Solid State Phenomena Vols. 181-182

Abstract: Novel well-defined ABA-type triblock copolymers, (PMAIPGal-b-PLA-b-PMAIPGal), were synthesized by a three-step procedure: (a) melt polycondensation of L-lactic acid using stannous chloride (SnCl₂•2H₂O) as a catalyst, resulting in a hydroxyl-terminated prepolymer by alkyd condensation with 1,4-butanediol, followed by (b) esterification of the PLA hydroxyl end-groups with 2-bromoisobutyryl bromide, and (c) ATRP of 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose (MAIPGal) by the bromoisobutyryl initiating groups. The resultant copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The biocompatible and biodegradable copolymers have potential applications as tissue engineering biomaterials or controlled release drug delivery systems.

Abstract: The reflectivity and transmission spectra will be discussed in an antiferromagnetic (AF) sandwich structure as ZnF₂/MnF₂/SiO₂. Such geometry is used, where the AF anisotropy axis and external static magnetic field both are parallel to the film surfaces and normal to the incident plane. The results show that the reflectivity and transmission spectra can be governed by the incident angles and the AF thickness.

Abstract: Si-based strained technology is currently an important topic of concern in the microelectronics field. The stress-induced enhancement of electron mobility contributes to the improved performance of Si-based strained devices. In this paper, Based on both the electron effective mass and the scattering rate models for strained-Si_1-xGe_x/Si (101), an analytical electron mobility model for biaxial compressive strained-Si_1-xGe_x /Si (101) is presented. The results show that the stress doesn’t make the electron mobility increased, but the electron mobility for [100] and [001] orientations decrease with increasing Ge fraction x, especially for [010] orientation expresses a sharp decrease. This physical phenomenon can be explained as: Although the applied stress (the higher the Ge fraction, the greater the applied stress) can enhance the electron mobility, alloy disorder scattering rate markedly increase. Overall the electron mobility decreases instead. The above result suggests that not all the mobilities for Si-based strained materials enhance with the stress applied. For the biaxial strained-SiGe material represented by Ge fraction, the effect of alloy disorder scattering on the enhancement of mobility must be concerned. The result can provide theoretical basis for the understanding of the improved physical characterizations and the enhanced mobility for Si-based strained materials.

Abstract: ZrO₂ and ZrO₂-PVP sol was obtained by hydrothermal synthesis. And the thin films were prepared with spin coating method. ZrO₂ thin films were characterized or examined by many kinds of instruments. Fourier-transform infrared spectroscopy was employed and some infrared absorption peaks weakened when the heating temperature increased. And 1-on-1 laser-induced damage threshold tests on ZrO₂ films were carried out. Refractive index and thickness of the ZrO₂-PVP films were measured by means of automatic scanning spectroscopic ellipsometer and the refractive index of ZrO₂ -PVP film changed with the addition of PVP content.

Abstract: Upon the 325 nm excitation from a helium-cadmium laser, the photoluminescence (PL) from aged porous silicon was investigated with fluorescence spectroscopy. Each PL spectrum of the aged porous silicon films contained two luminescent bands, one of the luminescent bands peaked at about 466.7 nm whereas the other luminescent band peaked at about 596.1 nm. The origin of the blue PL from aged porous silicon was discussed, and our results indicated that the blue photoluminescence of porous silicon films originated from the silicon oxide itself.

Abstract: Solving the Schrödinger equation with strain Hamiltonian and combining with KP theory, we obtained the conductivity effective mass and density of states effective mass of strained Si_1-xGe_x(001) in this paper. On the basis of conductivity effective mass and density of states effective mass, considered of Fermi golden rule and Boltzman collision term approximation theory, scattering rate model was established in strained Si_1-xGe_x(001). Based on the conductivity effective mass and scattering rate models we discussed the dependence of electron mobility on stress and doping concentration in strained Si_1-xGe_x(001), it shows that electron mobility decrease with the increasing of stress and doping concentration. This result can provide valuable references to the research of electron mobility of strained Si_1-xGe_x materials and the design of devices.

