Annealing studies of highly doped boron superlattices

Abstract

Coevaporation of B2 O3 during silicon molecular-beam epitaxy at growth temperatures (TG ) varying from 540 to 800 °C has been used to prepare superlattice structures (pipi’s) of varying boron concentration (3×1018 –3×1020 B cm−3). The superlattices were subsequently subjected to various annealing procedures and the layers were examined by secondary ion mass spectrometry, electrochemical profiling, and cross-sectional transmission electron microscopy. A significant redistribution of boron was observed even before annealing for TG >700 °C and high boron concentrations. In addition, significant oxygen was incorporated for TG ≤700 °C, with a growth rate of 0.5 nm s−1 and a B2 O3 flux of 2×1013 cm−2 s−1. After annealing, the boron diffusion coefficients were determined for the layers and found to vary significantly with TG.

Mapping electrically active dopant profiles by field-emission scanning electron microscopy

“…8 SIMS and electrochemical CV ͑eCV͒ measurements were performed to profile the atomic and free carrier concentrations of boron. One sample consists of five sets of heavily doped boron layers ͑50 nm͒ grown at five different temperatures in the range 600-800°C.…”

“…The separation distance between individual layers was 100 nm, and between each temperature set was 200 nm; details of the growth conditions can be found elsewhere. 8 Boron clustering is usually observed when the concentration exceeds the solid solubility limit (ϳ3ϫ10 19 cm Ϫ3 ), and when the temperature is high enough to initiate the clustering process. Figure 1͑a͒ shows the SIMS profile of the as-grown structure.…”

Ion Beam Doping of MBE Silicon by As+

“…Epitaxial growth apparently proceeds unimpeded by the As + ion beam. The small asymmetry is believed to be a SIMS artifact (22,23) rather than due to segregation effects observed in coevaporation of dopants (23,24). At 350~ extended defects appear and a heavily faulted columnar microstructure results, which from our previous experience becomes polycrystalline as the temperature is reduced further (19,20).…”

Mechanical ventilation and the total artificial heart: optimal ventilator trigger to avoid post-operative autocycling - a case series and literature review

“…TAH oscillations induce significant pulmonary volume displacement as there are large pneumatic pressure changes for each beat[14,15]. A patient with post-operative respiratory failure after Jarvik-7 TAH placement showed significant lung displacement during apnea[15].…”

“…A patient with post-operative respiratory failure after Jarvik-7 TAH placement showed significant lung displacement during apnea[15]. In fact, this patient's cardiac oscillations were large enough for sustained alveolar ventilation with an arterial pCO 2 of 61 after one hour of total apnea.…”