共查询到19条相似文献,搜索用时 203 毫秒
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本文用X射线径向分布函数法研究了室温到1000℃不同退火条件下的纳米非晶氮化硅样品的微结构和键合特征。观察到占庞大体积百分数界面不是“gas-like”结构,而是与非晶纳米粒子不同的新的短程序结构。Si—N键长和最近邻原子配位数(CN)均比传统Si3N4小,并存在大量的Si悬键和不饱和键。纳米氮化硅与传统Si3N4饱和共价键不同,是含有大量非饱和键和悬键的非典型共价键结构。由于键配位的不饱和特征,纳米非晶氮化硅的分子式应写作Si3-xN4-y。纳米非晶氮化硅出现强极性与非饱和键和悬键有密切的关系。
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利用原位扫描隧道显微镜和低能电子衍射分析了Si的纳米颗粒在Si3N4/Si(111)和Si3N4/Si(100)表面生长过程的结构演变.在生长早期T为350—1075K范围内,Si在两种衬底表面上都形成高密度的三维纳米团簇,这些团簇的大小均在几个纳米范围内,并且在高温退火时保持相当稳定的形状而不相互融合.当生长继续时,Si的晶体小面开始显现.在晶态的Si3N4(0001)/S
关键词:
氮化硅
扫描隧道显微镜
纳米颗粒 相似文献
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采用反应磁控溅射法制备了一系列具有不同Si3N4层厚度的AlN/Si3N4纳米多层膜,利用X射线衍射仪、高分辨透射电子显微镜和微力学探针表征了多层膜的微结构和力学性能.研究了Si3N4层在AlN/Si3N4纳米多层膜中的晶化现象及其对多层膜生长结构与力学性能的影响.结果表明,在六方纤锌矿结构的晶体AlN调制层的模板作用下,通常溅射条件下以非晶态存在的Si3N4层在其厚度小于约1nm时被强制晶化为结构与AlN相同的赝形晶体,AlN/Si3N4纳米多层膜形成共格外延生长的结构,相应地,多层膜产生硬度升高的超硬效应.Si3N4随层厚的进一步增加又转变为非晶态,多层膜的共格生长结构因而受到破坏,其硬度也随之降低.分析认为,AlN/Si3N4纳米多层膜超硬效应的产生与多层膜共格外延生长所形成的拉压交变应力场导致的两调制层模量差的增大有关.
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3N4纳米多层膜')" href="#">AlN/Si3N4纳米多层膜
外延生长
赝晶体
超硬效应 相似文献
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本文研究了掺杂(B和P)和未掺杂的a-Si1-xCx:H和a-Si1-xNx:H膜在高温下的电子自旋共振(ESR)特性。ESR的测量是在温度连续变化的过程中进行的。实验结果表明:掺B的a-Si1-xCx:H和a-Si1-xNx:H膜的ESR吸收谱,可以分解成两种性质不同的ESR吸收谱的叠加(g1≈2.005和g2≈2.010),g1是硅悬挂键(Si)的贡献,g2是价带尾态定域化空穴的贡献。随温度的上升,定域化空穴的密度比Si下降得更快。在温度不太高时,定域化空穴的密度远大于Si,但在温度较高时,Si的贡献是主要的。
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用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G*基组水平上对(Ca3N2)n(n=1—4)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构.并对最稳定结构的振动特性、成键特性、电荷特性和稳定性等进行了理论分析.结果表明,(Ca3N2)n(n=1—4)团簇最稳定构型中N原子为3—5配位,Ca—N键长为0.231—0.251nm,Ca—Ca键长为0.295—0.358nm;N原子的自然电荷在-1.553e—-2.241e之间,Ca原子的自然电荷在1.035e—1.445e之间,Ca和N原子间相互作用呈现较强的离子性,Ca3N2和(Ca3N2)3团簇有相对较高的动力学稳定性.
