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基于太赫兹(THz)时域频谱技术研究了飞秒激光激发下氧化钒纳米薄膜的光致绝缘体-金属相变特性。利用直流磁控溅射法在不同条件下制备了一系列蓝宝石基底上的氧化钒薄膜,通过测量薄膜发生光致相变后太赫兹波的透射率来评估成膜质量,得出在溅射时间60min不变的情况下,退火时间和退火温度分别为60s和560℃时可以得到性能非常良好的氧化钒薄膜。在上述最佳条件下制备的氧化钒薄膜的相变深度可达80%。利用薄膜近似计算了太赫兹波段氧化钒薄膜在光致相变过程中电导率的变化,计算结果表明电导率实部在103Ω-1·cm-1量级,并基于Drude模型得到了金属态氧化钒薄膜的复介电常数以及复折射率。在绝缘衬底上制备的具有明显阈值激发功率且相变深度大的氧化钒薄膜将在太赫兹调制器件中有重要应用。 相似文献
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采用射频磁控溅射法在室温柔性衬底PET上制备了掺锆氧化锌(ZZO)透明导电薄膜.利用不同方法提高了ZZO薄膜的电阻率而未使其可见光透过率降低.X射线衍射(XRD)和扫描电子显微镜(SEM)表明,ZZO薄膜为六角纤锌矿结构的多晶薄膜.在有机衬底和玻璃衬底上制备ZZO薄膜的择优取向不同,前者为(100)晶面,而后者为(002)晶面.在有ZnO缓冲层的PET衬底上制备的ZZO薄膜电阻率比直接生长在玻璃衬底样品上的小.通过优化参数,在PET衬底上制备出了最小电阻率为1.7×10-3Ω·cm、可见光透过率超过93%的ZZO薄膜.实验表明,镀膜之前在柔性衬底上沉积ZnO缓冲层能有效地提高ZZO薄膜的质量. 相似文献
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钒的氧化物具有对温度敏感的半导体-金属可逆相变特性.在多种钒氧化合物中,VO2的相变温度点约为68℃,适用于很多应用领域.VO2长期暴露在空气中时,会被氧化.研究了通过制备VO2/Al2O3复合膜系来保持氧化钒薄膜的稳定性的方法.采用TFCalc薄膜设计软件,设计了VO2/Al2O3复合膜系.依据材料的折射率和消光系数,优化了膜系各膜层的厚度,分析了复合膜系的相变特性.采用磁控溅射方式制备了氧化钒薄膜,再通过氧氩混合气氛热处理得到VO2占主要成分的氧化钒薄膜.在氧化钒薄膜上采用射频磁控溅射方法封装了120 nm厚的Al2O3膜.利用分光光度计测量分析了膜系的相变特性,Al2O3膜对VO2膜的相变性能影响很小.Al2O3膜适于VO2薄膜的封装. 相似文献
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利用磁控溅射法在玻璃衬底上淀积铝掺杂氧化锌(AZO)薄膜作为缓冲层,在其上制备了ZnO薄膜。重点研究了AZO薄膜作为缓冲层对玻璃衬底上ZnO薄膜特性的影响。扫描电子显微镜(SEM)图像和X射线衍射(XRD)图谱分析结果表明,玻璃衬底上加入厚度为1μm的AZO缓冲层后,提高了衬底材料和ZnO薄膜之间的晶格匹配程度,有助于增大ZnO薄膜晶粒尺寸,提高其(002)取向择优生长特性、薄膜结晶特性及晶格结构完整性。室温下的透射光谱结果表明玻璃/AZO和玻璃衬底上ZnO薄膜的透光特性没有显著不同。光致发光(PL)谱研究结果表明AZO缓冲层可以有效阻止衬底表面硅原子从ZnO薄膜中"俘获"氧原子,减少ZnO薄膜中的缺陷,改善ZnO薄膜的结晶质量。 相似文献
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采用脉冲直流磁控溅射方法在Si(100)衬底上制备了ScAlN薄膜。以溅射的ScAlN作为缓冲层,在Si(100)衬底上用金属有机化学气相沉积(MOCVD)技术外延了GaN薄膜。使用高分辨X射线衍射、原子力显微镜和拉曼光谱研究了ScAlN缓冲层的厚度对ScAlN缓冲层和GaN外延层的影响。研究结果表明,ScAlN缓冲层的厚度是影响GaN薄膜晶体质量的重要因素。随着ScAlN厚度的增加,ScAlN的(002)面X射线衍射摇摆曲线半高宽持续减小,GaN的(002)面X射线衍射摇摆曲线半高宽先减小后增大。当ScAlN缓冲层厚度为500nm时,得到的GaN晶体质量最好,其中GaN(002)面的X射线衍射摇摆曲线半高宽为0.38°,由拉曼光谱计算得到的张应力为398.38MPa。 相似文献
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采用直流磁控溅射的方法在普通玻璃上制备了低价的氧化钒薄膜,在氧气和氩气混合气氛中,对所制备的薄膜进行不同时间的热处理,得到具有相变特性的VO2薄膜。分别利用X射线衍射(XRD)和场发射扫描电镜(SEM)分析了薄膜的组分、结晶结构和表面形貌,利用四探针法测试了薄膜的电阻。结果表明:热处理前的氧化钒薄膜主要成分为V2O3,经过热氧化处理后,低价的氧化钒被氧化,薄膜中VO2含量增加,薄膜发生金属-半导体相变,其中450℃、2h为最佳处理参数,其电阻相变幅度超过2个数量级,薄膜的相变温度仅为30℃。 相似文献
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Vanadium oxide VO2 is a material that transforms from semiconductor to a metal state at a temperature of 67 °C. This phase transformation is accompanied by a dramatic change in its electrical and optical properties. Therefore, vanadium oxide thin films are most attractive for switching applications. Non-stoichiometric thin films of VOx, including VO2, also present such thermal response.This paper presents the optical and electrical properties of vanadium oxide thin films deposited by vacuum thermal evaporation of a metal vanadium with follows oxidation. We have studied the electro-physical behavior of these films during their phase transition. It was shown that the electrical transport mechanism of the obtained vanadium oxide films differ in low and high electrical fields. In low electrical fields, conductivity is obtained by the Schottky transport mechanism, whereas in high electrical fields, conductivity ranges from Ohmic, for medium fields, to Poole-Frenkel for higher fields. Also, FTIR and near IR reflectance characteristics of the obtained films are presented. 相似文献
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S. Lysenko V. Vikhnin G. Zhang A. Rua F. Fernandez H. Liu 《Journal of Electronic Materials》2006,35(10):1866-1872
Light-induced insulator-to-metal phase transition of vanadium dioxide films was studied by ultrafast optical pump-probe spectroscopy.
The transient optical reflection measurement shows that both heating and laser illumination contribute to the phase transition
