  We report low frequency tunnel current noise characteristics of an organic
monolayer tunnel junction. The measured devices, n-Si/alkyl chain (C18H37)/Al
junctions, exhibit a clear 1/ f^y power spectrum noise with 1< y <1.2. We
observe a slight bias dependent background of the normalized current noise
power spectrum (SI/I^2). However, a local increase is also observed over a
certain bias range, mainly if V > 0.4 V, with an amplitude varying from device
to device. We attribute this effect to an energy-dependent trap-induced tunnel
current. We find that the background noise, SI, scales with (\partial
I/\partial V)^2 . A model is proposed showing qualitative agreements with our
experimental data.