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3N2)n(n=1—4)团簇')" href="#">(Ca3N2)n(n=1—4)团簇
密度泛函理论
结构与性质 相似文献
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利用脉冲激光沉积的方法制备掺铒 Si/Al2O3多层结构薄膜,获得了由纳米结构的Si作为感光剂增强的Er3+在1.54 μm高效发光.利用拉曼散射、高分辨透射电镜和光致发光测量研究了在不同退火温度下(600—1000 ℃)纳米结构Si层的结晶形态变化,及对Er3+在1.54 μm的发光的影响特征.研究发现最佳发光是在退火温度600—700 ℃.在这个条件下纳米Si的尺寸和密度,Si和Er的作用距离以及Er3+
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铒
纳米硅
能量转移
氧化铝 相似文献
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采用非晶半导体中间层键合(SIB)实现键合界面失配晶格的阻断是实现高质量Si基InGaAs薄膜制备的最佳选择。本文在InGaAs/Si键合界面插入一层非晶锗硅(a-Si1-xGex)键合层,模拟了不同Ge组分对InGaAs/Si APD复合率、能带、隧穿、电荷堆积等参数的影响。器件在室温下获得极低的暗电流(~10-10A@95%雪崩电压),增益和增益带宽积分别高达30 GHz和60 GHz。本文将为低噪声近红外APD的研制提供理论指导。 相似文献
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G GimmlerM Havenith 《Journal of Molecular Spectroscopy》2002,216(2):315-321
We report high-resolution infrared vibrational-rotational spectra of the weakly bound complexes N2O-H2O and N2O-D2O in the higher frequency N2O stretching mode region (ν3=2223.756693(124) cm−1). The measurements were carried out using a free jet expansion in combination with a lead salt diode laser spectrometer. Rotational constants, quartic centrifugal distortion constants, and band origins have been derived for both isotopomers. The geometrical structure is determined using isotopic substitution. The deduced structure shows evidence for a second hydrogen bond interaction within the complex. The nonrigidity of the complexes gives rise to an internal rotation of the water molecule around its own C2v symmetry axis. For N2O-H2O, a tunneling splitting arising from this internal motion has been observed in the spectra. According to symmetry considerations, the observed splitting in the spectrum of N2O-H2O corresponds to the difference between the tunneling frequencies in the ground and vibrationally excited states. 相似文献
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4fN-15d energy levels of lanthanides: aquasi-angular-momentum approach and its application to Cs2NaYF6:Er3+ 下载免费PDF全文
<正>The spin-orbit interaction of the 5d electron needs to be taken into account to give the proper energy structure for the 4fN-15d configuration of heavy lanthanide ions occupying a site with ligands forming an octahedron.This paper derives theoretical results for the energy structure by treating the t2 orbitals as quasi p orbitals and then using angular-momentum coupling techniques.An analytic expression for the electric dipole absorption line strengths between 4fN multiplets and 4fN-15d states is given in terms of various angular-momentum quantum numbers and re-coupling coefficients.The result is then applied to interpret the excitation spectrum of Cs2NaYF6:Er3+.The high-spin and low-spin states of Cs2NaYF6:Er3+ are discussed in terms of the wavefunctions obtained by using the developed theoretical model. 相似文献
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The Al Kα excited M4,5N4,5N4,5 Auger spectrum of Ba has been measured from the metallic sample evaporated on a Ag substrate. The spectrum has been decomposed into individual line components after the background subtraction. The decomposed spectrum has been compared with the theoretical spectrum calculated for the 4d?2 final state configuration in the mixed coupling scheme applying jj-coupling for the initial state and intermediate coupling for the final state. The most prominent structure of the spectrum shows the two 4d-hole coupling, but the structure which is caused by the Auger transitions M,45N2,3V has also been observed. The screening of the core holes in Ba metal seems to be produced by (5d6s) electrons. The simple excited atom model HF-calculations give an Auger kinetic energy shift (metal-free atom) of 16.7 eV, which is comparable to the experimental value 14–18 eV. 相似文献
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The structural, electronic and thermodynamic properties of cubic Zn3N2 under hydrostatic pressure up to 80 GPa are investigated using the local density approximation method with pseudopotentials of the ab initio norm-conserving full separable Troullier-Martin scheme in the frame of density functional theory. The structural parameters obtained at ambient pressure are in agreement with experimental data and other theoretical results. The change of bond lengths of two different types of Zn-N bond with pressure suggests that the tetrahedral Zn-N bond is slightly less compressible than the octahedral bond. By fitting the calculated band gap, the first and second order pressure coefficients for the direct band gap ofthe Zn3N2 were determined to be 1.18×10−2 eV/GPa and −2.4×10−4 eV/(GPa)2, respectively. Based on the Mulliken population analysis, Zn3N2 was found to have a higher covalent character with increasing pressure. As temperature increases, heat capacity, enthalpy, product of temperature and entropy increase, whereas the Debye temperature and free energy decrease. The present study leads to a better understanding of how Zn3N2 materials respond to compression. 相似文献
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V. A. Gritsenko Yu. N. Novikov A. V. Shaposhnikov H. Wong G. M. Zhidomirov 《Physics of the Solid State》2003,45(11):2031-2035
The electronic structure and capturing properties of threefold coordinated silicon atoms (≡Si·) and the Si-Si bond in silicon nitride (Si3N4) were studied using the ab initio density functional theory. The results show that the previously proposed negative correlation energy (NCE) model is not applicable to Si3N4. The NCE model was proposed for interpreting the absence of the ESR signal for threefold coordinated silicon defects and suggested that an electron can transfer between two silicon defects. We proposed that the absence of this ESR signal is due to the creation of neutral diamagnetic Si-Si defects in Si3N4. This model offers the most fundamental theory for explaining the hole localization (memory) effect in silicon nitride. 相似文献
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本文利用分子光谱理论系统的计算和分析N2第二正带系(C3∏u→B3∏g)的发射光谱, 以研究光谱强度的分布规律与不同温度条件和气体条件的关系. 基于N2的三重态能级结构特性, 重点计算和讨论了发射光谱的概个重要参数: 通过求解高、低电子态的哈密顿矩阵得到了振转能级特性; 利用r质心近似法求取了能级间跃迁的电偶极矩函数和爱因斯坦跃迁概率; 进而计算了不同振动和转动温度条件下谱线的强度分布. 进行了N2和Ar的混合放电实验, 利用实验光谱数据同理论结果进行拟合分析, 确定了N2分子的振动温度和转动温度分别约为4300 K和800 K. 另外由于潘宁离化效应, N2浓度减小时谱线强度呈现先增强后减弱的趋势. 实验结果很好的验证了N2第二正带系光谱理论计算的正确性. 相似文献