Nitrogen Concentration Profiles Research Articles

Morphology, Composition, and Residual Stresses of Compound Layers of Nitrocarburized Iron and Steels

Specimens of pure iron, an iron-carbon (1 wt-%C) alloy, and steels Ck 45 and En 40B (=24CrMo13) were salt bath nitrocarburized. M etallographic examination was performed after Murakami etching. This etchant provides a sensitive discrimination between pure nitrides and carbon containing nitrides (carbonitrides). Thus the two-phase (ε and γ’) constitution, as well as the carbon concentration profile within the compound layer, was revealed. Nitrogen, carbon, oxygen, and sulphur concentration profiles were quantitatively determined by electron microprobe analysis. Residual stress measurement and phase analysis were carried out by X-ray diffraction methods. Both macros trains (by analysis of line shift using the sin2 Ψ method) and microstrains (by analysis of line broadening using a Voigt single-line method) were determined. In view of a possible interaction between residual stresses in the compound layer and the diffusion zone, residual stresses were also determined in the diffusion zone beneath the compound layer. The results obtained provide a basis for a model to describe the constitution of the compound layer.

The application of nitrogen ion implantation in silicon technology

During the past decade numerous studies have dealt with the effects of nitrogen ion implantation in silicon, such as insulating properties, oxidation inhibition, crystal regrowth and doping effects. However, the lack of detailed knowledge of nitrogen concentration profiles in silicon has been an obstacle to elucidating the mechanism of some of these effects and finding the optimum conditions for their applications in semiconductor device technology. Recently we found 15N (p, αγ) 12C resonant nuclear reaction analysis to provide a valuable technique to measure nitrogen concentration profiles. It appears that remarkable redistributions of nitrogen profiles in silicon take place during annealing and oxidation, which result in the formation of extremely thin nitrogen rich layers at the Si-SiO 2 interface. From these observations it is explained that moderate doses of nitrogen ions can induce an oxidation resistance which is sufficient to provide self-aligned contact windows in MOS technology. Finally some of the results on nitrogen ion implantation reported in the past decade will be discussed in view of these new analyses.

The development of nitrogen concentration profiles on nitriding iron

On nitriding iron specimens nitrogen concentration profiles within the specimens are built up. A numerical method for the calculation of such concentration profiles was developed. The results calculated were compared with experimental data. It was found that during nitriding the nitrogen surface concentration approached relatively slowly the equilibrium value. This effect strongly influenced the development of the nitrogen concentration profile. The model predicted correctly the incubation time for compound(i. e., iron nitride) layer formation at the surface. If the fatigue resistance is strongly dependent on the (compressive) residual surface stress, the present treatment allows calculation of anoptimum nitriding time by determining when the maximum (compressive) residual surface stress occurs.

Ion Implanted Ti-6Al-4V

ABSTRACTTitanium and many of its alloys show very poor wear resistance considering their hardness. This together with high thermodynamic driving forces to form very hard compounds between titanium and nitrogen or carbon made titanium based alloys obvious candidates for ion implantation. In this paper the effects of similar implanted concentration profiles of nitrogen and carbon in two titanium alloys are compared. The wear behavior of pin on disk wear tests are reported along with the ultramicrohardness of the four samples.

The Oxidation Inhibition in Nitrogen‐Implanted Silicon

In order to reveal the mechanism of oxidation inhibition in nitrogen‐implanted silicon, the 15N(p, αγ)12C resonant nuclear reaction has been applied to obtain detailed information on nitrogen concentration profiles in silicon. It appears that the oxidation resistance is caused by an extremely thin (<3 nm) nitrogen‐rich layer at the interface. The formation of this interfacial nitride‐like layer is the result of complicated redistributions of the nitrogen which take place during annealing and oxidation. It is shown that implantation of nitrogen ions into source and drain areas of an MOS transistor can be used to inhibit further growth of the gate oxide in these areas during a subsequent oxidation and thus allows a selective oxidation of polysilicon gates. This provides a novel technique for obtaining self‐aligned contact windows to the source and drain regions. Finally reverse current measurements on gate‐controlled diodes show that the bulk and surface generation currents in the nitrogen‐implanted layer are as low as for unimplanted reference wafers, provided adequate experimental conditions are applied.

Microhardness and nitrogen concentration profiles for nitrided 316 steel

The quantitative relationship between microhardness and nitrogen content for a nitrided type 316 stainless steel specimen has been determined, using the scanning nuclear microbeam technique to measure accurate nitrogen concentration values. For the inner nitrided zone, over which the nitrogen concentration falls from 8 to 1 at.%, a linear relationship holds. A tentative explanation based on the form of the nitride precipitation process in this region is proposed. In the outer zone (the nitride “case”) the microhardness is approximately constant over the range 9 – 12 at.% nitrogen. Edge effects interfere with the measurement of microhardness at the 12 – 14 at.% level. The experimental difficulties and the limitations of the technique are discussed.

