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1.
Amorphous Si and Ge are doped with Mn by co-sputtering. The electrical conductivity is incresed by as much as a factor of 106~107 in some cases by the addition of several at .% Mn. The temperature dependence of the conductivity shows the variable range hopping conduction for both samples with and without Mn. The results can be interpreted by the presence of two conduction processes; the variable range hopping through dangling bonds and that through Mn sites. 相似文献
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Intervalley Umklapp matrix elements, with inclusion of local field screening effects, are computed for substitutional and interstitial point-charge impurity potentials in Si and Ge. The shallow character of substitutional donors is not affected in Ge and is even reinforced in Si, where a 20% reduction of the binding energy is obtained as a consequence of the local field effect. In both semiconductors the local field corrections strongly reinforce the non-effective-mass, deep-level character of interstitial point-charge donors. 相似文献
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ESR signal with hyperfine structure due to Mn and that due to dangling bonds are observed. From the magnitude of the hyperfine structure constant, Mn is considered to locate within voids without making a covalent bond with the host atom in the form of Mn2+. The intensity of the ESR signal due to dangling bonds decreases with the increase of that due to Mn, so it is likely that electrons are transfered from Mn to dangling bonds and their unpaired electrons are paired up. 相似文献
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A. F. Zinovieva V. A. Zinovyev A. I. Nikiforov V. A. Timofeev A. V. Mudryi A. V. Nenashev A. V. Dvurechenskii 《JETP Letters》2016,104(12):823-826
The luminescence properties of double Ge/Si quantum dot structures are studied at liquid helium temperature depending on the Si spacer thickness d in QD molecules. A seven-fold increase in the integrated photoluminescence intensity is obtained for the structures with optimal thickness d = 2 nm. This enhancement is explained by increasing the overlap integral of electron and hole wavefunctions. Two main factors promote this increasing. The first one is that the electrons are localized at the QD base edges and their wavefunctions are the linear combinations of the states of in-plane Δ valleys, which are perpendicular in k-space to the growth direction [001]. This results in the increasing probability of electron penetration into Ge barriers. The second factor is the arrangement of Ge nanoclusters in closely spaced QD groups. The strong tunnel coupling of QDs within these groups increases the probability of hole finding at the QD base edge, that also promotes the increase in the radiative recombination probability. 相似文献
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We study the electronic structure of the various charge states of a substitutional S impurity in Si in the tight-binding approximation. We take into account the changes in the diagonal elements of the host Hamiltonian on the impurity site and on its nearest neighbors and the changes in the off-diagonal elements between the impurity site and its nearest neighbors. Good agreement is found with experimental results and with more a priori calculations. 相似文献
6.
Rongjin Huang Laifeng Li Zhixiong Wu Xinxin Chu Xiangdong Xu Lihe Qian 《Solid State Communications》2010,150(35-36):1617-1620
Antiperovskite manganese nitrides (, 0.1, 0.15) were prepared and their negative thermal expansion, magnetic and specific heat properties were investigated. A frozen state with a freezing temperature was found at ~207 K in . This indicates that exhibits a spin glass state at low temperatures. We discussed the cause of spin glass behavior and correlated this spin glass behavior with broadening of the negative thermal expansion operation-temperature window of the manganese nitrides . 相似文献
7.
Oscillatory spectra and single-phonon state densities are calculated in the Keating atomic interaction model for the ultrathin superlattices Si3Ge1 and Si1Ge3. Fundamental features of the superlattice phonon spectra and their relationship to the spectra of Si and Ge crystals are analyzed. Conditions required for oscillation localization in the interface region are studied and the role of the Si-Ge bond in formation of interlayer oscillations is considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii. Fizika, No. 8, pp. 40–44, August, 1993. 相似文献
8.
Morellon L Arnold Z Magen C Ritter C Prokhnenko O Skorokhod Y Algarabel PA Ibarra MR Kamarad J 《Physical review letters》2004,93(13):137201
Effects of temperature and pressure on magnetic, elastic, structural, and thermal properties of Tb5Si2Ge2 have been studied by means of macroscopic (thermal expansion and magnetization) and microscopic (neutron powder diffraction) techniques. We present evidence that the high-temperature second-order ferromagnetic transition can be coupled with the low-temperature first-order structural phase change into a single first-order magnetic-crystallographic transformation at and above a tricritical point in the vicinity of 8.6 kbar. This pressure-induced coupling has a remarkable effect on the magnetocaloric effect, transforming Tb5Si2Ge2 from an ordinary into a giant magnetocaloric effect material. 相似文献
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基于密度泛函理论(DFT)的第一性原理计算方法,对本征Mn4Si7以及Ge,Al单掺杂和共掺杂Mn4Si7的晶体结构,能带结构,态密度以及光学性质进行了计算和分析.计算结果表明:本征态Mn4Si7的禁带宽度为0.810 eV,为直接带隙半导体材料,掺杂后晶体结构稍微变化,禁带宽度减小,且共掺杂时禁带宽度最小,电导率最好.Al以及Ge,Al共同掺杂时会产生杂质能级.掺杂后光子能量向低能级方向移动,光电导率,光吸收,反射系数都有所增大,说明掺杂改善了Mn4Si7的光学性质,从而可以提高光伏发电效率. 相似文献
13.
