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Raman spectra of SrBi4Ti4O15 (SBTi4) thin films were measured as a function of temperature from 80 to 820 K. Below room temperature, no phonon modes were detected between 200 and 815 cm-1, which indicates the existence of a phonon band gap in this material. Differences between the Raman spectra of the thin film and bulk polycrystalline samples are discussed. The asymmetric Raman band at high frequency can be interpreted as the superposition of two main distinct Raman lines. Temperature dependence of the Raman shifts and full widths at half maximum (FWHMs) for the two phonon modes is discussed as well, which provides information about the vibration energy levels within the film. Theoretical fittings of their FWHMs indicate that the higher-energy phonon mode is apparently more anharmonic than the lower one. [ABSTRACT FROM AUTHOR]

c-axis epitaxial thin films of Bi-layered homologous Sr[sub m - 3]Bi[sub 4]Ti[sub m]O[sub 3m+3] (m = 3, 4, 5, and 6) were fabricated on (001) SrTiO[sub 3] single crystal substrates by pulsed laser deposition, respectively. Microstructures of the films were systematically characterized by x-ray diffraction (including θ-2θ scans, rocking curve scans and φ scans), atomic force microscopy, and transmission electron microscope. Epitaxial relations were established to be (001) Sr[sub m - 3]Bi[sub 4]Ti[sub m] O[sub 3m + 3](001) SrTiO[sub 3] and [1&1macr;0]Sr[sub m - 3]Bi[sub 4]Ti[sub m]O[sub 3m+3][010]SrTiO[sub 3] by φ scans and selected area diffraction. A special kind of atomic shift along the [001] direction and a slight atomic vibration of TiO[sub 6] octahedra were revealed and discussed. The room-temperature dielectric constants of these epitaxial films measured by using an evanescent microwave probe were 245±23, 237±13, 272±19, and 221±20 for films with m = 3, 4, 5, and 6 respectively. [ABSTRACT FROM AUTHOR]

Polycrystalline thin films of Bi-layered Sr[SUBm - 3] Bi[SUB4]Ti[SUBm]O[SUB3m + 3] (referred to as BTO for m = 3 and SBTi[SUBm] for m = 4,5, and 6 respectively) were fabricated on Pt-coated silicon substrates by pulsed laser deposition. Structures were characterized by x-ray diffraction, atomic force microscopy, and scanning electron microscopy. Electric properties were investigated systematically. It was revealed that the remnant polarization P[SUBr] depended greatly on the parity of m. This dependence was well explained by using a rotating oxygen octahedra model along the a axis. The superior fatigue properties of SBTi[SUBm] (m = 4,5,6) over BTO films were discussed in detail. The high dielectric constants and low dissipation factors of the films were demonstrated. [ABSTRACT FROM AUTHOR]

La2/3Ca1/3MnO3 thin films have been grown on SrTiO3, LaAlO3, and yttria-stabilized zirconia buffered silicon-on-insulator (SOI) substrates by the pulsed laser deposition technique. While full cube-on-cube epitaxy was achieved on the SrTiO3 and LaAlO3 substrates, a coexistence of the cube-on-cube and cube-on-diagonal epitaxy was observed in the the manganite films on SOI substrates. Besides the intrinsic four-fold magnetocrystalline anisotropy, a uniaxial anisotropy also exists in the films, which is determined by the demagnetization field and the mismatch-induced strain. A tensile strain leads to an easy plane, while a compressive strain favors an easy axis. The different magnetization configurations in the films on different substrates are the reason for their varied transport and magnetic properties. Due to a combined effect of these magnetic anisotropy, the magnetization in the two crystallography domains in the film on SOI tends to lie in the film plane but align in their respective easy axes. There are always large spin angles across the domain boundaries. As a result, a quite large low-field magnetoresistance (LFMR) based on spin-dependent tunnelling was observed. It shows a resistance change of ∼20% at 50 K in a magnetic field ∼700 Oe, which is promising for real applications. [ABSTRACT FROM AUTHOR]

Polycrystalline (Pb0.75La0.25)TiO3 (PLT25) thin films have been fabricated on Pt/Ti/SiO2Si substrates by pulsed laser deposition. The room-temperature structures and dielectric properties are studied by x-ray diffraction, scanning electron microscopy, and HP4294A impedance/phase analyzer. The temperature-dependent ferroelectric properties are systematically investigated by using a RT66A ferroelectric tester combined with a temperature-controllable vacuum chamber. For well-saturated hysteresis loops, with the temperature decrease from 295 to 97 K, the coercive field (Ec) and remanent polarization (Pr) increase and the saturated polarization (Ps) is almost temperature-independent. However, this is not the case for the unsaturated hysteresis loops. Temperature-dependent fatigue-resistance of the PLT25 films is also experimentally established: after 2.22 x 109 switching cycles, the nonvolatile polarization decreases 38% when measured at room-temperature and it decreases 15% at 97 K. The nature and population of point defects and their effects on the subtle variations of the Ec, Ps, Pr, and fatigue-resistance against temperature are discussed in detail. [ABSTRACT FROM AUTHOR]

