Studies of oxygen-related and carbon-related defects in high-efficiency solar cells

Oxygen and carbon related defects in silicon, particularly as related to high-efficiency silicon solar cells were studied. A summary of oxygen processes in silicon versus process temperature was shown along with experimental results. The anamolous diffusion of oxygen was explained by the dissociation of the center allowing O sub i to move through the lattices

Oxygen and carbon in silicon

The properties of the early transistors were determined by the minority-carrier lifetime, as is the silicon photovoltaic solar cell. Most of the devices on the modern integrated circuits are majority carrier devices, in part to avoid this lifetime dependence. The micro-electronics industry typically starts with wafers with a minority-carrier lifetime of 1000 micro-seconds, but during device fabrication this lifetime is reduced to beflow 1 micro-second, in spite of extraordinary cleanliness and precautions. Process-induced defects (PID) include point defects, defect complexes, line defects, and bulk precipitates. One of the aspects that needs to be better understood is the nature of minority carrier recombination at line defects and at precipitates. Some of the PIDs are known to be related to the fast-diffusers of the iron-series transition elements. One of the common techniques of dealing with these elements is intrinsic gettering by the oxygen precipitates. But even in the gettered state, there may be a residual effect on the lifetime. Oxygen is an almost ubiquitous impurity in silicon and plays an important role in both integrated circuits and solar cells. The isolated oxygen interstitial is electrically inactive, but in its various aggregated forms it has a variety of electrical activities. The agglomeration and precipitation of oxygen, including impurity gettering and the complicating role of carbon, is discussed

Investigation of critical slowing down in a bistable S-SEED

A simulation of S-SEED switching based upon experimental data is developed that includes the effect of critical slowing down. The simulation's accuracy is demonstrated by close agreement with the results from experimental S-SEED switching. The simulation is subsequently used to understand how the phenomenon of critical slowing down applies to switching of an S-SEED and how the effect on photonic analog-to-digital (A/D) converter performance may be minimized.B. A. Clare, K. A. Corbett, K. J. Grant, P. B. Atanackovic, W. Marwood and J. Munc

Modeling of radiation damage in silicon solar cells

One MeV electron irradiation produces preponderantly isolated vacancy interstitial pairs. If neither of these defects is mobile, the concentration of each grows linearly with fluence. Annealing of damage depends on the nature of the damage. Vacancy interstitial pairs which are bound by an interaction such that they mutually annihilate rather than dissociate are termed close pairs; close pair recovery usually occurs at a lower temperature than the temperature at which long distance defect migration occurs. Annealing of the remaining frozen in damage occurs when a temperature is reached where the vacancy or interstitial is mobile; usually the interstitial is more mobile than the vacancy. The recovery occurs in two regimes which may be resoluable

Impurity-Concentration Profile for an Exponentially Decaying Diffusion Coefficient in Irradiation Enhanced Diffusion

The diffusion equation is solved for a semi-infinite region in the case of irradiation-enhanced diffusion produced by a diffusion coefficient falling off exponentially in the medium. Near the surface the concentration profile due to enhanced diffusion has a larger concentration than the profile due to thermal diffusion; conversely far from the surface the enhanced-diffusion profile has a lower concentration than that due to thermal diffusion. Thus, this type of enhanced diffusion results in a more abruptly changing profile than does thermal diffusion

Pseudotumor cerebri and pregnancy.

Journal ArticlePseudotumor cerebri (PTC) is most commonly seen in obese women of reproductive age. We studied 109 women with PTC between ages 16 and 44 years. In 11, PTC started during pregnancy. Thirteen women with previous diagnosis of PTC, including two of the aforementioned 11, had an additional 17 documented pregnancies. Patients were matched by age and parity with controls. Obstetric complications occurred more frequently in the controls. Visual loss occurred with the same frequency in pregnant and nonpregnant patients. Treatment of PTC patients in pregnancy should be the same as for nonpregnant PTC patients, except that calorie restriction and diuretic use are contraindicated. Obstetric management is no different from that of normal pregnancy

Debugging real accelerators

Particle losses and emittance growth in the injection process can result form mismatched injected beams arising from quadrupole errors in the ring and injection line. We describe a method, based on carefully analyzing the BPM-corrector response matrix, which allows the accurate determination of quadrupole errors and, at the same time, determines BPM and corrector calibration errors as well as the BPM resolution. Results from SPEAR, NSLS, ALS, and CELSIUS will be briefly described

Measurements of the Temperature and E-mode Polarization of the CMB from 500 Square Degrees of SPTpol Data

We present measurements of the E-mode polarization angular auto-power spectrum (EE) and temperature–E-mode cross-power spectrum (TE) of the cosmic microwave background (CMB) using 150 GHz data from three seasons of SPTpol observations. We report the power spectra over the spherical harmonic multipole range 50 1050 and ℓ > 1475, respectively. The observations cover 500 deg^2, a fivefold increase in area compared to previous SPTpol analyses, which increases our sensitivity to the photon diffusion damping tail of the CMB power spectra enabling tighter constraints on ΛCDM model extensions. After masking all sources with unpolarized flux > 50 mJy, we place a 95% confidence upper limit on residual polarized point-source power of D_ℓ = ℓ(ℓ +1 )C_ℓ/2 π 1000 results in a preference for a higher value of the expansion rate (H_0 = 71.3 ± 2.1 km s^-1 Mpc^-1) and a lower value for present-day density fluctuations (σg_8 = 0.77 ± 0.02)

High-energy electron-induced damage production at room temperature in aluminum-doped silicon

DLTS and EPR measurements are reported on aluminum-doped silicon that was irradiated at room temperature with high-energy electrons. Comparisons are made to comparable experiments on boron-doped silicon. Many of the same defects observed in boron-doped silicon are also observed in aluminum-doped silicon, but several others were not observed, including the aluminum interstitial and aluminum-associated defects. Damage production modeling, including the dependence on aluminum concentration, is presented