Revealing Controllable Anisotropic Magnetoresistance in Spin–Orbit Coupled Antiferromagnet Sr2IrO4

Antiferromagnetic spintronics actively introduces new principles of magnetic memory, in which the most fundamental spin‐dependent phenomena, i.e., anisotropic magnetoresistance effects, are governed by an antiferromagnet instead of a ferromagnet. A general scenario of the antiferromagnetic anisotropic magnetoresistance effects mainly stems from the magnetocrystalline anisotropy related to spin–orbit coupling. Here magnetic field driven contour rotation of the fourfold anisotropic magnetoresistance in bare antiferromagnetic Sr₂IrO₄/SrTiO₃ (001) thin films hosting a strong spin–orbit coupling induced J_eff = 1/2 Mott state is demonstrated. Concurrently, an intriguing minimal in the magnetoresistance emerges. Through first principles calculations, the bandgap engineering due to rotation of the Ir isospins is revealed to be responsible for these emergent phenomena, different from the traditional scenario where relatively more conductive state is obtained usually when magnetic field is applied along the magnetic easy axis. These findings demonstrate a new efficient route, i.e., via the novel J_eff = 1/2 state, to realize controllable anisotropic magnetoresistance in antiferromagnetic materials.     

Substrate‐Dependent Spin–Orbit Coupling in Hybrid Perovskite Thin Films

Solution‐processing hybrid metal halide perovskites are promising materials for developing flexible thin‐film devices. This work reports the substrate effects on the spin–orbit coupling (SOC) in perovskite films through thermal expansion under thermal annealing. X‐ray diffraction (XRD) measurements show that using a flexible polyethylene naphthalate (PEN) substrate introduces a smaller mechanical strain in perovskite MAPbI_3?xCl_x films, as compared to conventional glass substrates. Interestingly, the linear/circular photoexcitation‐modulated photocurrent studies find that decreasing mechanical strain gives rise to a weaker orbit–orbit interaction toward decreasing the SOC in the MAPbI_3?xCl_x films prepared on flexible PEN substrates relative to rigid glass substrates. Simultaneously, decreasing the mechanical strain causes a reduction in the internal magnetic parameter inside the MAPbI_3?xCl_x films, providing further evidence to show that introducing mechanical strain can affect the SOC in hybrid perovskite films upon using flexible substrates toward developing flexible perovskite thin‐film devices. Furthermore, thermal admittance spectroscopy indicates that the trap states are increased in the perovskite films prepared on flexible PEN substrates as compared to glass substrates. Consequently, PEN and rigid glass substrates lead to shorter and longer photoluminescence lifetimes, respectively. Clearly, these findings provide an insightful understanding on substrate effects on optoelectronic properties in flexible perovskite thin‐film devices.     

Anomalous Anisotropic Magnetoresistance of Antiferromagnetic Epitaxial Bimetallic Films: Mn2Au and Mn2Au/Fe Bilayers

Recently intensive efforts have been devoted to the emerging field of antiferromagnetic (AFM) spintronics, where ferromagnetic electrodes are substituted by antiferromagnets. This study investigates the anisotropic magnetoresistance (AMR) of epitaxial tetragonal antiferromagnetic bimetallic films: Mn₂Au and Mn₂Au/Fe bilayers. An anomalous AMR effect with additional peaks is observed. This study theoretically and experimentally demonstrates that the AFM spins of Mn₂Au can be viewed and controlled at room temperature, and this is achievable with a notably relatively small magnetic field of 200 mT. Strong hybridization between Au and Mn, and strong modification of the intrinsic quadratic anisotropy of Mn₂Au from interfacial biquadratic anisotropy result in an additional anomalous AMR component of 1%. The findings suggest that Mn₂Au films can be used in room temperature antiferromagnetic spintronics.     

Gold‐Nanoparticle‐Doped TiO2 Semiconductor Thin Films: Optical Characterization

A simple procedure for creating titania sol–gel‐based semiconductor thin films is described. Gold nanoparticles are doped homogeneously into the precursor mixture and the particles are homogeneously distributed in the resultant films when prepared using spin‐coating. The effects of particle loading and annealing temperature on the optical properties of the resultant films are characterized. Ellipsometry, X‐ray diffraction, atomic force microscopy, and surface plasmon spectroscopy are used to monitor the crystallization and porosity changes during film synthesis.     

