Electrical and optical properties of ITO and ITO/Cr-doped ITO films

In this paper we report on the effects of the insertion of Cr atoms on the electrical and optical properties of indium tin oxide (ITO) films to be used as electrodes in spin-polarized light-emitting devices. ITO films and ITO(80 nm)/Cr-doped ITO(20 nm) bilayers and Cr-doped ITO films with a thickness of 20 nm were grown by pulsed ArF excimer laser deposition. The optical, structural, morphological and electrical properties of ITO films and ITO/Cr-doped structures were characterized by UV–Visible transmission and reflection spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Hall-effect analysis. For the different investigations, the samples were deposited on different substrates like silica and carbon coated Cu grids. ITO films with a thickness of 100 nm, a resistivity as low as ～4×10^?4 Ω?cm, an energy gap of ～4.3 eV and an atomic scale roughness were deposited at room temperature without any post-deposition process. The insertion of Cr into the ITO matrix in the upper 20 nm of the ITO matrix induced variations in the physical properties of the structure like an increase of average roughness (～0.4–0.5 nm) and resistivity (up to ～8×10^?4 Ω?cm). These variations were correlated to the microstructure of the Cr-doped ITO films with particular attention to the upper 20 nm.     

ITO/Au/ITO multilayer thin films for transparent conducting electrode applications

Transparent and conducting ITO/Au/ITO multilayered films were deposited without intentional substrate heating on polycarbonate (PC) substrate using a magnetron sputtering process. The thickness of ITO, Au and ITO metal films in the multilayered structure was constant at 50, 10 and 40 nm, respectively.Although the substrate temperature was kept constant at 70 °C, ITO/Au/ITO films were polycrystalline with an (1 1 0) X-ray diffraction peak, while single ITO films were amorphous. Surface roughness analysis indicated ITO films had a higher average roughness of 1.76 nm, than the ITO/Au/ITO film roughness of 0.51 nm. The optoelectrical properties of the ITO/Au/ITO films were dependent on the Au thin film, which affected the ITO film crystallinity. ITO/Au/ITO films on PC substrates were developed with a resistivity as low as 5.6 × 10⁻⁵ Ω cm and a high optical transmittance of 71.7%.     

Enhanced resistance switching stability of transparent ITO/TiO2/ITO sandwiches

We report that fully transparent resistive random access memory(TRRAM) devices based on ITO/TiO2/ITO sandwich structure,which are prepared by the method of RF magnetron sputtering,exhibit excellent switching stability.In the visible region(400-800 nm in wavelength) the TRRAM device has a transmittance of more than 80%.The fabricated TRRAM device shows a bipolar resistance switching behaviour at low voltage,while the retention test and rewrite cycles of more than 300,000 indicate the enhancement of switching capability.The mechanism of resistance switching is further explained by the forming and rupture processes of the filament in the TiO 2 layer with the help of more oxygen vacancies which are provided by the transparent ITO electrodes.     

Transparent conductive ITO/Ag/ITO multilayer electrodes deposited by sputtering at room temperature

ITO/Ag/ITO multilayers have been prepared onto conventional soda lime glass substrates by sputtering at room temperature. The optical and electrical characteristics of single layer and multilayer structures have been investigated as a function of the Ag and ITO film thicknesses. Transmittance and sheet resistance values are found mainly dependent on the Ag film thickness; whereas the wavelength range at which the maximum transmittance is achieved can be changed by adjusting the ITO films thickness. ITO/Ag/ITO electrodes with sheet resistance below 6 Ω/sq have been obtained for Ag film thickness above 10 nm and ITO layers thickness in the 30-50 nm range. These multilayers also show high transmittance in the visible spectral region, above 90% by discounting the glass substrate, with a maximum that is located at higher wavelengths for thicker ITO.     

