Structure Of Modified Layer Research Articles

The internal modified layer structure of silicon carbide induced by ultrafast laser and its application in stealth dicing

Silicon carbide (SiC) is widely applied in high-power electronic devices due to its excellent properties. Stealth dicing (SD) as one of the dicing methods, exhibits the advantages of few thermal surface damage and low edge-chipping. In this study, we use an ultrafast laser to induce the modified layer structure inside the SiC wafers. The effects of laser processing parameters on the modified layers are studied. The formation mechanism of the modified layer and its influence on SD are analyzed. The result shows that the number of modified layer structures is mainly determined by the moving velocity. The different modified layer structures will affect the surface roughness of the SD cross-section and critical fracture load of the 4H–SiC wafers. Finally, we achieved the high-quality SD of SiC wafers, and a cross-section with the minimum surface roughness is approximately 381 nm.

Anodic Plasma Electrolytic Nitrocarburizing of VT22 Titanium Alloy in Carbamide Electrolyte

The influence of the carbamide concentration on the nitrocarburizing temperature and changes in the mass of titanium samples, which are related to the anodic dissolution and high-temperature oxidation of titanium in a vapor‒gas shell, is investigated. The modified layer structure is revealed to contain an external oxide layer (rutile) and an intermediate diffusion layer whose microhardness reaches 770 HV. It is demonstrated that an increase in the nitrocarburizing temperature stimulates growth in the oxide-layer thickness, and the diffusion-layer thickness depends on the carbamide concentration in the solution. It is found that, at 850°С, the surface roughness decreases from 1.0 to 0.3–0.5 μm and the wear rate reduces from 6.7 × 10–7 to (1.2–1.7) × 10–7 due to nitrocarburizing in an electrolyte incorporating 10–15 wt % ammonium chloride and 10–12.5 wt % carbamide.

Features of nitroquenching of medium-carbon steel during anodic electrolyte–plasma processing

The research described in this paper is devoted to short-term anodic nitriding of grade 45 steel with postquenching (nitroquenching) in the aqueous solution of ammonia and ammonia chloride. The modified layer structure, as revealed, is composed of alternate layers: a surface oxide layer composed of FeO and Fe3O4; a layer of dispersed nitrides Fe4N and Fe2–3N with retained austenite; next, a martensitic zone composed of nitrogen and carbon; and the initial nitrogen-enriched ferrite–pearlitic structure. It is found that concentrations of electrolyte components and processing conditions affect the formation character and properties of diffusion layers. The possibility is shown for obtaining a nitroquenched layer 130 µm in thickness with a surface microhardness of to 1200 HV with a decrease in roughness Ra from 0.57 to 0.55 µm, Rz from 1.75 to 1.62 µm, and Rmax from 5.74 to 4.00 µm.

The increase in eutectic silumin fatigue life caused by electron beam processing

Eutectic silumin was processed with a high-intensity pulsed electron beam, and a multi-fold increase in the material fatigue life was discovered. Scanning electron microscopy was used to study the modified layer structure and the fracture surface of silumin subjected to high-cycle fatigue breakdown tests. The factors responsible for the increase in fatigue life of silumin were identified and analyzed.

Effect of Electrolytic-Plasma Carbonitriding on Structure and Microhardness of Low Carbon Steel 18CrNi3Mo

In this paper modified gradient layer was under research, the resulting electrolytic-plasma carbonitriding of low carbon steel 18CrNi3Mo surface was investigated. Aiming to improve the structure and strength properties of the layer, the possibility of application have been shown. Plasma carbonitriding optimized mode is presented as well. Regime of electrolyte plasma carbonitriding which consists in heating the steel sample to 8500C with aggregate exposure at this temperature for 3-7 min. and quenching in cold electrolyte has been optimized. We studied the processes of modified layer structure formation under different conditions

Reduced Threshold Current and Enhanced Extinction Ratio in a Magnetically Controllable Fe50Co50–InGaAlAs/InP Nonreciprocal Semiconductor Laser