二氧化钒薄膜的制备及性能表征

通过激光脉冲沉积法,分别在Csapphire和R—sapphire衬底上制备了单相二氧化钒（VO2）薄膜。用x射线衍射法表征了不同实验条件下制备的二氧化钒薄膜的结构性质,分析表明在600℃,10^-2torr的氧气分压下,生长15min可得到单相的二氧化钒（VO2）薄膜;重点研究了激光能量对薄膜电学性质的影响,实验结果表明激光能量在500-600MJ对制备的二氧化钒薄膜具有最好的电学性质。     

Al掺杂ZnO薄膜的XPS谱及电学性质研究

采用直流反应磁控溅射法在玻璃基底上用Zn(99.99%)掺杂Al(1.5%)靶制备出高质量的Al掺杂的ZnO(AZO)薄膜。用X射线光电子能谱仪对退火处理后的薄膜进行了成分和元素的价态分析,并用Van der Pauw方法对样品的电学特性进行了测量。实验结果表明,Zn和Al元素都以氧化态的形式存在,O元素主要是以晶格氧和吸附氧的形式存在。AZO薄膜的电学性质受退火温度和氧氩比的影响较大。随着退火温度的升高,电阻率减小,载流子浓度和迁移率增大。随着氧氩比的增大,电阻率增大,迁移率减小。因此可得到用直流反应磁控溅射法制备AZO薄膜的最佳氧氩比和退火温度分别为0.3/27和400℃,在此条件下制备出的薄膜电阻率可低至10-4Ω.cm,载流子浓度可达1020cm-3。     

掺TiO2的ZnO薄膜气敏特性研究

用直流磁控溅射法分别在Si(111)基片及陶瓷基片上制备掺有TiO2的ZnO薄膜,并进行500℃、700℃退火处理,对掺杂前后ZnO薄膜进行XRD分析,测试各掺杂样品气敏特性.500℃退火后,各掺杂样品对有机气体有较高的灵敏度,随着掺杂时间延长,气敏特性提高.700℃退火后,2 min掺杂的样品对乙醇有很高的灵敏度和很好的选择性,最佳工作温度为220℃左右.而其他掺杂量的样品对乙醇气体灵敏度低,随着掺杂时间延长,气敏特性降低.     

BST薄膜的Sol-Gel法制备及其电学性能的研究

应用溶胶-凝胶（Sol-Gel)工艺制备了组分为r（Ba:Sr)=0.65:0.35的BST薄膜，研究了BST薄膜的显微结构、介电特性和漏电流特性，实验结果表明：BST薄膜经650℃热处理后，巳形成完整的立方钙钛矿结构，薄膜经900℃热处理后，其表面光滑、致密、无裂纹、无针孔，圆球形的小颗粒均匀分布。当偏置电压为0时，BST薄膜的介电常数和损耗因子分别为542和0.035。漏电流特性分析结果表明：采用RuO2作为底电极，在1.5V的偏压下BST薄膜的漏电流密度为0.52μA/Cm^2，该值比Pt/RuO2混合底电极上制备的BST薄膜的漏电流密度（72nA/cm^2)大1个数量级，因此，Pt/RuO2混合底电极既克服了RuO2底电极漏电流大的缺点，又解决了Pt底电极难以刻蚀的困难，是制备大规模动态随机存取存储器的电容器列阵的最低底电极材料。     

溅射压强对Sc掺杂ZnO薄膜绒面结构的影响

采用射频磁控溅射方法,分别在0.5Pa,1.0Pa,1.5Pa以及2.0Pa的溅射压强下制备出了Sc:ZnO(SZO)薄膜,并用X射线衍射仪、扫描电子显微镜、紫外可见光分光光度计等设备对样品的晶体结构、表面形貌及光学性质进行了表征。结果表明,当溅射压强为1.5Pa时,SZO薄膜沿平行于衬底的(100)方向择优生长,形成了织构化的表面形貌,陷光效果增强,可见光透过率达到87%,同时其光散射能力也有了显著提高。     

Incipient Ferroelectricity in Al‐Doped HfO2 Thin Films

Incipient ferroelectricity is known to occur in perovskites such as SrTiO₃, KTaO₃, and CaTiO₃. For the first time it is shown that the intensively researched HfO₂ thin films (16 nm) also possess ferroelectric properties when aluminium is incorporated into the host lattice. Polarization measurements on Al:HfO₂ based metal–insulator–metal capacitors show an antiferroelectric‐to‐ferroelectric phase transition depending on annealing conditions and aluminium content. Structural investigation of the electrically characterized capacitors by grazing incidence X‐ray diffraction is presented in order to gain further insight on the potential origin of ferroelectricity. The non‐centrosymmetry of the elementary cell, which is essential for ferroelectricity, is assumed to originate from an orthorhombic phase of space group Pbc2₁ stabilized for low Al doping in HfO₂. The ferroelectric properties of the modified HfO₂ thin films yield high potential for various ferroelectric, piezoelectric, and pyroelectric applications. Furthermore, due to the extensive knowledge accumulated by various research groups regarding the HfO₂ dielectric, an immediate relevance of ferroelectric hafnium oxide thin films is anticipated by the authors.     

