Browsing by Subject "Kinetic energy"

Now showing 1 - 6 of 6

Open Access
Differential charging in SiO2/Si systems as determined by XPS
(American Chemical Society, 2004) Karadas, F.; Ertas, G.; Süzer, Şefik
The Si2p binding and the SiKLL kinetic energy difference between the SiO2 layer and Si substrate is shown to be influence 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 and Auger parameter. It is also shown that citrate-capped gold nanoclusters deposited on the SiO2/Si system experience differential charging similar to that of the oxide layer rather than the silicon substrate.
Open Access
Electrical properties from photoinduced charging on Cd-doped (100) surfaces of CuInSe2 epitaxial thin films
(AVS Science and Technology Society, 2016) Johnson, N.; Aydogan, P.; Süzer, Şefik; Rockett, A.
The photoresponse of Cd-doped CuInSe2 (CIS) epitaxial thin films on GaAs(100) was studied using x-ray photoelectron spectroscopy under illumination from a 532 nm laser between sample temperatures of 28-260 °C. The initial, air-exposed surface shows little to no photoresponse in the photoelectron binding energies, the Auger electron kinetic energies or peak shapes. Heating between 50 and 130 °C in the analysis chamber results in enhanced n-type doping at the surface and an increased light-induced binding energy shift, the magnitude of which persists when the samples are cooled to room temperature from 130 °C but which disappears when cooling from 260 °C. Extra negative charge trapped on the Cu and Se atoms indicates deep trap states that dissociate after cooling from 260 °C. Analysis of the Cd modified Auger parameter under illumination gives experimental verification of electron charging on Cd atoms thought to be shallow donors in CIS. The electron charging under illumination disappears at 130 °C but occurs again when the sample is cooled to room temperature.
Open Access
Energy dissipation in atomic force microscopy and atomic loss processes
(American Physical Society, 2001) Hoffmann, P. M.; Jeffery, S.; Pethica, J. B.; Özer, H. Ö.; Oral, A.
Atomic scale dissipation is of great interest in nanomechanics and atomic manipulation. We present dissipation measurements with a linearized, ultrasmall amplitude atomic force microscope which is capable of measuring dissipation at chosen, fixed separations. We show that the dynamic dissipation in the noncontact regime is of the order of a few 10–100 meV per cycle. This dissipation is likely due to the motion of a bistable atomic defect in the tip-surface region. In the contact regime we observe dc hysteresis associated with nanoscale plasticity. We find the hysteretic energy loss to be 1 order of magnitude higher for a silicon surface than for copper.
Open Access
Trapped interacting Bose gas in nonextensive statistical mechanics
(The American Physical Society, 2002) Tanatar, Bilal
We study the Bose-Einstein condensation (BEC) phenomenon in an interacting trapped Bose gas using the semiclassical two-fluid model and nonextensive statistical mechanics. The effects of nonextensivity characterized by a parameter are explored by calculating the temperature dependent thermodynamic properties, fraction of condensed particles, and density distributions of condensed and thermal components of the system. It is found that nonextensivity in the underlying statistical mechanics may have large effects on the BEC transition temperature.
Open Access
Vortices in trapped boson-fermion mixtures
(Springer, 2005) Taşgin, M. E.; Subaşi, A. L.; Oktel, M. Ö.; Tanatar, Bilal
We consider a trapped system of atomic boson-fermion mixture with a quantized vortex. We investigate the density profiles of bosonic and fermionic components as functions of the boson-boson and boson-fermion short-range interaction strengths within the mean-filed approach. Stability of a vortex and conditions for the phase segregation are studied. We compare and contrast our results with the related system of droplets of 3He-4He mixtures.
Open Access
XPS characterization of Au (core)/SiO2 (shell) nanoparticles
(American Chemical Society, 2005) Tunc, I.; Süzer, Şefik; Correa-Duarte, M. A.; Liz-Marzán, L. M.
Core-shell nanoparticles with ca. 15-nm gold core and 6-nm silica shell were prepared and characterized by XPS. The Au/Si atomic ratio determined by XPS is independent of the electron takeoff angle because of the concentric spherical shape of the nanoparticles. The formula given by Wertheim and DiCenzo (Phys. Rev. B 1988, 37, 844) for spherical nanoparticles and the modified one by Yang et al. (J. Appl. Phys. 2005, 97, 024303) for core-shell nanoparticles are used to correlate the XPS-derived composition with the geometry of the nanoparticles only after significantly modifying either the bulk density of the silica shell or the attenuation length of the photoelectrons. © 2005 American Chemical Society.