Creep of CdZnTe at high homologous temperatures
- PDF / 203,594 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 272 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Creep of CdZnTe at high homologous temperatures T.E. Stevens, J.C. Moosbruggera) and F.M. Carlson Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, New York 13699–5725 (Received 15 June 1999; accepted 27 July 1999)
The creep behavior of single-crystal Zn-doped CdTe was examined in the small strain regime. Specimens from two different sources, with tensile axes [110] and [112], were deformed at 1073 and 1173 K. Strain rates were of order 10−6 to 10−7 s−1. A laser interferometer was constructed to measure the small sample displacement. Cadmium overpressure was used to inhibit sublimation of test specimens at elevated temperatures. Some tests showed a transition from secondary to tertiary creep at low levels of strain. An activation energy for steady-state creep was calculated as QC ⳱ 1.46 eV, and the creep exponent was found to be approximately n ⳱ 4.2. These results, coupled with reported activation energies for self-diffusion of Cd in Cd(Zn)Te, indicate a dislocation creep mechanism. Etch pit density was measured before and after deformation and approached a common level regardless of initial etch pit density.
I. INTRODUCTION
The production of compound semiconductor devices requires high-quality single-crystal substrate materials. For this reason, a low density of crystalline defects is essential in these substrate materials. Processes for the production of high-quality CdTe (and its alloys), such as horizontal and vertical Bridgman techniques, however, are not yet proved to ensure consistent crystal quality. Interest in these materials stems from applications such as substrates for Hg1−xCdxTe infrared detectors, highspeed switches, and communication systems.1 Inelastic deformation of the crystal during solidification may result from thermal gradients, the weight of the melt over the ingot, and the differential thermal expansion (contraction) between the solidified ingot and the crucible used for containment. This inelastic deformation gives rise to the formation and propagation of dislocations. To understand and model these processes, useful information about the elevated temperature inelastic deformation behavior of these materials is necessary. Previous elevated temperature, mechanical property measurements in this material2–7 have focused on collecting stress–strain data, including critical resolved shear stress (CRSS), for CdTe-based compounds. Since inelastic deformation is time- and rate-dependent, especially at high homologous temperatures, CRSS does not uniquely define the stress required to initiate inelastic
a)
Address all correspondence to this author.
3864
http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 10, Oct 1999 Downloaded: 15 Mar 2015
deformation. These tests have been performed primarily at moderate strain rates (e.g., 10−3 to 10−4 s−1), and specimens were deformed to relatively large strains. In this work, single-crystal Zn-doped CdTe was deformed to 1% to 2% strain under constant load at homologo
Data Loading...
