and 6.8 nm～ 11.5 nm, respectively. Moreover, the trapped level, the Schottky barrier height, the constant and the effective Richardson constant are 0.56 V, 0.49 V, 0.227A/cm² · V and 1.15 × 10^?7 A/cm² · K², respectively.     

TiO2纳米管掺杂Pt/C催化剂对甲醇电氧化性能影响

利用电化学方法研究了TiO2纳米管掺杂商业Pt/C催化剂(JM公司)对甲醇电氧化性能的影响.通过对不同掺杂量、不同制备方法等研究,利用循环伏安法和恒电位氧化法等手段,表明:掺杂20%TiO2纳米管的电催化剂对甲醇氧化具有较高活性,这可能是由于Pt和Ti之间产生的相互作用,使得甲醇更容易被活化,而二氧化钛本身携带的氧源,更有助于催化氧化甲醇反应的中间产物,减弱了Pt催化剂中毒程度.     

Influence of Au particles on the photocurrent of TiO2 films

Au/TiO₂ composite films were employed in an attempt to improve the photon-electron conversion efficiency of TiO₂ film in the visible region, using the surface plasma resonance (SPR) of Au nanoparticles. For investigating the relationship between SPR of Au particle and photocurrent of TiO₂ film, a series of Au/TiO₂ films with different Au concentrations were synthesized by sol-gel method. Results of studies on the influence of Au particle size on crystallization of TiO₂ film, UV-vis absorption and photocurrents generated are discussed. It was shown that SPR performance of the Au nanoparticles was not only related to their size, but also to their distribution in the TiO₂ matrix. Even in TiO₂ films with large Au particle sizes (100 nm), SPR in visible region was still observed. However, this SPR performance did not contribute to the photon-electron conversion of TiO₂ film in the visible region. Contrarily, embedded Au nanoparticles depressed the photocurrent generated by the TiO₂ film in UV region. The reason for this decrease is thought to be partly due to the Au simply blocking some of the light and partly because the extent of crystallization of TiO₂ decreased with high Au levels.     

Hysteresis analysis in capacitance-voltage characteristics of Pt/(Ba,Sr)TiO3/Pt structures

Abstract

Capacitance-Voltage (C-V) characteristics of Pt/(Ba, Sr)TiO₃/Pt MIM capacitor were investigated. Hysteresis observed in the C-V characteristics of BST films was analyzed. The dependence of the C-V characteristics on the sweeping direction of applied voltage indicates that the hysteresis is caused by the interface trap charge between the BST film and the Pt electrode. A new method was proposed to characterize the interface traps from the hysteresis of C-V characteristics of MIM capacitor. The trapped electron density near the lower interface of the BST thin films was constant (～ 3 × 10¹²cm^?2) for all the film thickness ranging from 500 Å to 2000 Å, which suggests that the hysteresis is not caused by the bulk property of the BST film but caused by the interfacial property.     

Structural and electrical properties of low resistance Pt/Pd/Au contact on p-GaN

We have investigated electrical and structural properties of Pt/Pd/Au ohmic contact on p-type GaN:Mg (2.5 × 10¹⁷ cm⁻³) using Auger electron spectroscopy (AES) and glancing angle x-ray diffraction (GXRD) analysis. It was shown that the specific contact resistivity improved with increasing annealing temperature. The annealing of the contact at 600^∘C for 2 min in flowing N₂ atmosphere resulted in a specific contact resistivity of 3.1 × 10⁻⁵ Ω cm². Both GXRD and AES depth profile results show that Ga₃Pt₅, Ga₂Pd₅, and Au₇Ga₂ phases are formed at the interface region between metal and GaN when annealed at temperatures 600^∘C. Possible explanation is suggested to describe the annealing dependence of the specific contact resistivity of the Pt/Pd/Au contacts.     

