M EASUREMENT of the average grain size in a set of high purity aluminum specimens heated for various periods of time, ranging from 20 seconds to 11 days at a series of constant temperatures from 350°C to 650°C gave the following results:(A) For isothermal grain growth the average grain size D at time t can be expressed asThe exponent n increases linearly with temperature from tt = 0.06 at 350°C to w = 0.16 at 500°C.(B) The D = Dot n relation holds true only until the grain size is well below the thickness of the specimen. When D (measured in the plane of the sheet specimen) is somewhat larger than the specimen thickness, grain growth completely stops; the grains extend through the thickness of the specimen, and their boundary surfaces are approximately perpendicular to the specimen surface. At 650°C this condition was fully reached in 20 seconds, and up to 11 days no further change occurred in the average grain size. At lower annealing temperatures the same maximum grain size was approximated in longer periods of time. The maximum grain size obtainable in a specimen through grain growth was found to increase linearly with the specimen thickness over a wide range.As a result of the variation of n with temperature, it is not possible, strictly speaking, to derive a heat of activation from grain growth data. The Q value derived from plotting logt vs. the reciprocal absolute temperature, for a certain grain size, varies with both the grain size and the temperature. The values thus obtained, however, are in the approximate range of 55 to 65 kcal./g atom. It is interesting to note that this range is in agreement with the Q values obtained by Anderson and Mehl 1 for growth during recrystallization of high purity aluminum. These values are considerably higher than the heat of activation for self-diffusion in aluminum, estimated to 37.5±4 kcal./g atom. 2 Perhaps this may be interpreted to mean that the energy for the activation of an aluminum atom to jump across a grain boundary is higher than that required to produce an exchange of position within the same lattice, as in diffusion.Attempting to check the relative magnitude of the heat of activation derived from grain growth data and that for self-diffusion with other materials than high purity aluminum, we were unable to find satisfactory grain growth data in the literature. However, the data available for brass could be used if certain idealizing assumptions were made.Let us assume the validity of the D = D 0 t n relation, the independence of n on temperature, and the existence of a heat of activation Q for the process. Under such idealized conditions the following general formula can be derived D=D 0 (te-Ql RT ) n ,(2) and for constant timeThe grain growth data by R. S. French 3 on brass satisfy the isothermal relation Eq. (1), if a correction of 10 min. is made in order to allow for the heating-up period. The corrected data for both 575°C and 640°C give rc = 0.16. By using the grain size vs. temperature data given in Fig.

Denuded zones in the near‐surface regions of Czochralski silicon wafers were investigated by means of both optical microscopy (OPM) and transmission electron microscopy (TEM). The results of this investigation show that the (nearly defect‐free) denuded zones formed near the wafer surface depend strongly on the initial oxygen concentration and the thermal history of the wafers, e. g., wafer annealing‐temperature sequence, gas ambient, and annealing duration. Clear denuded zones were observed in wafers annealed under conditions in which the oxygen out‐diffusion process is enhanced,e. g., in a high‐low, two‐step anneal (1050°C for 16h and 800°C for 16h), in a nonoxidizing ambient. A high initial oxygen concentration false(1.5×1018

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Precipitation in CZ-silicon during post-growth two-stage heat treatment has been examined using the methods of high resolution analytical electron microscopy. Electron transparent specimens prepared from these specimens, exhibited a low density of plate type precipitates on {100} planes. Microdiffraction experiments showed the precipitates to be consistently non-crystalline. Electron energy loss spectra showed that the precipitates contained oxygen, but carbon was not detected. It was found that carbon artifact absorption edges could be induced in spectra by specimen contamination in the microscope. The use of a low temperature stage eliminated this problem. Complementary characteristic x-ray microanalysis showed that metallic impurities had not segregated to these precipitates in this particular case, although this has been observed elsewhere.