We have studied the effects of an uniaxial stress on the binding energy of a shallow donor impurity in a parallelepiped-shaped GaAs–(Ga,Al)As quantum dot. In the calculations we have used a variational technique within the effective-mass approximation. The stress was applied in the z direction and the donor impurity was located at various positions along the z axis. Our results show that the donor binding energy increases with increasing stress and for decreasing sizes of the quantum dot. Also, we have found that the binding energy for various values of the donor position along the z axis for constant quantum well box size increases with the proximity of the impurity to the center of the structure. Moreover, we obtain the shallow-donor binding energies as functions of uniaxial stress in the limit in which the quantum dot turns into either a quantum well or a quantum-well wire.

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Seventeen standard platinum resistance thermometers from five commercial sources have been subjected to repeated thermal cycling over all or most of the range -196 "C to +650 "C to determine whether strain effects occur in the platinum sensors, and to what precision they affect temperature measurements. It is found that the resistance at the triple point of water, when measured repeatedly during thermal cycling, does undergo reversible changes in many thermometers that can be attributed to either elastic or anelastic strain. The magnitude of this resistance irreproducibility is usually between the equivalent of 0.1 m "C and 1.8 m "C near 0 "C. It is concluded that thermal strain effects pose a small, but significant, limitation on the ultimate performance of most of these thermometers.

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