Nature © Macmillan Publishers Ltd 19988 localizing effect will lead to saturation of the magnetoresistance. Yet all the data except for the perovskite manganites and the strongly localized Eu 0.99 Gd 0.01 Se (n ¼ 0:0002 per unit cell) are on samples that satisfy k F l Ͼ 1, indicating the weakly localizing nature of pure spin scattering, as expected.At low carrier densities, one should be wary of magnetizationdependent bandshift, because the exchange energy might be comparable to the Fermi energy. When the carriers are introduced by doping, this is not important, but for semimetals (Tl 2 Mn 2 O 7 may be an example 19,20 ) and mixed valent compounds 21 the carrier density itself might become field-and temperature-dependent.We conclude that on elementary theoretical grounds and with some support from the limited data available, the very simplest Born approximation gives a good account of the trends in bulk magnetoresistance over two decades in density, in materials and in models of magnetism that have otherwise very little in common. The most evident deviation from a simple scaling law is in the perovskite manganites, for which there is overwhelming evidence that their 'colossal' magnetoresistance arises from the localization of carriers by lattice distortions that are themselves coupled to the magnetic degrees of freedom.This organizing principle suggests that insulating ferromagnets, lightly doped into the metallic regime, are a promising class of materials in which to search for large bulk magnetoresistance. As a final cautionary note, we also point out that the scaling shown in equation (4) and in Fig. 1 nevertheless implies rather small values of the absolute bulk magnetoresistance at the millitesla fields of technological interest. Ⅺ

We have studied the effect of H2 dilution on the growth of polycrystalline silicon (poly-Si) using SiF4/SiH4/H2 by a remote plasma chemical vapor deposition. With an increase of H2 dilution ratio the grain size decreases and the polycrystalline fraction increases, probably due to enhancement of the nucleation rate with H2 flow rate. We have deposited polycrystalline silicon films with a crystalline fraction of 89% at a substrate temperature of 330 °C. The peak of the deconvoluted Raman spectrum contributed from the microcrystalline (or amorphous) Si portion in the deposited poly-Si film increases and the full width at half maximum decreases with increasing H2 flow rate.

The electrical and optical properties of the hydrogenated amorphous silicon (a-Si:H) films deposited by inductively coupled plasma (ICP) chemical vapor deposition (CVD) have been investigated. The ICP-CVD a-Si:H films deposited at the pressure of 30 mTorr exhibited the hydrogen content of 17 at. %, a photosensitivity of 106 at 100 mW/cm2 and a conductivity activation energy of 0.9 eV. A novel coplanar self-aligned a-Si:H thin film transistor was fabricated using Ni-silicide gate and source/drain electrodes. The simultaneous Ni-silicide formation of gate and source/drain regions using the stacked layers of thin a-Si:H, silicon nitride (SiNx) and a-Si:H reduces the offset length between gate and source/drain, which leads to the coplanar a-Si:H thin film transistor (TFT). This self-aligned a-Si:H TFT exhibited a field effect mobility of 0.44 cm2/V s, threshold voltage of 5.3 V and subthreshold slope of 0.5 V/dec. The coplanar geometry reduces the parasitic capacitance and parasitic resistance compared with those of conventional staggered a-Si:H TFTs.

Amorphous InGaZnO 4 (a-IGZO) thin film transistors (TFTs) are promising devices in backplane technology. Since a-IGZO TFTs are very sensitive to the fabrication processes, they need stable process to keep their initial deposition properties. Herein we improved the stability of a-IGZO by applying N 2 O plasma. The stability characteristic of a-IGZO TFT was improved with N 2 O plasma. V th shift was 1.5V for 10,000s under NBTS with illumination which was the best result in the world.

Abstract. We will prove that if f is a polynomial of even degree then the Fourier transform F (e −f )(ξ) can be estimated by e − f * (ξ) where f * (ξ) is the Legendre). This result was previously proved by H. Kang [K] for a case of a convex polynomial which is a finite sum of monomials of even order with positive coefficients. Our result is the most general one for the polynomial f (x) since the convexity condition is not imposed and e −f (x) belongs to the space L 1 if and only if f (x) is a polynomial of even degree with the coefficient of the highest degree a 2m > 0. Also, we will make a more precise estimate of constants.

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We have grown microcrystalline silicon by a remote plasma chemical vapor deposition technique using silane and helium only, without hydrogen dilution. The optimum growth temperature and rf power are 330 °C and 100 W, respectively. These results indicate that an atomic hydrogen environment on the growing surface is not always necessary to grow microcrystalline (μc-)Si at low temperatures. It is found that the exposure of He plasma on the growing surface of μc-Si etches the Si layer, explaining the growth of μc-Si by using only silane and He and no hydrogen.