Fabrication and characterization of Pt intermediate transparent and conducting ITO/Pt/ITO multilayer films

Platinum intermediate transparent and conducting ITO/metal/ITO (IMI) multilayered films were deposited by RF and DC magnetron sputtering on polycarbonate substrates without intentional substrate heating. Changes in the microstructure and optoelectrical properties of the films were investigated with respect to the thickness of the intermediate Pt layer in the IMI films. The thickness of Pt film was varied from 5 to 20 nm.In XRD measurements, neither ITO single-layer films nor IMI multilayer films showed any characteristic diffraction peaks for In₂O₃ or SnO₂. Only a weak diffraction peak for Pt (1 1 1) was obtained in the XRD spectra. Thus, it can be concluded that the Pt-intermediated films in the IMI films did not affect the crystallinity of the ITO films. However, equivalent resistivity was dependent on the presence and thickness of the Pt-intermediated layer. It decreased as low as 3.3×10⁻⁴ Ω cm for ITO 50 nm/Pt 20 nm/ITO 30 nm films. Optical transmittance was also strongly influenced by the Pt-intermediated layer. As Pt thickness in the IMI films increased, optical transmittance decreased to as low as 30% for ITO 50 nm/Pt 20 nm/ITO 30 nm films.     

ITO/Au/ITO multilayer thin films on transparent polycarbonate with enhanced EMI shielding properties

ITO/Au/ITO multilayer thin films were deposited onto polycarbonate substrate via magnetron sputtering technique without intentional heating. The deposition times of both ITO and Au layers were studied to optimize the overall transparency and conductivity. As-prepared thin films were characterized using X-ray diffraction analysis, secondary ion mass spectroscopy, scanning and transmission electron microscopy, atomic force microscopy and physical property measurement system. The optical measurement results revealed that the transmittance of the films were enhanced by increasing the gold deposition time up to 15 s. Beyond this point, further increasing the duration caused a decrease in optical transmittance. Upon optimization of the Au deposition time, the deposition duration of ITO layers was also studied to increase electromagnetic interference (EMI) shielding effectiveness (SE). Maximum EMI SE in this work was measured as 26.8 dB, yielding 99.8% power attenuation, which was verified by simulation results.     

Low temperature deposition of transparent conducting ITO/Au/ITO films by reactive magnetron sputtering

Transparent conducting indium tin oxide/Au/indium tin oxide (ITO) multilayered films were deposited on unheated polycarbonate substrates by magnetron sputtering. The thickness of the Au intermediated film varied from 5 to 20 nm. Changes in the microstructure, surface roughness and optoelectrical properties of the ITO/Au/ITO films were investigated with respect to the thickness of the Au intermediated layer. X-ray diffraction measurements of ITO single layer films did not show characteristic diffraction peaks, while ITO/Au/ITO films showed an In₂O₃ (2 2 2) characteristic diffraction peak. The optoelectrical properties of the films were also dependent on the presence and thickness of the Au thin film. The ITO 50 nm/Au 10 nm/ITO 40 nm films had a sheet resistance of 5.6 Ω/□ and an average optical transmittance of 72% in the visible wavelength range of 400-700 nm. Consequently, the crystallinity, which affects the optoelectrical properties of ITO films, can be enhanced with Au intermediated films.     

Giant magnetoresistance of Co/ITO multilayers

The electrical and magnetic properties of Co/ITO multilayers with various ITO layer thickness are studied. Negative giant magnetoresistance with a maximum of −1.9% at room temperature and −2.57% at 15 K are observed. The magnitudes of GMR oscillate with a period of about 1 nm when varying the thickness of ITO layer.     

Dependence of intermediated noble metals on the optical and electrical properties of ITO/metal/ITO multilayers

Sn doped In₂O₃ (ITO) single layer and a sandwich structure of ITO/metal/ITO (IMI) multilayer films were deposited on a polycarbonate substrate using radio-frequency and direct-current magnetron sputtering process without substrate heating. The intermediated metal films in the IMI structure were Au and Cu films and the thickness of each layer in the IMI films was kept constant at 50 nm/10 nm/40 nm. In this study, the ITO/Au/ITO films show the lowest resistivity of 5.6 × 10⁻⁵ Ω cm.However the films show the lower optical transmission of 71% at 550 nm than that (81%) of as deposited ITO films. The ITO/Cu/ITO films show an optical transmittance of 54% and electrical resistivity of 1.5 × 10⁻⁴ Ω cm. Only the ITO/Au/ITO films showed the diffraction peaks in the XRD pattern. The figure of merit indicated that the ITO/Au/ITO films performed better in a transparent conducting electrode than in ITO single layer films and ITO/Cu/ITO films.     

