Overcoming Probe-Sample Charging “Drifting Effect”

As mentioned in the earlier chapters, one of the greatest technical challenges in this work is the probe-sample charging “drifting effect” that is undesirable in NSOM and AFM measurements of nano-scale structures. One solution is to effectively find a way to ground the AFM/NSOM probe to reduce the charging effects substantially. Alternatively, a forward-biased solar cell structure can be utilized to illuminate the desired location, such as the gap of the bowtie and collect the spatially resolved emission in the near-field, removing the role of the electron beam to generate the light.

2. Investigating Secondary Effects of the Enhanced Diffusion in GaN Nanowires

It has been observed that the diffusion effect of luminescence from the GaN nanowires was larger and longer when a NSOM probe of a larger aperture was used. Although more light can be collected via a larger aperture, the diffusion length of the GaN nanowires should remain unchanged. Initial deduction to this observation is that the nanowires actually act like waveguides which could have allow the progression of light further along the wire and this could have only be collected by apertures of a certain size due to their difference in efficiency

[17]. Future work should include a quantitative study to the relationship between measured “pseudo-diffusion length” and the aperture size of the AFM/NSOM probe.

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