ABSTRACT

In the TDCM, a unipolar step wave is applied to the MISM structure and the charge response Q(t) is measured by a charge amplifier just after the step wave is applied (t=O) and both when the Ca is fully charged and when Cs is discharged (t=oo). The output voltage of the charge amplifier V(t) is assumed to be equivalent to Q(t)ICFa!though it is modulated by the transfer function G( m) of the charge amplifier. The resistivity is derived from the V(O), V(oo), and the charge relaxation time <e. This method has an advantage that it is not necessary to estimate da and d5 • It is noted that the V(O) and V(oo) is influenced by G(m) because they are the fastest and slowest responses of the step wave, respectively. Furthermore, the unipolar step wave accumulates a certain amount of charge in the capacitances of Ca and Cs in the MISM structure at the end of each measurement and therefore it should be forced to discharge before starting the next measurement. Therefore, the TDCM apparatus should be carefully designed to overcome these issues discussed above.