In this thesis, a technique is developed to manipulate individual atoms on an ionic surface, with great precision and at a large scale, to study the quantum mechanical properties of atomic assemblies on the nanoscale. We use the needle of a scanning tunnelling microscope (STM) to approach missing atoms - vacancies - in a chlorine monolayer on a copper crystal, inducing a neighbouring Cl atom to jump to the vacancy position by ramping up the tunnel current. This procedure is automated - with sometimes up to 99% reliability - to construct a 1 kB memory where each bit is represented by an atom-vacancy pair. The data storage is stable at low temperatures and can be rewritten automatically, leading to an information density of 502 terabits per square inch, or 0.778 bits/nm^2. Atom manipulation is then used to build other one- and two-dimensional structures with varying sizes and atom densities. In artificial crystals made of vacancies, standing wave patterns are observed at certain energies, suggesting that it is possible to tune electronic properties of the material, such as the dispersion, by controlling the local geometry with atomic assembly. In the rest of the thesis, more structures were built by atom manipulation in order to investigate the coupling between assemblies of vacancies that form 'artificial molecules'. Resonances in scanning tunnelling spectroscopy measurements indicate the existence of quantum dots on the apex of the STM tip, of which the properties are explored. The chlorine terminated copper surface is also investigated for its use as a decoupling layer suitable for magnetic adatoms.

Within the last three decades Scanning Probe Microscopy has been developed to a powerful tool for measuring surfaces and their properties on an atomic scale such that users can be found nowadays not only in academia but also in industry. This development is still pushed further by researchers, who continuously exploit new possibilities of this technique, as well as companies that focus mainly on the usability. However, although imaging has become significantly easier, the time required for a safe approach (without unwanted tip-sample contact) can be very time consuming, especially if the microscope is not equipped or suited for the observation of the tip-sample distance with an additional optical microscope. Here we show that the measurement of the absolute tip-sample capacitance provides an ideal solution for a fast and reliable pre-approach. The absolute tip-sample capacitance shows a generic behavior as a function of the distance, even though we measured it on several completely different setups. Insight into this behavior is gained via an analytical and computational analysis, from which two additional advantages arise: the capacitance measurement can be applied for observing, analyzing, and fine-tuning of the approach motor, as well as for the determination of the (effective) tip radius. The latter provides important information about the sharpness of the measured tip and can be used not only to characterize new (freshly etched) tips but also for the determination of the degradation after a tip-sample contact/crash.

The interaction of electrons with a periodic potential of atoms in crystalline solids gives rise to band structure. The band structure of existing materials can be measured by photoemission spectroscopy and accurately understood in terms of the tight-binding model, however not many experimental approaches exist that allow to tailor artificial crystal lattices using a bottom-up approach. The ability to engineer and study atomically crafted designer materials by scanning tunnelling microscopy and spectroscopy (STM/STS) helps to understand the emergence of material properties. Here, we use atom manipulation of individual vacancies in a chlorine monolayer on Cu(100) to construct one-and two-dimensional structures of various densities and sizes. Local STS measurements reveal the emergence of quasiparticle bands, evidenced by standing Bloch waves, with tuneable dispersion. The experimental data are understood in terms of a tight-binding model combined with an additional broadening term that allows an estimation of the coupling to the underlying substrate.

The interaction of electrons with a periodic potential of atoms in crystalline solids gives rise to band structure.The band structure of existing materials can be measured by photoemission spectroscopy and accurately understood in terms of the tight-binding model, however not many experimental approaches exist that allow to tailor artificial crystal lattices using a bottom-up approach.The ability to engineer and study atomically crafted designer materials by scanning tunnelling microscopy and spectroscopy (STM/STS) helps to understand the emergence of material properties.Here, we use atom manipulation of individual vacancies in a chlorine monolayer on Cu(100) to construct one-and two-dimensional structures of various densities and sizes.Local STS measurements reveal the emergence of quasiparticle bands, evidenced by standing Bloch waves, with tuneable dispersion.The experimental data are understood in terms of a tight-binding model combined with an additional broadening term that allows an estimation of the coupling to the underlying substrate.

The control of atomic vacancies on a chlorine-terminated Cu(100) surface by means of a scanning tunnelling microscope tip makes it possible to construct a rewritable atomic memory of over a kilobyte in size with an information density as high as 502 terabits per square inch. The advent of devices based on single dopants, such as the single-atom transistor1, the single-spin magnetometer2,3 and the single-atom memory4, has motivated the quest for strategies that permit the control of matter with atomic precision. Manipulation of individual atoms by low-temperature scanning tunnelling microscopy5 provides ways to store data in atoms, encoded either into their charge state6,7, magnetization state8,9,10 or lattice position11. A clear challenge now 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 the potential for expanding large-scale atomic assembly towards ambient conditions.

Straying off-course can lead to unexpected far-reaching results, says Floris Kalff.