| 摘要 |
The invention is an instrument for determining the work functions (unbiased) or absolute surface potentials (biased) of conducting sample surfaces. These values are inferred from measured surface potential differences between the sample and the instrument's non-contacting sensor. Charge incurred in the sensor by the proximity and surface potential of the sample surface alters the impedance of a semiconductor channel within the sensor. The deviation in the charge dependent impedance of the sensor from a calibrated zero-field reference is used by a feedback controller to alter the base potential of the sensor to eliminate the deviation signal. In this state, the surface potential of the sensor matches that of the sample thus forming a zero-field condition, as a result no charge is induced in the sensor. The surface potential difference between the sample and the sensor is then equal to the sensor base voltage, which is directly measured by a voltmeter. Due to the absence of induced charge in the zero-field condition, the measurement is independent of the sample/sensor separation.
|
