Communication: Enhancement of dopant dependent x-ray photoelectron spectroscopy peak shifts of Si by surface photovoltage

Cataloged from PDF version of article.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. (C) 2011 American Institute of Physics

XPS for chemical- and charge-sensitive analyses

Cataloged from PDF version of article.By recording X-ray photoelectron spectroscopic binding energy shifts, while subjecting samples to a variety of optical and electrical stimuli, information about charge accumulation on materials or surface structures can be obtained. These stimuli included d.c. as well as a.c. electrical and/or optical pulses covering a wide frequency range (10−3 to 106 Hz) for probing charging and/or photovoltage shifts, stemming from impurities, dopants, defects, etc., whether created intentionally or not. The methodology is simple to implement and provides several new dimensions for thin films and materials analyses

Probing the charge build-up and dissipation on thin PMMA film surfaces at the molecular level by XPS

Cataloged from PDF version of article.What's the charge? X-ray photoelectron spectroscopy was used to determine the charge state and dynamics of charge build-up and decay on a thin poly(methyl methacrylate) film. The film is initially negatively charged to around −2 V and becomes progressively positively charged during the course of the XPS analysis

XPS Investigation of a CdS-Based Photoresistor under Working Conditions: Operando−XPS

Cataloged from PDF version of article.A noncontact chemical and electrical measurement X-ray photoelectron spectroscopy (XPS) technique is performed to investigate a CdS-based photoresistor during its operation. The main objective of the technique is to trace chemical- and location-specified surface potential variations as shifts of the XPS Cd 3d(5/2) peak position without and under photoillumination with four different lasers. The system is also modeled to extract electrical information. By analyzing the measured potential variations with this model, location-dependent resistance values are represented (i) two dimensionally for line scans and (ii) three dimensionally for areal measurements. In both cases, one of the dimensions is the binding energy. The main advantage of the technique is its ability to assess an element-specific surface electrical potential of a device under operation based on the energy deviation of core level peaks in surface domains. Detection of the variations in electrical potentials and especially their responses to the energy of the illuminating source in operando, is also shown to be capable of detecting, locating, and identifying the chemical nature of structural and other types of defects

Chemical Visualization of a GaN p-n junction by XPS

We report on an operando XPS investigation of a GaN diode, by recording the Ga2p 3/2 peak position under both forward and reverse bias. Areal maps of the peak positions under reverse bias are completely decoupled with respect to doped regions and allow a novel chemical visualization of the p-n junction in a 2-D fashion. Other electrical properties of the device, such as leakage current, resistivity of the domains are also tapped via recording line-scan spectra. Application of a triangular voltage excitation enables probing photoresponse of the device

Transient surface photovoltage in n- and p-GaN as probed by x-ray photoelectron spectroscopy

Cataloged from PDF version of article.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. (C) 2011 American Institute of Physics

Victim Identification, Framing Heuristic and Stress Effects on the Donation Decision

The tendency of an individual to share his beings with other people arises from the social aspect of human nature. Especially in today's conditions where the gap between advantageous and disadvantaged groups is getting deeper, donation is extremely important to reach a global level of welfare and to create fair living standards for all. Due to the stated priorities, donation behavior has an important place among both religious and moral values. However, the factors that lead an individual towards donation behavior are not only social rules. In addition to external factors, important internal factors such as emotions also play a big role in the donation decision. In addition, there are many variables such as the donated thing itself, total assets of the donor and indeed the characteristics of the donor. Donation behavior, which is widely examined in the literature, is also considered as an important decision making subject. In our study, the effects that motivate an individual towards a donation; along with the donation amount and the ratio of donation, were examined with framing heuristics which express the individual's knowledge of the victim. The mentioned variables were associated with stress as one of the strongest negative arousal output, to understand the emotional aspect of a donation decision. The stress levels of the participants, who manipulated by two different scenarios, were monitored with galvanic skin response to determine the decision-making scenarios which triggered stress. As a result; it has been found that the individual's effort to gain the money he donates and the features of the donation call significantly affect the decision

Yield and quality response of drip-irrigated pepper under Mediterranean climatic conditions to various water regimes

This study examines the effects of different irrigation regimes on yield and water use of pepper irrigated by a drip system under field conditions during the 2004 growing season at the Soil and Water Resources Research Institute in Tarsus, Turkey under Mediterranean climatic conditions. The field trials consisted of three irrigation intervals (IF1:20±2, IF2:40±2 and IF3:60±2 mm of cumulative pan evaporation) and evaluated by three irrigation levels (DI1=0.50, DI2=0.75 and DI3=1.00). Both the irrigation levels (DI) and intervals (IF) had significantly different effects on pepper yields. The maximum and minimum yields were obtained from the IF1DI3 and IF3DI1 treatment plots as 35920 and 21390 kg ha-1, respectively. The yields and yield components decreased as irrigation levels decreased for each irrigation interval. However, the larger irrigation interval (IF3) resulted in lower yields with all irrigation levels. Pepper seasonal evapotranspiration varied from a low 327 mm in the more stressfull treatment (IF3DI1) to a high 517 mm in the well irrigated control (IF1DI3). Significant linear relations were found between the pepper yield and the total water use for each irrigation interval. Irrigation intervals resulted in similar water use in the treatments with the same irrigation level. Water use efficiency (WUE) and irrigation water use efficiency (IWUE) values were significantly influenced by the irrigation intervals and levels. WUE ranged from 6.0 kg m-3 in IF3DI2 to 7.8 kg m-3 in the IF1DI1. The maximum IWUE was observed in IF1DI1, and the minimum IWUE was in IF3DI3 treatment. Both irrigation levels and frequencies had significantly different effects on quality parameters such as the first and second quality yield, number of fruit, mean fruit weight, pepper length and width, as well as plant height at harvest. In conclusion, the IF1DI3 irrigation regime is recommended for field grown pepper in order to attain higher yields with improved quality. Economic evaluation revealed that full irrigation treatment (IF1DI3) generated the highest net income. However, under water scarcity conditions, IF1DI2 treatment can provide an acceptable net income.Key words: Pepper, deficit irrigation, water use efficiency, yield response factor, economic evaluation