In this paper we show that the electronic properties of ultrathin tetrahedral amorphous carbon (ta-C) films are heavily dependent on their thickness. By using scanning tunnelling spectroscopy, Raman spectroscopy, and conductive atomic force microscopy, it was found that a decrease of ta-C thickness from 30 to 7 nm leads to (i) the narrowing of the band gap; (ii) appearance of shallower monoenergetic traps as well as the increase of their concentration; (iii) the increase of the equilibrium concentration of free charge carriers and their mobility; which were caused by (iv) the increase in the sp(2) fraction. However, beyond a certain ta-C thickness (7 nm) the electronic properties of the studied samples start to deteriorate, which is highly likely related to titanium oxide formation at the Ti/ta-C interface. The same tendency is observed for the sample with beforehand air-formed native titanium oxide at the interface. With respect to the last point, it is suggested that the ta-C layer has no uniform coverage if its thickness is small enough (less than 7 nm). The experimental results were rationalized by detailed atomistic simulations. By using the so-called "Tauc plot" we introduce the possibility of the coexistence of bulk and surface band gaps originating from the large increase in sp(2) bonded carbon atoms in the surface region compared to that in the bulk ta-C. The results from the simulations were found to be consistent with the experimental measurements. The previously stated variation in the electronic properties of the layers as a function of their thickness was also exhibited in the electrochemical properties of the samples. It appears that the thinner ta-C layers had more facile electron transfer kinetics as determined with a ferrocenemethanol (FcMeOH) outer sphere redox system. However, if the ta-C layer thickness was reduced too much, the films were not stable anymore.

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Influence of fabrication technology on field electron emission properties of nanoporous carbon (NPC) was investigated. Samples of NPC derived from different carbides via chlorination at different temperatures demonstrated similar low-field emission ability with threshold electric field 2-3 V/μm. This property correlated with presence of nanopores with characteristic size 0.5–1.2 nm, determining high values of specific surface area (>800 m2/g) of the material. In most cases, current characteristics of emission were approximately linear in Fowler-Nordheim coordinates (excluding a low-current part near the emission threshold), but the plots’ slope angles were in notable disagreement with the known material morphology and electronic properties, unexplainable within the frames of the classical emission theory. We suggest that the actual emission mechanism for NPC involves generation of hot electrons at internal boundaries and that emission centers may be associated with relatively large (20–100 nm) onion-like particles observed in many microscopic images. Such particles can serve two functions: to provide additional “internal” enhancement of the electric field and to inhibit relaxation of hot charge carriers due to the “phonon bottleneck” effect.

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An ultrafast compact classical Mott detector is described. The efficiency of the polarimeter is epsilon = 6 x 10(-4) and the maximum counting rate approximately 2000 kcps. The Mott polarimeter employs photomultipliers with scintillators as electron energy sensitive detectors with low dark noise. The photomultipliers and scintillators are placed in vacuum. With this choice of technology, it will be possible to build a classical Mott detector with a bulk size of cubic decimeter in the future.