Cluster and Thickness Dependence of Ferromagnetism in Nickel In Situ-Doped Amorphous AlN Thin Films

We report on magneto-optical investigations of Ni-doped amorphous AlN (a-AlN) thin films. The a-AlN was grown by radiofrequency (rf) sputtering on Si (0001) substrates at low temperature and doped with Ni at fixed concentrations with different a-AlN layer thicknesses. As-grown a-AlN:Ni layers were annealed up to 900°C for 5 min and 15 min time duration in nitrogen ambient at atmospheric pressure. Each sample was characterized by the magneto-optical Kerr effect (MOKE) in both polar and longitudinal geometries. Only the 65-nm-thick a-AlN:Ni layers showed linear enhancement of magnetization after thermal treatment up to 900°C, indicating the presence of a critical a-AlN:Ni layer thickness supporting the formation of magnetic domains. No measurable MOKE signal was observed in the longitudinal geometry for any tested samples with different thicknesses. This observation confirms that the easy magnetization axis in a-AlN:Ni layers is out of plane due to the strong magnetic anisotropy observed in polar MOKE geometry. The morphology of as-grown and annealed a-AlN:Ni films was characterized by atomic force microscopy (AFM), magnetic force microscopy (MFM), and scanning electron microscopy (SEM) and revealed the existence of nanoclusters. The size distribution of nanoclusters was studied as a function of annealing time and temperature, and the results correlate well with those obtained from the MOKE measurements.     

Ambipolar carrier transport in an optically controllable diarylethene thin film transistor

Ambipolar carrier transport is demonstrated in an optically controllable organic field-effect transistor, where a benzothienothiophene-substituted diarylethene (BTT-DAE) thin film is employed directly as the transistor channel. A closed-ring isomer, which is produced by ultraviolet (UV) light irradiation, allows the carrier injection of both holes and electrons from source-drain electrodes into the BTT-DAE layer. Moreover, alternate UV or visible (VIS) light irradiation induces marked switching in the drain currents caused by reversible photoisomerization between closed-ring (semiconductor) and open-ring (insulator) isomers. The light-driven on/off ratio, which is defined by the ratio of the drain currents in the sample after UV or VIS light irradiation, reaches 240 for hole transport. The value is comparable to the gate-voltage-induced on/off ratio of 160. Our findings, therefore, have a potential to lead to the construction of new optoelectronic devices such as photoreconfigurable logic circuits and light emitting transistors.     

Magnetic interference gonioapparent thin film based on metal-dielectric-metal structure for optical security devices

In recent years, magnetic interference thin films have gained wide attention in optical security devices field by virtue of their gonioapparent and dynamic 3D effects. Based on the color mechanism of metal-dielectric Fabry-Perot structure, a novel seven-layer magnetic thin film structure is proposed by adopting the ultrathin metal layer as a bonding layer and a pure metallic Ni layer as a magnetic layer as well as a reflective layer. Color target optimization optimac method is utilized that realizes the seven-layer metal-dielectric optically variable magnetic thin film structure with green at the normal incidence and purple-red at 60°. The structure effectively solves the delaminate problem and simplifies the multilayer structure. Through different combined magnetic field designs, the magnetic orientation experiment of the prepared magnetic optically variable thin film is carried out, and the 3 D anti-counterfeiting with remarkable dynamic color change effect is obtained, which provides a new solution for optical security devices.     

2D Janus Hybrid Materials of Polymer‐Grafted Carbon Nanotube/Graphene Oxide Thin Film as Flexible,Miniature Electric Carpet

Ultrathin, freestanding polymer hybrid film with macroscopic sizes and molecular thicknesses have received significant interest due to their applications as functional devices, microsensors or nanoactuators. Herein, a 2D Janus hybrid of polymer‐grafted carbon nanotubes/graphene oxide (CNTs/GO) thin film is fabricated using microcontact printed CNTs/GO as photo active surface to grow polymer brushes by self‐initiated photografting and photopolymerization selectively from one side of CNTs/GO film. This achieved 2D Janus hybrid materials with grafted polymer layer as insulative carpet and supported CNTs/GO thin film as conductive element have the potential application as flexible and miniature electric carpet for heating micro‐/nano devices locally.     

