Contactless hall coefficient measurement apparatus and method for piezoelectric material
AssigneeThe United States of America as represented by the Secretary of the Army
InventorsArthur Ballato, Herbert A. Leupold
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Abstract
A method and apparatus for the contactless, non-destructive measurement of Hall coefficient and resistivity of a piezoelectric semiconductor sample. The material to be tested is formed in a disk which is supported at its edge by a holder. The disc is free to vibrate. Two pairs of electrodes, placed above and below the sample, excite the sample into and beyond piezoelectric resonance. Then a magnetic field is applied to the sample and the sample again driven into and beyond resonance. Comparison between the performance of the disk before and after application of the magnetic field yields data from which Hall coefficient can be determined.
Claims9
Apparatus for the non-destructive, contactless measurement of the Hall coefficient of a piezoelectric material comprising:
- first and second pairs of spaced apart electrodes, said electrode pairs defining an air gap between said electrode pairs;
- means for positioning a disk of said piezoelectric material within said air gap, said disk having upper and lower surfaces which are generally parallel;
- means for establishing a magnetic field within said air gap, said magnetic field being generally perpendicular to said upper and lower surfaces of said disk;
- means, connected to said electrodes, for establishing a first alternating electric field in said air gap, said first alternating electric field causing said disk to vibrate piezoelectrically and to generate a second alternating electric field;
- means for measuring said second electric field caused by said piezoelectric vibration, said measuring means being connected to at least one pair of said electrodes.
A non-destructive, contactless method of measuring the Hall coefficient of a piezoelectric material comprising the steps of:
- supporting a disk of said piezoelectric material in a gap such that said disk is free to vibrate;
- creating an alternating electric field in said gap thereby causing said disk to vibrate piezoelectrically;
- creating an alternating magnetic field in said gap thereby inducing the Hall effect in said disk;
- adjusting the frequency of said alternating electric field to drive said disk to approximately said disk's resonance frequency;
- receiving the signal within said gap generated by said disk;
- and
- measuring the modulation of said signal to determine said Hall coefficient.
Dependencies are inferred from the claim text.