INFLUENCE OF DEPOSITION TEMPERATURE AND N2 FLOW RATE ON HIGH QUALITY ZNO THIN FILM DEPOSITED ON SiO2/SI SUBSTRATE BY ULTRASONIC SPRAY PYROLYSIS

ABSTRACT

ZnO thin films were prepared on SiO₂/Si substrate by ultrasonic spray pyrolysis (USP) method using the aqueous solution of zinc acetate dehydrate. X-ray diffraction (XRD) and atomic force microscopy (AFM) were employed to analyze the crystalline and microscopic structure of the films. The properties of ZnO films were investigated with respect to deposition temperature (T_s) and N₂ flow rate (f). The results show that ZnO thin films exhibit hexagonal wurtzite structure and the highly preferential orientation along c-axis under T_s = 320°C and f = 5 L/min deposition condition.     

Film Thickness Dependence of Electrical Properties for Pb(Zr,Ti)O3 Thin Films Prepared on (111)Ir/TiO2/SiO2/Si and (111)Pt/TiO2/SiO2/Si Substrates by Pulsed-Metalorganic Chemical Vapor Deposition

Polycrystalline Pb(Zr,Ti)O₃ (PZT) films with various film thicknesses were deposited on (111)Ir/TiO₂/SiO₂/Si and (111)Pt/TiO₂/SiO₂/Si substrates at 540°C by source-gas-pulsed metalorganic chemical vapor deposition (pulsed-MOCVD). PZT films deposited on (111)Ir/TiO₂/SiO₂/Si substrates showed good surface flatness and lower leakage current density. The rate of the decrease of remanent polarization (P _r ) and the rate of increase of coercive field (E _c ) for the films with decreasing the film thickness smaller on (111)Ir/TiO₂/SiO₂/Si substrates than those of (111)Pt/TiO₂/SiO₂/Si substrates. In addition, P _r and E _c values saturated at low voltage when the film thickness was the same. As a result, good ferroelectricity with P _r and E _c values of 40 μC/cm² and 140 kV/cm were obtained for 35 nm-thick films prepared on (111)Ir/TiO₂/SiO₂/Si substrates by pulsed-MOCVD.     

Interface potential barrier height and leakage current behavior of Pt/(Ba,Sr)TiO3/Pt capacitors fabricated by sputtering process

Abstract

Variations of the leakage current behaviors and interface potential barrier height (φ _B ) of rf-sputter deposited (Ba, Sr)TiO₃ (BST) thin films, with thickness ranging from 20nm to 150 nm are investigated as a function of the thickness and bias voltages. The top and bottom electrodes are dc-sputter-deposited Pt films. φ _B critically depends on the BST film deposition temperature, postannealing atmosphere and time after the annealing. The postannealing under N₂ atmosphere results in a high interface potential barrier height and low leakage current. Maintaining the BST capacitor in air for a long time reduces the φ _B from about 2.4 eV to 1.6eV due to the oxidation. φ _B is not so dependent on the film thickness in this experimental range. The leakage conduction mechanism is very dependent on the BST film thickness; the 20nm thick film shows tunneling current, 30 and 40 nm thick films show Schottky emission current and the thicker films show a mixed characteristics and bulk and interface limited currents although the mechanism is not clearly understood at this moment.     

TiO2/NiCuZn复合材料的电磁性能

铁电铁磁复合材料是一种由铁电相和铁磁相复合而成的重要功能材料,将对电子设备的小型化和高度集成化起到相当关键的作用.研究以铁电性的TiO2和铁磁性的NiCuZn铁氧体为原料,采用固相反应法合成一系列TiO2/NiCuZn复合材料,考察了材料配比和烧结温度对复合材料介电性能和磁性能的影响.实验表明,随着TiO2含量的增加,复合材料的磁导率显著降低,但同时介电性能会得到改善.对于NiCuZn含量为80wt%的材料,在900～1200 ℃的烧结温度范围,随着烧结温度的升高介电常数与磁导率也都会随之升高.这种TiO2/NiCuZn复合材料同时具有电感和电容两种特性,有望在未来的集成电路中广泛使用.     

