In Situ Thin Film Stress Measurements – A Path to Understanding the Structure and Morphology of Electron Beam Evaporated ZnS

2002 ◽  
Vol 749 ◽  
Author(s):  
Vincent Barrioz ◽  
Stuart J. C. Irvine ◽  
D. Paul
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Electron Beam ◽  
Stress Reduction ◽  
Float Glass ◽  
Film Stress ◽  
Intrinsic Stress ◽  
Ex Situ ◽  
Stress Measurements

ABSTRACTZnS is a material of choice in the optical coating industry for its optical properties and broad transparency range. One of the drawbacks of ZnS is that it develops high compressive intrinsic stress resulting in large residual stress in the deposited layer. This paper concentrates on the evolution of residual stress reduction in ZnS single layers, depending upon their deposition rate or the substrate temperature during deposition (i.e. 22 °C and 133 °C). The substrate preparation is addressed for consideration of layer adhesion. Residual stress of up to − 550 MPa has been observed in amorphous/poor polycrystalline ZnS layers, deposited on CMX and Float glass type substrates, by electron beam evaporation at 22 °C, with a surface roughness between 0.4 and 0.8 nm. At 133 °C, the layer had a surface roughness of 1 nm, the residual stress in the layer decreased to − 150 MPa, developing a wurtzite structure with a (002) preferred orientation. In situ stress measurements, using a novel optical approach with a laser-fibre system, were carried out to identify the various sources of stress. A description of this novel in situ stress monitor and its advantages are outlined. The residual stress values were supported by two ex situ stress techniques. The surface morphology analysis of the ZnS layers was carried out using an atomic force microscope (AFM), and showed that stress reduced layers actually gave rougher surfaces.

scholarly journals Thin film stress and microstructure analysis by energy-dispersive diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C724-C724
Author(s):  
Christoph Genzel
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Residual Stress ◽  
Film Growth ◽  
High Energy ◽  
Energy Dispersive ◽  
Film Stress ◽  
Ex Situ ◽  
Near Surface

The most important advantage of energy dispersive (ED) diffraction compared with angle dispersive methods is that the former provides complete diffraction patterns in fixed but arbitrarily selectable scattering directions. Furthermore, in experiments that are carried out in reflection geometry, the different photon energies E(hkl) of the diffraction lines in an ED diffraction pattern can be taken as an additional parameter to analyze depth gradients of structural properties in the materials near surface region. For data evaluation advantageous use can be made of whole pattern methods such as the Rietveld method, which allows for line profile analysis to study size and strain broadening [1] or for the refinement of models that describe the residual stress depth distribution [2]. Concerning polycrystalline thin films, the features of ED diffraction mentioned above can be applied to study residual stresses, texture and the microstructure either in ex-situ experiments or in-situ to monitor, for example, the chemical reaction pathway during film growth [3]. The main objective of this talk is to demonstrate that (contrary to a widespread opinion) high energy synchrotron radiation and thin film analysis may fit together. The corresponding experiments were performed on the materials science beamline EDDI at BESSY II which is one of the very few instruments worldwide that is especially dedicated to ED diffraction. On the basis of selected examples it will be shown that specially tailored experimental setups allow for residual stress depth profiling even in thin films and multilayer coatings as well as for fast in situ studies of film stress and microstructure evolution during film growth.

Intrinsic Stress Measurements in CVD Diamond Films

1999 ◽  
Vol 593 ◽  
Author(s):  
Jin Yu ◽  
J.G. Kim ◽  
Y. C. Sohn ◽  
Y. S. Lee
Keyword(s):  
Film Thickness ◽  
Diamond Films ◽  
Strain Analysis ◽  
Chemical Vapor ◽  
Film Stress ◽  
Intrinsic Stress ◽  
Ex Situ ◽  
Chemical Vapor Deposition Method ◽  
Si Substrate ◽  
Curvature Measurements

ABSTRACTDiamond films were grown over Si substrate at 1253K by the hot filament chemical vapor deposition method using CH4/H2 gas mixture, and intrinsic stresses in the film were deduced from the ex-situ curvature measurements. In order to account for the creep deformation of the Si substrate, an elastic/plastic stress and strain analysis were conducted. Results showed that intrinsic stresses were generally several times larger than the average film stresses and always positive increasing with the film thickness. For the film thickness larger than 10μm, stress relaxation by creep of the substrate became significant, and must be considered for the accurate assessment of the film stress in diamond. Later, an analysis based on the grain growth accounted for the development of intrinsic stresses reasonably well

scholarly journals Visualizing Ligand-Mediated Bimetallic Nanocrystal Formation Pathways with In Situ Liquid Phase Transmission Electron Microscopy Synthesis

2020 ◽  
Author(s):  
Mei Wang ◽  
Asher Leff ◽  
Yue Li ◽  
Taylor Woehl
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Ex Situ ◽  
Formation Mechanisms ◽  
Transmission Electron ◽  
Thiolate Complexes ◽  
Nanocrystal Formation ◽  
Phase Transmission

