Quenching dangling bonds

A pentacene OFET process is shown in Fig. 4.13, based on the processes proposed by Kelley and Baude, et al. in [74], [75] and [40]. All four layers in the device are shadow masked, and a passivation layer is used to quench reactive sites on the e-beam thermally deposited AI2O3 layer, which has a high density of dangling bonds. 

The optical band gap of silicon clusters increases with decreasing cluster size and all surface atoms with dangling bonds contribute to mid-gap electronic states (defects) which are assumed to quench photoluminescence. Saturation of the surface dangling bonds with hydrogen is the simplest way to eliminate defects, and therefore theoretical studies of the electronic structure of silicon clusters without defects are most easily performed on hydrogenated silicon clusters. The thermodynamic stability of these species is also of interest, because hydrogenated silicon clusters are formed in thermal and plasma CVD of silane. ... 

Figure 16 shows the ODMR spectra observed by Street (1982) for two different types of a-Si H samples, i.e., high-defect-density samples and low-defect-density samples. He identified a quenching line Q, observed in high-defect-density samples as being a coupled resonance of the dangling bond... 

The obtained results show a change (quenching) in the PL intensity after treatment of PS in a weak constant magnetic field. For the same period of time the PL intensity of the reference PS sample did not change. Additional studies carried out with the use of the IR spectroscopy indicated the disruption of a part of Si-0 bonds in the sample. The latter correlates well with the effect of PL quenching that can be attributed to an increase in the number of non-radiative recombination centers. Such centers in PS are silicon dangling bonds. 

Since the discovery of the intense red photoluminescence of porous silicon [1,2], much work has been devoted to this particular nanostructured material [4, 5] and, in the meantime, also to silicon nanoparticles [6, 7]. An important issue of current studies is the influence of the surface passivation on the photoluminescence properties. It has already been said that, in the quantum confinement model, it is essential that the surface is well passivated to avoid any dangling bonds [8]. Being middle-gap defects, these dangling bonds will quench the PL. On the other hand, the surface itself may lead to surface states that can be the origin of another kind of photoluminescence [9,10]. 

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