聚酰亚胺 /纳米二氧化钛复合物的合成与性能研究

采用原位聚合方法制备了聚酰亚胺／纳米二氧化钛(TiO2)复合物,用TEM、FTIR研究了其形态结构及纳米颗粒在复合物中的分散性,用红外光谱验证了复合物中纳米颗粒的存在,同时分析研究了纳米复合物的机械、介电性能,结果表明：纳米颗粒在复合物中分散性良好;纳米TiO2的加入导致纳米复合物的常规机械、介电性能下降,但随着纳米TiO2含量的增加,复合材料的耐电晕能力和拉伸强度得到了提高。     

Effects of Ar post-annealing on the electrical properties of Pt/YMnO3/p-Si and Pt/YMnO3/Y2O3/p-Si

Abstract

YMnO₃ thin films were prepared on p-Si(111) and Y₂O₃/p-Si(111) substrates by chemical solution deposition and annealed at 800°C for 1 hour under the oxygen pressure of 2 Torr. The YMnO₃ thin films showed good crystallinity and c-axis preferred orientation. Effects of Ar post-annealing on electrical properties were examined in Pt/YMnO₃/p-Si and Pt/YMnO₃/Y₂O₃/p-Si structures. Leakage current densities decreased considerably by Ar post-annealing. The Pt/YMnO₃/p-Si and Pt/YMnO₃/Y₂O₃/p-Si showed clockwise C-V hysteresis induced by ferroelectric polarization after Ar post-annealing and memory windows of MFS and MFIS structure were 1.1V and 0.6V, respectively.     

EFFECTS OF DEPOSITION PARAMETERS AND FILM THICKNESS ON THE PHASES AND ELECTRICAL PROPERTIES OF Pb(Mg1/3Nb2/3)O3 THIN FILMS MADE BY MOCVD USING ULTRASONIC NEBULIZATION

ABSTRACT

PMN thin films were deposited by MOCVD using ultrasonic nebulization and the effects of deposition parameters and film thickness on the phases and electrical properties of the PMN films were investigated. The low deposition temperature and RTA treatment were favorable to deposit the PMN films with a low content of pyrochlore phase. Excess Mg enhanced the formation of perovskite phase of PMN films also. As the film thickness was increased, the portion of pyrochlore phase in PMN films was decreased. The dielectric constant of PMN films increased with the film thickness and showed the value of 25–230.     

Effect of O<Superscript>2-</Superscript> migration in Pt/HfO<Subscript>2</Subscript>/Ti/Pt structure

In this paper, we study the post-fabrication phenomenon of natural oxidation of the Ti layer observed in a Pt/HfO₂/Ti/Pt Resistive Random Access Memory (OxRRAM) stack with no external influence. We identify that the resistance ratio decreases by 100 × in a month time period due to the natural oxidation of the Ti layer in contact of the HfO₂ layer. We then propose two paths to control both the final properties of the device and the aging process. The first approach consists in carefully optimizing the thickness of the Ti layer to reduce the aging effect. However, the resistance ratio is proportional to the thickness of the layer, leading to an unwanted trade-off between device properties and aging effect. The second approach consists in adding a TiO₂ inter-layer, creating a Pt/HfO₂/TiO₂/Ti/Pt OxRRAM stack that is more stable over time with similar resistive states. The obtained OxRRAM stack presents a resistance ratio in the order of 10⁴ with no observable post-fabrication aging degradation.     

PHASE TRANSITION IN Pb(Mg1/3Nb2/3)0.68TiO0.32O3 SINGLE CRYSTAL

ABSTRACT

Phase transition of (001)-cut Pb(Mg_1/3Nb_2/3)_0.68Ti_0.32O₃(PMNT32%) single crystal have been investigated by polarizing light microscopy in the temperature ranged form room temperature to 200 K. The transformation from monoclinic (M_A) to cubic (C) phase through an intermedial monoclinic (M_C) phase, i.e. M_A-M_C-C, was observed in the heating run, and the C-M_C-M_A phase transition sequence was observed in the cooling run. The temperature-induced rotation of extinction position, which was the result of polarization rotation, was observed in M_C phase. It is interesting that tetragonal (T) phase has not been reached before the M_C phase turn into cubic phase. The existing phase diagram for PMNT system was improved by this experimental result. In addition, it was found the phase transition processes of M_C-M_A and cubic-M_C show distinct characters though both of they are first-order.     