Dependence of the transversal magneto-optic Kerr effect on the incidence angle of light for ultrathin films of cobalt and Co/Cu/Co multilayers

The transversal magneto-optic Kerr effect in thin cobalt films and Co/Cu/Co structures obtained by magnetron sputtering in the magnetic field is investigated. It is shown that the dependences of the TMOKE and reflection intensity on the incidence angle of light substantially vary upon varying the thickness of the cobalt layer from 6 to 0.7 nm. The theoretical evaluation of the obtained data in the context of the classic theory of propagation of light in the conducting medium is presented     

Transparent conductors with an ultrathin nickel layer for high-performance photoelectric device applications

A thin nickel (Ni) layer of thickness 5 nm was inserted in between the indium tin oxide (ITO) layers of thickness 50 nm each so as to increase the conductivity of ITO without affecting much of its transmittance nature. ITO layers with and without Ni film were prepared by reactive DC sputtering on both Si and glass substrates. The influence of Ni layer on the optical and electrical properties of prepared devices was investigated. Due to the insertion of thin Ni layer, the resistivity of ITO/Ni/ITO sample (3.2×10⁻⁴ Ω cm) was reduced 10 times lesser than that of ordinary ITO layer (38.6×10⁻⁴ Ω cm); consequently it increased the mobility of ITO/Ni/ITO device. The external and internal quantum efficiencies (EQE and IQE) of ITO/Ni/ITO device exhibited better performance when compared to ITO layer that has no Ni film. At wavelengths of 350 and 600 nm, the photoresponses of ITO/Ni/ITO device were predominant than that of reference ITO device. This highly conductive and photoresponsive Ni inserting ITO layers would be a promising device for various photoelectric applications.     

GaAs吸收衬底生长的立方相GaN发光二极管的工艺设计与实现

利用光学薄膜原理,计算了采用晶片键合技术来提高以GaAs为衬底的立方相GaN的出光效率的理论可行性.以Ni为粘附层,Ag为反射层的Ni/Ag/Au薄膜体系可以使立方GaN的出光效率从理论上提高2.65倍左右.实验结果证实,利用键合方法实现的以Ni/Ag/Au作为反射膜的样品的光反射率比未做键合的GaN/GaAs样品的光反射率在理论计算的459.2nm处提高了2.4倍.     

Mixing of nickel and silicon by incoherent-light-pulse annealing

Mixed layers of Ni and Si were formed by pulsed incoherent-light annealing of Ni thin films evaporated on Si substrates. Incoherent light pulse of 36 μs produced in an arc-discharge plasma system was used as the energy source for annealings. A thin layer (300 Å) of amorphous silicon (a-Si) deposited on 800–1000 Å thick Ni films was found to increase light absorption significantly. The light energy needed to form uniform mixing was measured to be about 23 J/cm². Rutherford backscattering and Auger electron spectroscopy techniques were used for qualitative analysis of a-Si/Ni/Si samples. Optimum operating conditions of the light source was determined.     

Fabrication of CNTs/Cu composite thin films for interconnects application

Carbon nanotubes/copper (CNTs/Cu) composite thin films were fabricated by combined electrophoresis and electroplating techniques. Electrical properties and structure of both CNTs/Cu thin films and the reference pure Cu thin films were investigated after annealing at different temperatures. The sheet electrical resistance of CNTs/Cu films decreases faster than that of pure Cu films with increase of annealing temperature. The grain size of CNTs/Cu film becomes much larger than that of pure Cu film at the same annealing temperature. The peak relative intensity of Cu (1 1 1) plane in CNTs/Cu film was stronger than that of pure Cu film. CNTs/Cu composite thin films, with better electrical properties than that of conventional pure Cu thin films, have been fabricated by electrophoresis and electroplating deposition techniques.     