Fe–N films with 20 nm thick Fe underlayers were deposited on Si(100) substrates by RF magnetron sputtering, and their structure and magnetic properties were investigated. It was found that the optimum nitrogen partial pressure for α" phase formation is about 2 × 10-4 Torr, and the saturation magnetization measured at room temperature of the Fe–N films deposited at this pressure is as high as 2179 emu cc-1, which is much higher than that of pure iron. Film thickness dependence of the saturation magnetization shows that it initially increases with the increase in film thickness and reaches a maximum of ~2179 emu cc-1 in the thickness range of 300–570 nm, and decreases with a further increase in film thickness. [ABSTRACT FROM AUTHOR]

SrBi[sub 2]Ta[sub 2]O[sub 9](SBT)/LaNiO[sub 3](LNO)/Si and SBT/Pt/TiO[sub 2]/SiO[sub 2]/Si multilayers were fabricated by pulsed laser deposition. With Pt top electrodes, the measured remanent polarization (2P[sub r]) of Pt/SBT/LNO/Si and Pt/SBT/Pt/TiO[sub 2]/SiO[sub 2]/Si capacitors was 6.5 μC/cm[sup 2] and 5.2 μC/cm[sup 2], respectively. Using LNO as both bottom electrodes and buffer layers, enhanced non-c-axis crystalline SBT films were induced, which resulted in a 2P[sub r] greater than that of the Pt/SBT/Pt/TiO[sub 2]/SiO[sub 2]/Si capacitor. The hysteresis loop of the Pt/SBT/LNO/Si capacitor showed a great external-field-dependent horizontal shift. Using an electron-injection model, this dependence was addressed. The fatigue-free property of the Pt/SBT/LNO/Si capacitor was experimentally established, in that the non-volatile polarization decreased by less than 5% of the initial value after 1.44×10[sup 9] switching cycles . [ABSTRACT FROM AUTHOR]

(001) textured PbTiO[sub 3] thin films have been deposited on (001) redoping n-Si substrates by metalorgnic chemical vapor deposition (MOCVD) under reduced pressure, and the film ferroelectricity has been measured using the substrate as bottom electrode directly. Besides this investigation, a set of analysis including AFM surface morphology, SEM cross section morphology, electron-probe element analysis, XRD θ-2θ scan and high temperature X-ray diffraction have been carried out to study the microstructure and phase transition process of the PbTiO[sub 3] thin film. [ABSTRACT FROM AUTHOR]

Raman spectra have been investigated in PbTiO[sub 3] thin films grown on Si by metalorganic chemical vapor deposition. A large grazing-angle scattering technique was taken to measure the temperature dependence of Raman spectra below room temperature. All Raman modes in the thin films are assigned and compared with those in the bulk single crystal, a new A[sub 1] (TO) soft mode at 104 cm[sup -1] was recorded which satisfies the Curie-Weiss relation ω[sup 2] =A(T[sub c] -T). Intensities of the A[sub 1] (1TO) and E(1TO) modes were anomalously strengthened with increasing temperature. Raman modes for the thin films exhibit remarkable frequency downshift and upshift which is related to the effect of internal stress. [ABSTRACT FROM AUTHOR]

The magnetoelectric effect has been demonstrated based on the composite of InGaN/GaN multiple quantum wells (MQWs) and FeCo thin film. By applying an external magnetic field, the ferromagnetic layer will be deformed due to magnetostriction. This deformation is transmitted to the piezoelectric layers and results in piezoelectric effect, which induces electric polarization in the piezoelectric layers. The induced electric polarization changes the strain and the built-in internal electric field in the InGaN/GaN MQWs and therefore, the optical properties of the InGaN/GaN MQWs change. The results shown here open up a possibility for the application of nitride semiconductors in magneto-optical and magnetoelectric engineering. [ABSTRACT FROM AUTHOR]

La2/3Ca1/3MnO3 thin films have been grown on yttria-stabilized zirconia (YSZ) buffered silicon-on-insulator (SOI) substrates by the pulsed laser deposition technique. While full cube-on-cube epitaxy was achieved for the YSZ layer, the top manganite layer was multioriented in plane, with a coexistence of cube-on-cube and cube-on-diagonal epitaxial structures. Due to a combined influence from the magnetocrystalline, shape, and stain-induced magnetic anisotropy, in zero field and low temperatures the local spin orientation varies across the large-angle grain boundaries. As a result, a quite large low-field magnetoresistance (LFMR) based on spin-dependent tunneling was observed. The film shows a resistance change of ∼20% in a magnetic field <1000 Oe at 50 K, which is promising for real applications. [ABSTRACT FROM AUTHOR]

x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectrometry, and cathodoluminescence measurements have been employed to study the correlation between optical and structural properties in InGaN epitaxial films. In-rich quantum dots were found to be dispersed throughout the film. By the combination of these measurements, we clearly identify that brighter luminescence arises from In-rich regions while dimmer luminescence corresponds to the Ga-rich matrix regions. [ABSTRACT FROM AUTHOR]

