Transient photoconductivity study of shallow electron traps in [Ru(CN)6]4- doped AgCl microcrystals:: effects of doping concentration and position

Cubic AgCl microcrystals doped with K4Ru(CN)(6) were studied by transient microwave photoconductivity (TMPC) in X-band. The dopant was introduced in either the core, the subsurface shell or the outer shell of the microcrystals and its concentration was varied between 0 and 100 ppm. [Ru(CN)(6)](4-) increases strongly the photoelectron response time at both room temperature (RT) and 120 K, the increase being smaller when the doping level decreases and when the doping position is closer to the surface of the microcrystals. This can be semiquantitatively explained by a model in which [Ru(CN)(6)](4-) introduces shallow electron traps (SETs), the density of which increases with the doping level. Within this model, the photoelectron response time is controlled by competitive trapping processes in the doping area and at the surface. Evidence is presented showing that [Ru(CN)(6)](4-) related centres may interact at higher local concentrations. The knowledge obtained from this study may be useful for practical microcrystal design making use of SETs introduced by dopants in AgX (X = Cl, Br). Finally, good agreement with experimental results obtained by other techniques, e.g. Q-band TMPC at RT and electron paramagnetic resonance at low temperature, will be demonstrated.