Fabrication of nanodiodes using atomic-force microscope lithography

Unipolar nanodiodes, known as the self-switching diodes (SSDs), have recently been demonstrated as terahertz (THz) detectors at room temperature. The SSDs have also shown promising properties as THz emitters and nanomemory devices. Here, we report the fabrication of SSDs on a GaAs/AlGaAs substrate using an atomic-force microscope (AFM) lithography which utilizes AFM-tip ploughing technique and the use of a suitable polymethyl methacrylate layer with thermal-annealing treatment. This approach has successfully overcome some typical problems associated with the tip-ploughing method including the refilling of the SSD's trenches by debris generated during the ploughing process. In this report, all SSDs defined using the AFM lithoghraphy have shown standard diode-like I-V characteristics, indicating the reproducibility of the abovementioned approach. In addition, this method might be useful to realize electronic devices in nanoscale dimensions.