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Thin silicon nitride films ͑less than 20 nm͒ deposited on ͑100͒ silicon substrates via low pressure chemical vapor deposition ͑LPCVD͒ at three temperatures ͑730, 760, and 825°C͒ were analyzed by spectroscopic ellipsometry ͑SE͒, attenuated total reflection ͑ATR͒, and other tools. Films appeared to have similar optical bandgaps ͑ϳ5 eV͒, and the values decreased slightly with the higher deposition temperature. Second ionic mass spectroscopy results showed that a similar amount of oxygen exists in the interface between silicon and silicon nitride. ATR spectra showed no sign of Si-H bonds and decreasing N-H bonds at higher deposition temperature in the thin films. The electrical properties of the films are also discussed.Silicon nitride films have been widely used in very large scale integration ͑VLSI͒ technologies, such as diffusion mask, passivation, antireflection coatings, and gate dielectrics. 1-4 Various processing methods of silicon nitride films were reported, such as thermal nitridation, 5 atmospheric pressure chemical vapor deposition ͑CVD͒, 6 plasma-enhanced CVD ͑PECVD͒, 7 hot wall CVD ͑HWCVD͒, 8 and low pressure CVD ͑LPCVD͒. 9 Among the fabrication techniques, LPCVD is commonly chosen. Even though LPCVD nitride films cannot be used for gate dielectrics due to their poor interface quality and high bulk trap density, they are widely chosen for applications such as diffusion mask, nitride spacers, etc. We studied the LPCVD silicon nitride thin films deposited by using a mixture of dichlorosilane ͑DCS͒ and ammonia (NH 3 ) with nitrogen as dilute at three temperatures in a conventional batch reactor.The purpose of this work was to analyze the optical properties of thin to ultrathin ͑below 10 nm͒ silicon nitride films via spectroscopic ellipsometry ͑SE͒ analysis and directly study the bond structure ͑es-pecially bonds with hydrogen such as Si-H and N-H͒ of the films by attenuated total reflection ͑ATR͒. SE is a nondestructive optical technique used to determine the optical properties of substrates and thin films based on measuring the polarization ellipse of a light beam reflected off a sample at a given angle. From this data, the complex index of refraction and film thickness can be determined using a computer model fit. ATR provides a way of directly analyzing very thin films with much higher sensitivity than normal Fourier transform infrared ͑FTIR͒ analysis. A schematic plot of ATR measurement is shown in Fig. 1. The infrared radiation signal penetrated into the monolayer film only once during the measurement. Typical thickness for normal FTIR analysis is equal or larger than 1000 Å to get desirable signal noise ratio. However, the actually used films in electronic devices may not necessarily meet this thickness requirement. In this work, all the films' thicknesses are less than 20 nm. By using ATR and Woollam SE analysis we can directly study the optical properties of these ultrathin nitride films. Other films properties like electrical data were also discussed. ExperimentalSingle crystal ͑100͒ p-type silico...

The Polaris high intensity, medium resolution, time-of-flight neutron diffractometer at ISIS has been used in a real-time study to observe phase evolution in rods of melt-cast Bi1.6Pb0.4Sr2Ca3Cu4Oy in situ as they were recrystallized by passage of a dc current under a series of controlled atmospheres. Together with simultaneous measurement of current and resistance to facilitate control over sample heating, the experiment required visual monitoring of the sample during neutron diffraction data collection. This article describes the apparatus constructed to carry out these experiments, along with the necessary modifications made to Polaris and its control systems, and presents results which demonstrate the effectiveness of the technique. The results presented show that the initial appearance of the Bi-2201 phase occurred before hot zone formation. On formation of the hot zone, development of Bi-2212 took place at the expense of Bi-2201. Finally, passage of the zone saw the Bi-2212 redissolve and Bi-2201 reform.

The melt casting route has been shown to be a promising synthesis technique for the fabrication of bulk Bi-Sr-Ca-Cu-0 superconductor. Precursors produced via this technique may be converted into superconducting material through conventional radiative heating or, as has been shown, through direct electrical resistance heating. For processing via the latter technique, a precursor with homogeneous electrical properties is preferred. In this paper melt cast precursor rods of composition Bi1.6Pb0.4Sr~Ca3Cu40y have been prepared through casting a melt into a preheated copper mould and the influence of the temperature to which the mould was preheated on the electrical resistance and homogeneity of the precursor was studied.