of VO2. Within 10−11–10−9 sec, these two mechanisms are competitive. Excited-state dynamics were found to be strongly dependent on the concentration
of structural defects and the pump laser power as well. Comparison of the transient reflection of VO2 films deposited on different substrates suggests that the excitonic-controlled light-induced insulator-to-metal phase transition
in VO2 proceeded through an intermediate state. The transient reflection measurement of VO2 in metallic phase shows a three-stage relaxation process. A polaron excitation model is introduced to describe the dynamical
process for metallic VO2. 相似文献
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Hf-O-N and HfO2 thin films were evaluated as barrier layers for Hf-Ti-O metal oxide semiconductor capacitor structures. The films were processed by sequential pulsed laser deposition at 300 °C and ultra-violet ozone oxidation process at 500 °C. The as-deposited Hf-Ti-O films were polycrystalline in nature after oxidation at 500 °C and a fully crystallized (o)-HfTiO4 phase was formed upon high temperature annealing at 900 °C. The Hf-Ti-O films deposited on Hf-O-N barrier layer exhibited a higher dielectric constant than the films deposited on the HfO2 barrier layer. Leakage current densities lower than 5 × 10 A/cm2 were achieved with both barrier layers at a sub 20 Å equivalent oxide thickness. 相似文献
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Vanadium oxide undergoes a sharp metal-insulator transition in the vicinity of room temperature and there is considerable interest in exploring novel device applications that utilize this phase transition. Using experimentally determined values of the thermal conductivity across the metal-insulator transition in VO2 thin films, we estimate the switching characteristics of two-terminal VO2 devices. The minimum switching time for both heating (“on” state) and cooling (“off” state) processes is explored using a simple resistance-capacitance thermal circuit model. The estimated minimum switching time is on the order of ∼1 ns for 20 nm VO2 films which is comparable to experimentally observed switching times. Optimal operating temperatures to maximize switching times are estimated. Methods to further enhance the switching kinetics by device thickness, carrier doping/strain, interfacial thermal resistance and input thermal energy are discussed. The simulations are compared with a 3-D model for VO2 devices on Si substrates utilizing COMSOL. The results are of potential relevance to the emerging field of correlated oxide electronics with fast phase transitions. 相似文献
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Metal‐Insulator Transition in ALD VO2 Ultrathin Films and Nanoparticles: Morphological Control
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Antony P. Peter Koen Martens Geert Rampelberg Michael Toeller James M. Ablett Johan Meersschaut Daniel Cuypers Alexis Franquet Christophe Detavernier Jean‐Pascal Rueff Marc Schaekers Sven Van Elshocht Malgorzata Jurczak Christoph Adelmann Iuliana P. Radu 《Advanced functional materials》2015,25(5):679-686
Nanoscale morphology of vanadium dioxide (VO2) films can be controlled to realize smooth ultrathin (<10 nm) crystalline films or nanoparticles with atomic layer deposition, opening doors to practical VO2 metal‐insulator transition (MIT) nanoelectronics. The precursor combination, the valence of V, and the density for as‐deposited VO2 films, as well as the postdeposition crystallization annealing conditions determine whether a continuous thin film or nanoparticle morphology is obtained. It is demonstrated that the films and particles possess both a structural and an electronic transition. The resistivity of ultrathin films changes by more than two orders of magnitude across the MIT, demonstrating their high quality. 相似文献
