The thesis is devoted to the experimental study of electronic processes of charge transport in the nanostructured insulator containing the silicon nanoclusters. The aim of the work is to study the transport, capture and emission processes of the charge occurring in the nanostructured dielectric of metal-dielectric-silicon structures for the development of non-volatile memory devices and the construction of models of the charge-capture physical processes in nanocrystal memory structures. The importance of this work is caused the wide application and development of non-volatile memory devices. Nanocrystalline memory is the result of the evolution of standard flash memory, which eliminates the disadvantages of the latter. Replacing the continuous solid floating gate with the array of electrically unconnected centers (nodes) improves the reliability of the device and allows us to reduce the thickness of the tunnel dielectric and the floating gate layer. However, there remain a number of unresolved problems associated with physical processes in structures with silicon nanocrystals. Therefore, there is a need for the detailed study of the electrophysical properties, especially transport, capture and emission processes of the charge in the structures of non-volatile nanocrystal memory for their further development. The object of the research in the work are: a) MIS pSi / SiO2(Si) / Al structures of the nanocrystalline memory with one and two layers of Si nanoclusters in the SiO2 dielectric; b) MIS structures with nanocomposite SiOx(Si), SiOx(Si, Fe) films containing Si and Fe nanoclusters.
For the experimental study of the transport, capture and emission processes of the charge occurring in a nanostructured insulator of metal-dielectric-silicon structures, the unique installation for measurements of the capacitance-voltage characteristics was developed and manufactured, and the number of original methods for the measurement and processing of the results were used, namely: the method of successive approximations, the method of the memory window formation in the bipolar and unipolar modes, the method of dynamics of accumulation and erasure of the charge, the method for studying the storage of accumulated charge.
For the first time, the possibility of unipolar programming of nanocrystalline memory devices, which is associated exclusively with small nanocrystal sizes and local enhancement of the electric field in nanocrystal, was demonstrated. The 3-stage model of the charge leakage was proposed, which is based on the existence of both signs charges in the insulator and the presence of interconnected processes. It is established that the two-layer nanocrystalline floating gate effectively provides blocking of accumulated charge from decay. The energy characteristics of nanocrystalline memory structures with one and two layers of nanocrystals are determined and energy band diagrams are constructed.
The last chapter of the work is devoted to the study of electronic transport in structures containing silicon nanocrystals and silicon and iron nanocrystals at constant and alternating currents. The mechanisms of electronic transport have been established, depending on the electric field and temperature, and the energy positions of traps and their concentration were determined. It has been shown for the first time that the impedance of structures with a SiOx(Si, Fe) film has the inductive character up to the frequency of 1 MHz, which allows us to offer such structure as film inductor in high frequency devices. The clear hysteresis of С-V characteristics was found, both in the case of SiOx(Si) films, and in the case of SiOx(Si, Fe) films, which indicates the accumulation and erase of charge from the nanocrystals. The larger value of the memory window of MIS structures with SiOx(Si, Fe) films is due to the features of the energy band diagram and the higher available electron state density in the case of Fe nanoclusters.