MBE-grown ZnSSe thin films on ITO substrates for liquid-crystal light valve applications

The MBE growth of ZnSSe alloy thin films on ITO substrates using ZnS and Se sources was studied and various structural and opto-electronic properties of the as-grown thin films were characterised. The XRD rocking curves resulting from these films indicate that the as-grown polycrystalline ZnSSe thin films have a preferred orientation along (1 1 1) direction. The evaluated crystal sizes as deduced from the FWHM of the XRD layer peaks were found to show a strong growth temperature dependence with the optimised temperature at about 290°C. TEM measurements done on these thin films also indicate a similar growth temperature dependence. The TEM cross-sectional micrograph of the sample grown at the optimised temperature shows a well-defined columnar structure whose nucleation seems to be highly correlated with the ITO grains. UV responsivity as high as 0.01 A/W and more than three orders of magnitude in rejection power for wavelengths longer than 450 nm have been achieved. It was also found that the sample grown at the optimised temperature has the lowest resistivity of 4.3×10¹¹ Ω cm, which provides a good match with that of a liquid-crystal layer. These results indicate that MBE-grown ZnSSe thin film is a promising candidate as the photoconductive material of liquid-crystal light valves for UV imaging applications.     

螺吡喃6-nitroBIPS掺杂聚苯乙烯膜的全光调制特性研究

测量了螺吡喃 1',3',3' trimethylindolino 6 nitrospirobenzopyran(6 nitroBIPS)掺杂聚苯乙烯薄膜在紫外光抽运前后的吸收光谱 ,利用其吸收光谱的显著改变 ,对 5 90nm探测光的全光调制特性进行了研究。对调制随染料掺杂浓度和紫外光激发能量的依赖性进行了测量 ,理论模拟得出其光化学反应量子效率为 0 2 4和螺吡喃光化学产物光半花菁在 5 90nm处的摩尔吸收系数为 2 0× 10 4Lmol- 1 cm- 1 。被调制信号的前沿和后沿时间常数分别约为 131ns和 18μs。     

应力对薄膜偏振分束镜性能的影响及改进工艺

为了研究应力对薄膜偏振分束镜性能的影响和减少应力的方法,通过在镀制分光膜之前预镀Al2O3过渡层,镀制过程中提高真空度、升高基底温度、减慢薄膜沉积速率,以及封装过程中采用光学光敏胶紫外光照射快速凝固法来减少薄膜应力。利用CCD采集了工艺改进前后薄膜偏振分束镜反射光和透射光的光斑图像,利用消光比测试系统测量了工艺改进前后薄膜偏振分束镜反射光和透射光的消光比。结果表明,改进工艺后反射光和透射光的光斑能量更加集中,散斑现象变小;反射光和透射光的消光比特性明显提高。由此可见,通过改进镀制工艺和封装工艺可以使薄膜偏振分束镜的指标达到使用要求。     

Tricolor microcavity OLEDs based on P-nc-Si:H films as the complex anodes

A P+-nc-Si:H film (boron-doped nc-Si:H thin film) was used as a complex anode of an OLED. As an ideal candidate for the composite anode, the P+-nc-Si:H thin film has a good conductivity with a high work function (～5.7 eV) and outstanding optical properties of high reflectivity, transmission, and a very low absorption. As a result, the combination of the relatively high reflectivity of a P+-nc-Si:H film/ITO complex anode with the very high reflectivity of an Al cathode could form a micro-cavity structure with a certain Q to improve the efficiency of the OLED fabricated on it. An RGB pixel generated by microcavity OLEDs is beneficial for both the reduction of the light loss and the improvement of the color purity and the efficiency. The small molecule Alq would be useful for the emitting light layer (EML) of the MOLED, and the P+-nc-Si film would be used as a complex anode of the MOLED, whose configuration can be constructed as Glass/LTO/P+-nc-Si:H/ITO/MoO3/NPB/Alq/LiF/Al. By adjusting the thickness of the organic layer NPB/Alq, the optical length of the microcavity and the REB colors of the device can be obtained. The peak wavelengths of an OLED are located at 486, 550, and 608 nm, respectively.The CIE coordinates are (0.21,0.45), (0.33,0.63), and (0.54,0.54), and the full widths at half maximum (FWHM)are 35, 32, and 39 nm for red, green, and blue, respectively.     

