Preparation of Highly Textured Bi and MnBi Films by the Pulsed Laser Deposition Method

Textured Bi and MnBi/Bi thin films are prepared by the pulsed laser deposition method. The highly c-axis textured MnBi films are obtained by annealing the bilayer consisting of textured Bi and Mn films. The eoercivities of the MnBi/Bi film are 1.5 T and 2.35 T at room temperature and at 373K, respectively, showing a positive temperature coefficient. Microstructural investigations show that the textured MnBi film results from the orientated growth induced by the textured Bi under-layer.

Effects of atomic corrugations on electronic structures in Pb_(1-x)Bi_(x) thin films

We carried out experimental investigations of the geometric effect on the electronic behavior in Pb_(1-x)Bi_(x) thin films by scanning tunneling microscopy and spectroscopy.Single crystal monolayer Pb_(0.74)Bi_(0.26) and two-monolayer Pb_(0.75)Bi_(0.25)Pb_(1-x)Bi_(x) thin films were fabricated by molecular beam epitaxy,where large surface corrugations were observed.Combined with tunneling spectroscopic measurements,it is found that atomic corrugations can widely change the electronic behaviors.These findings show that the Pb_(1-x)Bi_(x) system can be a promising platform to further explore geometry-decorated electronic behavior in two-dimensional metallic thin films.

Film and Television Website Scores Authenticity Verification Based on the Emotional Analysis

Sentiment analysis is a method to identify and understand the emotion in the text through NLP and text analysis. In the era of information technology, there is often a certain error between the comments on the movie website and the actual score of the movie, and sentiment analysis technology provides a new way to solve this problem. In this paper, Python is used to obtain the movie review data from the Douban platform, and the model is constructed and trained by using naive Bayes and Bi-LSTM. According to the index, a better Bi-LSTM model is selected to classify the emotion of users’ movie reviews, and the classification results are scored according to the classification results, and compared with the real ratings on the website. According to the error of the final comparison results, the feasibility of this technology in the scoring direction of film reviews is being verified. By applying this technology, the phenomenon of film rating distortion in the information age can be prevented and the rights and interests of film and television works can be safeguarded.

Preparation of dendritic bismuth film electrodes and their application for detection of trace Pb(Ⅱ)and Cd(Ⅱ)

In this paper,dendritic Bi film electrodes with porous structure had successfully been prepared on glassy carbon electrode using a constant current electrolysis method based on hydrogen bubble dynamic templates.The electrode prepared using a large applied current density showed an increased internal electroactive area and a significantly improved electrochemical performance.The analytical utility of the prepared dendritic Bi film electrodes for the determination of Pb(Ⅱ)and Cd(Ⅱ)in the range of 5–50 μg·L^(-1)were presented in combination with square wave stripping voltammetry in model solution.Compared with non-porous Bi film electrode,the dendritic Bi film electrode exhibited higher sensitivity and lower detection limit.The prepared Bi film electrode with dendritic structure was also successfully applied to real water sample analysis.

Effects of Thickness and Temperature on Thermoelectric Properties of Bi2Te3-Based Thin Films

Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices of different thicknesses are prepared on the silicon dioxide substrates by magnetron sputtering technique and thermally annealed at 573 K for 30 min. Thermoelectric（TE）measurements indicate that optimal thickness and thickness ratio improve the TE performance of Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices, respectively. High TE performances with figure-of-merit（ZT） values as high as 1.32 and 1.56 are achieved at 443 K for 30 nm and 50 nm Bi_2Te_3 thin films, respectively. These ZT values are higher than those of p-type Bi_2Te_3 alloys as reported. Relatively high ZT of the GeTe/B_2Te_3 superlattices at 300-380 K were 0.62-0.76. The achieved high ZT value may be attributed to the unique nano-and microstructures of the films,which increase phonon scattering and reduce thermal conductivity. The results indicate that Bi_2Te_3-based thin films can serve as high-performance materials for applications in TE devices.

