Influence Of Substrate Off-Cut On The Defect Structure In Relaxed Graded Si-Ge/Si Layers

1996 ◽  
Vol 442 ◽  
Author(s):  
Srikanth B. Samavedam ◽  
F. Romanato ◽  
M. S. Goorsky ◽  
E. A. Fitzgerald
Keyword(s):  
Surface Roughness ◽  
Dislocation Structure ◽  
High Speed ◽  
High Surface ◽  
Substantial Improvement ◽  
Threading Dislocation ◽  
Threading Dislocation Density ◽  
Graded Layers ◽  
Spatially Variant ◽  
Edge Dislocations

AbstractRelaxed graded Si-Ge/Si layers can be used in a variety of micro-electronics applications such as templates for III-V/Si integration, in high speed field effect transistor (FET) structures and as detectors in optical communication. Each of these applications requires a different final Ge concentration in the graded Si-Ge layer. With increasing Ge content in the graded layer, some of the materials concerns that need to be addressed are- (i) a high surface roughness, (ii) the formation of dislocation pile-ups, and (iii) an increase in the threading dislocation density. We have shown that there is a substantial improvement in the surface roughness and the dislocation pile-up density of the graded Si-Ge layers by depositing on (001) 6° off-cut substrates. The substrate miscut also facilitates favorable intersections of {111} planes that aid reactions between the 60° dislocations to form edge dislocations with Burgers vectors of the type 1/2<110> and <100> resulting in a novel hexagonal dislocation structure. Such reactions occurred more readily in the Ge-rich regions of the graded layers where the growth temperature was high enough to aid dislocation climb. The edge dislocations with in-plane Burgers vectors lack a tilt component and the decreased rate of tilting in the Ge-rich regions is confirmed by triple crystal X-ray reciprocal space maps. This novel dislocation structure offers opportunities to explore new processes which may eliminate spatially variant strain fields in relaxed epitaxial layers.

scholarly journals Micro-Machining Characteristics in High-Speed Magnetic Abrasive Finishing for Fine Ceramic Bar

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 464 ◽  
Author(s):  
Joonhyuk Song ◽  
Takeo Shinmura ◽  
Sang Don Mun ◽  
Minyoung Sun
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
High Surface ◽  
Stable Region ◽  
Micro Machining ◽  
Fine Ceramic ◽  
Magnetic Abrasive Finishing ◽  
Abrasive Finishing ◽  
Machining Characteristics ◽  
Diameter Change

The research aims to describe the micro-machining characteristics in a high-speed magnetic abrasive finishing, which is applicable for achieving the high surface accuracy and dimensional accuracy of fine ceramic bars that are typically characterized by strong hardness and brittle susceptibility. In this paper, the high-speed magnetic abrasive finishing was applied to investigate how the finishing parameters would have effects on such output parameters as surface roughness, variation of diameters, roundness, and removed weight. The results showed that, under variants of diamond abrasives sizing between (1, 3 and 9 µm), 1 µm showed comparatively good values as for surface roughness and roundness within shortest processing time. When the optimal condition was used, the surface roughness Ra and roundness (LSC) were improved to 0.01 µm and 0.14 µm, respectively. The tendency of diameter change could be categorized into two regions—stable and unstable. The finding from the study was that the performance of ultra-precision processing linear controlling was possibly achievable for the stable region of diameter change, while linearly controlling diameters in the workpiece.

Engineering Dislocation Dynamics in Inx(AlyGa1−y)1−xP Graded Buffers Grown on Gap by Movpe

1998 ◽  
Vol 510 ◽  
Author(s):  
A.Y. Kim ◽  
E.A. Fitzgerald
Keyword(s):  
Surface Roughness ◽  
Dislocation Density ◽  
Growth Conditions ◽  
Dislocation Nucleation ◽  
Dislocation Dynamics ◽  
Threading Dislocation ◽  
High Quality ◽  
Movpe Growth ◽  
Threading Dislocation Density ◽  
Buffer Design

AbstractTo engineer high-quality Inx(AlyGa1−y)1−x P/Ga1−xP graded buffers, we have explored the effects of graded buffer design and MOVPE growth conditions on material quality. We demonstrate that surface roughness causes threading dislocation density (TDD) to increase with continued grading: dislocations and roughness interact in a recursive, escalating cycle to form pileups that cause increasing roughness and dislocation nucleation. Experiments show that V/III ratio, temperature, and grading rate can be used to control dislocation dynamics and surface roughness in InxGa1−xP graded buffers. Control of these parameters individually has resulted in x = 0.34 graded buffers with TDD = 5 × 106 cm−2and roughness = 15 nm and a simple optimization has resulted in TDD = 3 × 106 cm −2and roughness = 10 un. Our most recent work has focused on more sophisticated optimization and the incorporation of aluminum for x > 0.20 to keep the graded buffer completely transparent above 545 nm. Given our results, we expect to achieve transparent, device-quality Inx(AlyGa1−y)1−x P/GaP graded buffers with TDD < 106 cm−2

