  Silicon spin qubits are promising candidates for realising large scale
quantum processors, benefitting from a magnetically quiet host material and the
prospects of leveraging the mature silicon device fabrication industry. We
report the measurement of an electron spin in a singly-occupied gate-defined
quantum dot, fabricated using CMOS compatible processes at the 300 mm wafer
scale. For readout, we employ spin-dependent tunneling combined with a
low-footprint single-lead quantum dot charge sensor, measured using
radiofrequency gate reflectometry. We demonstrate spin readout in two devices
using this technique, obtaining valley splittings in the range 0.5-0.7 meV
using excited state spectroscopy, and measure a maximum electron spin
relaxation time ($T_1$) of $9 \pm 3$ s at 1 Tesla. These long lifetimes
indicate the silicon nanowire geometry and fabrication processes employed here
show a great deal of promise for qubit devices, while the spin-readout method
demonstrated here is well-suited to a variety of scalable architectures.
