Hongyi He

Based on the three-dimensional (3D) linear elasticity theory of piezoelectric semiconductor (PS) structures, inspired by the variational principle and the Mindlin plate theory, a two-dimensional (2D) higher-order theory and equations for thin-film devices are established for a rectangular coordinate system, in which Newton’s law (i.e., stress equation of motion), Gauss’s law (i.e., charge equation of electrostatics), Continuity equations (i.e., conservation of charge for holes and electrons), drift–diffusion theory for currents in semiconductors, and unavoidable thermo-deformation-polarization-carrier coupling response in external stimulus field environment are all considered. As a typical application of these equations, the static characteristic analysis of electromechanical fields for the extensional deformation of a PS thin-film device with thermal field excitations is carried out by utilizing established zeroth-order equations and the double trigonometric series solution method. It is revealed that the extensional deformations, electric potential, electron and hole concentration perturbations, and their current densities can be controlled actively via artificially tuning thermal fields of external stimuli. Especially, a higher temperature rise can induce a deeper potential well and a higher potential barrier, which can play a vital role in driving effectively motions and redistributions of electrons and holes. Overall, the derived 2D equations as well as the quantitative results provide us some useful guidelines for investigating the thermal regulation behavior of PS thin-film devices.

The strain measurement technology of resistance strain gauges has been widely used in various types of superconducting magnets. Based on electrical signal transmission, the resistance strain gauges and electrical signal lines will be affected by temperature and electromagnetic field, which will cause interference to strain measurement. Therefore, it is challenging to make high precision measurements using resistance strain gauge measurement technology. In order to improve the measurement method, the symmetrical compensation bridge is proposed to compensate the influence of temperature gradient and magnetic field noise. This method is verified in the temperature and electromagnetic changing field during cooling and excitation processes on the NbTi superconducting magnet. The results show that the symmetrical compensation bridge can further reduce the error caused by wire resistance and environmental noise strain measurement in variable temperature and strong magnetic field environment. The proposed compensation bridge can enrich the strain measurement method in extreme environment, and provide an important strain detection method for the testing and operation of superconducting magnet structures.