P. Grutter
McGill University,
Canada
Keywords: defects in semiconductors, random telegraph fluctuations, 1/f noise
Summary:
In frequency-modulated atomic force microscopy (fm-AFM) the measured frequency shift is quadratic in applied bias for metallic samples and probes. However, for semiconducting samples, band bending effects must be considered, resulting in non-parabolic bias curves. We have developed a framework to quantitatively describe a metal-insulator semiconductor (MIS) device formed out of a metallic AFM tip, vacuum gap, and semiconducting sample. We show how this framework allows us to measure dopant concentration, bandgap and band bending timescales of different types of defects on semiconductors with nm scale resolution. We have applied this method to investigating defects in semiconductors, 2D materials and organic thin films. In all these systems, we have observed spatially localized low-frequency noise due to two level fluctuations. Such random telegraph noise inhibits the reliability and performance of nanoscale semiconductor devices, and challenges the scaling of emerging spin based quantum sensors and computers. Here, I will present and discuss the measurement of temporal two-state fluctuations of individual defects at the Si/SiO2 interface with nanometer spatial resolution using atomic force microscopy. When measured as an ensemble, the observed defects have a 1/f power spectral trend at low frequencies. The presented method and insights provide a more detailed understanding of the origins of 1/f noise in silicon-based classical and quantum devices, and could be used to develop processing techniques to reduce two-state fluctuations associated with defects.