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Polycrystalline lead lanthanum titanate thin film having perovskite structure was fabricated by metalorganic deposition (MOD) on a ZrO[sub 2]/SiO[sub 2]/Si substrate at 600 °C for 1 h in O[sub 2] atmosphere. Columnar structured ZrO[sub 2] buffer layer was also prepared by a MOD process under the same condition. Electrical measurements were conducted on interdigitated electrodes. The crystalline structure and growth behavior of the films have been studied by x-ray diffraction and scanning electron microscopy. It is observed that dielectric response of the film is effected by the cable length used in the measurement and by the values of the ac voltage. Long cable gives rise to an additional resonance peak at high frequency caused by the stray inductance of the contacts and cables. The capacitance and loss tangent over low frequency range shows significant variations due to the trapped charges and space charges in the film. These variations are very dependent on the values of the ac voltage and the length of cable. Meanwhile, the trapped charges and space charges lead to abnormal P–E loops, in which the measured remanent polarization and coercive field increase with increasing frequency. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A study of the structure and in-plane dielectric properties of BaZr0.2Ti0.8O3 thin film epitaxially grown on (LaAlO3)0.3(Sr2AlTaO6)0.35 (001) single-crystal substrates through pulsed-laser deposition has been carried out. X-ray diffraction measurements revealed a good crystallinity and tensile in-plane stress in the film. Fine grains with an average size of ∼20 nm were observed using atomic force microscopy. Curie temperature of the film was found to be ∼120 °C, which is 100 °C higher than that of the ceramic. Butterfly-shaped C-V curve confirmed the in-plane ferroelectric state in the film. A large dielectric tunability of ∼50% was found in the film. [ABSTRACT FROM AUTHOR]

The evolutions of localized states, dielectric functions, and electronic band structure for nitrogen (N) incorporated GeTe (NGT) as functions of temperature (210-660 K) and N concentration (0%-18%) have been investigated with the aid of temperature dependent spectroscopic ellipsometry experiments. The increased Urbach absorption energy, caused by band-tail localized states, can be attributed to the increment of structure defects with N concentration, which is generated from the N atoms bonding with Ge. Besides, the details of the dynamic crystallization process and the role of nitrogen in NGT films have been elucidated by the abnormal behavior of interband transition energy and the evolutions of surface morphology, namely, the nitrides separation before crystallization and the inhibition on GT crystallization. The dynamic crystallization process and the nitrogen behavior in NGT are of great significance for further study on the reliability and endurance of the NGT-based data storage devices. [ABSTRACT FROM AUTHOR]

Tungsten (W) doping effects on Ge2Sb2Te5 (GSTW) phase change films with different concentrations (3.2, 7.1, and 10.8%) have been investigated by variable-temperature spectroscopic ellipsometry. The dielectric functions from 210 K to 660 K have been evaluated with the aid of Tauc-Lorentz and Drude dispersion models. The analysis of Tauc gap energy (Eg) and partial spectral weight integral reveal the correlation between optical properties and local structural change. The order degree increment and chemical bond change from covalent to resonant should be responsible for band gap narrowing and electronic transition enhancement during the phase change process. It is found that the elevated crystalline temperature for GSTW can be related to improved disorder degree. Furthermore, the shrinkage of Eg for GSTW should be attributed to the enhanced metallicity compared with undoped GST. [ABSTRACT FROM AUTHOR]

A crystallized Si2Sb2Te5 thin film was observed to extrude single-crystalline [0001] oriented tellurium nanowires at room temperature. The single crystalline Te nanowires nucleation and extruded outgrowth can be greatly accelerated by electron-beam-illumination (EBI) in a transmission electron microscope by an order as high as four. The EBI-enhanced outgrowth speed of Te nanowires is a function of electron beam flux and can be described as v=k ln(J+m). This Te nanowires self-outflow phenomenon comes from a decomposition process of the Si2Sb2Te5 matrix and provides an interesting model and mechanism of the nanowires’ growth, which is distinctive to the vapor-liquid-solid (VLS) mechanism. [ABSTRACT FROM AUTHOR]

Cup-shaped tungsten (W) bottom electrode contact (BEC) was proposed for phase-change memory (PCM) cell and compared with the same size solid BEC. The reset voltage of 2.5 V and the shortest reset time of 10 ns were obtained for cup-shaped W-BEC based PCM cell, which is much better than those of the solid BEC based PCM cell. The improved performance of the cup-shaped W-BEC based PCM cell is attributed to the mushroom heating region with high heating efficiency, the inner edge contact of W-BEC and Ge2Sb2Te5, and the reduced thermal diffusion from the bottom electrode, which is further verified by theoretical simulation. [ABSTRACT FROM AUTHOR]

