Variable temperature conducting tip atomic force microscopy of cobalt silicide on n-type Si(111):7$\times $7 and n-type Si(100):2$\times $1

Cobalt silicide (CoSi$_{2})$ nanoislands have been formed by ultrahigh vacuum deposition of thin films ($\sim $0.3 -- 1.0 $\pm $ 0.1 nm) of cobalt on clean n-type Si(111) and n-type Si(100) surfaces followed by annealing to $\sim $900$^{\circ}$C. Contact areas of the nanoislands were found to range from $\sim $50 $\times $ 10$^{3}$ -- 450 $\times $ 10$^{3}$ nm$^{2}$ when grown on Si(111) and from $\sim $100 $\times $ 10$^{3}$ -- 700 $\times $ 10$^{3}$ nm$^{2}$ when grown on Si(100). Conducting tip atomic force microscopy ($c$-AFM) has been used to record current-voltage (I-V) curves from the nanoislands at several temperatures between room temperature and $\sim $-200$^{\circ}$C. The I-V curves are analyzed using thermionic emission theory to determine the Schottky barrier height, $\Phi _{B}$, and the ideality factor, n, of the nanoislands. Room temperature values of $\Phi_{B}$ and n are found to be in the range of 0.35 -- 0.63 eV and 1.1 -- 1.8, respectively. Comparisons of $\Phi_{B}$ and n are performed for nanoislands of different shapes, and the temperature dependence of both $\Phi_{B}$ and n is analyzed. Richardson plots for the nanoislands are created and found to be non-linear at low temperature. The nanoislands were etched off the silicon surface using \textit{ex} \textit{situ} hydrofluoric acid (HF) etching and AFM was used to examine the shape of the nanoisland-substrate interfaces, and nanoisland properties are that shape.