  We used low-temperature scanning electron microscopy (LTSEM) for imaging
quantized magnetic flux (vortices) in direct current (dc) superconducting
quantum interference devices (SQUIDs) with approximately 1 micron spatial
resolution at temperature T=77 K in a controllable magnetic field up to 20
microTesla. We demonstrate that LTSEM allows to image the spatial distribution
of vortices in a YBa2Cu3O7/SrTiO3/YBa2Cu3O7 multilayer thin-film structure
consisting of a dc SQUID washer with an integrated input coil on top.
Simultaneously, we are able to measure the low-frequency noise of the sample
under test, which allows to correlate the spatial distribution of vortices with
low-frequency noise in the SQUID.
