Reduction of Thermal Stress in Mbe Grown GaAs/Si by Patterning

1989 ◽  
Vol 145 ◽  
Author(s):  
J. P. Van Der Ziel ◽  
Naresh Chand ◽  
J. S. Weiner
Keyword(s):  
Thermal Stress ◽  
Tensile Stress ◽  
Layer Thickness ◽  
No Reduction ◽  
Stress Relief ◽  
Patterned Growth ◽  
A Value ◽  
Pattern Size ◽  
Biaxial Tensile Stress ◽  
Weakly Dependent

AbstractThe biaxial tensile stress of 2.65 kbar in as-grown GaAs/Si for T < 100K is reduced by post-growth patterning of the GaAs and the reduction in stress, as determined by photoluminescence and cathodoluminescence, is dependent on the pattern size and shape. For stripe patterns less than 15 gm wide the stress is largely uniaxial with stress relief normal to the stripe direction. Rectangular patterns exhibited stress relief in orthogonal directions, and a 9 x 12 µm2 rectangle exhibited an average stress of 0.5 kbar. For as-grown GaAs/Si layers 0.9 to 3.25 µm thick, the stress is weakly dependent on layer thickness. For T > looK the stress in as-grown GaAs/Si is reduced and at 295K a value of 1.51 ± 0.21 kbar is obtained. With patterned growth, using a native SiO2 mask, no reduction in stress was observed irrespective of the pattern size, indicating the importance of free GaAs edges in obtaining stress relief.

scholarly journals UV Nanoimprint Lithography: Geometrical Impact on Filling Properties of Nanoscale Patterns

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 822
Author(s):  
Christine Thanner ◽  
Martin Eibelhuber
Keyword(s):  
Layer Thickness ◽  
Process Parameters ◽  
Nanoimprint Lithography ◽  
Failure Modes ◽  
Production Method ◽  
Efficient Production ◽  
Comprehensive Overview ◽  
Replication Method ◽  
Wide Range ◽  
Pattern Size

Ultraviolet (UV) Nanoimprint Lithography (NIL) is a replication method that is well known for its capability to address a wide range of pattern sizes and shapes. It has proven to be an efficient production method for patterning resist layers with features ranging from a few hundred micrometers and down to the nanometer range. Best results can be achieved if the fundamental behavior of the imprint resist and the pattern filling are considered by the equipment and process parameters. In particular, the material properties and pattern size and shape play a crucial role. For capillary force-driven filling behavior it is important to understand the influencing parameters and respective failure modes in order to optimize the processes for reliable full wafer manufacturing. In this work, the nanoimprint results obtained for different pattern geometries are compared with respect to pattern quality and residual layer thickness: The comprehensive overview of the relevant process parameters is helpful for setting up NIL processes for different nanostructures with minimum layer thickness.

Effects of Stress-Relief Annealing on the Residual Stress and the Microstructure of TA15 Welded Joint

2016 ◽  
Vol 849 ◽  
pp. 281-286 ◽  
Author(s):  
Teng Ma ◽  
Xiao Yun Song ◽  
Wen Jun Ye ◽  
Song Xiao Hui ◽  
Rui Liu
Keyword(s):  
Residual Stress ◽  
Tensile Stress ◽  
Fusion Zone ◽  
Maximum Stress ◽  
Electron Beam Welding ◽  
Welded Joint ◽  
Stress Relief ◽  
Welding Zone ◽  
Weave Structure ◽  
Effects Of Stress

The effects of stress-relief annealing on the distribution of residual stress and on the microstructure of TA15 (Ti-6.5Al-2Zr-1Mo-1V) alloy joints by electron beam welding (EBW) were investigated. The results indicated that the microstructure of welded joint presented a transitional change, i.e. basket-weave structure appeared in the fusion zone while equiaxed α structure in base metal. No significant change occurred in microstructure after annealing at 650°C for 2 h. The residual stress in fusion zone was mainly tensile stress and the maximum longitudinal stress value was 473MPa. After annealing, the residual stress near the welded joint exhibited a uniform distribution and the maximum stress droped to 150 MPa. The yield stress and tensile stress of the TA15 welding zone were 1016 MPa and 1100 MPa respectively.

