Cylindrical Films for Electronics in Low Background Physics Searches

A technique for manufacturing thin-film resistors on cylindrical substrates is demonstrated. These devices are aimed for application in rare-event detectors that must minimize radioactive backgrounds from trace impurities in electronic components inside the detector. Cylindrical, conducting Ni films were created via Electron Beam Deposition, using a mechanism that rotates the substrate, to demonstrate proof of principle and measure the resistivity on axis and in azimuth. These films are characterized by measurements using a facsimile of the Van Der Pauw method combined with electrostatic simulations. In the two cylindrical samples made we observe anisotropic electrical behavior with resistivities of 1392.5, 888.5 $n \Omega m$ around the azimuth and of 81.9, 72.8 $n \Omega m$ along the axis of the sample. We show that this anisotropy is not caused just by the electron beam evaporation by measuring a planar rectangle sample made in the same process but without spinning which has estimated resistivities of 66.5, and 71.9 $n \Omega m$ in both directions, and calculated resistivity using the standard Van der Pauw equation of $66.1\pm2.8$ $n \Omega m$. In spite of the anisotropy in the cylindrical samples, we show that these films can be used as resistors.