退火温度对SnF2掺杂SnO2薄膜性能的影响

利用电子束蒸镀技术在石英玻璃上沉积SnF2掺杂SnO2(FTO)薄膜.研究了不同退火温度对FTO薄膜结构和光电性能的影响.研究结果表明:升高退火温度可促进FTO薄膜中晶粒逐渐变大,结晶度变好,同时薄膜在可见光范围内的透射率随着退火温度升高逐渐增加,吸收边发生蓝移,禁带宽度显著变宽,这是由于载流子浓度增加导致的Moss-Burstein效应.升高温度时,薄膜电学性能随着退火温度升高有了很大改善,700℃退火处理后得到电阻率低至2.74×101 Ω·cm、载流子浓度为2.09×1020 cm-3、迁移率为9.93 cm2·V 1·s 1的FTO薄膜.     

Enhanced Electrical Switching and Electrochromic Properties of Poly(p‐phenylenebenzobisthiazole) Thin Films Embedded with Nano‐WO3

The electrical switching and electrochromic phenomena of a novel nanocomposite comprising poly(p‐phenylenebenzobisthiazole) (PBZT) and tungsten oxide (WO₃) nanoparticles are investigated as a function of the nanoparticle loading. Both dissolving PBZT and doping PBZT backbone structure with acid are achieved by one simple step. Chlorosulfonic acid (CSA) is used as a solvent and spontaneously transformed to sulfuric acid upon exposure to moisture. The formed sulfuric acid serves as doping agent to improve the electrical conductivity of PBZT. The most significant enhancement of electrical switching is observed in the nanocomposites with low weight fraction (5%). The electrical conductivity of 5% WO₃/PBZT nanocomposite thin film is increased by about 200 times and 2 times, respectively, as compared to those of the as‐received PBZT and PBZT/CSA thin films. As the nanoparticle loading increases to 20% and 30%, the nanocomposites follow an ohmic conduction mechanism. Stable electrical conductivity switching is observed before and after applying a bias on the pristine PBZT and WO₃/PBZT nanocomposite thin films. Electrochromic phenomena of both PBZT and WO₃/PBZT nanocomposite thin films with high contrast ratio are observed after applying a bias (3 V). The mechanisms of the nanoparticles in enhancing the electrical switching and electrochromic properties are proposed.     

钇掺杂锆钛酸铅铁电薄膜的电性能研究

对采用Sol-Gel法制备的钇掺杂锆钛酸铅铁电薄膜的电性能进行了研究。实验结果表明，由于钇离子（Y^3 ）的引入造成晶格畸变，使掺钇后的PZT铁电薄膜比未掺钇时具有更大的剩余极化强度、更小的矫顽场和漏电流。此外，钇掺杂锆钛酸铅铁电薄膜具有良好的介电性能，在室温和10kHz频率下，其介电常数和介电损耗分别为437和0．043。     

脉冲法电沉积SnS:Ag薄膜

用脉冲电沉积技术,在ITO玻璃基片上制备了SnS:Ag薄膜.用X射线衍射(XRD)和原子力显微镜(AFM)观察了薄膜的物相结构和表面形貌,结果表明SnS:Ag薄膜出现了新物相Ag6SnS6,结晶度好,颗粒度大.用光电流测试研究了其导电性能,表明SnS:Ag薄膜是p型半导体材料.霍尔测量表明掺杂后载流子浓度增大,电阻率降低.     

本征和Al3+掺杂ZnO薄膜的特性研究

采用溶胶-凝胶方法在载玻片衬底上制备了本征及不同Al3+掺杂浓度的ZnO:Al薄膜,利用X射线衍射(XRD)、原子力显微镜,紫外-可见光吸收光谱及霍尔效应研究了Al3+掺杂浓度对ZnO:Al薄膜结构和光电性能的影响。结果显示,ZnO:Al薄膜为六角纤锌矿晶体结构,具有很高的沿c轴的(002)择优取向,Al3+掺杂并没有改变ZnO的晶体结构,只是Al取代了Zn;掺杂前后薄膜样品均在ZnO带边吸收的位置有较强的吸收而在可见光范围吸收较小;并且当Al3+掺杂浓度为1.5%(摩尔百分比)时所获得的ZnO:Al薄膜具有最小的电阻率,为26Ωcm。     

Block‐Copolymer‐Templated Synthesis of Electroactive RuO2‐Based Mesoporous Thin Films

