(by Alex Holtschneider, Engineering Team)
Last week, our primary focus was on fabricating our temperature-dependent
resistors (RTD). The process heavily focuses on lithography. We start with our
substrate, glass, with chromium and nickel spun onto the substrate. The
chromium is used to adhere the nickel to the substrate and the nickel is used
since it is a conducting metal capable of carrying current.
We then spin a
layer of photoresist onto the nickel layer using a centrifuge so that we can
etch parts of the surface away. After the photoresist layer has hardened, we
apply the mask of our RTD design onto the photoresist layer. We then expose the
photoresist layer and mask to ultraviolet light, which weakens the photoresist
everywhere but where the mask has markings (i.e. the wires for the RTD). Once
the photoresist is weakened, we wash away the weakened photoresist, excess nickel, and
excess chromium using their respective etchants. We are then left with only the
nickel wires attached to a plate of glass by a thin layer of chromium.
Our next
task is to develop our own RTD so that it has a resistance of 100 Ω at 20°C
using the formula R = ρL/A, where R is resistance, ρ is resistivity, L is
length of the wire, and A is cross-sectional area. Once we have fabricated our
RTD we will test its accuracy and then integrate it into our circuit with the
Anderson Loop.