  The demonstration of universal quantum logic operations near the
fault-tolerance threshold establishes ion-implanted near-surface donor atoms as
a plausible platform for scalable quantum computing in silicon. The next
technological step forward requires a deterministic fabrication method to
create large-scale arrays of donors, featuring few hundred nanometre
inter-donor spacing. Here, we explore the feasibility of this approach by
implanting low-energy ions into silicon devices featuring an enlarged 60x60
$\mu$m sensitive area and an ultra-thin 3.2 nm gate oxide - capable of hosting
large-scale donor arrays. By combining a focused ion beam system incorporating
an electron-beam-ion-source with in-vacuum ultra-low noise ion detection
electronics, we first demonstrate a versatile method to spatially map the
device response characteristics to shallowly implanted 12 keV $^1$H$_2^+$ ions.
Despite the weak internal electric field, near-unity charge collection
efficiency is obtained from the entire sensitive area. This can be explained by
the critical role that the high-quality thermal gate oxide plays in the ion
detection response, allowing an initial rapid diffusion of ion induced charge
away from the implant site. Next, we adapt our approach to perform
deterministic implantation of a few thousand 24 keV $^{40}$Ar$^{2+}$ ions into
a predefined micro-volume, without any additional collimation. Despite the
reduced ionisation from the heavier ion species, a fluence-independent
detection confidence of $\geq$99.99% was obtained. Our system thus represents
not only a new method for mapping the near-surface electrical landscape of
electronic devices, but also an attractive framework towards mask-free
prototyping of large-scale donor arrays in silicon.