掺杂Bi的β-Cu_(2)Se薄膜的微观结构与热电性能

目的 探究在β-Cu_(2)Se薄膜中掺杂元素Bi对其组织结构及其热电性能的影响,探求Bi元素对载流子传输过程和热电性能的影响规律,为将来该类热电薄膜的研究和应用提供宝贵的经验。方法 使用粉末烧结制得Cu-Bi-Se合金靶材,使用磁控溅射的方法在含有SiO_(2)层的单晶Si衬底上制备了不同Bi含量的β-Cu_(2-x)Bi_(x)Se热电薄膜。利用X射线衍射仪、扫描电子显微镜、能谱仪分别研究了沉积薄膜的XRD谱、表面与截面形貌以及元素含量与分布。利用LSR-3电阻率/塞贝克系统测量了沉积薄膜的Seebeck系数与电导率。利用霍尔试验测量了沉积薄膜的室温载流子浓度和迁移率。结果 沉积薄膜主要由单一的β-Cu_(2)Se相构成,在Bi掺杂量最大为1.07%(原子数分数)的薄膜还含有非常少量的α-Cu_(2)Se相;在β-Cu_(2)Se相薄膜中Bi的掺杂没有生成单质相而是替换点阵中的Cu而形成替位式固溶体。在沉积的β-Cu_(2-x)Bi_(x)Se薄膜中,([Bi]+[Cu])/[Se]>2.0且具有p型导电特征。随着温度的增加,电导率降低而Seebeck系数增加,彰显沉积薄膜的简并或半简并半导体的导电特性。当温度低于225℃时,沉积薄膜功率因子随Bi掺杂量的增加而增大;当温度高于225℃时,掺杂量为0.29%(原子数分数)的薄膜具有最大的功率因子,进一步增加Bi掺杂量,沉积薄膜的功率因子却逐渐减小。结论 使用磁控溅射的方法可制备β-Cu_(2)Se薄膜,掺杂适量的Bi可显著提高薄膜的功率因子。

High temperature thermoelectric properties of highly c-axis oriented Bi_2Sr_2Co_2O_y thin films fabricated by pulsed laser deposition

High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa （001）. Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices,

Studies on Preparation of Co-Bi Alloy Films by Electrodeposition From Nonaqueous Medium

Cyclic voltammetry and potentiostatic electrolysis were used to investigate the preparation of Co-Bi alloy films in a LiClO 4-DMSO system. The experimental results indicate that the Co-Bi alloy films containing 14 35%-29 77% Co can be prepared via potentionstatic electrolysis on Cu substrates, at deposition potential -1 10--1 65 V( vs. SCE) and by controlling the system composition and deposition condition. They are uniform gray films with a metallic luster and they are adhered firmly to the Cu substrate. The films were analyzed by EDS, SEM and XRD. After heat treatment of crystallization at 275 ℃ for 1 h, the alloy phase of Co-Bi can be confirmed via the XRD pattern.

Preparation of Dy-Bi alloy films by electrodeposition in organic bath

The cyclic voltammetry and potentiostatic electrolysis were used toinvestigate the preparing of Dy-Bi alloy films in LiCl-DMSO (dimethylsulfoxide) system. The effectsof several factors including the potential of deposition, concentrations of main salts, and theconcentration ratio of DyCl_3 to Bi(NO_3)_3 were studied. Dy-Bi alloy films containing 4.82%-80.62%(mass fraction) dysprosium were prepared in DyCl_3-Bi(NO_3)_3-LiCl-DMSO system by controlling thesystem composition and deposition conditions. The films are gray, uniform, metallic luster andadhere firmly to the copper substrates analyzed by SEM (scanning electron microscope), EDS (X-rayenergy dispersive analysis), and XRD (X-ray diffraction). After heat treatment at 718 K for 1 h, thealloy phase of Dy-Bi was found in XRD patterns.

