  The advent of devices based on single dopants, such as the single atom
transistor, the single spin magnetometer and the single atom memory, motivates
the quest for strategies that permit to control matter with atomic precision.
Manipulation of individual atoms by means of low-temperature scanning
tunnelling microscopy provides ways to store data in atoms, encoded either into
their charge state, magnetization state or lattice position. A defining
challenge at this stage is the controlled integration of these individual
functional atoms into extended, scalable atomic circuits. Here we present a
robust digital atomic scale memory of up to 1 kilobyte (8,000 bits) using an
array of individual surface vacancies in a chlorine terminated Cu(100) surface.
The memory can be read and rewritten automatically by means of atomic scale
markers, and offers an areal density of 502 Terabits per square inch,
outperforming state-of-the-art hard disk drives by three orders of magnitude.
Furthermore, the chlorine vacancies are found to be stable at temperatures up
to 77 K, offering prospects for expanding large-scale atomic assembly towards
ambient conditions.