Research on Surface Topography and Roughness of Micro Parts by High Speed Turn-Milling

2014 ◽  
Vol 800-801 ◽  
pp. 607-612 ◽  
Author(s):  
Cheng Zhe Jin ◽  
Rui Fang
Keyword(s):  
Surface Roughness ◽  
Surface Topography ◽  
High Speed ◽  
Orthogonal Experiment ◽  
High Surface ◽  
Cutting Speed ◽  
Machined Surface ◽  
High Surface Quality ◽  
Micro Parts ◽  
Turn Milling

High speed turn-milling has superiority on the productivity and the quality of work pieces, and is more suitable to machine micro-shaft parts and desirable miniature parts based on the turn-milling technology. In this papers adopting orthogonal experiment method cutting experiments of orthogonal turn-milling Aluminum alloy have been done. The relation between turn-milling regimes (cutter rotate speed, axial feed, feed per tooth etc.) and machined surface roughness has been ascertained. Finally, primary and secondary order of cutting regimes impacting surface roughness has more been confirmed through orthogonal experiments variance analysis, the rotate speed of cutter (cutting speed) influence greatly on surface roughness. Through 2-dimension surface topography diagram and 3-dimension surface topography of processed surface, it can be seen that high speed turn-milling processing technology can process micro miniature component of high surface quality, and features excellent development prospect and application value.

High Quality Germanium Photodiodes on Silicon Substrates Using an Intermediate Chemical Mechanical Polishing Step

1997 ◽  
Vol 486 ◽  
Author(s):  
Srikanth B. Samavedam ◽  
Matthew T. Currie ◽  
Thomas A. Langdo ◽  
Steve M. Ting ◽  
Eugene A. Fitzgerald
Keyword(s):  
Dislocation Density ◽  
Chemical Mechanical Polishing ◽  
Mechanical Polishing ◽  
Quantum Yields ◽  
Threading Dislocation ◽  
Thermal Mismatch ◽  
High Quality ◽  
Si Substrates ◽  
Threading Dislocation Density ◽  
Graded Layers

AbstractGermanium (Ge) photodiodes are capable of high quantum yields and can operate at gigahertz frequencies in the 1–1.6 μm wavelength regime. The compatibility of SiGe alloys with Si substrates makes Ge a natural choice for photodetectors in Si-based optoelectronics applications. The large lattice mismatch (≈4%) between Si and Ge, however, leads to the formation of a high density of misfit and associated threading dislocations when uniform Ge layers are grown on Si substrates. High quality Ge layers were grown on relaxed graded SiGe/Si layers by ultra-high vacuum chemical vapor deposition (UHVCVD). Typically, as the Ge concentration in the graded layers increases, strain fields from underlying misfit dislocations result in increased surface roughness and the formation of dislocation pile-ups. The generation of pile-ups increases the threading dislocation density in the relaxed layers. In this study the pileup formation was minimized by growing on miscut (001) substrates employing a chemical mechanical polishing (CMP) step within the epitaxial structure. Other problems such as the thermal mismatch between Si and Ge, results in unwanted residual tensile stresses and surface microcracks when the substrates are cooled from the growth temperature. Compressive strain has been incorporated into the graded layers to overcome the thermal mismatch problem, resulting in crack-free relaxed cubic Ge on Si at room temperature. The overall result of the CMP step and the growth modifications have eliminated dislocation pile-ups, decreased gas-phase nucleation of particles, and eliminated the increase in threading dislocation density that occurs when grading to Ge concentrations greater than 70% Ge. The threading dislocation density in the Ge layers determined through plan view transmission electron microscopy (TEM) and etch pit density (EPD) was found to be in the range of 2 × 106/cm2. Ge p-n diodes were fabricated to assess the electronic quality and prove the feasibility of high quality photodetectors on Si substrates.