The authors prepared Yb-doped bismuth iron oxide ceramics (Bi1-xYbxFeO3, with 0≤x≤0.20) by rapid liquid phase sintering method and investigated the material’s structures and electrical properties. The x-ray diffraction measurements showed that the doping of Yb has induced noticeable lattice distortion in the ceramics, and a largest distortion was observed when the concentration of Yb was 15%. By doping electrical resistivity, ferroelectric and dielectric properties of the ceramics were improved. Among all samples, BiFeO3 doped with 15% Yb was found to have the smallest leakage current density (<10-7 A/cm2) and the largest remnant polarization (8.5 μC/cm2) [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO)-based film bulk acoustic resonator consisting of a piezoelectric element (Au/ZnO/Pt) and a Bragg reflector (ZnO/Pt multilayer structure) has been fabricated by magnetron sputtering. The transmission electron microscopy and x-ray diffraction measurements revealed that all thin film layers in the device were well crystallized and highly textured. By electrical measurements, it was found that the device had a high resonant frequency (3.94 GHz) and mass sensitivity (8970 Hz cm2/ng). The use of the device as a biosensor was demonstrated by comparing the resonant properties of the device with/without coatings of biospecies. [ABSTRACT FROM AUTHOR]

Stack nanocrystalline-Si (nc-Si) based metal-insulator-semiconductor memory structure was put forward and fabricated by plasma-enhanced chemical vapor deposition. The capacitance hysteresis, and asymmetric current peaks were observed at room temperature, which confirm the memory effects and results from the nc-Si. The sharper upward current peak and the broader upward current peak for the annealed sample are explained by resonant tunneling of electrons into stack nc-Si and single nc-Si, respectively. The stack nc-Si has better charge-storage ability than single nc-Si, and a model was put forward to explain the retention mechanism of this stack nc-Si based memory structure. [ABSTRACT FROM AUTHOR]

SnO2 nanowires synthesized by thermal evaporation method are investigated as a possible anode electrode for Li-ion batteries. In the first discharge process, the capacity of Li ions is 2133 mA h g-1, which is much more than the theoretical total capacity of the bulk SnO2, 1494 mA h g-1. During the successive 15 cycles, the reversible capacity stays in the range of 1250–700 mA h g-1 with a capacity fading of 3.89% per cycle at a constant current density of 0.5 mA cm-2. These results demonstrate that SnO2 nanowires are a promising anode material for Li-ion battery applications. [ABSTRACT FROM AUTHOR]

A trilayer metal-oxide-semiconductor structure containing a HfAlO tunnel layer, isolated Ge nanocrystals, and a HfAlO control layer, was obtained using pulsed-laser deposition (PLD). Self-organized Ge nanocrystals were formed by PLD at 600 °C, suggesting a useful low-temperature process for fabricating Ge nanocrystals embedded in dielectric materials. The self-organized Ge nanocrystals so formed were uniform in size and distribution with a density approaching 1012 cm-2. The effects of deposition temperature and growth rate in forming Ge nanocrystals were investigated and it was revealed that a relatively low temperature and growth rate are favorable for the formation of Ge nanocrystals. The memory effect of the Ge nanocrystals with storage charge density of up to 1012 cm-2 has been demonstrated by the presence of hysteresis in the capacitance-voltage curves. [ABSTRACT FROM AUTHOR]

An in situ doping approach was adopted to synthesize single-crystalline Sn-doped In2O3 [indium tin oxide (ITO)] nanowhiskers. Similar synthesis strategy could be used in the production of various doped metal oxide nanowhiskers. The growth mode of ITO nanowhiskers was discussed based on a self-catalytic vapor-liquid-solid growth mechanism. At room temperature, a photoluminescence peak at 510 nm was observed, which was likely related to the surface defects of ITO nanowhiskers. In air ambient, the resistivity of individual ITO whisker was measured to be 0.40 Ω cm, which was much higher than that of ITO films. A possible explanation for the high resistivity was proposed based on the influence of surface oxygen absorption. [ABSTRACT FROM AUTHOR]

Pb[sub 0.9]La[sub 0.1]Ti[sub 0.975]O[sub 3] (PLT10) thin films were deposited on SiO[sub 2]/Si(100) substrates coated with a ZrO[sub 2] buffer layer. Studies by x-ray diffraction and scanning electron microscopy reveal that the ZrO[sub 2] film consists of both tetragonal and monoclinic phases, with the tetragonal phase being the dominant one. The PLT10 film has a perovskite structure and the grains in the film have a rather uniform size of about 50 nm. By using interdigital transducer (IDT) electrodes the in-plane electrical properties, hysteresis loop, and pyroelectric coefficient of the PLT10 film were measured. The dielectric constant and loss factor vary only slightly with frequency in the range 10[sup 3]–10[sup 6] Hz, with the loss factor being less than 0.01 over the entire range. The leakage current density is lower than 2×10[sup -8] A/cm[sup 2] at a bias field of 5 kV/cm. The remnant polarization and coercive field are 12.6 μC/cm[sup 2] and 9.93 kV/cm, respectively. The film exhibits a reasonably high pyroelectric coefficient (95 μC/m[sup 2] K) after it has been poled by applying 120 V ac at 0.1 Hz across the IDT electrodes. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]