Apparatus and method for scanning capacitance microscopy and spectroscopy
AssigneeAsylum Research Corporation
InventorsMaarten Rutgers, William H. Hertzog, Keith M. Jones, Amir A. Moshar
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Abstract
An apparatus and technique for measuring the electrical capacitance between a conducting tip of a scanning probe microscope and a sample surface is described. A high frequency digital vector network analyzer is connected to the probe tip of the cantilever of an atomic force microscope, and data collection is coordinated by a digital computer using digital trigger signals between the AFM controller and the vector network analyzer. Methods for imaging tip-sample capacitance and spectroscopic measurements at a single point on the sample are described. A method for system calibration is described.
Claims2
A method of making a spectroscopic measurement with a scanning capacitance microscope, including an atomic force microscope, having a conductive sample, a cantilever with a conductive tip and means for sending a DC or low frequency bias voltage to the tip, and a vector network analyzer receiving S11 signals reflected from the resonator circuit formed by the sample substrate and the tip in response to signals from the network analyzer or a bias voltage, comprising:
- positioning the tip far above the surface of the sample and emitting a high frequency electromagnetic signal from the network analyzer and capturing the frequency and amplitude of the S11 signal reflected from the resonator circuit;
- setting the excitation frequency of the network analyzer slightly above or below the resonant frequency of the reflected S11 signal determined in step one and commanding network analyzer to excite the resonator circuit at that frequency;
- bringing the tip into contact with the surface of the sample;
- sending a DC or low frequency bias voltage sweep to the tip;
- commanding the network analyzer to acquire the amplitude and phase of the S11 signal for each value of the bias voltage sweep reflected from the resonator circuit;
- calculating in the computer of the AFM plots of S11 amplitude and phase vs. each bias voltage applied to the tip.
Dependencies are inferred from the claim text.