Papers by Keyword: Strain Relaxation

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Authors: Wolfgang Gruber, Florian Strauß, Harald Schmidt
Abstract: Self-diffusion in thin nanocrystalline Pt films was investigated using secondary ion mass spectrometry. Our experiments are motivated by recent investigations on stress relaxation where self-diffusion of Pt is supposed to play an important role, especially at temperatures below 250 °C and annealing times of a few hours. For the diffusion experiments, double layers of natPt/194Pt were deposited on oxidized silicon wafers using ion beam sputtering. At 180 °C no significant diffusion induced broadening of the profiles could be observed even after an annealing time of 64 h. However, the concentration of 195Pt in the top layer decreases slightly after an annealing time of 16 h and remains constant for higher annealing times. At 600 °C a broadening of the profiles was observed after an annealing time of 5 minutes. From our results we conclude that at 180 °C only atoms in the grain boundaries are mobile. After about 16 h the isotopes in the grain boundaries are completely interdiffused. From the change of the 195Pt concentration in the top layer we estimate the amount of grain boundary phase in the Pt films to be about 5 %. The broadening of the profile after annealing at 600 °C is attributed to bulk diffusion.
Authors: O. Yastrubchak, T. Wosiński, J.Z. Domagała, E. Łusakowska
Abstract: Partially relaxed III–V heterostructures: GaAs/InGaAs and InP/InAlAs/InGaAs, with a small lattice mismatch, grown using molecular beam epitaxy under compressive or tensile misfit stress at the (001) interface, have been investigated by means of high-resolution X-ray diffractometry, atomic force microscopy and generalized ellipsometry. Additionally, transmission electron microscopy and electron-beam induced current in a scanning electron microscope have been employed to reveal misfit dislocations at the heterostructure interface. Chemical etching was used to determine polarity of the crystals and threading dislocation densities in the epitaxial layers. Our findings are interpreted in terms of the dependent on growth conditions, material’s composition and doping glide velocities of two types of misfit dislocations: α and β, differing in their core structure and lying along two orthogonal 〈110〉 crystallographic directions at the (001) interface.
Authors: B. Daudin, F. Widmann, G. Feuillet, Y. Samson, J.-L. Rouvière, N. Pelekanos
Authors: Hyo Seon Park, W.H. Lee, K.S. Yun, Hong C. Rhim
Abstract: A wide variety of residual stress measurement methods can be used to measure the axial stress in a column. One of the most widely used techniques for measuring residual stress is slotting method since it is relatively simple and cost-effective to implement at vertical columns in field. However, the slotting method is considered to be semi-destructive or destructive method depending on the amount of material to be removed. Therefore, in this paper, optimal depth of slots for measuring actual stress is presented to minimize the amount of material to be removed. Finite element method is used to estimate the minimum depth of the slot in H-shaped steel column. By performing actual saw cutting, optimality of the simulated depth of the slot is investigated.
Authors: Y. Bogumilowicz, J.M. Hartmann, F. Laugier, G. Rolland, Thierry Billon
Abstract: We have focused in this paper on the impact of the growth rate and of the grading rate on the structural properties of Si0.8Ge0.2 virtual substrates grown at 900°C in a commercial reduced pressure chemical vapour deposition reactor. Adopting a grading rate of 4% Ge / $m together with a growth rate around 140 nm min.-1 yields very high quality Si0.8Ge0.2 virtual substrates. Their macroscopic degree of strain relaxation is indeed very close to 100%, their surface root mean square roughness is around 2.3 nm and most importantly their field threading dislocation density is of the order of 6x104 cm-2 only, with almost no pile-ups.
Authors: M. Kamruzzaman Chowdhury, B. Vissouvanadin, Mireia Bargallo Gonzalez, N. Bhouri, Peter Verheyen, H. Hikavyy, O. Richard, J. Geypen, H. Bender, Roger Loo, Cor Claeys, Eddy Simoen, V. Machkaoutsan, P. Tomasini, S.G Thomas, J.P. Lu, J.W. Weijtmans, R. Wise
Abstract: This paper presents an investigation of the impact of a Highly Doped Drain (HDD) implantation after epitaxial deposition on Si1-xGex S/D junction characteristics. While the no HDD diodes exhibit the usual scaling of the leakage current density with Perimeter to Area (P/A) ratio, this is not the case for the HDD diodes, showing a smaller perimeter current density JP for smaller window size structures, corresponding with larger P/A. This points to a lower density of surface states at the Shallow Trench Isolation (STI)/silicon interface, which could result from a lower compressive stress. In order to examine the role of the HDD implantation damage, Transmission Electron Microscopy (TEM) inspections have been undertaken, which demonstrate the presence of stacking faults in small active SiGe regions. These defects give rise to local strain relaxation and, therefore, could be at the origin of the lower STI/Si interface state density. The window size effect then comes from the active area dependence of the implantation defect formation.
Authors: Sook Hyun Hwang, Yu Mi Park, Hoon Ha Jeon, Kyung Seok Noh, Jae Kyu Kim, Joon He Moon, Han Jung Song, Jae Young Leem, Min Hyon Jeon
Abstract: We have grown delta-doped In0.5Ga0.5As /In0.5Al0.5As heterostructures on GaAs substrate applying with InxAl1-xAs compositional graded-step buffers, called metamorphic structures, grown by molecular beam epitaxy. Three types of buffer layers with different compositional gradients and thicknesses have designed to investigate the influence of the strain relaxation process. We characterized the samples by using transmission electron microscopy, triple-axis X-ray diffraction and Hall measurement. Two samples with different compositional gradient show almost same results in electrical properties. On the other hand, it is found that samples with different step thicknesses had shown the large differences in epilayer tilt and mosaic spread in the step-graded buffers. These results indicate that there exists an interrelation between the strain-relaxed buffer and 2DEG transport properties.
Authors: G. Leo, T. Peluso, N. Lovergine, Anna Maria Mancini, L. Vasanelli, C. Giannini, L. Tapfer, F. Romanato, A.V. Drigo
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