Ferroelectric Capacitors

     Radiant testers as reference capacitors
     Radiant EDU

     Experimental circuits

 

Two 20/80 PZT capacitors with identical areas are packaged in a four-pin TO-18 transistor-type header. Capacitor areas range from 100 square microns to 100,000 square microns.  (See datasheet for area designations.)  The capacitors have a very square hysteresis loop, a thickness of ~2600 Ångstroms, a saturation voltage of less than 5 volts, a DC bias limit of 9 volts continuous, and switching speeds as fast as the driving circuit can deliver current. These capacitors have platinum electrodes so they do fatigue in about one million cycles and age strongly at room temperature.  These capacitors are excellent for self-education and experimentation not involving constant cycling.  They will last reliabily for approximately one year in an autonomous memory circuit at room temperature. 

 

Type AL capacitors are fatigue and imprint free versions of the Type AB capacitors.  They are intended for use in commercial products and have a life-time of at least 10 years below 85°C.  The capacitor structure has 2600 Ångstroms of 4% niobium-doped 20/80 PZT  (PNZT) and uses a thin layers of Lanthanum Strontium Cobalt Oxide (LSCO) on either side of the ferroelectric material.  The LSCO interfaces eliminate fatigue and imprint.  These cycles capacitors do not switch as fast as do the Type AB capacitors and should be used at 1kHz or slower but will lose only 10% of their remanent polarization in 1x10⁹ cycles.  The Type AL capacitors are packaged in the same manner as the Type AL.  There are slight differences in the areas of the Type AL capacitors from those of the Type AB capacitors.

 

The PFM Reference Die comes mounted on a TO-18 header which itself is soldered to a printed circuit board sized to fit most AFM chambers. The die is a Type AB (see above) with the RED capacitors bonded out. Unlike the standard Type AB parts, the PFM Reference Die was fabricated without any passivation so researchers can contact the top electrode with conductive cantilever tips. This product is an excellent training tool for verifying the operation of newly installed AFM and PFM equipment. As well, it provides a standard material sample for studying piezoelectric properties of a known good 20/80 PZT film.

 

 

The TO-18 Socket Board has a socket compatible with the Type AB and Type AL packaged ferroelectric capacitors.  A manual switch on the board connects Capacitor A or Capacitor B of the package to the two coaxial cable connectors.  The Socket Board is a convenient way to connect a packaged ferroelectric capacitor to test equipment for long period tests.