Static domain formation in doped semiconductor superlattices results in several current branches separated by abrupt discontinuities that exhibit hysteresis. The transition from one branch to its adjacent one is studied by time-resolved switching experiments. The mean value of the relocation time increases by more than one order of magnitude, when the final voltage on the adjacent branch is reduced to a value approaching the discontinuity. At the same time, the distribution function of the relocation time changes from a simple Gaussian to a first-passage time form.

Reactive scattering of CO molecules at oxygen-rich Ru(0001) surfaces with concentrations equivalent up to 16 monolayers and sample temperatures between 300 and 700 K led to the identification of two distinct reaction channels in the transient CO2 rate. The first reaction channel is related to the recombination of CO molecules with oxygen atoms already located on the surface. The second reaction channel, which can be observed at sample temperatures above about 400 K, is controlled by the diffusion of oxygen atoms from the near-surface region toward the surface.

The formation of static electric-field domains in doped semiconductor superlattices appears in the currentvoltage (I-V) characteristics as multiple current branches separated by abrupt discontinuities. The switching dynamics of the charge-accumulation layer forming the domain boundary is experimentally investigated at dc voltages in the first plateau of the I-V characteristic for different polarities and amplitudes of the applied voltage steps. When the voltage is decreased ͑down jumps͒ from its initial dc value, the accumulation layer can directly move from its initial position to its final position, in accordance with the direction of the applied voltage step. However, when the voltage is increased ͑up jumps͒, there are two different modes of the relocation motion of the accumulation layer. For small up jumps, the accumulation layer can still move directly from its initial to its final position. When the amplitude of the transient current peak is above a critical value, a charge dipole is injected at the emitter contact, in addition to the existing monopole formed by the domain boundary. The experimentally observed switching behavior is in excellent qualitative agreement with recent theoretical work ͓A.

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