The first four members of Bi-layered Sr[sub m-3]Bi[sub 4]Ti[sub m]O[sub 3m+3] homologous series with m = 3, 4, 5, and 6, i.e., Bi[sub 4]Ti[sub 3]O[sub 12], SrBi[sub 4]Ti[sub 4]O[sub 15], Sr[sub 2]Bi[sub 4]Ti[sub 5]O[sub 18], and Sr[sub 3]Bi[sub 4]Ti[sub 6]O[sub 21], were grown on SrTiO[sub 3] (001) single-crystal substrates by pulsed-laser deposition. X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) reveal that the films grew epitaxially with in-plane epitaxial alignment of [1&1macr;0]Sr[sub m-3]Bi[sub 4]Ti[sub m]O[sub 3m+3][010]SrTiO[sub 3]. HRTEM cross-sectional images show that the films with m = 3, 4, and 5 are nearly free of intergrowth, whereas a number of growth defects were observed in the film with m=6. Using an evanescent microwave probe, the room-temperature dielectric constants of these epitaxial films are measured to be 221 ± 13, 205 ± 15, 261±29, and 249 ± 17 for films with m=3, 4, 5, and 6, respectively. [ABSTRACT FROM AUTHOR]

Studies the capacitance and dissipation factor measurements of the dielectric properties on thin films in the high-temperature region. Debye-like relaxation in the dielectric response; Thermal activation of the relaxation rate; Pronounced feature of both the capacitance and dissipation factor curves.

Thermal diffusivity (α) of amorphous silicon carbon nitride (a-SiC[sub x]N[sub y]) thin films on crystalline silicon, prepared by ion beam sputtering, has been studied using the traveling wave technique. The variation of thermal diffusivity with carbon content in amorphous silicon carbon nitride samples are reported. Thermal diffusivity decreased from ∼0.35 cm[sup 2]/s for samples with carbon contents of less than 30 at. %, to about 0.15 cm[sup 2]/s for a-SiC[sub x]N[sub y] films with a carbon content of ∼70 at. %. A similar variation was found for the film density as measured by surface acoustic wave spectroscopy as a function of the carbon content. The results on a-SiC[sub x]N[sub y], elucidate the relation between thermal diffusivity and the bonding configuration, density and microstructure of the network. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a correction to the article 'Biexciton emission from high-quality ZnO films grown on epitaxial GaN by plasma-assisted molecular-beam epitaxy,' published in the year 2000 issue of the 'Applied Physics Letters' journal.

We have investigated the structural and optical properties of Ga-doped ZnO films grown on GaN templates by plasma-assisted molecular-beam epitaxy. The carrier concentration in Ga-doped ZnO films can be controlled from 1.33x10[sup 18]/cm[sup 3] to 1.13x10[sup 20]/cm[sup 3]. Despite high Ga incorporation, the linewidth of (0002) ω-rocking curves of Ga-doped ZnO films still lies in the range from 5 to 15 arc min. Photoluminescence (PL) spectra of Ga-doped ZnO films show dominant near-bandedge emission with negligibly weak deep-level emission, independent of carrier concentration. The PL spectrum exhibits a new emission line at 3.358 eV, which corresponds to exciton emission bound to a Ga donor. To avoid degradation of the PL intensity, the maximum dopability of Ga in ZnO is determined to be around 2.6x10[sup 19]/cm[sup 3]. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Crystalline thin films of SiCN have been grown by microwave plasma-enhanced chemical vapor deposition using H[sub 2], CH[sub 4], N[sub 2], and SiH[sub 4] gases. The ternary compound (C;Si)[sub x]N[sub y] exhibits a hexagonal structure and consists of a network wherein the Si and C are substitutional elements. While the N content of the compound is about 35–40 at. %, the extent of Si substitution varies and can be as low as 10 at. %. Optical properties of the SiCN compounds have been studied by photoluminescence (PL), piezoreflectance (PzR), and photothermal deflection (PDS) spectroscopies. From the PzR measurement, we determine the direct band gap of the new crystals to be around 3.8 eV at room temperature. PDS measurement shows two absorption features with the first peak at around 3.2 eV which is related to an indirect band gap. The second PDS peak occurred around 3.8 eV and is quite consistent with the direct band gap determined by PzR. From the PL measurement, it is also found that the SiCN compounds have a near band edge emission centered around 3.26 eV at room temperature, which is consistent with the fundamental band gap obtained from the PDS measurement. These optical results indicate the potential of SiCN for blue and uv optoelectronic applications. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]