The current–voltage and capacitance–voltage characteristics of Sb-n-InSb metal-semiconductor contacts with a Schottky barrier fabricated by pulsed laser deposition and subsequent thermal annealing were measured at 77 K. By comparing with the general theory for such contacts that takes into account the presence of a tunnel-transparent dielectric interfacial layer and surface states, all contact parameters were determined. The structures demonstrated large photosensitivity in the 3–5 μm spectral region and thus can be used for efficient, broadband, and fast photodetection in the mid-IR range.
Source:IOPscience
We have used scanning tunnelling microscopy (STM) at 77 K to investigate 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) molecules adsorbed on an ultrathin (1–2 monolayer (ML)) film of KBr grown on a c(8 × 2)InSb(001) substrate. The molecules are stabilized both at the KBr steps and on the terraces. On the 1 ML film the PTCDA molecules appear predominantly as single entities, whereas on the 2 ML film formation of molecular clusters is preferred. Differences in the adsorption configurations indicate that the interaction between the molecules and the surface differs significantly for the cases of 1 and 2 ML films. We present images of the molecules obtained with sub-molecular resolution for both filled and empty state sampling modes. We argue that the highest occupied molecular orbital (the lowest unoccupied molecular orbital) is responsible for intramolecular contrast in filled (empty) state images of the molecules, even though they are deformed due to strong interaction with the substrate.
Source:IOPscience