RuO₂‐based mesoporous thin films of optical quality are synthesized from ruthenium‐peroxo‐based sols using micelle templates made of amphiphilic polystyrene‐polyethylene oxide block copolymers. The mesoporous structure and physical properties of the RuO₂ films (mesoporous volume: 30%; pore diameter: ～30 nm) can be controlled by the careful tuning of both the precursor solution and thermal treatment (150–350 °C). The optimal temperature that allows control of both mesoporosity and nanocristallinity is strongly dependent on the substrate (silicon or fluorine‐doped tin oxide). The structure of the resulting mesoporous films are investigated using X‐ray diffraction, X‐ray photoelectron spectroscopy, and atomic force microscopy. Mesoporous layers are additionally characterized by transmission and scanning electron microscopy and ellipsometry while their electrochemical properties are analyzed via cyclic voltammetry. Thick mesoporous films of ruthenium oxide hydrates, RuO₂ · xH₂O, obtained using a thermal treatment at 280 °C, exhibit capacitances as high as 1000 ± 100 F g^?1 at a scan rate of 10 mV s^?1, indicating their potential application as electrode materials.     

掺Al对ZnO薄膜结构和光电性能的影响

采用溶胶-凝胶工艺在普通玻璃片上制备了ZnO∶Al薄膜。通过XRD、UV透射谱和电学测试等分析方法研究了掺Al对薄膜的组织结构和光电性能的影响。分析表明:所制备的薄膜具有c轴择优取向,随着掺Al浓度的增加,(002)峰向低角度移动,峰强逐渐减弱。薄膜电阻率随掺Al浓度变化,当掺Al浓度为1.5%(摩尔分数),薄膜电阻率降至6.2×10-4Ω·cm。掺Al量的增加同时使得薄膜的禁带宽度变大,光吸收边出现蓝移现象。     

Polaron Transport and Thermoelectric Behavior in La‐Doped SrTiO3 Thin Films with Elemental Vacancies

The electrodynamic properties of La‐doped SrTiO₃ thin films with controlled elemental vacancies are investigated using optical spectroscopy and thermopower measurement. In particular, a correlation between the polaron formation and thermoelectric properties of the transition metal oxide (TMO) thin films is observed. With decreasing oxygen partial pressure during the film growth (P(O₂)), a systematic lattice expansion is observed along with the increased elemental vacancy and carrier density, experimentally determined using optical spectroscopy. Moreover, an absorption in the mid‐infrared photon energy range is found, which is attributed to the polaron formation in the doped SrTiO₃ system. Thermopower of the La‐doped SrTiO₃ thin films can be largely modulated from –120 to –260 μV K^?1, reflecting an enhanced polaronic mass of ≈3 < m _polron/m < ≈4. The elemental vacancies generated in the TMO films grown at various P(O₂) influences the global polaronic transport, which governs the charge transport behavior, including the thermoelectric properties.     

Novel Method of Preparation of Gold‐Nanoparticle‐Doped TiO2 and SiO2 Plasmonic Thin Films: Optical Characterization and Comparison with Maxwell–Garnett Modeling

SiO₂ and TiO₂ thin films with gold nanoparticles (NPs) are of particular interest as photovoltaic materials. A novel method for the preparation of spin‐coated SiO₂–Au and TiO₂–Au nanocomposites is presented. This fast and inexpensive method, which includes three separate stages, is based on the in situ synthesis of both the metal‐oxide matrix and the Au NPs during a baking process at relatively low temperature. It allows the formation of nanocomposite thin films with a higher concentration of Au NPs than other methods. High‐resolution transmission electron microscopy studies revealed a homogeneous distribution of NPs over the film volume along with their narrow size distribution. The optical manifestation of localized surface plasmon resonance was studied in more detail for TiO₂‐based Au‐doped nanocomposite films deposited on glass (in absorption and transmittance) and silicon (in specular reflectance). Maxwell–Garnett effective‐medium theory applied to such metal‐doped nanocomposite films describes the peculiarities of the experimental spectra, including modification of the antireflective properties of bare TiO₂ films deposited on silicon by varying the concentration of metal NPs. The antireflective capabilities of the film are increased after a wet etching process.     

射频溅射功率对非晶Zn-Sn-O薄膜性能的影响

使用射频磁控溅射法,基于不同溅射功率(58、79、116、148和171W)条件在玻璃基底上室温制备了Zn-Sn-O(ZTO)薄膜,并探讨了溅射功率对薄膜的结构、电学性能和光学性能的影响。结果表明,提高溅射功率有助于提升薄膜的沉积速率;XRD分析表明不同溅射功率条件下制备的ZTO薄膜均具备稳定的非晶结构;随着溅射功率的增加,薄膜的电阻率下降,光学吸收边“红移”(光学禁带宽度从3.77eV减小到3.62eV);整体来看,在58~148W溅射功率范围内制备的ZTO薄膜具备较好的可见光透明性,其在380~780nm可见光范围内的平均透过率均超过85%。