A correlation between the lattice parameter and the carbon concentration in otherwise pure samples of silicon has been observed. Carbon content has been determined by mass spectrometry, infrared, and lattice parameter measurements. Typical values of the carbon concentration are given for some float-zoned silicon crystals and for a series of intentionally carbon-doped crystals.
The atomic radial distribution in amorphous selenium at room temperature was determined independently from x-ray and neutron-diffraction patterns. Correction techniques were applied to reduce spurious oscillations in the distribution. The two si(s) intensity functions are in good agreement, and both methods show peaks in the radial distribution at 2.33, 3.7, 4.6, 5.8, and 7.(3) Å. The intensity patterns show no appreciable damping out of intensity peaks even at the experimental limit of s=13. This behavior results from the presence of short and well-defined interatomic distances in amorphous selenium. The intensity function can largely be accounted for by considering only two interatomic distances between the first and second nearest neighbors along the c-axis chain structure of hexagonal crystalline selenium. Thus, the spiral chain structure persists in the amorphous state with nearly unchanged geometry out to second neighbors, but in random orientations.
The purpose of this Letter is to report length contractions in n-type germanium due to electron bombardment at liquid-helium temperature and to propose the interpretation that these length contractions are produced by an electronic effect which dominates over the expansions caused by the atomic effect. In contrast to n type, the length changes of a p-type sample irradiated under the same conditions are smaller by more than an order of magnitude.Simultaneous length and conductivity changes have been observed in degenerate rc-type germanium single crystals during bombardment by 4.5-MeV electrons at liquid-helium temperature and during subsequent isochronal annealing. The irradiated portion of the sample measured 5 mm long, 4 mm wide, and 0.7 mm thick. The linear-accelerator electron beam passed through the sample in the [001] direction, and the length changes were measured in the perpendicular [110] direction. Changes in length of the sample produced changes in the spacing of a system of parallel plate capacitors, and these capacitors were compared with a standard capacitor by means of an ac ratio bridge. All capacitors were of the three-terminal type and the method of measurement was similar in principle to that used by White. 1 The sample and supporting framework for the capacitors was shaped from one large single crystal of germanium to minimize extraneous effects. The sensitivity and long-term stability of the system were such that changes in length on the order of 0.3 angstrom were detectable. Annealing was of the isochronal type and was accomplished by means of a heater and double exchange gas-vacuum system. The sample was held at each annealing temperature for 10 minutes before recooling to liquidhelium temperature. All measurements were made at liquid-helium temperature.Degenerate w-type material was chosen for our initial experiments, rather than intrinsic material as used by other investigators, since the electrical measurements by Klontz and Mac-Kay 2 and the stored-energy measurements by Singh and MacKay 3 have shown that irradiation effects in w-type material are more than 100 times greater than in/>-type material. Figure 1 shows the length change in a degenerate rc-type sample as a function of the irradiation flux. From this plot &L/L = -6.2 x 10~2 4 per incident electron/cm 2 . Figure 2 shows the results for the same sample during a later run consisting of a relatively light bombardment followed by an isochronal anneal with points taken every 5 degrees. The general characteristics of the length and conductivity curves are quite similar. An annealing peak between 35 and 40°K is evident in both curves. A second sample of degenerate n -type material showed similar behavior.Irradiation of a degenerate />-type sample at liquid-helium temperature resulted in a barely detectable contraction. The length-change effect is at least an order of magnitude smaller in p type than in n type. The fact that length 609
A method of measuring the difference between the lattice parameter of a region of an unknown sample and that of a region of a standard reference crystal to a sensitivity of 1 part in 109 is presented. Problems inherent in multiple‐beam arrangements due to sample strains and non‐uniformity have been overcome by the use of a new double‐source arrangement in which the two X‐ray beams sample the same spot on a crystal under study. Ways of identifying and preventing errors from significant mechanical and thermal effects arising in the sensitivity region explored are indicated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.