1/fγ tunnel current noise through Si-bound alkyl monolayers

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(gamma) power spectrum noise with 1 <gamma < 1.2. We observe a slight bias-dependent background of the normalized current noise power spectrum (S-I/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, S-I, scales with (partial derivative I/partial derivative V)(2). A model is proposed showing qualitative agreements with our experimental data.