Tunneling density states

Fig. 4. Left Tunneling density of states measured at 60 mK at the Au surface of Nb-Au bilayer samples with a varying Au thickness Ln. Data from the 130 and 200 nm samples are not shown for ease of reading. Right, top Schematic cross section of the full Nb-Au bilayers sample. Right, bottom STM image (410 x 410 nm2) at 100 mK of the sample with a Au thickness of 72 nm. The rms roughness for this image is 3.4 nm.

Tuning, 19-46 found in references Tunneling barriers, 16-9, 16-14 Tunneling density of states, 16-7, 16-10... 

Tanuma et al. (1998) calculated the tunneling density of states on the uneven surface of d-wave superconductors and showed that their calculation reproduced various types of anomalous features observed in the actual tunneling experiments, such as ZBCP, double-peak and multiple-dip structures, and a suppressed superconducting gap. They claimed that the wide variety of experimental data showing these features are namral for anisotropic superconductors, and hence, should not be rejected as unidentified spectra observed on degraded surface or in bad junctions (Kashiwaya et al. 1994a). 

This suggests to exploit tunneling as an experimental tool to detect crystal field levels of RE-impurities (Fulde et al., 1970). The physical process which should enable this is the energy dependent life time of the conduction electrons. This leads to a frequency dependent superconducting order parameter. The latter causes a structure in the tunneling density of states which can be measured. In order to demonstrate the crystal-field effects we have plotted in fig. 17.25a the tunneling density of states of a superconductor containing RE-... 

Under Httle or no illumination,/ must be minimized for optimum performance. The factor B is 1.0 for pure diffusion current and approaches 2.0 as depletion and surface-mode currents become important. Generally, high crystal quality for long minority carrier lifetime and low surface-state density reduce the dark current density which is the sum of the diffusion, depletion, tunneling, and surface currents. The ZM product is typically measured at zero bias and is expressed as RM. The ideal photodiode noise current can be expressed as follows ... 

Scanning tunneling spectroscopy (STS) can, in principle, probe the electronic density of states of a singlewall nanotube, or the outermost cylinder of a multi-wall tubule, or of a bundle of tubules. With this technique, it is further possible to carry out both STS and scanning tunneling microscopy (STM) measurements at the same location on the same tubule and, therefore, to measure the tubule diameter concurrently with the STS spectrum. No reports have yet been made of a determination of the chiral angle of a tubule with the STM technique. Several groups have, thus far, attempted STS studies of individual tubules. 

---