Browsing by Subject "Surface photovoltages"

Now showing 1 - 3 of 3

Open Access
Communication: Enhancement of dopant dependent x-ray photoelectron spectroscopy peak shifts of Si by surface photovoltage
(2011) Sezen, H.; Süzer, Şefik
Binding energies measured by x-ray photoelectron spectroscopy (XPS) are influenced by doping, since electrons are transferred to (p-type) and from (n-type) samples when they are introduced into the spectrometer, or brought into contact with each other (p-n junction). We show that the barely measurable Si2p binding energy difference between moderately doped n- and p-Si samples can be enhanced by photoillumination, due to reduction in surface band-bending, which otherwise screens this difference. Similar effects are also measured for samples containing oxide layers, since the band-bending at the buried oxide-Si interfaces is manifest as photovoltage shifts, although XPS does not probe the interface directly. The corresponding shift for the oxide layer of the p-Si is almost twice that of without the oxide, whereas no measurable shifts are observable for the oxide of the n-Si. These results are all related to band-bending effects and are vital in design and performance of photovoltaics and other related systems.
Open Access
Dynamical XPS measurements for probing photoinduced voltage changes
(2010) Sezen, H.; Süzer, Şefik
Photoillumination with 405 nm laser causes shifts in XPS peaks of n-Si(100), and CdS. To distinguish between surface photovoltage (SPV), and charging, dynamical measurements are performed, while sample is subjected to square wave pulses of ± 10.00 V amplitude, and 10-3-10 5 Hz frequency. For n-Si, Si2p peaks are twinned at + 10.00 and -10.00, yielding always 20.00 eV difference. Photoillumination shifts the twinned peaks to higher energies, but the difference is always 20.00 eV. However, for CdS, the measured binding difference of Cd3d peaks exhibits strong frequency dependence due to charging, which indicates that both fast SPV and slow charging effects are operative.
Open Access
Transient surface photovoltage in n-and p-GaN as probed by x-ray photoelectron spectroscopy
(2011) Sezen, H.; Özbay, Ekmel; Aktas, O.; Süzer, Şefik
Transient surface photovoltage (SPV) of n and p-GaN was measured using x-ray photoelectron spectroscopy (XPS) with a time resolution of 0.1 s. The measured SPV transients for both n- and p-GaN are 0.1 s, and for the n-GaN they are not affected by flood-gun electrons. However, for the p-GaN, the transient character of the SPV is dramatically changed in the presence of flood-gun electrons. The combination of time-resolved XPS, flood gun, and laser illumination give us a new way to study the surface electronic structure and other surface properties of semiconducting materials in a chemically specific fashion.