Colloidal synthesis of alloyed multimetallic nanocrystals with precise composition control remains a challenge and a critical missing link in theory-driven rational design of functional nanomaterials. Liquid phase transmission electron microscopy (LP-TEM) enables directly visualizing nanocrystal formation mechanisms that can inform discovery of design rules for colloidal multimetallic nanocrystal synthesis, but it remains unclear whether the salient chemistry of the flask synthesis is preserved in the extreme electron beam radiation environment during LPTEM. Here we demonstrate controlled in situ LP-TEM synthesis of alloyed AuCu nanoparticles while maintaining the molecular structure of electron beam sensitive metal thiolate precursor complexes. Ex situ flask synthesis experiments showed that nearly equimolar AuCu alloys formed from heteronuclear metal thiolate complexes, while gold-rich alloys formed in their absence. Systematic dose rate-controlled in situ LP-TEM synthesis experiments established a range of electron beam synthesis conditions that formed alloyed AuCu nanoparticles with similar alloy composition, random alloy structure, and particle size distribution shape as those from ex situ flask synthesis, indicating metal thiolate complexes were preserved under these conditions. Reaction kinetic simulations of radical-ligand reactions revealed that polymer capping ligands acted as effective hydroxyl radical scavengers during LP-TEM synthesis and prevented metal thiolate oxidation at low dose rates. In situ synthesis experiments and ex situ atomic scale imaging revealed that a key role of metal thiolate complexes was to prevent copper atom oxidation and facilitate formation of prenucleation cluster intermediates. This work demonstrates that complex ion precursor chemistry can be maintained during LP-TEM imaging, enabling probing nanocrystal formation mechanisms with LP-TEM under reaction conditions representative of ex situ flask synthesis.

Residual Stress Modelling in a Thick-Sectioned Electron Beam Weld

2013 ◽  
Author(s):  
Ben Pellereau ◽  
Chris Gill ◽  
Paul Hurrell ◽  
Ed Kingston
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Electron Beam ◽  
Heat Source ◽  
Material Model ◽  
Hole Drilling ◽  
Electron Beam Weld ◽  
Element Analysis ◽  
Stress Measurements ◽  
Mesh Density

Previous work presented residual stress measurements in an electron beam weld in a thick section ferritic forging [1]; this weld was also modelled using finite element analysis. Due to the tool used to model the heat source, the mesh density in the region of the weld was limited. This work improves on the previous work by using a DFLUX subroutine to provide a mesh-independent heat source input, allowing a better mesh in the region of the weld. The modelling was carried out in Abaqus[2] using the VFT[3] user material model to allow phase transformation effects to be included. This however does not include creep properties and so the as-welded stresses were seeded on to a model that used Abaqus built-in material properties in order to model the heat treatment. The results of this analysis have been compared with analyses run using just the VFT material model (with no creep) and using just the Abaqus properties (with no phase transformation) in order to investigate the sensitivity of the stresses predicted to the material model used. The results of all three analyses have also been compared to the results of the original analysis and with the deep hole drilling residual stress measurements.

Cleaning of Silicon Surfaces for Nanotechnology

2008 ◽  
Vol 573-574 ◽  
pp. 77-117 ◽  
Author(s):  
Oliver Senftleben ◽  
Hermann Baumgärtner ◽  
Ignaz Eisele
Keyword(s):  
Surface Roughness ◽  
High Mobility ◽  
Crystal Defects ◽  
Silicon Surfaces ◽  
Ex Situ ◽  
Chemical Cleaning ◽  
Gas Atmosphere ◽  
Wet Chemical ◽  
Device Properties

An overview of various cleaning procedures for silicon surfaces is presented. Because in-situ cleaning becomes more and more important for nanotechnology the paper concentrates on physical and dry chemical techniques. As standard ex-situ wet chemical cleaning has a significant impact on surface quality und thus device properties, its influence on further processes is also considered. Oxygen and carbon are unavoidable contaminations after wet chemical treatment and therefore we discuss their in-situ removal as one of the main goals of modern silicon substrate cleaning. As surface roughness strongly influences the electrical quality of interfaces for epitaxy and dielectric growth, we concentrate on techniques, which meet this requirement. It will be shown that multi-step thermal sequences in combination with simultaneous passivation of the clean surface are necessary in order to avoid recontamination. This can be achieved not only for ultra hich vacuum but also for inert gas atmosphere. In this case the process gases have to be extremely purified and the residual partial pressure of contaminats such as oxygen and carbon has to be negligible. It will be demonstrated that 800°C is an upper limit for thermal treatment of silicon surfaces in the presence of carbon because at this temperature SiC formation in combination with a high mobility of silicon monomers leads to surface roughness. In addition mechanical stress causes dislocations and crystal defects.

Stress Reduction in PACVD Amorphous Diamond Coatings by Boron Addition

1996 ◽  
Vol 436 ◽  
Author(s):  
V. Wagner ◽  
E. H. A. Dekempeneer ◽  
J. Geurts ◽  
L. J. van IJzendoorn ◽  
R. Sporken ◽  
...  
Keyword(s):  
Internal Stress ◽  
Stress Reduction ◽  
High Hardness ◽  
Hard Coatings ◽  
Film Stress ◽  
Intrinsic Stress ◽  
Diamond Coatings ◽  
Depth Sensing ◽  
Capacitively Coupled ◽  
Raman And Infrared Spectroscopy

AbstractThe applications of super hard coatings of diamond-like carbon (DLC) films are often limited by adhesion problems caused by intrinsic stress in the deposited layer due to the PACVD growth process. One approach to reduce the stress are less optimal process parameters. However, they also affect the desired high hardness of the films. Our approach in this study is to add B2H6 to the gas mixture, which shifts the composition towards another very hard compound (B4C). A sequence of amorphous BxC1-x:H films with a thickness of 0.5μm and a boron content between 0 and 50 at.-% were deposited on silicon substrates using a capacitively coupled r.f PACVD reactor. The tribological film properties and the internal stress were determined by depth-sensing indentation and laser reflection measurements. For an addition of x ≥5 at.-% boron the decrease of the internal film stress is found to be clearly larger than the effect on the hardness value. For boron contents x > 18% the internal stress is reduced by a factor of 5 while the reduction of hardness is only a factor of 2.3. For microscopic structure analysis Raman and infrared spectroscopy are applied. They reveal an increasing hydrogenation of the carbon network. Therefore, the softening is attributed to a boron induced modification to a more polymeric-like material.

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