Low surface roughness and threading dislocation density Ge growth on Si (001)

2008 ◽  
Vol 310 (18) ◽  
pp. 4273-4279 ◽  
Author(s):  
Donghun Choi ◽  
Yangsi Ge ◽  
James S. Harris ◽  
Joel Cagnon ◽  
Susanne Stemmer
Keyword(s):  
Surface Roughness ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Threading Dislocation Density

High-Speed Growth of 4H-SiC Single Crystal Using Si-Cr Based Melt

2013 ◽  
Vol 740-742 ◽  
pp. 73-76 ◽  
Author(s):  
Motohisa Kado ◽  
Hironori Daikoku ◽  
Hidemitsu Sakamoto ◽  
Hiroshi Suzuki ◽  
Takeshi Bessho ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Single Crystal ◽  
High Speed ◽  
High Rate ◽  
Threading Dislocation ◽  
High Quality ◽  
X Ray ◽  
Interface Kinetics ◽  
Threading Dislocation Density ◽  
Rate Limiting

In this study, we have investigated the rate-limiting process of 4H-SiC solution growth using Si-Cr based melt, and have tried high-speed growth. It is revealed that the rate-limiting process of SiC growth under our experimental condition is interface kinetics, which can be controlled by such factors as temperature and supersaturation of carbon. By enhancing the interface kinetics, SiC crystal has been grown at a high rate of 2 mm/h. The FWHM values of X-ray rocking curves and threading dislocation density of the grown crystals are almost the same as those of seed crystal. Possibility of high-speed and high-quality growth of 4H-SiC has been indicated.

Prediction and Investigation of Surface Quality in High Speed End-Milling of Silicon to Eliminate Conventional Finishing Operations

2011 ◽  
Vol 418-420 ◽  
pp. 1237-1241
Author(s):  
A.K.M. Nurul Amin ◽  
Mohd Dali M Ismail ◽  
Muhammad Iqbal Musa ◽  
Anayet Ullah Patwari
Keyword(s):  
Surface Roughness ◽  
Surface Finish ◽  
High Speed ◽  
End Milling ◽  
High Surface ◽  
Small Diameter ◽  
Dimensional Accuracy ◽  
Cutting Parameters ◽  
Machining Process ◽  
Dry Cutting

Surface finish and dimensional accuracy are two of the most important requirements in machining process. High speed machining (HSM) is capable of producing parts that require little or no grinding/lapping operations within the required machining tolerances. In HSM determination of the optimum combination of cutting parameters for achieving the required level of quality, such as, minimum possible surface roughness and maximum tool life is a very important task. Silicon is conventionally finished using grinding followed by polishing and lapping to achieve required surface finish and surface integrity. In this study small diameter tools are used to achieve high rpm to facilitate the application of low values of feed and depths of cut to ensure high surface roughness values through achievement of ductile mode machining of silicon. Investigations on the effect cutting parameters of high speed end milling on surface finish and integrity of silicon has been conducted to minimizing the amount of finishing requirement in machining of silicon, with the objective of reducing cost and increasing effectiveness of silicon manufacturing process. In this work statistical models were developed using the capabilities of Response Surface Methodology (RSM) to predict the surface roughness in high speed flat end milling of silicon under dry cutting conditions.

Enhancement of EDM Performance by Using Copper-Silver Composite Electrode

2020 ◽  
Vol 38 (9A) ◽  
pp. 1352-1358
Author(s):  
Saad K. Shather ◽  
Abbas A. Ibrahim ◽  
Zainab H. Mohsein ◽  
Omar H. Hassoon
Keyword(s):  
Surface Roughness ◽  
Material Removal Rate ◽  
Material Removal ◽  
High Speed ◽  
Composite Electrode ◽  
Removal Rate ◽  
Pure Copper ◽  
High Speed Steel ◽  
Pulse On Time ◽  
Pulse Off Time

Discharge Machining is a non-traditional machining technique and usually applied for hard metals and complex shapes that difficult to machining in the traditional cutting process. This process depends on different parameters that can affect the material removal rate and surface roughness. The electrode material is one of the important parameters in Electro –Discharge Machining (EDM). In this paper, the experimental work carried out by using a composite material electrode and the workpiece material from a high-speed steel plate. The cutting conditions: current (10 Amps, 12 Amps, 14 Amps), pulse on time (100 µs, 150 µs, 200 µs), pulse off time 25 µs, casting technique has been carried out to prepare the composite electrodes copper-sliver. The experimental results showed that Copper-Sliver (weight ratio70:30) gives better results than commonly electrode copper, Material Removal Rate (MRR) Copper-Sliver composite electrode reach to 0.225 gm/min higher than the pure Copper electrode. The lower value of the tool wear rate achieved with the composite electrode is 0.0001 gm/min. The surface roughness of the workpiece improved with a composite electrode compared with the pure electrode.

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