Surface states and space charge layer dynamics on Si(111)2×1: A free electron laser-synchrotron radiation study

Abstract

Combining the use of a UV storage ring free electron laser and of synchrotron radiation, a time resolved core level spectroscopy study has been performed on photoexcited Si(111)2×1 surfaces with subnanosecond resolution. This enabled us to measure band bending fluctuations, caused by surface carrier dynamics, during the first nanosecond after photoexcitation; differences in the Si2p core level lineshape, dependent on the pump-probe time delay, were also observed. The presence of defects was found to reduce the fluctuations and make the carrier recombination process faster.

XPS for probing the dynamics of surface voltage and photovoltage in GaN

“…In conventional data gathering mode the sample is grounded, and the position as well as the intensity of the peaks are recorded in a static fashion [20]. Although several reports have appeared in the literature related to dynamical XPS measurements in the two extreme ends, very fast (nanoseconds to attoseconds) [21][22][23][24], and very slow (minutes to hours) [25][26][27] through various publications, the basic principles and techniques for implementing such measurements employing very simple modification to conventional instruments [28][29][30][31][32][33][34][35][36][37][38][39].…”

Le laser à électrons libres UV de super-ACO : source et applications

“…Ces mouvements sont suivis à l'échelle sub-ns par photoémission de coeur à l'aide du RS. Dans le cas de la surface de Si(lll) 2x1, nous avons ainsi pu mettre en évidence une dynamique de relaxation particulière faisant intervenir explicitement les états de surface dans les premières centaines de ps suivant l'excitation LEL [6]. D'autres interfaces comme Si/Si02, aussi étudiée, présentent des comportement différents en fonction de l'épaisseur de recouvrement d'oxyde, mettant en évidence des effets d'accumulation de charge à la surface de la couche d'oxyde [7].…”

Measurement of synchrotron pulse durations using surface photovoltage transients

“…A 'fast' component of decay is observed between 400 and 500 ps and is likely due to rapid electron-hole recombination at the semiconductor surface. Surface recombination is thought to be mediated by trap states (which lie within the semiconductor bandgap) and as such will depend on the nature of the surface [1][2][3]. Measurements of surface dynamics on annealed Si(111)2x1 surfaces indicate surface carrier decay times of order 100 ps …”

“…From an applications perspective, x-ray interactions with a laser-perturbed material may be used to characterize synchrotron x-ray pulses. The surface photovoltage effect has been studied previously [1,2] and provides an opportunity for such synchrotron x-ray pulse characterization. We describe time-resolved measurements of Si 2p photoemission peak shifts induced by surface photovoltage transients.…”

“…4 [2,3]. The samples used in the present experiments are Ar-ion sputtered Si(111)2x1 samples and the measurements of Fig.…”