Characteristic difference between ITO/ZrCu and ITO/Ag bi-layer films as transparent electrodes deposited on PET substrate

The metallic-glass film of ZrCu layer deposited by co-sputtering was utilized as the metallic layer in the bi-layer structure transparent conductive electrode of ITO/ZrCu (IZC) deposited on the PET substrate using magnetron sputtering at room temperature. In addition, the pure Ag metal layer was applied in the same structure of transparent conductive film, ITO/Ag, in comparison with the IZC film. The ZrCu layer could form a continuous and smooth film in thickness lower than 6 nm, compared with the island structure of pure Ag layer of the same thickness. The 30 nm ITO/3 nm ZrCu films could show the optical transmittance of 73% at 550 nm wavelength. The 30 nm ITO/12 nm ZrCu films could show the better sheet resistance of 20 Ω/sq, but it was still worse than that of the ITO/Ag films. It was suggested that an alloy system with lower resistivity and negative mixing heat between atoms might be another way to form a continuous layer in thickness lower than 6 nm for metal film.     

原子力显微镜与x射线光电子能谱对LiBq4/ITO和LiBq4/CuPc/ITO的表面分析

利用原子力显微镜对8-羟基喹啉硼化锂(LiBq4)/铟锡氧化物和8-羟基喹啉硼化锂/酞菁铜(CuPc)/铟锡氧化物表面分别进行了扫描,显示了LiBq4在不同衬底上的形貌差异,并进一步利用样品表面的x射线光电子能谱图验证了这一差异.实验表明,CuPc层的加入改善了LiBq4的成膜质量,并将这种改善归因于分子构型与电子亲和势的不同.     

Characterization of ITO/porous silicon LED structures

The electrical behavior and the electroluminescence (EL) obtained from n- and p-type ITO/porous silicon LEDs have been characterized simultaneously at different temperatures. Stability and aging in air were investigated, and means for avoiding their detrimental effects in the experiments are suggested. The dominating current carrying mechanism responsible for visible light emission in both substrate types has been identified to be Fowler–Nordheim tunneling. This emphasizes the contribution of embedded nanoparticles (quantum dots) rather than the role of nanowires in efficient EL.     

原子力显微镜与x射线光电子能谱对LiBq4/ITO和LiBq4/CuPc/ITO的表面分析

利用原子力显微镜对8-羟基喹啉硼化锂(LiBq₄)/铟锡氧化物和8-羟基喹啉硼化锂/酞菁铜(CuPc)/铟锡氧化物表面分别进行了扫描，显示了LiBq₄在不同衬底上的形貌差异，并进一步利用样品表面的x射线光电子能谱图验证了这一差异.实验表明，CuPc层的加入改善了LiBq₄的成膜质量，并将这种改善归因于分子构型与电子亲和势的不同. 关键词： 原子力显微镜 x射线光电子能谱 电子亲和势     

基于Au/ITO纳米复合材料的自参照SPR传感器

利用Au/ITO纳米复合材料设计了一种自参照表面等离子体共振传感器.该传感器产生的光谱有两个共振峰,即共振峰1和共振峰2.共振峰1随着待测介质折射率和入射角的变化产生漂移,而共振峰2仅随入射角的变化产生漂移,两个共振峰相互参照,降低了入射角偏移对测量结果的影响,提高了测量的准确性.在纳米复合材料的4种不同体积分数下,仿真分析了入射角、待测介质折射率和薄膜厚度变化对两个共振波长的影响.在入射角θ为80°,且金的体积分数f为0.65,薄膜厚度d为40nm和45nm,或金的体积分数f为0.85,薄膜厚度d为45nm和50nm时,共振峰2不随待测介质折射率的变化而变化,只有共振峰1随待测介质折射率的变化而变化,达到自参照传感器的理想状态.     

