Oxygen precipitation in Czochralski (CZ) grown silicon crystal was quantitatively investigated using transmission electron microscopy (TEM) and etching technique. Oxide precipitate growth was found to be limited by interstitial oxygen diffusion, and to proceed two dimensional growth between 750°C and 1050°C. Nucleation rate dependence on annealing temperature, annealing time and oxygen content was determined. The result was analyzed using classical nucleation theory. It is clarified that homogeneous nucleation takes place under high supersaturation of oxygen. Existence of microprecipitates in the asgrown crystal was confirmed and their size and density were determined. Their formation mechanism and role in device characteristic degradationare discussed. Dislocation loops are nucleated at these microprecipitates on device fabrication process and contribute to leak current or dark current.
The purposes of the present note are to introduce the recent development and theusefulness of the in situ observation technique and to provide some prospects onnew applications and extensions of the unique advantages of in situ high voltageelectron microscopy for physical and materials research in future. First, theexperimental procedures developed so far are introduced and the possibilities ofin situ observation in a high voltage electron microscope for deriving meaningful results in the research field of materials science are discussed. Secondly, some valuable results obtained so far mainly in the studies of dynamic behavior ofdislocations and dislocationrelated phenomena are illustrated. Thirdly, the capacity of this technique to investigate crystalline deformation as well as other dynamic processes are assessed. Finally, some prospects on new applications and extensions of this in situ observation technique for physical and materials research, which can be expected by the instrumental improvement and methodological development, are presented.
With regard to its function as a differential pressure flowmeter, the movable tube flowmeter of the straight flow type previously reported by the present authors may be considered to correspond to the Venturi meter while the movable orificeflowmeter, here reported, corresponds to an orifice meter. An orifice meter should be considered to be composed of not only the orifice plate but a part of the tube including the pressure taps should also be included as an essential component. Similarly, in the movable orifice flowmeter, the short tube connected movably by a bellows to the fixed pipe should also be considered. From the viewpoint of measuring principle, however, the movable orifice flowmeter is a kind of a movable tube flowmater of the straight flow type, in which the movable tubewith a smaller diameter becomes extremely short. Therefore, the true flow rates are obtained by the movable orifice flowmeter without the need of a discharge coefficient. The results of experiments with the trial flowmeters show good agreement with the theory.
Samples of nondoped ptype CdTe were heat-treated in the temperature range of 100-900°C for 30min or 300min in a vacuum. Dissociations of Cd and Te from CdTewere observed at temperatures higher than 300°C and 600°C, respectively.The number of Cd dissociated was nearly equal to that of Te at temperatures above 700°C. Effects of the heat treatment on the lattice constant, the carrier concentration and the photoluminescence appeared even at 200°C. Annealing at500°C resulted in a minimum in the lattice constant, the intensity of the photoluminescence and the acceptor concentration. A high resistivity layer was formed at a depth of 2-4μm from the surface for all the samples annealed at temperatures above 400°C.
The present stage of knowledge on the fundamental dielectric breakdown of polymers is surveyed. At first, the existing theories are briefly described, involvingones presented from a consideration of the inherent nature of polymers. On the basis of them, the relation between their molecular and morphological feature andthe electric strength is discussed with particular attention to the crystallinity and molecular motions. Polar groups, impurities, tacticity, crosslink, etc. influence the breakdown process directly and indirectly through the modificationofthe crystallinity and phase transitions. The importance of space charges and internal strain is also shown.
Thermally stimulated currents (TSC) in polymers are due to several kinds of charged particles such as dipoles, electronic trapped charges and mobile ions. Generation mechanism of their TSC are discussed and it is shown that the characteristics of such TSC are different to each other. So charged particles contributing to TSC in polymers can be distinguished by TSC measurements. For example, TSC in Polyethylene is caused by trapped electrons, and three TSC peaks in Poly (ethylene terephthalate) are caused by two kinds of dipoles and mobile ions. TSC of dipoles of single relaxation time are well analyzed and the calculation method of dielectric constant by TSC measurements is shown with the examples. TSC of trapped charges and mobile ions have not been completely analyzed, however electronic trap levels and ionic space charge polarization can be evaluated by TSC measurements.