IMC Growth at the Interface of Sn–2.0Ag–2.5Zn Solder Joints with Cu,Ni, and Ni–W Substrates

Growth of intermetallic compounds (IMC) at the interface of Sn–2.0Ag–2.5Zn solder joints with Cu, Ni, and Ni–W substrates have been investigated. For the Cu substrate, a Cu₅Zn₈ IMC layer with Ag₃Sn particles on top was observed at the interface; this acted as a barrier layer preventing further growth of Cu–Sn IMC. For the Ni substrate, a thin Ni₃Sn₄ film was observed between the solder and the Ni layer; the thickness of the film increased slowly and steadily with aging. For the Ni–W substrate, a thin Ni₃Sn₄ film was observed between the solder and Ni–W layer. During the aging process a thin layer of the Ni–W substrate was transformed into a bright layer, and the thickness of bright layer increased with aging.     

缺陷诱导光学薄膜光场增强损伤分析

高损伤阈值的光学薄膜是高功率激光系统的关键器件。众多研究显示,纳米量级的缺陷是光学薄膜激光损伤的主要诱因,是制约光学薄膜向高损伤阈值发展的主要因素。基于有限差分时域方法分析了纳米大小的缺陷诱导SiO₂光学薄膜的局部光场增强导致的激光损伤。结果显示:缺陷的存在使SiO₂单层薄膜的光场分布发生了变化,无缺陷的SiO₂薄膜峰值光场位于膜层表面,而有缺陷的SiO₂薄膜峰值光场位于缺陷与薄膜的边界处,光场增强了约2.3倍;同时缺陷诱导的光场局部增强不仅依赖于缺陷与膜层之间的相对折射率,而且也依赖于缺陷的大小、缺陷在膜层中的分布深度,以及入射激光波长。缺陷与膜层的相对折射率越大,缺陷的直径越大,缺陷在膜层中的深度越小,入射激光波长越短,光场增强越大。研究结果显示光学薄膜中纳米大小的缺陷诱导的光场增强不可忽视,在研究光学薄膜的激光损伤过程中应予以考虑。     

GaAs衬底上Mn／Sb多层铁磁膜的磁光克尔效应

利用超高真空电子束蒸发技术GaAs(100）上生长Mn/Sb多层膜,并经短时间热退火处理分别研究了其退火前后的磁性、磁光克尔效应及相应规律,退火前Mn/Sb膜在室温下即具有较强的铁磁特性,其易磁化轴在膜面内,样品表面由密集的岛状铁磁颗粒组成,未能观测到纵向（H//平面）克尔效应,经350℃、20min退火的样品显示了最大饱和磁化强度Ms和最小矫顽力Hc,X射线衍射测量表明膜为MnSb单晶并具有均匀的铁磁特性,能观测到显著的要有向和纵向磁光克尔效应,其随磁场变化表现出相应于磁化强度的磁带行为。     

Ultraviolet photodetectors based on low temperature processed ZnO/PEDOT:PSS Schottky barrier diodes

In this work, vertical Schottky barrier diodes (SBDs) were fabricated using a thin film of ZnO (50 nm) and PEDOT:PSS deposited by RF Sputtering and micro-drop casting, respectively. ITO and Au were used as ohmic contacts to ZnO and PEDOT:PSS films, respectively. The final structure consisted on Glass/ITO/ZnO/PEDOT:PSS/Au. The SBDs performance was characterized under dark and four different wavelengths conditions. From current–voltage characteristics, under dark and ambient conditions, a diode ideality factor of 1.4; a saturation current density of 1×10⁻⁹ A/cm²; a Schottky barrier height of 0.9 eV and a rectification ratio of 5 orders of magnitude at ±1 V were obtained. A carrier density of 5×10¹⁷ cm⁻³ for the ZnO film was estimated from capacitance–voltage measurements. For their characterization as photodiodes, the SBDs were illuminated with an ultra-bright UV (~380 nm) LED. A maximum UV responsivity of 0.013 A/W was obtained. The transient response of the SBDs was also analyzed with the UV LED connected to a pulsed signal of 0.5 Hz, demonstrating rise and fall times in the order of 200 ms. With a low temperature processing (<80 °C), visible-blind and UV photon-detection characteristics, the fabricated SBDs are candidates for flexible optoelectronics devices such as optical receivers for digital signal processing and measurement of light intensity.     

