Utility and constraint on the use of pump-probe photoelectron spectroscopy for detecting time-resolved surface photovoltage

Utility and constraints on using the pump-probe photoelectron spectroscopy for detecting the time-resolved surface photovoltage on the semiconductor surface are discussed by solving the equation of motion for the electron from the sample to the analyzer. The escape time, which is defined as the time for the electron to achieve the 99% of the photovoltage, determines the basic temporal resolution. It can be derived from a simple formula with the pump beam radius and the initial kinetic energy of the electron and lies in a range of nano seconds with a usual experimental condition so far. However, an analysis revealed that a time constant for the decay in the SPV can be correctly measured with the decay in the kinetic-energy shift as a function of the pump-probe time difference even for a much shorter time constant than the escape time. Meanwhile, the value of the kinetic-energy shift does not agree with the true SPV. The relation between the true SPV and the observed kinetic-energy shift is estimated. (c) 2012 Elsevier B.V. All rights reserved.