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采用水热法和电化学沉积法,成功制备了包覆有SnO2纳米颗粒的WO3纳米棒阵列薄膜,退火处理后形成WO3/SnO2异质结复合薄膜。通过改变SnO2的沉积时间得到了复合薄膜的最佳制备条件。采用XRD,FESEM对WO3/SnO2复合薄膜的物相和形貌进行了分析,通过电化学工作站对WO3/SnO2复合薄膜的光电性能进行了研究,结果表明,电沉积时间为120 s时,WO3/SnO2复合薄膜具有最小的阻抗,且在0.6 V的偏压下光电流密度为0.46 mA/cm2,相比于单一WO3纳米棒薄膜,表现出更好的光电化学性能。 相似文献
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S.K. Ray R. Mahapatra S. Maikap A. Dhar D. Bhattacharya Je-Hun Lee 《Materials Science in Semiconductor Processing》2004,7(4-6):203
Ultrathin HfO2 gate dielectrics have been deposited on strain-compensated Si0.69Ge0.3C0.01 layers by rf magnetron sputtering. X-ray diffraction spectra show the films to be polycrystalline having both monoclinic and tetragonal phases. The formation of an interfacial layer has been observed by high-resolution transmission electron microscopy. Secondary ion mass spectroscopy and Auger electron spectroscopy analyses show the formation of an amorphous Hf-silicate interfacial layer between the deposited oxide and SiGeC films. The average concentration of Ge at the interfacial layer is found to be 2–3 at%. The leakage current density of HfO2 gate dielectrics is found to be several orders of magnitude lower than that reported for thermal SiO2 with the same equivalent thickness. 相似文献
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J.M. Wang 《Microelectronic Engineering》2008,85(9):1920-1923
Lead-magnesium niobate-lead titanate (PMN-PT) thin films with and without the TiO2 seed layer were deposited on Pt/Ti/SiO2/Si substrates through pulsed laser deposition. The study aimed to characterize the effect of the TiO2 seed layer on the phase composition and properties of PMN-PT film. Without the TiO2 seed layer, the pure perovskite phase could be obtained in the thinner PMN-PT film while with the TiO2 seed layer, the pure perovskite phase was formed in the thicker PMN-PT film. The ferroelectric properties of PMN-PT films with the TiO2 seed layer were exhibited. As a result, the maximum amount of remnant polarization reached the amount of 32 μC/cm2 for the PMN-PT thin film with the TiO2 seed layer. 相似文献
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E Atanassova D SpassovA Paskaleva J KoprinarovaM Georgieva 《Microelectronics Journal》2002,33(11):907-920
The effect of the oxidation temperature (673-873 K) on the microstructural and electrical properties of thermal Ta2O5 thin films on Si has been studied. Auger electron spectroscopy and X-ray photoelectron spectroscopy results revealed that the films are non-stoichiometric in the depth; an interfacial transition layer between tantalum oxide and Si substrate, containing presumably SiO2 was detected. It has been found by X-ray diffraction that the amorphous state of Ta2O5 depends on both the oxidation temperature and the thickness of the films—the combination of high oxidation temperature (>823 K) and thickness smaller than 50 nm is critical for the appearance of a crystal phase. The Ta2O5 layers crystallize to the monoclinic phase and the temperature of the phase transition is between 773 and 823 K for the thinner layers (<50 nm) and very close to 873 K for the thicker ones. The electrical characterization (current/voltage; capacitance/voltage) reveals that the optimal oxidation temperature for achieving the highest dielectric constant (∼32) and the lowest leakage current (10−8 A/cm2 at 1 MV/cm applied field) is 873 K. The results imply that the poor oxidation related defects are rather the dominant factor in the leakage current than the crystallization effects. 相似文献