Abstract: A scanning SQUID microscope capable of high frequency magnetic field measurements uses a hysteretic SQUID detector and a pulsed sampling technique which permits to extend the bandwidth of the SQUID microscope to above GHz region. The system can be readily incorporated into a 4.2k scanning SQUID microscope for imaging chips at room temperature. By biasing the hysteretic SQUID with pulses of a predetermined amplitude, and adjusting a modulation flux applied to the hysteretic SQUID at a plurality of time delays between the activation of the sample under study and the bias pulse, the hysteretic SQUID can be switched on, and the modulation flux value corresponding to such a switching event as a function of time is considered as representation of the magnetic field emanating from the sample under study.

Abstract: A technique for eliminating edge artifacts in magnetic microscopy includes the steps of scanning a SQUID over an object under study to acquire values of magnetic fields produced by currents running in the object to create a first data set having N data points. At the end of the first data set, N zero data points are added to create a second data set having 2N data points. Fast Fourier Transform (FFT) is further applied to the 2N data set to obtain k-space having b(k) values. The b(k) values of the k-space are averaged, and the averaged b(k) values corresponding to k exceeding a predetermined k value are filtered off. A set of current density representations i(k) in the k-space are obtained to which inverse FFT is applied to obtain a map of current densities I(x,y) of the object. A system for performing the method of the present invention includes a software designed to suppress (or eliminate) edge artifacts present in the obtained images.

Abstract: A method of, an and apparatus for, creating an image of currents flowing through current paths in a microelectronic circuit such that the image of the currents has improved spatial resolution using filters. The filters increase the spatial resolution and eliminate noise and edge artifacts in magnetic field and electric field images of electronic circuits. In accordance with the method, a magnetic field image is created with a scanning SQUID microscope. A magnetic inversion technique is then used to convert the magnetic field image into a current density image. The current density image is filtered based upon known restrictions on the wiring geometry of the microelectronic circuit being imaged. The technique can also be applied to convert electric fields of a circuit from a scanning single electron transistor microscope into images of the voltage levels on the wires in the circuit.

Abstract: The microscope includes a microwave generator connected to a mismatched transmission line which terminates in a probe with an exposed end. When a sample is brought into close proximity with the exposed end of the probe, the frequencies and quality factors of the standing wave resonances on the transmission line between the source and the probe are modified. The microwave signal reflected from the end of the probe varies as the capacitance between the probe and the sample changes and as the conductivity of the sample changes. Scanning the sample relative to the probe allows generation of an image from the variation of the reflected signal. Alternatively, to image a device with the microscope, a microwave signal is applied to the device, the probe is scanned over the device, and the signal that is picked up is recorded. In a second embodiment, a first lock-in amplifier is used to lock in the microscope at the resonant frequency, and a second lock-in amplifier is used to detect a curvature of the resonance.

Abstract: A cryogenic apparatus for microscopy of physical properties of an object including a thin, stiff, transparent substrate or window within the outer wall of the vacuum space of a dewar and a cryogenic sensor within the vacuum space and spaced very close distances to the window. This construction allows for positioning a sample for measurement outside of the vacuum space, at room temperature or higher and for microscopy of physical properties of the sample by monitoring the output from the cryogenic sensor as it is scanned along the surface of the sample.