Si nanocrystals in sandwiched SiNx structures

The structure and composition of multilayered SiNx structures prepared by low pressure chemical vapour deposition were studied by cross-sectional transmission electron microscopy and spectroscopic ellipsometry. Using appropriate deposition parameters and post deposition annealing, well separated Si nanocrystals were obtained with avarage grain size of 8-10 nm

Charging behavior of silicon nitride based non-volatile memory structures with embedded semiconductor nanocrystals

The charging behavior of MNS (metal-nitride-silicon) and MNOS (metal-nitride-oxide-silicon) structures containing Si or Ge nanocrystals were studied by capacitance-voltage (C-V) and memory window measurements and by simulation. Both the width of hysteresis of C-V characteristics and the injected charge exhibited exponential dependence on the charging voltage at moderate voltage values, while at high voltages the width of hysteresis of C-V characteristics and the injected charge exhibited saturation. The memory window for reference MNS structure without nanocrystals was wider than that for reference MNOS structures. The presence of nanocrystals enhanced the charging behavior of MNOS structures, but in MNS structures nanocrystals exhibited the opposite effect. The main conclusion is that the presence of nanocrystals or other deep levels close to the Si surface enhances the charge injection properties due to the increased tunneling probability, but nanocrystals or other deep levels located far from the Si surface in the nitride layer do not enhance, but even can degrade the charging behavior by the capture of charge carriers. © 2012 Elsevier B.V. All rights reserved

Effect of location of Si or Ge nanocrystals on the memory behavior of MNOS structures.

Charge injection and retention behaviors of metal-nitride-oxide-silicon (MNOS) memory structures with Si or Ge nanocrystals embedded at a depth of 3 nm in the nitride layer were studied. The effect of Si nanocrystals on these properties was opposite in comparison with that of Ge nanocrystals. To understand the origin of these opposite effects, the influence of the oxide thickness and of the depth, size and location of semiconductor nanocrystals has been studied on the charging behavior of MNOS non-volatile memory structures by the calculation of electron and hole tunneling probabilities, and by the simulation of memory window, memory hysteresis and retention behavior. For MNOS structures it is obtained that the presence of nanocrystals enhances the charge injection resulting in better performance, but only for structures with thin tunnel oxide layer (below 3 nm), and if the nanocrystals are located close to the oxide/nitride interface. In the case of very high tunneling probability, i.e., of high tunneling currents the system approaches equilibrium and the memory behavior collapses. There is a narrow range of oxide thickness or depth of nanocrystals, where the charging properties change very fast. Retention exhibits a very sharp dependence on the oxide thickness and on depth of nanocrystals as well. Most part of the experimental results can be explained on the basis of the results of simulations

Charging Behaviour of Metal-Nitride-Oxide-Semiconductor Memory Structures with Embedded Si or Ge Nanocrystals

The charging behaviour of MNS (metal-nitride-silicon) and MNOS (metalnitride- oxide-silicon) structures containing Si or Ge nanocrystals were studied by capacitance-voltage (C-V) and memory window measurements and by simulation. Both the width of hysteresis of C-V characteristics and the injected charge exhibited exponential dependence on the charging voltage at moderate voltage values, while at high voltages the width of hysteresis of C-V characteristics and the injected charge exhibited saturation. The memory window for reference MNS structure without nanocrystals was wider than that for reference MNOS structures. The presence of nanocrystals enhanced the charging behaviour of MNOS structures, but in MNS structures nanocrystals exhibited the opposite effect. The main conclusion is that the presence of nanocrystals or other deep levels close to the Si surface enhances the charge injection properties due to the increased tunneling probability, but nanocrystals or other deep levels located far from the Si surface in the nitride layer do not enhance, but even can degrade the charging behaviour by the capture of charge carriers

Introduction: Dispersed Minorities and Non-Territorial Autonomy

The concept of non-territorial autonomy gives rise to at least two important questions: the range of functional areas over which autonomy extends, and the extent to which this autonomy is indeed non-territorial. A widely used early description significantly labelled this ‘national cultural autonomy’, implying that its focus is mainly on cultural matters, such as language, religion, education and family law. In many of the cases that are commonly cited, ‘autonomy’ may not even extend this far: its most visible expression is the existence of separate electoral registers or quotas for the various groups. Part of the dilemma lies in the difficulty of devolving substantial power on a non-territorial basis: to the extent that devolved institutions are state-like, they ideally require a defined territory. Ethnic groups, however, vary in the extent to which they are territorially concentrated, and therefore in the degree to which any autonomous arrangements for them are territorial or non-territorial. This article explores the dilemma generated by this tension between ethnic geography (pattern of ethnic settlement) and political autonomy (degree of selfrule), and introduces a set of case studies where the relationship between these two features is discussed further: the Ottoman empire and its successor states, the Habsburg monarchy, the Jewish minorities of Europe, interwar Estonia, contemporary Belgium, and two indigenous peoples, the Sa´mi in Norway and the Maori in New Zealand