H. Höhler N. Atodiresei K. Schroeder R. Zeller P. H. Dederichs 《Hyperfine Interactions》2004,158(1-4):37-40
We examine the electronic and geometrical structure of impurity-vacancy complexes for 11 sp-impurities in Si and Ge, using
the pseudopotential plane wave (PPW) and the all-electron Kohn–Korringa–Rostoker (KKR) methods. We find that all impurities
of the 5sp and 6sp series prefer the split-vacancy configuration. For Cd and Sn we obtain good agreement of the calculated
hyperfine parameters with experimental PAC and EPR data. Impurities of the 3sp and 4sp series form distorted substitutional
complexes (except Al, which forms a split complex in Si). This trend strongly correlates with the lattice relaxations of nearest
neighbors around the isolated (without vacancy) substitutional impurities. 相似文献
14.
研究了自组织生长SiGe岛(量子点)中Si组分对形状演化的影响.采用UHV/CVD方法生长了 不同Si组分的SiGe岛,用AFM对其形状和尺寸分布进行了分析,实验结果表明SiGe岛从金字 塔形向圆顶形转变的临界体积随Si组分的增大而增大.通过对量子点能量的应变能项进行修正,解释了量子点中Si组分对形状演化的影响.在特定的工艺条件下得到了单模尺寸分布的 金字塔和圆顶形量子点.结果表明,通过调节SiGe岛中的Si组分,可以实现对SiGe岛形状和 尺寸的控制.
关键词:
自组织生长SiGe岛
Si组分
临界体积 相似文献
15.
The anisotropic thermoelectric transport properties of bulk silicon strained in the [111]-direction were studied by detailed first-principles calculations focusing on a possible enhancement of the power factor. Electron and hole doping were examined in a broad doping and temperature range. At low temperature and low doping an enhancement of the power factor was obtained for compressive and tensile strain in the electron-doped case and for compressive strain in the hole-doped case. For the thermoelectrically more important high-temperature and high-doping regime a slight enhancement of the power factor was only found under small compressive strain with the power factor overall being robust against applied strain. To extend our findings the anisotropic thermoelectric transport of a [111]-oriented Si/Ge superlattice was investigated. Here, the cross-plane power factor under hole doping was drastically suppressed due to quantum-well effects, while under electron doping an enhanced power factor was found. For this, we state figures of merit of ZT?=?0.2 and 1.4 at T?=?300?and 900?K for the electron-doped [111]-oriented Si/Ge superlattice. All results are discussed in terms of band structure features. 相似文献
16.
The low frequency velocity of sound for a Young's modulus mode in sputtered amorphous films of Ge and Si is found to be only ~55?60% of the value expected for the crystalline state. The reduction is one of the largest associated with crystalline-amorphous polymorphs. 相似文献
17.
L. Liu 《Solid State Communications》1978,25(10):805-807
The effect of the non-parabolicity of the valence band on the electron-hole droplets in Si and Ge under a large uniaxial stress is discussed. It is found that this stress-induced band feature helps to lower the ground state energy of the droplet relative to that of the free excitons. 相似文献
18.
B. D. Patterson E. Holzschuh R. F. Kiefl K. W. Blazey T. L. Estle 《Hyperfine Interactions》1984,18(1-4):599-602
Measurements of the normal muonium depolarization rate in high purity silicon and germanium have been performed between 1.5 and 4.2 K. Two different Si samples and one Ge sample were investigated in a transverse field of 5 G, and in all cases, a temperature-independent depolarization rate was observed. The silicon results disagree with earlier work which showed a depolarization rate which decreased with increasing temperature in this temperature range. These results are compared with measurements of the direct muonium hyperfine transition.The authors wish to acknowledge the support of the N.S.F. grant DMR-79-09223. 相似文献
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A. G. Milekhin A. I. Nikiforov O. P. Pchelyakov S. Schulze D. R. T. Zahn 《JETP Letters》2001,73(9):461-464
Ge/Si superlattices containing Ge quantum dots were prepared by molecular beam epitaxy and studied by resonant Raman scattering. It is shown that these structures possess vibrational properties of both two-and zero-dimensional objects. The folded acoustic phonons observed in the low-frequency region of the spectrum (up to 15th order) are typical for planar superlattices. The acoustic phonon lines overlap with a broad emission continuum that is due to the violation of the wave-vector conservation law by the quantum dots. An analysis of the Ge and Ge-Si optical phonons indicates that the Ge quantum dots are pseudoamorphous and that mixing of the Ge and Si atoms is insignificant. The longitudinal optical phonons undergo a low-frequency shift upon increasing laser excitation energy (2.54–2.71 eV) because of the confinement effect in small-sized quantum dots, which dominate resonant Raman scattering. 相似文献