Bi-Cu film deposition in aqueous solutions

The relatively uniform bismuth-copper film was electrodeposited between -15 and -20 mV in the sulfate electrolyte containing 4 mmol/L bismuth ion and 2 mmol/L copper ion.Only copper was electrodeposited at -5 mV.The dendritic bismuth-copper film was electrodeposited under -20 mV.The cathodic current became constant between -20 and -400 mV.Therefore,bismuth-copper electrodeposition changes from charge transfer controlling to diffusion controlling at -20 mV.On the other hand,the uniform bismuth-copper film was electrodeposited between -5 and -35 mV in the methanesulfonate electrolyte containing 4 mmol/L bismuth ion and 2 mmol/L copper ion.The dendritic bismuth-copper film was electrodeposited under -35 mV.The potential region for good electrodepositon in methanesulfonate electrolyte is wider than that in sulfate electrolyte.Therefore,it is easy to control electrodeposition conditions by using methanesulfonate electrolyte.

Cyclic Electrodeposition of Yb-Bi Thin Films

Deposition of Yb-Bi thin films was carried out from a nonaqueous solution by using cyclic electrodepositon. During electrodeposition the substrate potential was continuously cycled between two potentials. The effects of several factors including the potential of deposition, time of deposition and sweep rate on the Yb content in the thin films and surface morphology were studied. Experimental results indicate that the amorphous Yb-Bi thin films containing Yb 21.04%～36.36% (mass fraction) can be prepared in 0.10 mol·L^(-1) YbCl_3+0.10 mol·L^(-1) Bi(NO_3)_3+0.10 mol·L^(-1) LiCl+DMSO by controlling deposition conditions of the system. They are black, uniform, metallic luster and adhered firmly to the copper substrates. The films were characterized by X-ray energy dispersive analysis (EDS), scanning electron microcoscope (SEM) and X-ray diffraction (XRD).

Structural and electrical properties of single crystalline and bi-crystalline ZnO thin films grown by molecular beam epitaxy

C-oriented ZnO epitaxial thin films are grown separately on the a-plane and c-plane sapphire substrates by using a molecular-beam epitaxy technique. In contrast to single crystalline ZnO films grown on a-plane sapphire, the films grown on c-plane sapphire are found to be bi-crystalline; some domains have a 30~ rotation to reduce the large mismatch between the film and the substrate. The presence of these rotation domains in the bi-crystalline ZnO thin film causes much more carrier scatterings at the boundaries, leading to much lower mobility and smaller mean free path of the mobile carriers than those of the single crystalline one. In addition, the complex impedance spectra are also studied to identify relaxation mechanisms due to the domains and/or domain boundaries in both the single crystalline and bi-crystalline ZnO thin films.

Electrochemical preparation of Er-Co-Bi thin film in organic bath by cyclic electrodeposition method

Cyclic electrodeposition was used to investigate the preparation of Er-Co-Bi alloy thin film in DMSO system. Experimental results indicate that Er-Co-Bi alloy thin film containing 14.83 %32.65 % Er is prepared from 0.1 mol/L ErCl3+0.1 mol/L CoCl2+0.1 mol/L Bi（NO3）3+0.1 mol/L LiCl +DMSO system by cyclic electrodeposition on Cu substrate. The optimum cyclic potential of electrodeposition is that upper potential is within a potential range from -0.50 V to -1.00 V and lower potential is within a potential range from -2.00 V to )-2.60 V.) The surface of alloy thin film observed by scanning electron microscope is black, adhesive and has metallic luster. The film is amorphous proved by the X-ray diffractometry.

STUDY ON CO-ELECTRODEPOSITION OF Bi-Fe ALLOY FILMS IN ORGANIC BATH

The cyclic voltametry and potentiostatic electrolysis was used to investigate the preparation of Bi-Fe alloy films in LiClO4-DMSO (dimethylsulfoxide) system. The effects of several factors including the potential of deposition, current density and concentration of iron and bismuth in the solution on the Fe content in the alloy deposits were studied. Experimental results indicated that the amorphous alloy films of Bi-Fe containing Fe 4.40wt%-33.67wt% could be prepared by controlling the system composition and deposition conditions. They were gray, uniform, metallic luster and adhered firmly to the copper substrates analyzed by EDS, SEM and XRD. After heat treatment of crystallization at 270℃ for 1h, the crystal phase of Bi-Fe can be found in XRD patterns.

