Improved Induced Diode Photodetectors by Increased Fixed Charge in PECVD Amorphous Silicon Nitride

The predictable quantum efficient detector (PQED) is a cheaper, more practical alternative to the current radiometric primary standard, the cryogenic radiometer. The PQED is made of an induced diode, a rectifying junction based on a positively charged dielectric film which induces an n-type inversion layer on a p-type silicon substrate. Increasing the fixed charge Qf in the dielectric has been theoretically predicted to improve the quantum efficiency of the diode by decreasing the surface recombination velocity (SRV) at the dielectric-silicon interface, as well as improving the performance of the diode at high intensities. In this work, we purpose the replacement of silicon oxide (SiOx) with silicon nitride (SiNx) as the inversion-inducing dielectric layer as a means of increasing Qf.Amorphous PECVD SiNx has been shown to have a significantly higher Qf than thermally grown SiOx. A sixfold increase of Qf in SiNx by means of charge injection via bias soaking has also been demonstrated. The dielectric ideality of the nitride increases with the atomic nitrogen concentration x, and a high-x film has shown superior charge retention properties. The absorption in the high-x film is far less than 1% in the applicable wavelength ranges, but is larger in the low-x film. The impact of Qf on the SRV has been experimentally demonstrated, and may be fit to the extended SRH theory with the inclusion of a sub-surface damage term. Finally, it has been demonstrated that the aluminium contacts deposited for the purpose of charging the SiNx may be chemically removed while the injected charge remains. SiNx has thus been shown to be an interesting candidate for the PQED application

Angular dependence of wide altitude ion line enhancements (WAILEs) during ionospheric heating at the EISCAT Tromsø Facility

This thesis presents the first sub-radar beam resolution determination of the angular width of wide altitude ion line enhancements (WAILEs), found to be 0.5 degrees around magnetic zenith, observed during a HF radio wave heating experiment at the EISCAT Tromsø Heating facility on 27 November 2014. The results of ray tracing simulations are detailed. The simulations are based on the hypothesis that WAILEs are caused by ducting of UHF radio waves due to artificial field aligned irregularities and the results of the experiment. Ducting of a 930 MHz radio wave was caused by 15.7% depletions from the background density in an IRI model atmosphere with fOF2 = 10.04 MHz. The data analysis and modelling methods used to achieve these results are explained. The fundamentals of HF radio wave interactions in plasma and the theory of incoherent scatter radar are discussed. The thesis concludes with recommendations for further research on WAILEs and field aligned irregularities caused by X-mode heating

Resistance Analysis of Spherical Metal Thin Films Combining Van Der Pauw and Electromechanical Nanoindentation Methods

Although micron-sized metal-coated polymer particles are an important conductive filler material in anisotropic conductive adhesives, the resistance of the particles in adhesive is not well understood. In this study, a van der Pauw method for spherical thin films is developed and applied to determine the resistivity of 30 µm silver-coated poly(methyl methacrylate) (PMMA) particles. The resistivity is used to interpret resistance contributions in single particle electromechanical nanoindentation measurements, which simulate the compression particles undergo in application. The resistivity was found to be coating thickness dependent for thin films in the range 60-270 nm. Estimation of the resistance of the metal shell using the measured resistivity did not account for the total resistance measured in electromechanical nanoindentation. We therefore deduce a significant contribution of contact resistance at the interfaces of the particle. The contact resistance is both coating thickness and particle deformation dependent.acceptedVersionThis is a post-peer-review, pre-copyedit version of an article published in [Journal of Electronic Materials] Locked until 25.8.2019 due to copyright restrictions. The final authenticated version is available online at: https://doi.org/10.1007/s11664-018-6613-

Contact area measurement of micron-sized metal-coated polymer particles under compression

The contact problem of a sphere under compression by a rigid plate is pertinent to understanding electrical contact formation in anisotropic conductive adhesive (ACA) applications. However, no work has experimentally verified existing contact models for the metal-coated sphere-plate contact problem. Herein, compression tests on metal-coated polymer spheres were performed by flat punch nanoindentation with in-situ scanning electron microscopy (SEM) monitoring, and the resultant contact area was measured using SEM images. The obtained results were compared to Tatara and Abbott-Firestone models, along with finite element analysis (FEA). The measured contact area falls between Tatara and Abbott-Firestone models, indicating a mixture of elastic and plastic deformation. The contact area as a function of force is dominated by the polymer core and independent of the metal coating for the thin metal coatings tested. The work provides guidelines for bonding parameters for ACA assembly.acceptedVersion© 2019. This is the authors’ accepted and refereed manuscript to the article. Locked until 5.10.2021 due to copyright restrictions. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0