Differential Charging in SiO₂/Si System As Determined by XPS

Abstract

The Si2p binding and the Si KLL kinetic energy difference between the SiO 2 layer and Si substrate is shown to be influenced by application of external voltage bias to the sample holder due to the differential charging as was already reported earlier (Ulgut, B.; Suzer, S. J. Phys. Chem. B 2003, 107, 2939). The cause of this bias induced (physical)-shift is now proven to be mostly due to partial neutralization by the stray electrons within the vacuum system by (i) introducing additional stray electrons via a filament and following their influence on the measured binding energy as a function of the applied voltage, (ii) measuring the Auger parameter. It is also shown that citrate-capped gold nanoclusters deposited on the SiO 2 /Si system experience differential charging similar to that of the oxide layer rather than the silicon substrate.

X-ray Photoelectron Spectroscopic Analysis of Si Nanoclusters in SiO2 Matrix

“…This is judged by the measured difference between the Si2p(Si 4+ ) and the Au4f 7/2 peaks to be larger than the theoretical value of 19.4 eV. 26 When we examine the oxide sample containing Si(nc), we observe that the charging is much more severe, and the Si2p peaks shift more than 15 eV when we change the bias from +10 and -10 V. This intense charging is related to the way the sample is prepared; PECVD produces many defects for trapping the charges induced by photoemission, as was also observed for the near stoichiometric SiO 2 films. However, within our experimental capabilities, we were not able to induce additional differential charging (neither reduced nor enhanced) between the Si(nc) and the SiO 2 host, as opposed to the case of a uniform 6-nm thermal oxide layer on silicon substrate.…”

“…As we reported recently, one can control the charging of various surface structures by the application of voltage stimuli in static and/or pulsed modes to the sample rod while recording XPS spectra. [24][25][26][27][28][29] In this contribution, we extend our application to samples containing silicon nanoclusters Si(nc) in ca. 300 nm thin SiO 2 films prepared using the PECVD technique; we are attempting to offer further experimental data for elucidating various chemical/ physical shifts of small nanoparticles measured by XPS.…”

X-ray-Induced Production of Gold Nanoparticles on a SiO2/Si System and in a Poly(methyl methacrylate) Matrix

“…64 In other words, Au4f levels follow faithfully the potential developed on the SiO 2 layer so that the Si2p of the oxide can be taken as the reference. 65 The other issue is the value of the reference peak (i.e., Si2p of the Si 4+ ). For this purpose, a gold layer is deposited on the SiO 2 /Si system using physical vapor deposition with an estimated Au layer ranging from 2 to 10 nm until a uniform gold layer (as judged by scanning electron microscopy (SEM) images) could be grown on the SiO 2 /Si system.…”

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].…”