Effect of La Doping on Microstructure and Ferroelectric Prop-erties of Bi_4Ti_3O_(12) Thin Films Prepared by Sol-gel Method

The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.

Impurity Effects at Surfaces of a Photon-Dressed Bi2Se3 Thin Film

We investigate the impurity effects on surfaces of a thin film topological insulator, applied by an off-resonant circular polarized light. It is found that the off-resonant driving induces a quantized total Hall conductivity, when the driving strength is larger than a critical value and the Fermi level lies in the band gap, indicating that our system is converted into the topological phase. We also find that with the increasing disorder strength, the Dirac masses of top and bottom surfaces are renormalized and then fixed to half of their initial values, respectively,which will shrink the widths of the half-integer plateau of anomalous Hall conductivities.

High-Quality Bi_2Te_3 Single Crystalline Films on Flexible Substrates and Bendable Photodetectors

Recently, great efforts have been made in the fabrication of arbitrary warped devices to satisfy the requirement of wearable and lightweight electronic products. Direct growth of high crystalline quality films on flexible substrates is the most desirable method to fabricate flexible devices owing to the advantage of simple and compatible preparation technology with current semiconductor devices, while it is a very challenging work, and usually amorphous, polycrystalline or discontinuous single crystalline films are achieved. Here we demonstrate the direct growth of high-quality Bi2 Te3 single crystalline films on flexible polyimide substrates by the modified hot wall epitaxy technique. Experimental results reveal that adjacent crystallites are coherently coalesced to form a continuous film, although amounts of disoriented crystallites are generated due to fast growth rate. By inserting a quartz filter into the growth tube, the number density of disoriented crystallites is effectively reduced owing to the improved spiral interaction. Furthermore, flexible Bi2 Te3 photoconductors are fabricated and exhibit strong near-infrared photoconductive response under different degrees of bending, which also confirms the obtained fexible films suitable for electronic applications.

Effect of crystallization temperature on microstructure and ferroelectric property of Bi_(3.25)Eu_(0.75)Ti_3O_(12) thin films prepared by MOD method

Europium-substituted bismuth titanate (Bi3.25Eu0.75Ti3O12) thin films were deposited on the Pt/Ti/SiO2/Si(111) substrates by metal-organic decomposition (MOD) method using a repeated coating/drying cycle. Effect of crystallization temperature on microstructure of Bi3.25Eu0.75Ti3O12(BET) thin films was investigated by X-ray diffractometry(XRD), scanning electron microscopy (SEM) and Raman spectroscopy, and ferroelectric property was studied by Precision Workstation Ferroelectric Tester. The crystallinity of BET thin films is improved and the average grain size increases with the crystallization temperature from 600 to 750 ℃. Under 9 V applied voltage, the remnant polarization (2Pr) of BET thin films annealed at 700 ℃ is 50.7 μm/cm2, which is higher than that of the films annealed at 600, 650 and 750℃.

Effect of microstructure on the thermoelectric properties of CSD-grown Bi_2Sr_2Co_2O_y thin films

Three Bi2Sr2Co2Oy thin films with different microstructures have been prepared by chemical solution deposition on LaAlO 3（001） through varying the annealing temperature.With the decrease in the annealing temperature,both the size and c-axis alignment degree of grains in the film decrease as well,leading to an increase in the film resistivity.In addition,the decrease in the annealing temperature also results in a slight increase in the Seebeck coefficient due to the enhanced energy filtering effect of the small-grain film.The nanostructured Bi2Sr2Co2Oy film with an average grain size of about 100 nm shows a power factor comparable to that of films with larger grains.Since the thermal conductivity of the nanostructured films can be depressed due to the enhanced phonon scattering by grain boundary,a higher figure of merit is expected in Bi2Sr2Co2Oy thin film with grains in nanometer size.