Abstract: A series of zinc oxychloride tellurite glass based on (79 – z) TeO₂ - 10ZnO - (z) ZnCl₂ - 10Li₂O - 1Eu₂O₃ (where z = 0, 10, 20, 25 and 30 mol %) are successfully prepared by the melt quenching method. The optical properties are characterized by means of Raman spectra, UV-Vis and photoluminescence spectroscopy. It is found that the Raman spectrum of the glass shows three main peaks in the vibrational band in the vicinity of 430, 670 and 770 cm^-1. The intensity of all bands is decreased as the ZnCl₂ contents are increased from 0 to 30 mol % but the intensity ratio (I₇₇₀ / I₆₇₀) increased. This may arise from the change in the structural chains from TeO₄ to TeO₃₊₁ or to a TeO₃ polyhedron shape. Using the UV-Vis absorption spectrum, the Judd-Ofelt (J-O) analysis is performed to determine the J-O parameters (Ω₂, Ω₄, Ω₆) and it is found that Ω₂ > Ω₄ > Ω₆. The values of Ω₂, Ω₄ , Ω₆, the quality factor (Q) and the radiative lifetime (τ_rad) are found to increase with ZnCl₂ content up to 20 mol %. From photoluminescence spectrum, it is found that the value of the intensity ratio between ⁵D₀ →⁷F₂ and ⁵D₀ →⁷F₁ transition increase with ZnCl₂ contents which illustrates that this glass can easily become laser material.

Abstract: Applying KP theory combined with deformation potential we obtained the valence band structure, and based on this result we calculated the orientation-dependent effective mass which is also called conductivity effective mass in strained Si_1-xGe_x/(001)Si in this research, and furthermore ,we established the scattering rate model by using the density-of-states effective mass. On the basis of conductivity effective mass and scattering rate model, utilizing analytical method and relaxation time approximation we obtained the dependence of the value of hole mobility on stress and doping concentration in strained Si_1-xGe_x/(001)Si along different crystal orientations. Compare to the unstrained Si, the anisotropy of hole mobility is more obvious in strained Si_1-xGe_x/(001)Si, for example, It shows that under the same stress and doping concentration (Ni=1x1014cm-3, x=0.4), the value of hole mobility along [010] crystal orientation is visibly higher than other crystal orientations. This result can provide valuable references to the research of hole mobility of strained Si1-xGex materials and the design of devices.

Abstract: The spinel ferrites, MFe₂O₄ (where M=Fe, Mn, Co, Ni, Zn, Mg, etc.) have attracted considerable interest during the last few decades due to their potential applications in high frequency transformers, filters, high density storage devices, and microwave applications. In the latest several years, many synthesis technologies such as sol-gel, auto-combustion, thermal decomposition methods and hydrothermal reaction have been developed to prepare spinel ferrite nanoparticles. In this paper, the spinel ferrites Fe₃O₄ and MnFe₂O₄ nanoparticles were synthesized by using a solvothermal reduction method. X-ray diffraction (XRD) and Raman analysis shows that all the peaks are close to the data for Fe₃O₄ and MnFe₂O₄, indicating the prepared particles are single phase. The scan electronic microscopy (SEM) shows that the prepared Fe₃O₄ and MnFe₂O₄ are monodisperse nanospheres and with the average size of around 300nm.

Abstract: Thermal properties and phase behaviors of series of newly synthesized copolyacrylate esters with oligomeric-L-LA (OLLA) segments (DP = 10-40) and mesogens as side chains were characterized. The OLLAs prepared by ring opening polymerization of L-LA with active HO-group were modified to form polymerizable acrylate esters and then copolymerized with polymerizable mesogens. The thermal behaviors of these copolyacrylate esters were studied by DSC and POM measurements and phase structures by XRD measurements. The mesogens showed very good induce effect on the formation of layered structures. CD measurements were used to determine the helical structure and the optical rotation power of the side chain copolyacrylate esters.