Giant Magnetoresistance in a Molecular Thin Film as an Intrinsic Property

The magnetic, thin‐film structural, conductivity, and magnetoresistance properties of [Ni(quinoline‐8‐thiolate)₂] ([Ni(qt)₂]) are studied. The conducting and magnetoresistance properties are studied in single crystals and in evaporated thin films through deposition on an interdigitated electrode array. Non‐linear conductivity interpreted through a space‐charge limited conduction mechanism with charges injected from the electrodes is observed. Under applied magnetic field, the material displays giant negative magnetoresistance above 50% at 2 K in both single crystals and in evaporated thin films. The effect can still be observed at 200 K and is interpreted in terms of a double exchange mechanism with the shape of the curve determined by the magnetic anisotropy. The unique observation of giant magnetoresistance (GMR) as an intrinsic effect in an evaporated thin film of paramagnetic molecules opens up new possibilities in organic spintronics.     

Preferred orientation of Cu(In,Ga)Se2 thin film deposited on stainless steel substrate

The influences of process parameters and Fe diffusing into Cu(In,Ga)Se₂ (CIGS) films on the orientation of CIGS absorbers grown on the stainless steel (SS) foils are investigated. The structural properties, morphology, and elemental profiles are characterized using X‐ray diffraction, scanning electron microscopy, and second ion mass spectroscopy, respectively. The orientation of CIGS thin films on the SS substrates strongly depends on the texture of the (In,Ga)₂Se₃ precursor, determined by the substrate temperature at the first stage (Ts1) and the flux ratio of Se to (In + Ga). Among these factors, Ts1 is the prerequisite to achieve [300]‐oriented IGS layer, which will yield [200]‐oriented CIGS thin film in the later process. The results indicate that through the comparison of CIGS thin films on the Mo/SS substrates and on the Mo/ZnO/SS substrates and combined with simply calculation, Fe diffusing into the CIGS layer will hinder the growth of the CIGS grains along [112] orientation. The grazing‐incidence X‐ray diffraction results suggest that the surface of the [220]‐textured CIGS thin film on the SS substrate still has [220] predominance, whereas the surface texture of the [220]‐texture CIGS thin film on the Mo/soda‐lime glass substrate became [112] predominant, which is due to the different compensation ability between Fe and Na elements. Finally, the relations between the device parameters and the degrees of the preferred orientation of CIGS absorbers are investigated. Copyright © 2012 John Wiley & Sons, Ltd.     

基于纳米硅薄膜复合阳极的微腔调色法的研究

A P^＋-nc-Si：H film（boron-doped nc-Si：H thin film） was used as a complex anode of an OLED.As an ideal candidate for the composite anode,the P^＋-nc-Si：H thin film has a good conductivity with a high work function（- 5.7 eV） and outstanding optical properties of high reflectivity,transmission,and a very low absorption.As a result,the combination of the relatively high reflectivity of a P^＋-nc-Si：H film/ITO complex anode with the very high reflectivity of an Al cathode could form a micro-cavity structure with a certain Q to improve the efficiency of the OLED fabricated on it.An RGB pixel generated by microcavity OLEDs is beneficial for both the reduction of the light loss and the improvement of the color purity and the efficiency.The small molecule Alq would be useful for the emitting light layer（EML） of the MOLED,and the P^＋-nc-Si film would be used as a complex anode of the MOLED,whose configuration can be constructed as Glass/LTO/P^＋-nc-Si：H/ITO/MoO3/NPB/Alq/LiF/Al.By adjusting the thickness of the organic layer NPB/Alq,the optical length of the microcavity and the REB colors of the device can be obtained.The peak wavelengths of an OLED are located at 486,550,and 608 nm,respectively.The CIE coordinates are（0.21,0.45）,（0.33,0.63）,and（0.54,0.54）,and the full widths at half maximum（FWHM） are 35,32,and 39 nm for red,green,and blue,respectively.