, Uxbridge, UK) with 5.0 kV voltage and 10.0 μA current, on top and side views. After each heating stage, the specimens were scanned by home-made XPS. Core level and valance band photoelectron spectra were excited by monochromatic Al K radiation (1,487 eV) and collected, at take-off angle of 35°,

by a hemispherical analyzer with adjustable overall resolution between 0.8 and 1.2 eV. The surveys were conducted in various ranges of electron energies including the overall binding energy survey (0 to 1,000 eV) besides individual spectra for Si 2p (95.0 to Saracatinib order 110.0 eV), C 1 s (282.0 to 287.0 eV) and O 1 s (520 to 550 eV) which were monitored more accurately in a discrete number of scans. All spectra were taken at room temperature in a UHV chamber of about 10−10 Torr pressure. The resulting XPS spectra were analyzed by spectral decomposition using the XPS peak software and their oxide levels were determined. Results and discussion The VLS-grown Si NWs used in this study Tanespimycin mouse were randomly oriented with average diameter and length of 84.96 nm and 3.508 μm, respectively. The pristine Si NWs are covered by a native oxide layer of 1 to 4 nm. SEM and transmission electron microscopy (TEM) micrographs of the pristine Si NWs are depicted in Figure 1. Residual gold nanoparticles

were removed by rinsing the Si NWs into HNO3 solution preventing its catalytic effect on oxidation. Figure 1 SEM and transmission electron microscopy (TEM) micrographs of the pristine Si NWs. (a) Top-view SEM micrograph of the Si NWs grown by VLS mechanism showing their random orientation. (b) TEM image of an individual Si NW cross-section representing the continuous native oxide layer of 3 to 4 nm in diameter atop. Regarding the micrographs, the Si core diameter can be estimated as 50 ± 10 nm. The red dotted line

insists on the fact that TEM micrograph is taken for a single Si NW among the large ensemble observed through SEM. As an illustrative Si 2p spectrum of oxidized Si NWs, the Si 2p spectrum of the H-terminated Si NWs annealed at 500°C for 60 min is depicted in Figure 2. By formation of even very thin silicon dioxide layers, the Si 2p XPS survey of Si NWs changes, showing a peak between the binding energies of 102 to 104 eV. To quantitatively evaluate MycoClean Mycoplasma Removal Kit the oxidation process, Si 2p spectral decomposition was conducted on the spectra after Shirley background subtraction, through a curve-fitting procedure using Gaussian-Lorentzian functions [16]. Consequently, the Si 2p spectra can be divided into six different sub-peaks including two silicon spin-splitting peaks as Si 2p 1/2 and Si 2p 3/2, three silicon sub-stoichiometric oxides (known as suboxides) peaks as Si2O, SiO and Si2O3, and the silicon dioxide (SiO2) peak. The chemical shifts (Δ) of the sub-peaks obtained in Figure 2 relative to the Si 2p 3/2 (at 99.60 ± 0.02 eV) are as follows: Si 2p 1/2 (Δ = 0.60 eV), Si2O (Δ = 0.97 eV), SiO (Δ = 1.77 eV), Si2O3 (Δ = 2.50 eV), and SiO2 (Δ = 3.87 eV).