Effects of hydrogen dilution on electron density in multi-hollow discharges with magnetic field for A-Si:H film deposition
We have measured dependence of electron density n<inf>e</inf> on hydrogen dilution ratio R= [H<inf>2</inf>]/([SiH<inf>4</inf>]+[H<inf>2</inf>]) in the multi-hollow discharges with or without magnetic fields to obtain information about the deposition rate enhancement due to hydrogen dilution and applying the magnetic fields. The R dependence of the n<inf>e</inf> did not correlate with that of the deposition rate. The n<inf>e</inf> exponentially decreases with a distance from the discharges z. The n<inf>e</inf> decreases faster for higher R. These complicated behaviors of n<inf>e</inf> may be explained by electron attachment to the clusters generated in the SiH<inf>4</inf>+H<inf>2</inf> discharges. For R=0, the n<inf>e</inf> was almost same value regardless with or without magnetic fields. For R=1, n<inf>e</inf> with magnetic fields was 1/10 of that without magnetic fields. We also found that, for R=0, ne drastically decreased with increasing the z, while for R=1, ne showed a gradual decrease with z. The effects of applying magnetic fields on the deposition are unclear but applying the magnetic fields may affect the electron energy distribution.
Microcrystalline silicon and ‘micromorph’ tandem solar cells
The case for thin-film silicon as one of the main future options for cost-effective photovoltaic solar cells is outlined. The limitations of present amorphous silicon (a-Si:H) solar cells are briefly mentioned. Hydrogenated microcrystalline silicon (μc-Si:H) deposited by PECVD (plasma-enhanced chemical vapor deposition) at low substrate temperatures (approx. 200 °C) constitutes a new and additional possibility for solar cells. Properties of intrinsic μc-Si:H layers deposited by PECVD at VHF (very high frequency) excitation frequencies are listed, together with the necessary conditions for obtaining device-grade material. Performances obtained so far with μc-Si:H solar cells are given; the latter are compared with estimated limits for pn- and pin-type devices with Eg = 1.1 eV. Finally, present performances and future perspectives for 'micromorph' (μc-Si:H/a-Si:H) tandem solar cells are discussed. © 2002 Elsevier Science B.V. All rights reserved.
THE METABOLISM OF AMINO ACIDS IN DIABETES MELLITUS.
The amino acid content of fasting human blood appears to be quite constant. Extensive surveys (1) have revealed only a few diseases in which the blood amino acid level is modified significantly. Acute yellow atrophy of the liver is associated with a rise in amino acids in the blood, whereas hypoaminoacidemia has been reported in patients with nephrosis and in pneumococcal pneumonia (2). Concerning the fasting amino acid level in diabetes mellitus there is little agreement. Several investigators (la, 3) have observed elevated amino acid levels in a few of their diabetic subjects. Greene, Sandiford and Ross (lb) studied 116 diabetics and observed that the average amino acid level was within normal limits. No accurate data on the condition or treatment of these patients were given. On the other hand, a high blood amino acid content has been reported in dogs with experimentally induced diabetes (4). Luck, Morrison and Wilbur (5) observed that insulin lowered the amino acid content of blood in both experimental animals and normal human subjects. These results have been confirmed by several investigators (6) using the Folin colorimetric method and by Farr and Alpert (7) using Van Slyke and MacFadyen's manometric ninhydrin method (8). Luck also studied two diabetic patients under insulin treatment and observed low normal fasting amino acid levels. The lack of agreement of existing data on the blood amino acid content in human diabetes mellitus, together with the paucity of data on the clinical condition and therapy of the patients, suggested the present study.