The concentration profiles of projectiles and recoiled nitrogen in Si after ion implantation through Si3N4 films

The concentration profiles of ion-implanted boron, phosphorus, and arsenic, and recoil-implanted nitrogen atoms after ion implantation through Si3N4 films on Si have been measured using secondary ion mass spectrometry. The concentration profiles of the implanted ions in Si after ion implantation through Si3N4 films were found to agree with those implanted into bare Si within experimental errors, with the exception of a shifting of the concentration peak position. The concentration profiles of recoil-implanted nitrogen in Si are generally composed of high-concentration regions with steeply decaying distributions near the silicon surface and the exponential tails whose slopes are independent of ion mass, energy, dose, and film thickness. The concentration level of recoil-implanted nitrogen and maximum penetration range relative to the implanted ion range depend strongly on ion mass, film thickness, and ion energy. It was demonstrated that the concentration profiles for recoiled nitrogen in Si calculated using the Thomas-Fermi interaction potential agree better with the measured profiles than those calculated using 1/r2 potential, such as presented in the theory by Moline et al.

Depth distribution of knock-on nitrogen in Si by phosphorus implantation through Si3N4 films

The concentration profiles of phosphorus and knock-on nitrogen in silicon after phosphorous implantations into Si3N4-Si systems have been investigated by using secondary ion mass spectrometry (SIMS). The tails were found on the phosphorus distribution in silicon after the implantation through Si3N4 films. The concentration profiles of knock-on nitrogen in silicon have been determined by measuring both the in-depth profiles of knock-on nitrogen and those of nitrogen after additional nitrogen implantation into a bare silicon embedded with knock-on nitrogen. The concentration profiles of knock-on nitrogen show a very high concentration near the surface and extending tails. It was found that the tails were observed at the deeper portion in silicon as energy increased, for a given Si3N4 layer.

A nuclear microprobe method for the simultaneous determination of silicon and nitrogen profiles in metals

A nuclear microprobe method has been developed for the simultaneous determination of silicon and nitrogen concentration profiles in metals. The method was based on the reactions28Si(d, p0)29Si and14N(d, p0)15N plus14N(d, β0)12C with measurement of emitted charged particles during irradiation with 1.9 MeV deuterons. The nitrogen sensitivity was ten times that for silicon and the minimum concentrations detected were 0.002% and 0.03% respectively. The method was successfully applied to the measurement of silicon and nitrogen profiles in alloys contacted with silicon nitride at high temperature.

Nitrogen concentration profiles in oxy-nitrided high-speed steel

Nuclear microanalysis has been applied for the determination of in-depth concentration profiles of nitrogen in oxy-nitrided high-speed steel. The concentration profiles were deduced from measurements of the nitrogen content, determined by means of the14N(d, α)12C reaction, for the set of initially identical samples after the removal of surface layers of sequentially increasing thicknesses. Strong blocking of the nitrogen diffusion due to the presence of oxygen has been observed.

Flame structure and flame reaction kinetics II. Transport phenomena in multicomponent systems

The transport fluxes in multicomponent flame systems due to diffusion and thermal conduc­tion, and to thermal diffusion and its reciprocal effect, are considered from the standpoint of the extension of the Chapman–Enskog kinetic theory to polyatomic gases by Wang Chang, Uhlenbeck &amp; de Boer (1951, 1964) and the subsequent development by Mason, Monchick and coworkers (1961-66). Equations are given for the various diffusional, thermal diffusional and thermal fluxes which it is necessary to derive in order to obtain reaction rates from experimental temperature and composition profiles in flames; and the organization of com­puter programs for calculation of the multicomponent diffusion and thermal diffusion coefficients and the thermal conductivity is described. The use of matrix partitioning tech­niques in suitable circumstances to reduce the amount of computation is also discussed. The expressions for the transport fluxes are next used to derive equations for the mole fraction and temperature gradients in flowing reaction systems such as flames where trans­port processes and reaction occur side by side. From the mole fraction and temperature at one point in the system it is then possible by a numerical integration method such as the Runge–Kutta procedure to compute the complete composition and temperature profiles. Two methods of obtaining the mole fraction and temperature gradients are described, one of which, the Stefan–Maxwell formulation, leads to the more economical computation. A hydrogen–oxygen–nitrogen–steam mixture was chosen under conditions which simu­lated the pre-reaction region of a hydrogen–oxygen–nitrogen flame that had been studied experimentally, and the detailed composition profiles due to diffusion were computed. The experimental method of measurement involved continuous sampling from the flame and mass spectrometric analysis, a technique which had not previously been checked on a flame system itself. Good agreement between theory and experiment was found when thermal diffusion was considered in the calculation, although the computed hydrogen profile was slightly displaced with respect to the experimental one. This last observation is possibly due to diffusion effects in the pressure gradient at the probe tip. Otherwise the experimental technique seemed to be satisfactory. The computed profiles also showed a number of interesting features such as a maximum in the nitrogen concentration profile caused by thermal diffusion effects.