Determination of the Biaxial Anisotropy Coefficient Using a Single Layer Sheet Metal Compression Test

2021 ◽  
Vol 883 ◽  
pp. 303-308
Author(s):  
Peter Hetz ◽  
Matthias Lenzen ◽  
Martin Kraus ◽  
Marion Merklein
Keyword(s):  
Stress State ◽  
Tensile Stress ◽  
Sheet Metal ◽  
Compression Test ◽  
Test Procedure ◽  
Rolling Direction ◽  
Single Layer ◽  
Material Behavior ◽  
Biaxial Tensile ◽  
Biaxial Tensile Stress

Numerical process design leads to cost and time savings in sheet metal forming processes. Therefore, a modeling of the material behavior is required to map the flow properties of sheet metal. For the identification of current yield criteria, the yield strength and the hardening behavior as well as the Lankford coefficients are taken into account. By considering the anisotropy as a function of rolling direction and stress state, the prediction quality of anisotropic materials is improved by a more accurate modeling of the yield locus curve. According to the current state of the art, the layer compression test is used to determine the corresponding Lankford coefficient for the biaxial tensile stress state. However, the test setup and the test procedure is quite challenging compared to other tests for the material characterization. Due to this, the test is only of limited suitability if only the Lankford coefficient has to be determined. In this contribution, a simplified test is presented. It is a reduction of the layer compression test to one single sheet layer. So the Lankford coefficient for the biaxial tensile stress state can be analyzed with a significantly lower test effort. The results prove the applicability of the proposed test for an easy and time efficient characterization of the biaxial Lankford coefficient.

scholarly journals Calculations of energy band structure and mobility in critical bandgap strained Ge1-xSnx based on Sn component and biaxial tensile stress modulation

2018 ◽  
Vol 67 (2) ◽  
pp. 027101
Author(s):  
Di Lin-Jia ◽  
Dai Xian-Ying ◽  
Song Jian-Jun ◽  
Miao Dong-Ming ◽  
Zhao Tian-Long ◽  
...  
Keyword(s):  
Band Structure ◽  
Tensile Stress ◽  
Energy Band ◽  
Energy Band Structure ◽  
Biaxial Tensile ◽  
Biaxial Tensile Stress

Influence of Heat Insulation Material on Thermal Stress of Long Nozzle

2012 ◽  
Vol 535-537 ◽  
pp. 1609-1614 ◽  
Author(s):  
Hui Min Liu
Keyword(s):  
Thermal Stress ◽  
Layer Thickness ◽  
Outer Layer ◽  
Heat Insulation ◽  
Outer Wall ◽  
Symmetric Model ◽  
Insulation Material ◽  
Axially Symmetric ◽  
Coefficient Of Thermal Conductivity ◽  
Heat Insulation Material

To prevent a long nozzle (LN) of non-preheating from rupture caused by thermal shock, heat insulation material (HIM) with a lower coefficient of thermal conductivity (CTC) was compounded in the inner hole (inner layer) or around the outer wall (outer layer), and the thermal stress was investigated. The two-dimension axially symmetric model of LN was proposed by simplifying the structure and boundary conditions. The influences of the HIM to the thermal stress of LN were analyzed by finite element method. The results show that the thermal stress suffered by LN can be drastically reduced by the inner layer, making the slow variation, but when its thickness increases from 2 mm to 3 mm, it almost has no influence on the thermal stress. The maximum thermal stress at the neck of LN reduces with the depression of the CTC at the inner layer thickness of 2 mm. The maximum thermal stress of LN can’t be reduced by outer layer, but the lasting time of higher stress can be shortened, and the thermal stress at the later period of steel-irrigating can be lowed. When the outer layer thickness is more than 2 mm, the increase of it has little influence on the thermal stress of LN, and the change of its CTC has little influence on the thermal stress either. The LN with tri-layer has lower thermal stress during all the period of steel-irrigating.

Analytical Solutions for Flexural Stress of One-way UHPC-NC Hybrid Slab

2019 ◽  
Author(s):  
Zhao Liu ◽  
Wei D. Zhuo ◽  
Si Q. Yuan
Keyword(s):  
Tensile Stress ◽  
Layer Thickness ◽  
Analytical Solutions ◽  
High Performance Concrete ◽  
Limit State ◽  
Neutral Axis ◽  
Thickness Ratio ◽  
Slab Thickness ◽  
Flexural Stress ◽  
Axis Position

<p>Ultra‐high performance concrete (UHPC) is an advanced construction material that affords opportunities to innovate the structures made of conventional concrete (NC). The one‐way UHPC‐NC hybrid slab, designed to have the UHPC layer in tension and the NC layer in compression, can be an optimal use of UHPC for bridge deck. The analytical solutions for normal stress are essential under service limit state, but they cannot be found in the literature by now. Based on the elastic theory, analytical formulas for the neutral axis position and flexural stress are derived. The lowest neutral axis position is attained when the UHPC layer thickness ratio (UHPC layer thickness / hybrid slab thickness) approximates 0.4. The criteria to judge the position of neutral axis within UHPC or NC region are analytically established. To find out the ideal scenario to reach the allowable compressive stress in NC and allowable tensile stress in UHPC simultaneously, an inequality constraint with the elastic modulus ratio is proposed. Considering the UHPC tensile stress limitation and flexural moment capacity of the hybrid slab, the rational thickness ratio of UHPC layer of 0.4 is suggested, which can achieve better economy and efficiency of the hybrid slab.</p>

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