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121.
122.
MgO doped lithium alumino phosphate glasses (PLA: P2O5+Li2O+Al2O3+MgO) were prepared by melt quenching technique. Raman spectra display three significant peaks at 698, 1164 and 1383 cm−1 attributed to: symmetric stretching vibrations of the bridging oxygen (BO) in the P–O–P chains, symmetric stretching vibrations of the PO2 groups, and the asymmetric vibrations vas(PO2) of the non-bridging oxygen (NBO) atoms, respectively. Also, the density, molar volumes and ion concentration have been discussed and correlated with the structural changes within the glassy matrix. Some optical constants such as refractive index and dispersion parameters (Eo: single-oscillator energy and Ed: dispersive energy) of the glasses were determined. Finally, the values of the optical band gap for direct and indirect allowed transitions have been determined from the absorption edge studies. It is deduced that the values of Eopt increase with increasing MgO content. It was assigned to structural changes induced from the formation of non-bridging oxygen. The Urbach energy (ΔE) was found to decrease from 0.578 to 0.339 eV with increasing MgO content from 0.5 to 2 mol. 相似文献
123.
Rafa Lewandkw Miosz Grodzicki Piotr Mazur Antoni Ciszewski 《Surface and interface analysis : SIA》2021,53(1):118-124
Al2O3 insulator layers were deposited step by step by the physical vapor deposition (PVD) method onto gallium nitride in the wurtzite form, n‐type and (0001)‐oriented. The substrate surface and the early stages of Al2O3/n‐GaN(0001) interface formation were characterized in situ under ultra‐high vacuum conditions by X‐ray and ultraviolet photoelectron spectroscopy (XPS, UPS). The electron affinity (EA) of the substrate cleaned by annealing was 3.6 eV. Binding energies of the Al 2p (76.0 eV) and the O 1s (532.9 eV) confirmed the creation of the Al2O3 compound in the deposited film for which the EA was 1.6 eV. The Al2O3 film was found to be amorphous with a bandgap of 6.9 eV determined from the O 1s loss feature. As a result, the calculated Al2O3/n‐GaN(0001) valence band offset (VBO) is ?1.3 eV and the corresponding conduction band offset (CBO) 2.2 eV. 相似文献
124.
王月 《原子与分子物理学报》2015,32(6)
应用在位电阻率测量方法研究高压下锐钛矿TiO2的电学性质. 通过研究电阻率随压力变化的异常变化点, 观察到了TiO2从锐钛矿-柯铁矿-斜锆石的相变. 卸压后,电阻率和初始值相差2个数量级, 说明该相变为不可逆相变. 结合第一性原理计算结果表明, 柯铁矿结构更小的带隙是导致TiO2电阻率减小的根本原因. 相似文献
125.
采用紧束缚方法计算了石墨烯的价带(π)和导带(π*),考虑了非正交基矢下重叠矩阵效应,重叠积分参量s越小,导带越靠近费米面,而价带越远离费米面.在重叠积分参量s≤0.1时,基本保持了原子在实际空间中重叠所引起的能带的改变,太大(s=0.4)则会导致物理上失效.计算了石墨烯的能态密度,在费米面ε=0处(对应Dirac点)的能态密度为零,并且在Dirac点附近呈线性变化. 相似文献
126.
127.
利用平面波展开法,发现双原子正方晶格光子晶体中ΓM方向边界面存在着快慢两类边界模式,并且通过计算色散关系和电场分布研究了边界参量对这两类边界模式传输特性的影响.依据两种模式的色散关系,计算了群指数和群速度色散参量,结果表明边界参量的变化对第一类边界模式传输特性的影响较小,该模式的平均群指数始终维持在5.0左右;第二类边界模式与第一类模式明显不同,边界参量的变化能够有效地影响到这种模式的传输特性,该模式的最大平均群指数可达178左右.利用时域有限差分法记录了不同时刻电场强度在边界附近的分布及监测点处的电场幅度变化情况,结果表明,两类模式都能够被限制在边界附近并向前传播,时域有限差分法得到的群速度与平面波展开法的结果完全吻合. 相似文献
128.
《Current Applied Physics》2015,15(5):622-631
Lithium (Li) (0–5 wt%) doped V2O5 thin films were spray deposited at 450 °C onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V2O5 phase, presence of VO2 peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V2O5 samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V2O5 thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V2O5 film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V2O5 thin film to demonstrate the colour change. 相似文献
129.
A facile method is proposed to obtain microwave absorbing materials (MAMs), which possess strong microwave absorption properties in low‐frequency range. By simply mechanical mixing, the obtained Fe3O4–poly (3,4‐ethylenedioxythiophene) (PEDOT) hybrids exhibit more excellent microwave absorbing properties than that of Fe3O4 or PEDOT individually. The analysis on the microwave absorbing properties of the Fe3O4–PEDOT hybrids indicates that the excellent microwave absorbing properties are ascribed to several factors, like the dielectric loss, the interface polarization, eddy current effect, natural ferromagnetic resonance, and the impedance as well as the thickness of the coating. The Fe3O4–PEDOT hybrids with appropriate mass ratios of PEDOT to Fe3O4 (represented by (PEDOT)/(Fe3O4)) show superior microwave absorbing property at low frequency. When the thickness is 4 mm, the reflection loss of the sample reached ?15.8 dB at 3.2 GHz with (PEDOT)/(Fe3O4) of 3 and ?31.4 dB at 4.5 GHz with (PEDOT)/(Fe3O4) of 2, respectively. The obtained Fe3O4–PEDOT MAMs will have a promising application in the practical industry and commerce affairs. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
130.