The optical and topographical properties of the samples were investigated using an FEI Quanta 250 FEG scanning electron microscope, modified to capture room temperature cathodoluminescence (CL) spectra as well as a range of other information resulting from electron beam excitation. The SEM was operated in Low Vacuum mode with a chamber pressure of 1 mbar, this mode was necessary to prevent charging of the highly resistive samples. As the electron beam is scanned across the sample, impact ionisation generates electron-hole pairs which can recombine to produce the CL signal. This signal is collected by a reflecting objective telescopic mirror set-up to reflect towards a crossed Czerny-Turner spectrometer (Oriel MS125), which diffracts it towards a 1600-element electron multiplying charge-coupled device (EMCCD). For each of the samples investigated in this report, a 15 kV accelerating voltage was used to collect data in 50 nm steps across the sample, and a 600 lines/mm grating blazed at 200 nm diffracted the light collected via a 50 µm entrance slit. The exit slits are defined by the width of the pixel columns of the detector itself (16 µm) which operates in full vertical binning mode. The EMCCD was set to use 2× horizontal binning (to give an effective 800 channels), a vertical read-out time of 19.75 µs, a horizontal read-out rate of 2.5 MHz, and the electron multiplying capability was used. These settings were chosen to optimise the signal-to-noise ratio. Unless otherwise stated, a beam current of 7 nA was used for 1-2s of acquisition time. We estimate the excitation electrons to have lost 90% of their energy approximately 850 nm into the sample, based on CASINO software using Monte-Carlo simulations to emulate our samples under a 15 kV electron beam incident at 45° as in our set up.