We report on reduced threshold current and enhanced extinction ratio of a magnetically controllable Fe50Co50–InGaAlAs/InP nonreciprocal semiconductor laser. The improved device performance was consistent with calculated results for the modified layer structure and the use of ferromagnetic metal (Fe50Co50). The fabricated laser showed a threshold current 2.0 times smaller than our previous device having Fe. The extinction ratio, defined as the change in light intensity upon magnetization reversal, increased upon the appearance of the first-order transverse mode and reached 46% at a current of 100 mA. The reduced threshold current and enhanced extinction ratio should be useful for realizing low-operating-current, all-optical, robust signal processing devices using nonreciprocal semiconductor lasers.

Reduced Threshold Current and Enhanced Extinction Ratio in a Magnetically Controllable Fe50Co50–InGaAlAs/InP Nonreciprocal Semiconductor Laser

We report on reduced threshold current and enhanced extinction ratio of a magnetically controllable Fe50Co50–InGaAlAs/InP nonreciprocal semiconductor laser. The improved device performance was consistent with calculated results for the modified layer structure and the use of ferromagnetic metal (Fe50Co50). The fabricated laser showed a threshold current 2.0 times smaller than our previous device having Fe. The extinction ratio, defined as the change in light intensity upon magnetization reversal, increased upon the appearance of the first-order transverse mode and reached 46% at a current of 100 mA. The reduced threshold current and enhanced extinction ratio should be useful for realizing low-operating-current, all-optical, robust signal processing devices using nonreciprocal semiconductor lasers.

Structure of the modified surface layer formed by ion bombardment of SiO 2 films

The structure of thin (7–809 nm) SiO 2 films subjected to a bombardment of 40Ar ions of 2.7 keV is studied using infrared spectroscopy with computer analysis of the spectral shape, multiple-angle spectral ellipsometry and Auger spectroscopy. The formation of a surface modified layer (∼ 19 nm thick) is observed, which possesses the properties substantially different from those of the initial SiO 2 (a pronounced absorption in the visible and nearest ultraviolet spectral range, specific shape of the vibrational spectrum, the peak at ∼ 11 eV in the Auger electron spectrum). Deconvolution of the silicon-oxygen stretching band into gaussian profiles made it possible to separate new elementary bands (with peak positions of ∼ 1012 and ∼ 1038 cm −1), which being absent in the SiO 2 spectrum are the principal components of the SiO x absorption band. A model of the modified layer structure is developed in which a combination of SiO y Si 4− y ( O ⩽ y ⩽ 4) cluster is considered; the contribution of each cluster var ies in depth.

The crystal structure of ganophyllite; monoclinic subcell.

The crystal structure of monoclinic subcell (a′=5.534, b′=13.565, c′=25.09Å, β′=93.96°, I2⁄a) of ganophyllite has been determined and refined to an R of 0.078. The structure of true cell (a=3a′=16.60, b=2b′=27.13, c=2c′=50.18Å, β=β′=93.96°, A2⁄a) can be explained based on this average subcell structure. This mineral is a modified layer structure as suggested by Smith and Frondel (1968). The octahedral (sheet) layer is curved like a sine wave along the b-axis and is sandwiched by two tetrahedral layers, each composed of triple chains. The upper and lower chains sandwiching the octahedral layer are always at the outside of the curvature and the small tetrahedral layer is inside. Thus the layer misfit is elegantly minimized in this structure. The interlayer cation is eight coordinated to four oxygens or hydroxyls at the edges of the chains and to four water molecules. The ordering of interlayer cations and water molecules followed by the site preference of aluminum in the tetrahedra, and resultant slight changes in polyhedra of the subcell structure explain why ganophyllite has a large cell. The structural formula of ganophyllite determined from X-ray microprobe and structure analyses is (K, Na, Ca)x Mn8(Si, Al)12(O, OH)32(OH)4·nH2O, with x=1∼1.5, and n≥4; Z=24 in the true large cell. The average monoclinic subcell structure also can explain the structure of triclinic polytype recently found by Jefferson (1978).