Electrical Characteristics and Thermal Stability of Pt/HfO 2 /Si Metal-Insulatror-Semiconductror Capacitors

The HfO 2 thin films for use in gate dielectric applications were deposited at 300 onto p-type Si (100) substratee using Hf[OC(CH 3 ) 3 ] 4 as the precursor in the absence of oxygen by plasma-enhanced chemical vapor deposition. The HfO 2 films deposited in the absence of O 2 show excellent electrical properties such as low capacitance equivalent thickness (CET), good thermal stability and low charge trapping. The as-deposited films have an interfacial layer of approximately 1 nm in thickness, resulting in a decrease in the thickness of the interfacial layer by about 50% compared to films deposited in the presence of oxygen. The leakage current density of HfO 2 films was approximately 3 orders of magnitude lower than an electrically comparable SiO 2 at the same CET. The improvement of electrical properties can be attributed to the decrease in the SiO 2 interfacial layer. The thickness of the interfacial layer can be contolled by the deposition in the absence of oxygen after evacuation of the reaction chamber by means of an ultra-high vacuum.     

PVDF-HFP/TiO2多孔杂化电解质膜的研究

将溶胶-凝胶法与相转化法结合,以偏氟乙烯-六氟丙烯共聚物(PVDF-HFP)、钛酸四丁酯为主要原料,制备了PVDF-HFP/TiO2多孔杂化膜,经电解液活化后得到PVDF-HFP/TiO2多孔杂化电解质膜。采用扫描电子显微镜法(SEM)、透射电子显微镜法(TEM)、交流阻抗法等手段对多孔杂化电解质膜的结构和性能进行了测试分析。研究结果表明,与PVDF-HFP多孔电解质膜相比,PVDF-HFP/TiO2多孔杂化电解质膜在微孔结构、离子电导率等方面都有明显的改善;同时,随着TiO2含量的增加,也增大了多孔杂化膜的孔隙率和电导率。     

ZnO/TiO2复合薄膜的制备及性能表征

采用溶胶凝胶法结合丝网印刷法制备TiO2多孔薄膜,用溶液沉积法制备多孔ZnO/TiO2复合薄膜;用X-射线分析仪、扫描电镜、紫外-可见分光光度计等对薄膜的热处理制度、吸光度、表面形貌进行了测试;组装电池,用XJCM-8S型太阳电池测定仪测定了复合薄膜的电性能.结果表明以ZnO/TiO2复合薄膜做电极,吸光度和电池性能都有一定的提高,电池电压达到0.67 V.     

Photocatalytic property of SiO2/TiO2 nanoparticles prepared by sol-hydrothermal process

Silica-embedded nanocrystalline TiO₂ powders were synthesized by sol-hydrothermal process. The influence of the composition of the solvent and the embedded silica content on the phase transition, grain growth and subsequently, on the photoactivity of TiO₂ were investigated. The volume ratio of ethanol to water for the solvent composition was varied from 0.125 to 8 and the mole fraction of silica content was changed from 0 to 0.4, while the condition for hydrothermal reaction was fixed at 250^∘C for 2 hour. With an increase in ethanol content in solvent composition, the crystallite sizes of pure TiO₂ particles decreased from 15 nm to 6 nm and crystal phase changed from rutile/anatase mixed phase to pure anatase phase. Addition of silica to TiO₂ brought about an increase in the photocatalytic activity by suppressing the phase transition from anatase to rutile. Judging from the result of the decomposition of 1, 4-dichlorobenzene, the most efficient catalyst was found to be 0.2 mole fraction SiO₂ embedded TiO₂ prepared with ethanol-rich solvent (the volume ratio of ethanol to water is 4).