The methods of chemical strengthening for improving the mechanical properties of oxide glasses are reviewed. Chemical strengthening in compared with thermal strengthening and different methods of m ...

The technology of chemical glass strengthening : A review

Measurements of the transient behavior of both the second-harmonic generation signal and the poling current for type-II fused silica samples under a variety of poling histories are reported. The applied voltage was switched between +5 kV, 0 V, and −5 kV with the sample maintained at 275°C. Observations include: multiple time scales (seconds to minutes) for development of the non-linearity depending on the poling history; a transient second-harmonic signal on the new cathode side of the sample following voltage reversal; and hysteretic incubation intervals before growth of the non-linearity. These observations are incompatible with the usual single mobile ion (e.g. Na+) model for establishing the strong local electric field that leads to the non-linearity. An expanded model including ion-exchange between a high mobility ion (as Na+) and a much lower mobility ion (related to H+) provides a good qualitative fit to the experiments.

Space charge dynamics in thermally poled fused silica

Phosphorus and boron ion implantations were performed at various energies in the 50 keV–4 MeV range. Range statistics of P+ and B+ were established by analyzing the as-implanted secondary ion mass spectrometry depth profiles. Anneals were conducted in the temperature range of 1400–1700 °C using either a conventional resistive heating ceramic processing furnace or a microwave annealing station. The P implant was found to be stable at any annealing temperature investigated, but the B redistributed during the annealing process. The implant damage is effectively annealed as indicated by Rutherford backscattering measurements. For the 250 keV/1.2×1015 cm−2 P implant, annealed at 1600 °C for 15 min, the measured donor activation at room temperature is 34% with a sheet resistance of 4.8×102 Ω/□. The p-type conduction could not be measured for the B implants.

Phosphorus and boron implantation in 6H–SiC

A great deal of work has been devoted in the last decades to the study of the ion exchange process modelling, in order to tailor the physical properties of the modified layers, e.g. refractive index or stress profiles. The first models were based on simple ionic diffusion equations, while in the last years it became clear that the glass undergoes local restructuring during the ion exchange even at temperatures lower than the glass transition one. The aim of this work is to review the approaches that lead to the introduction of self-diffusion coefficients depending on the concentration of the migrating cations, and to outline a physical approach in selecting a phenomenological expression for the coefficients. In particular, this approach refers to models developed for describing the ionic diffusion in mixed-alkali glasses.

Modelling the ion exchange process in glass: Phenomenological approaches and perspectives

https://eprints.ncl.ac.uk/file_store/production/56841/2C554B8B-2635-4EA4-95F2-4A87B417D422.pdf

Product due date assignment for complex assemblies

A method is described whereby ion implantation profiles in amorphous materials may be accurately represented by Pearson frequency distribution curves. The type of Pearson distribution to be used depends upon the implantation conditions but it is shown that the three main types, I, IV and VI, together with the transition types II, III, V, VII and the Gaussian are all suitable representations. Previous attempts to fit Pearson curves to implantation profiles have often failed due to semi-infinite moments being used instead of infinite moments. This approximation is only valid when the surface concentration of implanted ions is negligibly small.

http://iopscience.iop.org/article/10.1088/0022-3727/23/7/018/pdf

Representation of ion implantation profiles by Pearson frequency distribution curves

Results are presented from a study of the field-assisted diffusion of silver ions from silver films into soda-lime glass. These indicate that it is necessary to take into consideration the concentration dependence of the self-diffusion coefficient of both the silver and the sodium ions in a pseudo-mixed-alkali effect in order to predict the silver diffusion profiles accurately. A field assisted diffusion model that incorporates this effect is developed and model coefficients are deduced. The model is applied to post-bake diffusions and deep field-assisted diffusion profiles. The model is applicable to the design and manufacture of optical waveguides and lenses in glass by field-assisted diffusion.

https://iopscience.iop.org/article/10.1088/0022-3727/28/4/006/pdf

The influence of the pseudo-mixed-alkali effect on the field-assisted diffusion of silver ions into glass for optical waveguides

A simple drift transport model is used to predict the depth of planar optical waveguides produced by the electric field assisted ion exchange of potassium ions into soda-lime glass. The guide depth can be represented by a simple universal function of the voltage-process time product. The model is fitted to experimental data over a wide range of applied potentials and times. Joule heating effects limit the accuracy of the model at large current densities.

Characterisation of electric field assisted diffused potassium ion planar optical waveguides

Several authors have reported difficulties in fitting Pearson curves to implants into amorphous targets. However, we show that accurate Pearson curve fitting to simulations of projected range profiles in amorphous targets is possible when implant profiles are available for which optimised moments can be generated. In previous literature few comparisons can be found between Pearson curve fits and the original implant profiles whereas, in the current paper, comparisons are made with high-resolution simulated profiles for B, P and As implanted into amorphous Si. These profiles were derived using Monte-Carlo simulations each of 1,000,000 ion trajectories. Fit coefficients that allow the regeneration of Pearson curves, optimised to fit Monte-Carlo implant profiles, are provided for the ions, B, P, As and Sb implanted, with energies in the range 25–300 keV, into targets of amorphous Si, silicon dioxide and silicon nitride. Comparisons of infinite and optimised moments, for B and P implants, show that the best fit moments (and corresponding Pearson type) can only be determined as part of an optimisation process, and not from infinite moments directly (such as moments from a backward Boltzmann transport equation solver).

Representation of ion implantation projected range profiles by Pearson distribution curves for silicon technology

The theoretical model and computer program (AAMPITS-3D) of Ashworth and coworkers (1985) for the calculation of three-dimensional distributions of implanted ions in multielement amorphous targets are extended to show that the lateral rest distribution is gaussian in a form with a lateral standard deviation (lateral-spread function) which is a function of depth beneath the target surface. A method is given whereby this function may be accurately determined from a knowledge of the projected range and chord range rest distribution functions. Examples of the lateral-spread function are given for boron, phosphorus and arsenic ions implanted into silicon and a detailed description is given of how the lateral-spread function may be used in conjunction with the projected range rest distribution function to provide a fully three-dimensional rest distribution of ions implanted into amorphous targets. Examples of normalised single ion isodensity contours computed from AMPITS-3D are compared with those obtained using the previous assumption of a lateral standard deviation which was independent of distance beneath the target surface.

https://iopscience.iop.org/article/10.1088/0022-3719/19/29/004/pdf

D.G. Ashworth

Papers

Representation of ion implantation profiles by Pearson frequency distribution curves

The influence of the pseudo-mixed-alkali effect on the field-assisted diffusion of silver ions into glass for optical waveguides

Characterisation of electric field assisted diffused potassium ion planar optical waveguides

Representation of ion implantation projected range profiles by Pearson distribution curves for silicon technology

Theoretical predictions of the lateral spreading of implanted ions