Elastic Properties of Encapsulation Epoxy for Vanadium Tetracyanoethylene Devices Measured Using Brillouin Light Scattering (BLS)

The organic-based ferrimagnetic coordination compound vanadium tetracyanoethylene (VTCNE) shows promise for microwave applications because it has low damping, similar to that of that of yttrium iron garnet (YIG), it exhibits conformal deposition on a variety of substrates, and the deposition process does not require high temperatures, which allows for simple integration into large scale semiconductor fabrication processes. Like many organic materials, however, it is sensitive to oxygen. The use of organic-friendly epoxy for encapsulation is a common method for protecting the organic that can easily be integrated into device fabrication processes on a large scale, and epoxies that protect the VTCNE without compromising the damping have been identified. Recent measurements suggest, however, that the magnetic properties, particularly the anisotropy, of VTCNE may be sensitive to strain. Consequently, understanding the mechanical properties of the encapsulating epoxy under typical device conditions is important. Here, we have used Brillouin light scattering (BLS) spectroscopy to probe the elastic properties of the cured encapsulating epoxy via phonon spectra measurements as a function of the angle of incidence and light polarization.