Magnetic property and magnetoresistance in Fe/ITO multilayers

Giant magnetoresistance was found in DC magnetron sputtering Fe/ITO multilayers. The magnetic properties, electrical properties and magnetoresistance were investigated. A critical temperature is found around 50 K where the temperature dependence of resistivity and magnetoresistance ratio exhibit an abruptly change. The temperature dependence of resistance is found to obey Mott's 1/4 law for low temperature. The max magnetoresistance ratio of 2.0% and 6.7% is found at room temperature and 12.5 K, respectively. The increase of magnetoresistance ratio at low temperature is due to the decrease of spin-mixing effect.     

ITO/BTEO-PPV：PUI/Al的光电特性

报道了用单离子导体聚氨酯酰亚胺磺酸钠(PUI)作为固体电解质和共聚[2,5-二(三乙氧基)-1,4-对苯乙炔]-[1,4-对苯乙炔](BETO-PPV)作为发光层的单离子聚合物发光电池(SLEC)的制作和测量。实验结果及其分析表明:不可移动阴离子的存在使SLEC的正反向稳态电流-电压(I-V)曲线不再对称;SLEC具有快速响应的主要原因是SLEC中固定的阴离子对阳离子的散射比LEC中运动的阴离子对阳离子散射小。SLEC的电容-频率(C-f)特性证实了阳离子在薄膜中具有较快的响应速度。     

Laser induced microrelief superstructure of Ag/ITO seed-mediated nanocomposites

The topography of indium tin oxide (ITO) films with incorporated silver nanoparticles and irradiated by single pulses of 18 ns Nd:YAG laser has been investigated. The study was carried out with two Ag/ITO films having resistances of 50 Ω/ITO sheet and 4 Ω/ITO sheet. The periodic structures in both samples were created after the laser treatment. The photo-induced periodic structures have a different character while the sheet resistance plays a major role in the growth process of these structures. The results of optical and non-linear optical investigations lead us to the conclusion that the temporary polarization of samples during laser treatment is responsible for the shape of periodic structures.     

ITO/有机半导体/金属结构OLED器件的数值模拟

基于稳态的小信号漂移扩散方程,建立了有电极的单层有机电致发光(OLED)器件的数值模型,编制的MATLAB程序,首先模拟了文献中的OLED器件电极附近正电荷层(面电荷)对器件J-V的影响,得到了和文献中一致的结果. 模拟了ITO/PPV/Ca结构的OLED器件,模拟时,考虑了OLED阳极附近存在正体电荷,得到的J-V曲线和文献中的实验结果一致,体电荷产生了势垒,影响了电流曲线. 关键词： 有机电致发光 数值模拟 漂移扩散模型     

基于ITO/聚甲基丙烯酸甲酯/Al的有机阻变存储器SPICE仿真

探索了ITO/PMMA/Al器件的阻变机理及其SPICE电路仿真, 通过优化聚甲基丙烯酸甲酯(PMMA)层退火温度, 器件可实现连续擦-读-写-读操作. 基于不同退火温度PMMA薄膜的表面形貌研究, 构建了单层有机阻变器件的非线性电荷漂移模型, 以及描述该模型掺杂区界面移动的状态方程, 并通过反馈控制积分器建立了SPICE仿真电路. 最后, 代入器件实际测量参数, 得到与器件实际结果基本一致的电流-电压模拟曲线. 结果验证了单层有机器件的阻变机理, 说明该非线性电荷漂移模型的SPICE仿真在有机阻变器件仿真中同样适用. 关键词： 有机阻变存储器 非线性电荷漂移 SPICE仿真     

Flexible resistance memory devices based on Cu/ZnO:Mg/ITO structure

Resistance memory devices based on a Cu/Mg‐doped ZnO/indium‐tin‐oxide structure on a PET (polyethylene terephthalate) flexible substrate were fabricated. The devices showed stable bipolar resistance switching property and good flexibility. The high to low resistance ratio was larger than 30 times, the endurance was more than 10² cycles, and the resistance retention was longer than 10⁴ s. The resistance values of both high and low resistance states were not significantly changed by bending in a radius (≥20 mm) for more than 10³ times. This resistance switching phenomenon of our devices can be explained by creation/rupture of metal conductive channels induced by electrochemical migration of Cu ions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)